Personal Research Database

Full Text: 2008\Wat Res42, 238.pdf

Abstract: Adsorption onto granular ferric hydroxide (GFH) with subsequent in-situ regeneration is studied as a new process for natural organic matter (NOM) removal from groundwater. Adsorbent equilibrium loadings of 10-30 mg DOC g(-1) GFH(-1) are obtained, whereas the non-adsorbable DOC fraction amounts to 1.5 mgL(-1) for all investigated groundwaters. The larger and UV-active NOM fractions (mainly fulvic acids) are well adsorbed while the smaller molecular fractions are poorly or not adsorbed. However, kinetic studies show that the smaller and medium-sized fulvic acids are removed first. The equilibrium is strongly dependent on pH but only weakly on ionic strength, pointing to ligand exchange as the dominant adsorption mechanism. With regard to NOM structure, prerequisites for adsorption onto GFH are both a minimum number of functional groups and a molecular size small enough to enter the GFH pores. NOM breakthrough curves are successfully simulated using the LDF model (homogeneous surface diffusion model (HSDM) with linear driving force approach for surface diffusion) and experimentally determined mass transfer coefficients. Regeneration of loaded GFH is possible either by use of NaOH or oxidatively by H2O2. The optimal quantities and concentrations are determined. (c) 2007 Elsevier Ltd. All rights reserved.

Keywords: Adsorbent, Adsorption, Breakthrough Curve, Carboxyl-Group Structures, Competitive Adsorption, Diffusion, DOC Isotherm, Driving, Equilibrium, Fixed-Bed Adsorption Filter, Fulvic-Acid, Functional, Goethite, Granular Ferric Hydroxide, Groundwater, Hsdm, Humic Substances, Iron-Oxide, Kinetics, Mass Transfer, Mass Transfer Coefficient, Mechanism, Model, Molecular, Natural Organic Matter, Natural Organic-Matter, pH, Regeneration, Removal, Sorption, Strength, Sulfate Adsorption, Suwannee River

? Rocher, V., Siauque, J.M., Cabuil, V. and Bee, A. (2008), Removal of organic dyes by magnetic alginate beads. Water Research, 42 (4-5), 1290-1298.

Full Text: 2008\Wat Res42, 1290.pdf

Abstract: This study deