Personal Research Database

Full Text: J\J Env Eng-ASCE124, 913.pdf

Abstract: The triple layer surface complexation model (TLM) is used to describe equilibria for lead, cadmium, and zinc adsorption on a recycled iron-bearing material that is treated as a hydrous oxide in aqueous solution. Using model constants derived from surface titration experiments and literature recommendations, equilibrium constants are estimated for metal adsorption reactions by calibration of pH-adsorption edge data. A method is then developed for integrating the TLM into a dual-resistance mass transport model in order to simulate the performance of completely mixed batch reactors and fixed beds for the treatment of heavy metals by porous sorbents. A sequential scheme is employed in which the coupled liquid-and solid-phase material balance equations of the dynamic model are solved at a given time step, followed by updating of the liquid-phase sorbate concentration at the sorbent particle surface by solving the set of nonlinear algebraic equations that define solid! liquid-phase equilibrium according to the TLM. The result is demonstrated with laboratory-scale kinetic data in both batch and fixed-bed reactors for lead adsorption onto the recycled iron sorbent.

Keywords: Ion-Exchange, Parameter-Estimation, Heavy-Metals, Adsorption, Water, Oxide, Transport, Behavior, Sorption, Lead

Kapoor, A. and Viraraghavan, T. (1998), Use of immobilized bentonite in removal of heavy metals from wastewater. Journal of Environmental Engineering-ASCE, 124 (10), 1020-1024.

Full Text: J\J Env Eng-ASCE124, 1020.pdf

Abstract: Bentonite is known to adsorb toxic metal ions from aqueous solutions. In this study bentonite was immobilized in a polymer matrix of polysulfone in the form of spherical beads to remove cadmium and copper ions. For this purpose a bead-producing unit was fabricated. The procedure for making beads is described. The beads exhibited a porous surface and surface area of up to 20 m²/g. 99.4% of beads were retained on a sieve size of 1.18 mm and were finer than 2.36 mm. Batch adsorption data was adequately described by the Freundlich isotherm model. The beads were able to remove more than 99% of copper and cadmium ions in the column mode. These beads can find application as filter media in the removal of toxic heavy metal ions from aqueous solutions.

Keywords: Aqueous Solutions, Adsorption, Sorption

Matsui, Y., Yuasa, A. and Li, F.S. (1998), Overall adsorption isotherm of natural organic matter. Journal of Environmental Engineering-ASCE, 124 (11), 1099-1107.

Full Text: J\J Env Eng-ASCE124, 1099.pdf

Abstract: Adsorption equilibrium data in lumped water quality indices obtained for diluted solutions of a peat water and effluents from a wastewater treatment were analyzed using the ideal adsorbed solution theory with the Freundlich equation. The use of the same value for Freundlich exponent 1/n in the ideal adsorbed solution theory resulted in a straightforward and less computationally demanding expression to describe an overall batch adsorption isotherm, A fictive component approach, assuming a logarithmic normal distribution of Freundlich K and a nonadsorbable fraction, adequately described and predicted the overall isotherms for different initial concentrations of diluted solutions presented as a lumped water quality index. The parameters in the distributed fictive component approach were independently sensitive to each portion of an isotherm curvature. Preferential adsorption of the smaller molecular weight (MW) components was observed by a size-exclusion high-performance liquid chromatography. Two-dimensional distribution analysis of organics in terms of Freundlich K and MW revealed a weak tendency of the adsorptive strength to decrease with the increase of the MW.

Keywords: Activated Carbon Adsorption, Humic Substances, Size-Exclusion, Equilibria

Chen, K.S., Tsai, Y.J. and Lou, J.C. (1999), Three-dimensional combustion modeling in municipal solid-waste incinerator. Journal of Environmental Engineering-ASCE, 125 (2), 166-174.

Full Text: J\J Env Eng-ASCE125, 166.pdf

Srinivasan, P.T. and Viraraghavan, T. (1999), Low-cost polymeric aluminum coagulant: Discussion. Journal of Environmental Engineering-ASCE, 125 (3), 298.

Full Text: J\J Env Eng-ASCE125, 298.pdf

Bajpai, S. and Chaudhuri, M. (1999), Removal of arsenic from ground water by manganese dioxide-coated sand. Journal of Environmental Engineering-ASCE, 125 (8), 782-784.

Full Text: J\J Env Eng-ASCE125, 782.pdf

Abstract: In a laboratory study, manganese dioxide-coated sand (MDCS), prepared by reacting potassium permanganate with manganese chloride under an alkaline condition and in the presence of sand, showed promise as a medium for use in small systems or home-treatment units in developing areas of the world, for removing arsenic(III) and arsenic(V) from ground water. In ten cycles of downflow column tests [bed depth 400 mm; empty-bed contact time 74 min; influent arsenic 0.5 mg As/L of arsenic(III) and 0.5 mg Asn of arsenic(V)], breakthrough bed volumes at the World Health Organization guideline value of 0.01 mg As/L for arsenic in drinking waterwere in the range of 153-185 per cycle. During regeneration (backwashing with 2 L, of a 0.2 N sodium hydroxide solution), 85.0% of the removed arsenic was recovered in the first cycle, and 94.6-98.3% was recovered in subsequent cycles. A low-cost, simple home arsenic removal unit, containing 6 kg (4 L) of the MDCS medium and operated at 6 L/h, produced 740 and 700 L of water in two cycles of runs when the influent arsenic concentration was 0.5 mg As/L of arsenic(III) and 0.5 mg As/L of arsenic(V). No arsenic(III) or leaching of manganese from the medium was detected in the effluent. A detailed study addressing the effects of some important factors (water pH, concentration and type of competing anions, and cations) on the process is needed. The home arsenic removal unit should be subjected to field trials to assess the long-term effects on performance.

Keywords: Amorphous Iron Hydroxide, Natural Waters, Oxidation, Adsorption, As(III), Oxides

Christophi, C.A. and Axe, L. (2000), Competition of Cd, Cu, and Pb adsorption on goethite. Journal of Environmental Engineering-ASCE, 126 (1), 66-74.

Full Text: J\J Env Eng-ASCE126, 66.pdf

Abstract: Competition of copper, lead, and cadmium adsorption on goethite was studied and found to be dependent on metal ion and oxide surface characteristics. In adsorption edges, ionic strength effects suggested copper, lead, and cadmium are specifically adsorbed on goethite. Metal capacity on the goethite surface was found to increase with metal electronegativity: Cu > Pb > Cd. On the other hand, the equilibrium constant For lead was greater than that of copper, which is in agreement: with their hydrated radii (Pb < Cu < Cd). Modeling revealed that the single-site Langmuir isotherm described the Cu-Cd and Pb-Cd adsorption and competition results within the error of the model. Furthermore, although the model provided a good fit for Pb and Cd data in the Pb-Cu and Pb-Cu-Cd systems, it underpredicted copper adsorption. The difference in site densities between copper and lead revealed a set of sites not available for competition. Using this approach where copper affinity is equivalent for both sites, the model provided a good fit for copper adsorption and competition. This study confirms that adsorption competition plays a crucial role in contaminant mobility in the environment.

Keywords: Oxide-Water Interfaces, Chromate Retention Mechanisms, Amorphous Iron Oxyhydroxide, Bond-Valence Determination, Pb(II) Sorption Products, Surface Complexation, Cadmium, XAFS, Mononuclear, Arsenate

Kim, B.R., Adams, J.A., Klaver, P.R., Kalis, E.M., Contrera, M., Griffin, M., Davidson, J. and Pastick, T. (2000), Biological removal of gaseous VOCs from automotive painting operations. Journal of Environmental Engineering-ASCE, 126 (8), 745-753.

Full Text: J\J Env Eng-ASCE126, 745.pdf

Abstract: Among the pollutants that automotive plants produce, volatile organic compound (VOC) emissions due to paint solvents from painting operations are the largest in quantity. The current control process, based on vapor-phase adsorption followed by thermal oxidation, is costly to install and operate. At Ford, a cost-effective method of removing VOCs has been investigated that involves converting an existing spraybooth scrubber system to a biological reactor. This paper reports the results of a pilot-scale investigation in which two activated-sludge bioreactors, one with and the other without powdered activated carbon (PAC), were operated in parallel for 16 months. The primary findings include (1) The biological VOC removal process was technically feasible, and a scrubber system at a typical assembly plant is sufficiently large to handle the solvent loading used under normal vehicle-production conditions; (2) as compared to the adsorption/thermal oxidation process, the biological process was found to be comparable in VOC removal efficiency, an order of magnitude more cost-effective in capital cost, and a factor of two more cost-effective in operating and maintenance cost; and (3) the bioreactors effectively captured and degraded hydrophilic paint solvents (methyl ethyl ketone, n-butanol, and butyl cellosolve) that were fed via the vapor phase. Toluene, a hydrophobic solvent, was also well-captured and degraded (74 to 91% without PAC and 86 to 93% with PAC).

Keywords: Solvents, Air

Jin, Y.C., Guo, Q.C. and Viraraghavan, T. (2000), Modeling of class I settling tanks. Journal of Environmental Engineering-ASCE, 126 (8), 754-760.

Full Text: J\J Env Eng-ASCE126, 754.pdf

Abstract: Sedimentation is one of the earliest and most important unit operations in water and wastewater treatment. Conventional approaches for studying sedimentation of Class I settling tanks did not present enough information on suspended particle size distribution in the effluent. This information is very important for further treatment units such as filtration. In this research, a relatively simple and practical mathematical model is introduced to study sedimentation of non-uniform particle size in Class I settling tanks. The model is capable of providing such information as removal efficiency, size distributions in sludge and in effluent suspension, and thickness of bottom sludge. If desired removal efficiency is provided, the length of the tank can also be determined. Through numerical experiments, a sensitivity analysis was performed to examine the effects of tank dimensions, overflow rate, and detention time on the removal efficiency. Comparison with other models and a set of experimental data indicates a goad agreement.

Chen, J.C., Wey, M.Y. and Liu, Z.S. (2001), Adsorption mechanism of heavy metals on sorbents during incineration. Journal of Environmental Engineering-ASCE, 127 (1), 63-69.

Full Text: J\J Env Eng-ASCE127, 63.pdf

Abstract: This study investigated the adsorption mechanism of heavy metals Cr, Cu, Pb, and Cd on the sorbent during incineration by the following technologies: (1) thermal desorption of heavy metals from the sorbent; (2) identification of heavy metal species in the adsorbed sorbent by x-ray diffraction technique; (3) thermodynamic equilibrium simulation of heavy metals and sorbent; and (4) micrography of the sorbent by scanning electron microscopy. Experimental results indicated that adsorption mechanism of heavy metals on sorbent is related to the volatility of heavy metal species formed at high temperatures and the chemical reactivity with the sorbent. For less volatile heavy metals Cr and Cu, chemical reaction is the major adsorption mechanism, and particle growth due to condensation, coagulation, and sedimentation will become important as the reacting time is increased. For highly volatile metal Cd and most metal chlorides, physical molecular adsorption and particle growth processes are the major mechanisms. Most volatile metal species are adsorbed/distributed on the surface of the sorbent. For Pb (which has been classified as medium to high volatility), chemical and physical adsorption mechanisms are all-important depending on the reacting environment.

Li, L.Y. and Li, F. (2001), Heavy metal sorption and hydraulic conductivity studies using three types of bentonite admixes. Journal of Environmental Engineering-ASCE, 127 (5), 420-429.

Full Text: 2001\J Env Eng-ASCE127, 420.pdf

Abstract: Bentonite, forest soil, and spruce bark were submitted to batch adsorption testing, leaching cell testing, and selective sequential extractions (SSEs) to investigate the heavy-metal compatibility of clay barriers and the potential of forest soil and spruce bark as clay barrier materials. The materials ranked as follows according to sorption capacity: forest soil > bentonite = spruce bark. The hydraulic conductivity values of heavy metal leachates were two orders of magnitude greater than those of the blank (0.01 mol calcium nitrate) leachate. The forest soil admix ranked first in terms of heavy-metal retention capacity and breakthrough points. The mobility of Cd was 4.5 times higher than that of Pb, and Cu was 2.5 times more mobile than Pb. The leaching cell and SSE results indicate that heavy metals cause significant preferential channeling. The SSE results show that the addition of forest soil and spruce bark to clay barrier mixes promotes heavy-metal fixation.

Keywords: Adsorption, Bark, Bentonite, Cd, Extraction, Heavy Metal, Heavy Metals, Heavy-Metal, Leaching, Metal, Metal Sorption, Metals, Pb, Sediments, Sludge Application, Soil, Soils, Sorption

Hedström, A. (2001), Ion exchange of ammonium in zeolites: A literature review. Journal of Environmental Engineering-ASCE, 127 (8), 673-681.

Full Text: J\J Env Eng-ASCE127, 673.pdf

Abstract: The objective of this review was to acquire knowledge concerning the ammonium ion exchange technique within the field of wastewater treatment. General concepts as well as details concerning the loading and the regeneration phases were included. Both chemical and biological regeneration processes were reviewed. Concerning ion exchangers, the study focused on different kinds of zeolites. The possibilities of employing the ion exchange technique for the recovery of nitrogen was also discussed. The study was carried out as a literature review. Conclusions from this study are that full-scale wastewater treatment plants that employ the ammonium ion exchange technique are scarce and few applications have been developed to recover ammonia nitrogen, for example, for agricultural purposes. Zeolites are somewhat heterogeneous because of natural variations of the minerals. Factors that influence the ammonium adsorption during the loading phase are well known. Biological regeneration has primarily been developed to decrease the brine consumption at regeneration or to improve the conventional nitrification-denitrification process. If the ion exchange technique is to be used to recover ammonium, both chemical and biological regeneration might be employed.

Keywords: Adsorption, Clinoptilolite, Removal, Wastewater, Wastewater Treatment

? Faur-Brasquet, C. and Le Cloirec, P. (2001), Neural network modeling of organics removal by activated carbon cloths. Journal of Environmental Engineering-ASCE, 127 (10), 889-894.

Full Text: 2001\J Env Eng-ASCE127, 889.pdf

Abstract: The adsorption of organic compounds onto an activated carbon cloth is studied in a dynamic reactor. An experimental design is carried out to investigate the influence of operating conditions (initial concentration C-o, flow velocity U-o, and bed thickness Z) and adsorbate’s characteristics. A slow intraparticular diffusion is shown by flattened breakthrough curves, and adsorption capacities are high and range between 50 and 250 mg g(-1). The transfer zone Z(o), assessed by the Adams and Bohart equation, is low (3 mm). All experimental results are modeled by a neural network to take into account the specific diffusion of cloths. Parameters related to the adsorbate-adsorbent affinity in a batch reactor are consequently introduced in the input layer of the neural network (intraparticular coefficient K-w and Freundlich parameters K-f and Un), added to operating conditions whose influence was shown (C-o, U-o, and Z) and time t. The statistical quality of the neural network modeling is high (r(2) = 0.956). Furthermore, the Garson connection weight method allows the relative influence of input neurons to be determined. This analysis confirms the influence of parameters relative to adsorbant-adsorbate affinity.

Keywords: Activated Carbon, Activated Carbon Cloth, Adsorption, Adsorption Data, Analysis, Aqueous-Solution, Breakthrough Curves, Carbon, Carbon Cloth, Design, Diffusion, Experimental, Fibers, Freundlich, Gac, Intraparticular Diffusion, Modeling, Neural Network, Organic Compounds, Organics, Prediction, Removal, Statistical, Systems, Velocity, Water-Treatment

Tang, Y.Z., Gin, K.Y.H. and Aziz, M.A. (2002), Equilibrium model for cadmium adsorption by green algae in a batch reactor. Journal of Environmental Monitoring, 128 (4), 304-312.

Full Text: J\J Env Eng-ASCE128, 304.pdf

Abstract: This paper reports the results of a study on the equilibrium behavior of cadmium adsorption by a tropical, indigenous single-cell algal species, identified as Oocystis sp., in a static reactor. An exponential equation, in the form of C-e/C-0 = alpha exp(betaM/C-0), was found to be statistically significant in expressing the relationship between the ratio of equilibrium cadmium (Cd) concentration in solution (C-e) to the initial cadmium concentration (C-0) and the ratio of algal biomass (M) to initial cadmium concentration (C,) for both living arid dead algal biomass. Based on the above equation and the mass balance of cadmium in the system, another two equations were developed and verified by a series of batch experiments. One equation, in the form of x/m =[1 - alpha exp(betaM/C-0)](M/C-0), describes the relationship between the cadmium content per unit algal biomass (x/m) and the ratio M/C-0. The other equation takes the form of x/m = beta(1-C-e/C-0)/ln(C-e/alphaC(0)) and describes the relationship between the ratio of equilibrium cadmium concentration to initial cadmium concentration and cadmium content per unit algal biomass. The above models for Cd adsorption were found to be applicable over a pH range of 4.5-10.5 even though it was found that pH affects the Cd adsorption potential significantly.

Keywords: Cadmium, Heavy Metal, Wastewater Treatment, Algae, Batch Processing, Chlorella-Vulgaris, Heavy-Metals, Sargassum Biomass, Aqueous-Solutions, Marine-Algae, Biosorption, Microalgae, Sorption, Binding, Water

Vaishya, R.C. and Gupta, S.K. (2003), Arsenic removal from groundwater by iron impregnated sand. Journal of Environmental Engineering-ASCE, 129 (1), 89-92.

Full Text: J\J Env Eng-ASCE129, 89.pdf

Abstract: A granular media known as iron impregnated sand (ITS), developed in the laboratory by impregnating iron on a quartz sand surface by a simple and easy process has proved more effective than iron oxide coated sand (IOCS). Kinetic and isothermal studies showed that the uptake potential of ITS media was much more than IOCS media. The sequence of anions studied competing with respect to As(III) on ITS media was SO₄^2- >HCO₃^->Cl^-. The presence of Ca²⁺ ions significantly improved the removal efficiency. During column studies the breakthrough loadings of IOCS (q(b) = 0.042 and 0.068) and IIS (q(b) = 0.097 and 0.217) for water and simulated water, respectively, show that q(b) for IOCS is lower than for ITS under similar experimental conditions. A filter effluent of 68 L of simulated water passed through 250 g IIS contained less than 0.05 mg As/L.

Keywords: Arsenic, Adsorption, Granular Media, Filters, Ground Water, Oxide-Coated Sand, Water, Filtration, Adsorption

Armagan, B., Ozdemir, O., Turan, M. and Çelik, M.S. (2003), Adsorption of negatively charged azo dyes onto surfactant-modified sepiolite. Journal of Environmental Engineering-ASCE, 129 (8), 709-715.

Full Text: J\J Env Eng-ASCE129, 709.pdf

Abstract: The adsorption of reactive dyes on sepiolite has been investigated in a series of batch adsorption experiments. Three reactive dyes (Everzol Black B, Everzol Red 3BS, Everzol Yellow 3RS H/C) were used in bottle adsorption studies. While no significant adsorption capacity was obtained for natural sepiolite, high-adsorptive capacities were observed upon using sepiolite modified with quaternary amines. The electrokinetic measurements along with calculations using the cross-sectional area reveal that the quaternary amines adsorb close to bilayer coverage. A mechanism involving electrostatic attraction of the anionic groups of dye molecules onto oppositely charged amine-modified sepiolite surface is proposed to be responsible for the uptake of dyes. The adsorption data were fitted to the Langmuir isotherm. It is found that the modified sepiolite yields adsorption capacities (q(e)) of 169, 120, and 108 mg/g for Yellow, Black, and Red, respectively. These results are comparable to the adsorption capacity of the same dyes onto activated carbon.

Keywords: Activated Carbon, Adsorption, Amines, Ammonium, Aqueous-Solutions, Capacity, Carbon, Clay-Minerals, Dye, Dyes, Isotherm, Langmuir Isotherm, Measurements, Mechanism, Modified, Natural, Quaternary, Reactive Dyes, Removal, Sepiolite, Sorption, Surface, Uptake, Wastewater Treatment, Water

Liu, D.F., Sansalone, J.J. and Cartledge, F.K. (2004), Adsorption characteristics of oxide coated buoyant media (_s < 1.0) for storm water treatment. II: Equilibria and kinetic models. Journal of Environmental Engineering-ASCE, 130 (4), 383-390.

Full Text: J\J Env Eng-ASCE130, 383.pdf

Abstract: Divalent metal species adsorption onto a manganese oxide coated polymeric medium (MOPM) was evaluated through batch adsorption experiments using a flow-through batch reactor. In this paper, Part 11, the batch equilibrium and kinetic data examined in Part I are modeled using a triple layer surface complexation model and a potential driving second order kinetic model. Surface complexation modeling using FITEQL-TLM generated intrinsic surface acidity constants for the MOPM of log K-a1(int) = 3.196 and log K-a2(int) = - 5.802. The intrinsic surface reaction constants for Pb(II), Cu(II), and Zn(II) were log K-Pb(int)= - 1.91, log K-Cu(int) = -2.53, and log K-Zn(int) = -4.45, respectively. A potential driving second order kinetic model was developed to predict sorption of the divalent metal ions onto the MOPM. The general adsorption kinetics for MOPM can be described as a fast reaction occurring within 30 min and a slower reaction continuing from 5 to 15 h. Kinetic results can be interpreted using assumptions of the potential driving second order model that the dominant control forces are the chemical potential of the MOPM activated surface sites and chemical potential of sorbate in the solution.

Keywords: Dsorption, Stormwater Treatment, Kinetics, Models, Metals, Hydrous Ferric-Oxide, Surface Complexation, Interface, Sorption, Cadmium, Desorption, Mechanisms, Birnessite, Soil

Jonsson, K., Johansson, H. and Wörman, A. (2004), Sorption behavior and long-term retention of reactive solutes in the hyporheic zone of streams. Journal of Environmental Engineering-ASCE, 130 (5), 573-584.

Full Text: J\J Env Eng-ASCE130, 573.pdf

Abstract: This paper analyzes the transport of sorbing solutes by extending the advective storage path model developed for longitudinal transport of inert solutes in streams coupled with flow-induced uptake in the hyporheic zone. Independent observations of a conservative (H-3) and a reactive (Cr-51) tracer in both the stream water and the hyporheic zone were used to differentiate between hydraulic and sorption processes. The method of temporal moments was found to be inadequate for parameter determination, whereas fitting versus the entire tracer breakthrough curves with special emphasis on the tail indicates that the proposed model could be used to represent both conservative and reactive transport. Information on the tracer inventory of the conservative tracer in the hyporheic zone was found to be of vital importance to the evaluation of the hydraulic exchange. A model evaluation based on stream water data alone can yield predictions of a wash-out in the hyporheic zone that deviates markedly from the observed wash-out. This prohibits long-term predictions of the wash-out from the hyporheic zone as well as the evaluation of sorption properties. The sorption in the hyporheic zone was found to follow a two-step model, where the first step is instantaneous and the second kinetic. A model with a single-step sorption process could not reproduce the observed breakthrough curves. An evaluation of the relative importance of including sorption kinetics in solute stream transport models is elucidated by means of the analytical expressions for the temporal moments. The omission of the kinetics in the second sorption step in the hyporheic zone will result in relative errors in the moments of second order or higher. The error will increase with decreasing residence time in the hyporheic zone. Especially, long-term predictions of the wash-out from the hyporheic zone require consideration of the rate-limited sorption.

Keywords: Sorption, Streams, Hydrologic Models, Transient Storage, Mass-Transfer, Bed Forms, Nonsorbing Solutes, Riffle Stream, Transport, Kinetics, Model, Tracer, Sediments

? Liu, D.F., Sansalone, J.J. and Cartledge, F.K. (2005), Adsorption kinetics for urban rainfall-runoff metals by composite oxide-coated polymeric media. Journal of Environmental Engineering-ASCE, 131 (8), 1168-1177.

Full Text: 2005\J Env Eng-ASCE131, 1168.pdf

Abstract: A manganese oxide-coated polymeric media (MOPM) utilized in sorptive filtration systems as a rainfall-runoff or snowmelt unit operation and process media was characterized using scanning electronic microscopy and adsorption kinetics were studied using a flow-through batch reactor. Results indicated the MOPM adsorption kinetics can be described as a fast adsorption reaction occurring within 30 min followed by a slower reaction that continued from 5 to 15 h, as a function of initial pH and sorbent dosages. A potential driving kinetic model was developed based on an elementary second-order rate law. Modeled results were compared to experimental data using this model and a series of comparative kinetic models. Manganese oxide surface morphology and the ability of a parabolic diffusion model to predict the adsorption kinetics of MOPM suggest diffusion-controlled adsorption for divalent heavy metals on MOPM. Based on a goodness of fit test, the potential driving model best represented the experimental data. Using the potential driving model, it was found that rate constants increased with increasing solution pH, but were independent of sorbent dosages. Results indicated that metal ions with the highest adsorption affinity had the highest rate constants. Observed porosity, the excellent fit of the potential driving model, and breaks in Elovich model plots all suggest a complex adsorption mechanism. Results suggest MOPM can be an effective media for rainfall-runoff and snowmelt metal adsorption.

Keywords: Runoff, Best Management Practices, Kinetics, Adsorption, Metals, Snowmelt, Polymers, Storm Water, Surface Precipitation, Elovich Equation, Buoyant Media, Sorption, Equilibrium, Desorption, Batch, Ions, Soil

? Nkhalambayausi-Chirwa, E.M. and Wang, Y.T. (2005), Modeling Cr(VI) reduction and phenol degradation in a cocoulture biofilm reactor. Journal of Environmental Engineering-ASCE, 131 (11), 1495-1506.

Full Text: 2005\J Env Eng-ASCE131, 1495.pdf

Abstract: A transient-state model was developed to simulate simultaneous Cr(VI) reduction and phenol degradation by a coculture of Cr(VI)-reducing/phenol-degrading bacteria growing on glass bead surfaces in a fixed-film bioreactor. The coculture consisted of the Cr(VI) reducers, Escherichia coli ATCC 33456, and the phenol degraders, Pseudomonas putida DMP-1. Phenol was supplied as the sole added carbon source and electron donor. The model simulated cell growth kinetics with E. coli utilizing metabolites formed from phenol degradation in P. putida as carbon sources. Substrate utilization and Cr(VI) reduction in the fixed-film bioreactor was represented by a system of (second-order) partial differential equations (PDEs). The PDE system was solved by the fourth-order Runge-Kutta method adjusted for mass transport resistance by the second-order Crank-Nicholson and backward Euler methods. A heuristic procedure, genetic search algorithm, was used to optimize the model against experimental data. The model predicted effluent concentration with 98.6% confidence for Cr(VI), 93.4% confidence for phenol, and 88.3% confidence for metabolites. Parameters determined showed higher Cr(VI) and phenol removal kinetics in the biofilm system than previously observed in batch systems.

Keywords: Phenol, Degradation, Biofilm, Algorithms, Reactors, Hexavalent Chromium Reduction, Escherichia-Coli ATCC-33456, Pseudomonas-Putida, Enzymatic Reduction, Bacteria, Coculture

? Murphy, P., Marquette, A., Reible, D. and Lowry, G.V. (2006), Predicting the performance of activated carbon-, coke-, and soil-amended thin layer sediment caps. Journal of Environmental Engineering-ASCE, 132 (7), 787-794.

Full Text: 2006\J Env Eng-ASCE132, 787.pdf

Abstract: In situ capping manages contaminated sediment on-site without creating additional exposure pathways associated with dredging, e.g., sediment resuspension, and potential human exposure during transport. treatment. or disposal of dredged material. Contaminant mass is not immediately removed in sediment capping, which creates concerns over its long-term effectiveness. Groundwater seepage can also decrease the effectiveness of in situ capping. This study compares the effectiveness of commercially available sorbents that can be used to amend sand caps to improve their ability to prevent contaminant migration from the sediments into the bioactive zone. Amendments evaluated include coke, activated carbon, and organic-rich soil. The properties relevant to advective-dispersive transport through porous media (sorption, porosity, dispersivity, and bulk density) are measured for each material, and then used as inputs to a numerical model to predict the flux of 2,4,5-polychlorinated biplienyl (PCB) through a sand cap amended with a thin (1.25-cm) sorbent layer. Systems with and without groundwater seepage are considered. Isolation times provided by the sorbent layers increased with increasing sorption strength and capacity (activated carbon “ coke approximate to soil “ sand). The effective porosity. dispersivity. and bulk density of the sorbent layer had little effect oil cap performance compared to sorption strength (K-f). In the absence of seepage, all sorbents could isolate PCBs in the underlying sediment for times greater than 100 years and Would be effective for most cap applications. With groundwater seepage (Darcy velocity=1 cm/day), activated carbon was the only sorbent that provided contaminant isolation times greater than 60 years. Long isolation times afforded by sorbent-amended caps allow time for inherently slow natural attenuation processes to further mitigate PCB flux.

KeyWords: POLYCHLORINATED BIPHENYL DECHLORINATION; NATURAL ORGANIC-MATTER; CONTAMINATED SEDIMENTS; IN-SITU; SORPTION; BIOAVAILABILITY; POLLUTANTS; 1,2-DICHLOROBENZENE; MICROORGANISMS; HYDROCARBONS

? Maurya, N.S. and Mittal, A.K. (2006), Applicability of equilibrium isotherm models for the biosorptive uptakes in comparison to activated carbon-based adsorption. Journal of Environmental Engineering-ASCE, 132 (12), 1589-1599.

Full Text: 2006\J Env Eng-ASCE132, 1589.pdf

Abstract: The adsorption isotherm models available in the literature have generally developed for sorption onto metallic surfaces or activated carbon-based sorbents. However, biosorptive uptakes involve interactions of biopolymer-based surfaces with different types of pollutants, which are quite different from metal surfaces or activated carbon. So, in the present study, 16 different types of adsorption isotherm models have been studied. For a ready reference both types of sorbents, i.e., a biosorbent and activated carbon have been employed. Results show that in general the accuracy of models to fit experimental data improves with the degree of freedom. The Fritz-Schluender model gives the most accurate fit (R-2 0.85-0.99) to all experimental data in comparison to other models used both for activated carbon and the biosorbent. However, most widely used isotherm models, i.e., Langmuir and Freundlich, could be used to describe the sorption equilibrium of biosorptive processes with a fair degree of accuracy, owing to the mathematical ease in the use of these models. Trends of the applicability of various sorption equilibrium models to biosorptive uptakes are similar to those of activated carbon-based sorptions. Comprehensive equilibrium analysis has assisted in understanding the mechanistic aspects associated with different types of sorbents.

Keywords: Adsorption, Dyes, Color, Pollutants, Pore-Diffusion-Model, Pressure Swing Adsorption, Dilute Aqueous-Solutions, Organic Solutes, Bulk Separation, Basic-Dyes, Sorption, Removal, Adsorbents, Component

? Den, W. and Huang, C.P. (2006), Electrocoagulation of silica nanoparticles in wafer polishing wastewater by a multichannel flow reactor: A kinetic study. Journal of Environmental Engineering-ASCE, 132 (12), 1651-1658.

Full Text: 2006\J Env Eng-ASCE132, 1651.pdf

Abstract: A simplistic and systematic procedure has been developed for the design and upscaling of a multichannel, continuous-flow electrocoagulation reactor of monopolar configuration for the removal of submicron particles from wastewater, Using wastewater generated from the chemical-mechanical planarization process as the target wastewater, a series of laboratory-scale studies were conducted to determine the required operating conditions for the efficient removal of the ultrafine silica particles. These operating criteria included charge loading (>= 8 F/m³), current density (>= 5.7 A /m²), hydraulic retention time (>= 60 min), as well as the initial pH (7-10). Furthermore, a steady-state transport equation with second-order reaction kinetics was employed to describe the rate of coagulation as the rate-limiting factor. The actual kinetic constant determined from the laboratory-scale experiments was approximately 1.210^-21 m³/s, which was three orders of magnitude smaller than that calculated based on Brownian coagulation. The model was subsequently validated with a series of experiments using a pilot-scale electrocoagulation reactor geometrically similar to the laboratory-scale reactor with nearly 20 times volumetric scaleup.

Keywords: Wastewater Management, Water Treatment, Silica, Colloids, Kinetics, Coagulation, Laminar Flow, Channel Flow, Particles, Electroflotation, Removal

? Yang, J., Peng, J., Jia, J.P. and Fang, H.J. (2007), Adsorption of carbon disulfide (CS₂) in water by different types of activated carbon-equilibrium, dynamics, and mathematical modeling. Journal of Environmental Engineering-ASCE, 133 (3), 294-302.

Full Text: 2007\J Env Eng-ASCE133, 294.pdf

Abstract: Adsorption equilibrium and kinetics of carbon disulfide in water by granular activated carbon (GAC), powdered activated carbon (PAC), and activated carbon fiber (ACF) were investigated and compared in an effort to elucidate the fundamentals for optimizing the control process design. It has been shown that the BET expression can satisfactorily describe the adsorption equilibrium of carbon disulfide (CS₂) on GAC, PAC, and ACF and the corresponding kinetic experimental data properly correlated with the second-order kinetic model, which indicates that the CS₂ adsorption is the rate-limiting step. A two-phase mathematical model was developed to simulate CS₂ transfer in fixed-bed operation filled with the GAC, PAC, and ACF, and the equilibrium and kinetics information is subsequently used in the model to characterize the dynamics of adsorption. The model includes mechanisms such as axial dispersion, advection, liquid-to-solid mass transport, and intraparticle mass transport by pore and surface diffusion. It is manifested that the model was able to predict the dynamic breakthrough curve Of CS₂ in a fixed-bed adsorption column filled with GAC, PAC, and ACF at varied conditions (standard deviations for 1.5 cm/min is 12.13% and for 2.2 cm/min is 16.12%), based on BET-3 equilibrium and second-order kinetics, which indicates that the methodology proposed by this work could be employed for adsorbents selection, adsorption design, and process optimization for CS₂ waste-water emission control.

Keywords: Activated Carbon, Adsorption, Equilibrium, Mathematical Models, Wastewater Management, Chitosan Beads, Pore Structure, Removal, Sulfide, Soils, Performance, Desorption, Oxidation, Sorption, Reactor

? Wei, X.C. and Viadero, R.C. (2007), Adsorption and precoat filtration studies of synthetic dye removal by acid mine drainage sludge. Journal of Environmental Engineering-ASCE, 133 (6), 633-640.

Full Text: 2007\J Env Eng-ASCE133, 633.pdf

Abstract: Adsorption tests of Congo Red, a commercial azo dye, by acid mine drainage (AMD) sludge were carried out at different pH, temperature, dye concentration, contact time, and adsorbent dosage. Precoat filtration was conducted to test if the dye could be removed during continuous filtration by a precoated AMD sludge layer. Adsorption of Congo Red onto AMD sludge followed the Langmuir isotherm model with a maximum adsorption capacity of 389.1 mg/g. Based on thermodynamic studies, adsorption was found to be exothermic, and an increase in temperature led to a decline in dye removal. Dye removal decreased with an increasing pH. Through metal leaching tests, it was observed that most metals associated with AMD sludge remained insoluble when adsorption occurred at pH 6-10. A rather rapid process was observed for the adsorption of Congo Red onto AMD sludge with more than 80% adsorption taking place within 5 min. Adsorption kinetics followed pseudo-second-order model. Precoat filtration continuously removed Congo Red from aqueous solution with success, and dye removal mechanism via precoat filtration was adsorption. The adsorption and precoat filtration studies showed dye removal could be a beneficial use of AMD sludge prior to its final disposal.

Keywords: Acid, Acid Mine, Acid Mine Drainage, Adsorbent, Adsorbent Dosage, Adsorption, Adsorption Capacity, Aqueous Solution, Aqueous-Solution, Azo Dye, Beneficial Use, Capacity, Carbon, Color Removal, Concentration, Congo Red, Congo-Red, Contact Time, Disposal, Dosage, Drainage, Dye, Dye Removal, Effluent, Exothermic, Filtration, Fly-Ash, Isotherm, Isotherm Model, Kinetics, Langmuir, Langmuir Isotherm, Langmuir Isotherm Model, Langmuir-Isotherm, Leaching, Leaching Tests, Mechanism, Metal, Metal Hydroxide Sludge, Metals, Mine, Mine Drainage, Model, pH, Process, Pseudo Second Order, Pseudo-Second-Order, Pseudo-Second-Order Model, Reactive Dyes, Removal, Removal Mechanism, Sludge, Synthetic, Temperature, Test, Tests, Textile Wastewaters, Thermodynamic, Thermodynamic Studies, Waste-Water

? Elouear, Z., Amor, R.B., Bouzid, J. and Boujelben, N. (2009), Use of phosphate rock for the removal of Ni²⁺ from aqueous solutions: kinetic and thermodynamics studies. Journal of Environmental Engineering-ASCE, 135 (4), 259-265.

Full Text: 2009\J Env Eng-Asc135, 259.pdf

Abstract: A study was carried out in batch conditions to examine the removal of nickel ions from an aqueous solution by phosphate rock. The effect of different sorption parameters, such as initial metal concentration, equilibration time, solution pH, and temperature on the amount of Ni²⁺ sorbed was studied and discussed. The sorption process followed pseudo-second-order kinetics with necessary time of 2 h to reach equilibrium. The maximum removal obtained is at initial pH around 8. Nickel uptake was quantitatively evaluated using the Langmuir and Dubinin-Kaganer-Radushkevich model. The Langmuir adsorption isotherm constant corresponding to adsorption capacity, Q(0), was found to be 7.63 mg/g. The possibility of metal recovery was investigated using several eluting agents. The desorbed amount of nickel decreased continuously with increasing pH, and increased with increasing Ca²⁺ concentration in leaching solution.

Keywords: Adsorption, Calcium Hydroxyapatite, Cd, Equilibrium, Heavy-Metal, Ions, Lead, Natural Zeolite, Nickel, Sorption

? Gerçel, O., Özcan, A., Özcan, A.S. and Gerçel, H.F. (2009), Capacity of activated carbon derived from peach stones by K₂CO₃ in the removal of acid, reactive, and Direct dyes from aqueous solution. Journal of Environmental Engineering-ASCE, 135 (5), 333-340.

Full Text: 2009\J Env Eng-Asc135, 333.pdf

Abstract: The present research deals with the production of activated carbon by chemical activation using peach stones and its adsorption behavior. The prepared activated carbon was used for the adsorption of three kinds of textile dyes, acid, reactive, and direct dyes, from aqueous solution. The results indicated that the overall adsorption process followed the pseudo-second-order kinetic model. The equilibrium data were found to be well represented by the Langmuir adsorption isotherm model. The calculated adsorption capacities for Reactive Orange 16, Acid Yellow 11, and Direct Red 23 onto activated carbon were 667, 539, and 427 mg g^-1 at 50 °C, respectively. Thermodynamic parameters, such as Delta G degrees, Delta H degrees, and Delta S degrees, were also calculated and indicated that the adsorption of dyes onto activated carbon was spontaneous and endothermic in nature.

Keywords: Adsorption, Ash, Bentonite, Equilibrium, Liquid-Phase Adsorption, Malachite Green, Methylene-Blue, Surfactant, Temperature, Waste, Water

? Pereira, F.V., Gurgel, L.V.A., de Aquino, S.F. and Gil, L.F. (2009), Removal of Zn²⁺ from electroplating wastewater using modified wood sawdust and sugarcane bagasse. Journal of Environmental Engineering-ASCE, 135 (5), 341-350.

Full Text: 2009\J Env Eng-Asc135, 341.pdf

Abstract: This paper describes the preparation of new adsorbents derived from sugarcane bagasse and wood sawdust (Manilkara sp.) to remove zinc (II) ions from electroplating wastewater. The first part deals with the chemical modification of sugarcane bagasse and wood sawdust, using succinic anhydride to introduce carboxylic acid functions into the material. The obtained materials (modified sugarcane bagasse MB2 and modified wood sawdust MS2) were then characterized by infrared spectroscopy (IR) and used in adsorption experiments. The adsorption experiments evaluates Zn²⁺ removal from aqueous single metal solution and real electroplating wastewater on both batch and continuous experiments using fixed-bed columns prepared in laboratorial scale with the obtained adsorbents. Adsorption isotherms were then developed using Langmuir model and the Thomas kinetic model. The calculated Zn²⁺ adsorption capacities were found to be 145 mg/g for MS2 and 125 mg/g for MB2 in single metal aqueous solution, whereas for the industrial wastewater these values were 61 mg/g for MS2 and 55 mg/g for MB2.

Keywords: Adsorption, Aqueous-Solutions, Cadmium, Cd(II), Chromium, Heavy-Metals, Ions, Ni(II), Recovery, Removal, Sorption, Wastewater

? Singh, R.P., Zahra, F., Savio, W. and Prasad, S.C. (2009), Axial dispersion and mass transfer controlled simulation study of chromium(VI) adsorption onto tree leaves and activated carbon. Journal of Environmental Engineering-ASCE, 135 (10), 1071-1083.

Full Text: 2009\J Env Eng-Asc135, 1071.pdf

Abstract: In this paper, the feasibility and efficacy of chromium (Cr(VI)) removal using three different kinds of tree leaves viz. Emblica officinalis, Azadirachta indica, Eucalyptus agglomerata, and the activated carbon is examined through batch and continuous flow experiments. Pretreatments were given to the selected tree leaf powders to remove the natural pigments and lignin present. Batch and continuous flow experiments have been conducted to study the kinetics of adsorption, effects of pH, adsorbent dose, contact time, bed depth, flow rate, and initial Cr(VI) concentration on Cr(VI) adsorption onto the selected adsorbents. The adsorption capacity is observed higher for Emblica officinalis followed by Eucalyptus agglomerata and Azadirachta indica. The adsorption equilibrium is reached in less than 30 min and the maximum Cr(VI) uptake occurred at pH 3.0 under the test conditions. The results are also compared with the commercially available activated carbon. A mathematical model incorporating diffusion, advection, and mass transfer mechanisms available in the literature has been simplified and is then tested to simulate the laboratory and literature data. A simple method for the determination of saturation Cr(VI) concentration along the length of column has been presented. The study reveals that the model incorporating the molecular diffusion and the mass transfer mechanisms simulates better the Cr(VI) adsorption onto tree leaf powders than the literature model and the advection term plays only a negligible role due to low flow rates applied during the experiments. The model parameters, i.e., axial dispersion coefficient, “D_L” and the external mass transfer coefficient, “k_f” are found in the order of 10^-5-10^-6 m²/s and 10^-9-10^-11 m/s, respectively.

Keywords: Activated Carbon, Adsorbent, Adsorbent Dose, Adsorbents, Adsorption, Adsorption Capacity, Adsorption Equilibrium, Advection, Azadirachta Indica, Batch, Biomass, Capacity, Carbon, Chromium, Column, Concentration, Cr(VI), Cr(VI) Adsorption, Data, Desorption, Diffusion, Dispersion, Efficacy, Equilibrium, Eucalyptus, Experiments, Feasibility, Flow, Flow Experiments, Flow Rate, Ions, Kinetics, Kinetics of Adsorption, Length, Lignin, Literature, Low Flow, Mass Transfer, Mass Transfer Coefficient, Mathematical Model, Mechanisms, Model, Natural, pH, Pyrolysis, Rates, Removal, Role, Saturation, Sorption, Term, Transfer Coefficient, Uptake, VI, Water

? Nourouzi, M.M., Chuah, T.G. and Choong, T.S.Y. (2009), Equilibrium and kinetic study on reactive dyes adsorption by palm kernel shell-based activated carbon: In single and binary systems. Journal of Environmental Engineering-ASCE, 135 (12), 1393-1398.

Full Text: 2009\J Env Eng-Asc135, 1393.pdf

Abstract: The adsorption of two reactive dyes, Reactive Black 5 and Reactive Red E, onto palm kernel shell-activated carbon (PKSAC) was studied. The effect of the presence of more than one dye in solution on the equilibrium and kinetics of adsorption was investigated. Equilibrium isotherm models were applied to describe the adsorption capacities of single and binary systems. Adsorption of reactive dyes for single system can be represented by the Freundlich and the Redlich-Peterson models. For binary system, the equilibrium was described successfully by the modified extended Freundlich model. Experimental data showed that competitive adsorption for active sites on the carbon surface resulted in a reduction in the overall uptake capacity of the reactive dyes. The rates of adsorption in single system were found to agree well with the pseudo second-order kinetic model. Finally, the chemical oxygen demand (COD) of the treated reactive dye solutions from single and binary systems showed that a minimum of 4 g/L dosage of PKSAC was needed to reduce the COD to an acceptable level according to the Water Quality Guidelines and the Pollutant Fact Sheets Guidelines.

Keywords: Activated Carbon, Adsorption, Aqueous-Solution, Basic Dye, Capacity, Carbon, COD, Competitive Adsorption, Decolorization, Dye, Dyes, Equilibrium, Fly-Ash, Freundlich, Isotherm, Kinetic, Kinetic Model, Kinetics, Kinetics of Adsorption, Model, Models, Reactive Black 5, Reactive Dye, Reactive Dyes, Removal, Solutions, Sorption, System, Water

? Chen, C. and Wang, J.L. (2010), Removal of heavy metal ions by waste biomass of Saccharomyces cerevisiae. Journal of Environmental Engineering-ASCE, 136 (1), 95-102.

Full Text: 2010\J Env Eng-ASCE136, 95.pdf

Abstract: The kinetics, equilibriums, and thermodynamics of metal ion (Pb²⁺, Ag²⁺, Cu²⁺, Zn²⁺, Co²⁺, Sr²⁺, and Cs⁺) biosorption by the waste yeast cells of Saccharomyces cerevisiae from a local brewery were investigated. The results showed that the biosorption of these metal ions on the biomass was a very rapid process, following the pseudo-second-order equation gave the better fitting results in describing the kinetic data than the pseudo-first-order equation. The equilibrium data could be fitted well with the Langmuir model. The maximum sorption capacity obtained from the Langmuir model followed Pb>Ag>Cu>Zn>Co>Sr>Cs (based on mmol g^-1). The biosorption process by the yeast was favorable for these metal ions removal according to the constant separation factor (0 < R_L < 1) from the Langmuir model. The dried yeast cells showed high affinity for Pb²⁺ uptake as soft ion and low affinity for Cs+ as hard ion biosorption. The calculated values of the thermodynamic constants demonstrated that the biosorption process of Ag⁺, Cu²⁺, Zn²⁺, or Co²⁺ was spontaneous and the entropy increased. pH increased during the metal biosorption by the yeast cells. Pb²⁺, Ag²⁺, Cu²⁺, Zn²⁺, or Co²⁺ exhibited a certain degree of covalent binding with the waste yeast cells. Cs⁺, as a typical hard ion, showed ionic binding with the biomass.

Keywords: Adsorption, Aqueous-Solution, Binding, Biomass, Biosorption, Biosorption, Brewery Biomass, Capacity, Co²⁺, Copper(II) Ions, Cu²⁺, Data, Entropy, Equilibrium, Heavy Metal, Ions, Kinetic, Kinetics, Kinetics, Langmuir, Langmuir Model, Local, Metal, Metal Ions, Metal Ions Removal, Model, Pb²⁺, pH, Pseudo First Order, Pseudo Second Order, Pseudo-First-Order, Pseudo-First-Order Equation, Pseudo-Second-Order, Pseudo-Second-Order Equation, Removal, Saccharomyces cerevisiae, Separation, Sorption, Sorption Capacity, Sphagnum Moss, Thermodynamic, Thermodynamic Parameters, Thermodynamics, Uptake, Waste, Waste Biomass, Wastewaters, Yeast, Zn²⁺

? Mittal, A.K. (2010), Development of a kinetic model for the biosorption of cationic dyes by dead macrofungi. Journal of Environmental Engineering-ASCE, 136 (5), 487-492.

Full Text: 2010\J Env Eng-Asc136, 487.pdf

Abstract: A new kinetic model has been proposed that describes the kinetics of the biosorptive processes. The proposed model is based on the concept of “available active sites.” The developed model has been investigated at different sorbent dose and temperature. Uptake of a cationic dye, Basic Violet 16 by a biosorbent prepared from the dead macrofungus, Fomitopsis cornea, has been considered to validate the model. This model has been used to determine the mass transfer coefficients under various sorption conditions. Sorbent concentration-time profiles generated by the model have been compared with the experimental data to validate the model. The model generated concentration profiles match the batch kinetic data closely.

Keywords: Batch, Biosorbent, Biosorption, Cationic Dye, Colored Wastewater, Concentration, Data, Dye, Dyes, Experimental, Isotherm, Kinetic, Kinetic Model, Kinetics, Mass Transfer, Model, Peat, Profiles, Sorbent, Sorbent Dose, Sorption, Temperature

? Zhang, N., Gang, D.C. and Lin, L.S. (2010), Adsorptive removal of parts per million level selenate using iron-coated GAC adsorbents. Journal of Environmental Engineering-ASCE, 136 (10), 1089-1095.

Full Text: 2010\J Env Eng-Asc136, 1089.pdf

Abstract: Selenate removal by adsorption using iron-coated granular activated carbons (Fe-GACs) is reported in this study. Adsorption kinetics and equilibrium experiments with initial selenium concentration of 1 mg/L were conducted under three different ionic strengths to study selenate adsorption behavior. Selenate adsorption reached equilibrium within 48 h with more than 85% of the equilibrium capacities being obtained within the first 6 h. High removal efficiency (i.e., >75%) was achieved for pH range of 2-5. Acid-base titration experiments showed point of zero charge (pH(pzc)) at pH 7.5 for the tested Fe-GAC. Pseudo-second-order kinetic model characterized selenate adsorption kinetics well (R-2=0.999) and the rate constant decreased with ionic strength. Adsorption capacity decreased significantly with increasing ionic strength, which was not observed in selenite adsorption with the same adsorbent. Competitive adsorption with other four oxyanions (SiO₃^2-, SO₄^2-, PO₄^3-, and CO₃^2-) showed that selenate removal efficiency was reduced to various degrees in the presence of each individual anion. Competitive adsorption of binary adsorbates (selenite and selenate) showed a decreasing trend of selenite adsorption capacity with decreasing ionic strength, indicating stronger competition of selenate against selenite under the low ionic strengths. The Sheindorf-Rebuhn-Sheintuch multiadsorbate competitive adsorption model was applied to quantify the binary competitive adsorption between selenate and selenite.

Keywords: Activated Carbons, Adsorbent, Adsorbents, Adsorption, Adsorption Behavior, Adsorption Capacity, Adsorption Kinetics, Anions, Behavior, Capacity, Charge, Competition, Competitive, Competitive Adsorption, Complexation, Concentration, Efficiency, Equilibrium, Experiments, First, GAC, Ionic Strength, Iron-Coated GAC, Isotherm, Isotherm, Kinetic, Kinetic Model, Kinetics, Model, Oxides, pH, Point of Zero Charge, Pseudo-Second-Order, Pseudo-Second-Order Kinetic Model, Rate Constant, Removal, Removal Efficiency, Selenate, Selenate Removal, Selenium, Soils, Sorption, Strength, Systems, Trend, Water

? Jovanović, B.M. and Rajaković, L.V. (2010), New approach: Waste materials as sorbents for arsenic removal from water. Journal of Environmental Engineering-ASCE, 136 (11), 1277-1286.

Full Text: 2010\J Env Eng-ASCE136, 1277.pdf

Abstract: The sorption of inorganic arsenic species (arsenite and arsenate) from aqueous solutions onto steel-mill waste and waste filter sand, under neutral conditions, was investigated in this study. Additionally, the steel-mill waste material was modified in order to minimize its deteriorating impact on the initial water quality and to meet the drinking water standards. The influence of contact time and initial arsenic concentration was investigated using batch system techniques. To evaluate the application for real groundwater treatment, the capacities of the obtained waste materials were further compared to those exhibited by commercial sorbents, which were examined under the same experimental conditions. Kinetic studies revealed that waste slag materials are the most efficient in arsenic removal, reaching equilibrium arsenic sorption capacities in the range 47.6-55.2 mu g/g, while waste filter sand exhibited capacities of 25.4-29.8 mu g/g (for an initial arsenic concentration C(o)=0.5 mg/L). The higher iron content in the slag materials was considered to be responsible for the better removal efficiencies, and the specific arsenic removal efficiency was estimated to be 220 mu gAs/gFe. The specific arsenic removal efficiency of the second active substance found in waste filter sand, manganese, was estimated to be 115 mu gAs/gMn. Equilibrium studies revealed the occurrence of both chemisorption and physical sorption processes. All the waste materials exhibited higher performances for As (V). The highest maximum sorption capacity was obtained by waste iron slag: 4040 mu g/g for As (V). The waste materials reached the arsenic removal capacities of the examined commercial materials, suggesting the feasibility of their application in real groundwater treatment.

Keywords: Activated Carbon, Adsorbents, Adsorption, Aqueous-Solution, Arsenic, Arsenic Removal, Contamination, Drinking Water, Equilibrium, Feasibility, Fly-Ash, Groundwater, Impact, Iron, Kinetic, Portland-Cement, Sorption, Sorption Isotherms, Sorption Kinetics, Sorption Kinetics, Standards, Steel Slag, Treatment, Waste, Waste Materials

? Saha, P., Datta, S. and Sanyal, S.K. (2010), Application of natural clayey soil as adsorbent for the removal of copper from wastewater. Journal of Environmental Engineering-ASCE, 136 (12), 1409-1417.

Full Text: 2010\J Env Eng-ASCE136, 1409.pdf

Abstract: Use of clayey soil has been explored in the laboratory scale experiment as a low cost adsorbent for the removal of copper from wastewater. The influence of metal ion concentration, weight of adsorbent, stirring rates, influence of temperature, pH are also evaluated and the results are fitted using adsorption isotherm models. From the experimental results it is observed that almost 90-99% copper can be removed from the solution using clay at optimized pH 5.5. Langmuir adsorption isotherm, Freundlich isotherm and Tempkin isotherm model have been used to describe the distribution of copper between the liquid and solid phases in batch studies and it has been observed that Langmuir isotherm better represents the phenomenon. From the experimental results rate constant, activation energy, Gibbs free energy, enthalpy, and entropy of the reaction are calculated to determine the mechanism of the sorption process. Thomas, Adams-Bohart, and Yoon-Nelson models are applied to the experimental data to determine the characteristic parameters of the column for process design.

Keywords: Activation, Activation Energy, Adsorbent, Adsorption, Adsorption Isotherm, Adsorption Isotherm Models, Adsorption Kinetics, Application, Aqueous-Solutions, Batch, Biosorbent, Biosorption, Clay, Column, Copper, Design, Energy, Error Analysis, Experimental, Fly-Ash, Freundlich, Freundlich Isotherm, Fruit Shell, Gibbs Free Energy, Heavy-Metals, Isotherm, Isotherm Models, Kinetics, Langmuir, Langmuir Adsorption, Langmuir Adsorption Isotherm, Langmuir Isotherm, Low, Low Cost, Mathematical Modeling, Mechanism, Metal, Metal Ion, Metal Ion Concentration, Model, pH, Rate Constant, Removal, Rice Husk, Soil, Sorption, Temperature, Thermodynamics, Wastewater

? Chowdhury, S. and Saha, P. (2011), Adsorption thermodynamics and kinetics of malachite green onto Ca(OH)₂-treated fly ash. Journal of Environmental Engineering-ASCE, 137 (5), 388-397.

Full Text: 2011\J Env Eng-Asc137, 388.pdf

Abstract: Fly ash, an industrial by-product abundant in India, was treated with alkali and tested as a low-cost adsorbent for the removal of malachite green from an aqueous solution in a batch adsorption procedure. Effects of stirring rate, temperature, pH, initial dye concentration, contact time, and adsorbent dose were investigated. The adsorption was found to be strongly dependent on pH of the medium and the adsorption capacity decreased with an increase in temperature. The Langmuir isotherm model showed a good fit to the equilibrium adsorption data at all temperatures. The mean free energy (E) estimated from the Dubinin-Radushkevich model indicated that the adsorption mechanism was chemical ion exchange. The kinetic data were found to follow the pseudo second-order kinetic model. The rate constant decreased with the increase in temperature indicating the exothermic nature of adsorption. Intraparticle diffusion was not the sole rate-controlling factor. The Arrhenius and Eyring equations were used to evaluate the activation parameters. The activation energy (E-a) was estimated to be 56.08 kJ mol^-1. Gibbs free energy (ΔG(0)) was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. Results suggest that alkali-treated fly ash is a potential low-cost adsorbent for removal of malachite green from an aqueous solution. DOI: 10.1061/(ASCE)EE.1943-7870.0000334. (C) 2011 American Society of Civil Engineers.

Keywords: Activation Parameters, Adsorbent, Adsorption, Aqueous Solution, Aqueous-Solutions, Biomass, Biosorption, Dye, Dye Removal, Equilibrium, Fly Ash, Intraparticle Diffusion, Ion Exchange, Isotherm, Kinetic, Kinetic Model, Kinetics, Langmuir, Langmuir Isotherm, Low-Cost Adsorbent, Malachite Green, Mechanism, Parameters, pH, Removal, Sorption, Tamarind Fruit Shell, Thermodynamics

? Gao, P., Feng, Y.J., Wang, C., Zhang, Z.H., Liu, J.F. and Ren, N.Q. (2011), Photolysis, biodegradation, and sorption behavior of three selected phenolic compounds on the surface and sediment of rivers. Journal of Environmental Engineering-ASCE, 137 (12), 1114-1121.

Full Text: 2011\J Env Eng-Asc137, 1114.pdf

Abstract: In this study, laboratory experiments were carried out to investigate the environmental behavior of three selected phenolic compounds [2,4-Dichlorophenol (DCP), 2,4-Dinitrophenol (DNP) and 2,4-Dimethylphenol (DMP)] in the aquatic environment. The results of batch sunlight photolysis experiments showed that the three phenolic compounds were photodegraded relatively easily (i.e., half-life < 151 h) in June, whereas these compounds were relatively stable against sunlight in September (i.e., half-life < 330 h). The results of batch biodegradation experiments using river water suggested relatively slow biodegradation (i.e., half-life < 2,310 h in June, half-life < 1; 155 h in September, and half-life < 3,466 h in January) of three phenolic compounds, and the rate constant was dependent on sampling time. Freundlich model and the pseudo second-order model can describe the sorption behaviors of phenolic compounds on sediments very well. The intraparticle diffusion model for adsorption was also investigated and compared with the pseudomodel to identify sorption mechanism. DOI: 10.1061/(ASCE)EE.1943-7870.0000440. (C) 2011 American Society of Civil Engineers.

Keywords: Activated-Sludge, Adsorption, Biodegradation, Freundlich, Kinetics, Liquid-Phase Adsorption, Mechanism, Pentachlorophenol, Pesticides, Pharmaceuticals, Phenolic Compounds, Photodegradation, Photolysis, Reactive Dyes, Sediment, Soils, Sorption, Water

? Suresh, S., Srivastava, V.C. and Mishra, I.M. (2011), Adsorption of hydroquinone in aqueous solution by granulated activated carbon. Journal of Environmental Engineering-ASCE, 137 (12), 1145-1157.

Full Text: 2011\J Env Eng-Asc137, 1145.pdf

Abstract: This paper reports the adsorptive removal of hydroquinone (HQ) from aqueous solution by granulated activated carbon (GAC). Physicochemical properties including surface area and surface texture of the GAC, before and after HQ adsorption onto GAC, were analysed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). The adsorption follows pseudo-second-order kinetics. An intraparticle diffusion study reveals that the pore diffusion is not the only rate-limiting step. The effective diffusion coefficient of HQ was of the order of 3: 19 x 10^-10 m²/s. Equilibrium isotherm data were generated for HQ solutions over an initial concentration range of 0.18-9.08 mmol/L for the GAC dosage of 10 g/L at temperatures of 288, 303, and 318 K. Equilibrium data were well represented by the Temkin isotherm model. An increase in the temperature increases adsorption. The entropy change (ΔS₀), heat of adsorption (ΔH₀), and Gibb’s free energy (ΔG₀) were determined. Elution of HQ from the loaded HQ showed that the thermal desorption may be a better option over that of solvent desorption. GAC worked well for at least five adsorption-desorption cycles, with continuous decrease in adsorption efficiency after each thermal desorption. Owing to its heating value, spent-GAC can be used as cofuel in the boiler-furnace. DOI: 10.1061/(ASCE)EE.1943-7870.0000443. (C) 2011 American Society of Civil Engineers.

Keywords: Activated Carbon, Adsorption, Adsorption-Desorption, Bagasse Fly-Ash, Bearing Waste-Water, Carbon, Catechol, Concentration, Degradation, Desorption, Entropy, Equilibrium, FTIR, GAC, GAC Characterization, HQ Adsorption, Isotherm, Kinetics, Nanotubes, Phenolic-Compounds, Removal, Resorcinol, Temperature, Thermodynamics, Thermodynamics, UASB Reactor, X-Ray Diffraction

? Zhang, Y., Li, Q., Sun, L. and Zhai, J.P. (2011), Adsorption of hydroquinone in aqueous solution by granulated activated carbon. Journal of Environmental Engineering-ASCE, 137 (12), 1158-1164.

Full Text: 2011\J Env Eng-Asc137, 1158.pdf

Abstract: This paper reports the adsorptive removal of hydroquinone (HQ) from aqueous solution by granulated activated carbon (GAC). Physicochemical properties including surface area and surface texture of the GAC, before and after HQ adsorption onto GAC, were analysed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). The adsorption follows pseudo-second-order kinetics. An intraparticle diffusion study reveals that the pore diffusion is not the only rate-limiting step. The effective diffusion coefficient of HQ was of the order of 3.19 x 10^-10 m²/s. Equilibrium isotherm data were generated for HQ solutions over an initial concentration range of 0.18-9.08 mmol/L for the GAC dosage of 10 g/L at temperatures of 288, 303, and 318 K. Equilibrium data were well represented by the Temkin isotherm model. An increase in the temperature increases adsorption. The entropy change (ΔS₀), heat of adsorption (ΔH₀), and Gibb’s free energy (ΔG₀) were determined. Elution of HQ from the loaded HQ showed that the thermal desorption may be a better option over that of solvent desorption. GAC worked well for at least five adsorption-desorption cycles, with continuous decrease in adsorption efficiency after each thermal desorption. Owing to its heating value, spent-GAC can be used as cofuel in the boiler-furnace. DOI: 10.1061/(ASCE)EE.1943-7870.0000443. (C) 2011 American Society of Civil Engineers.

Keywords: Activated Carbon, Adsorption, Adsorption-Desorption, Carbon, Concentration, Cr(Vi), Desorption, Entropy, Equilibrium, FTIR, Fungal Biomass, Gac, Gac Characterization, Heavy-Metals, Hexavalent Chromium Removal, Hq Adsorption, Humic-Acid Adsorption, Ions, Isotherm, Kinetics, Nanoparticles, Polyaniline, Reduction, Temperature, Thermodynamics, Waste-Water, X-Ray Diffraction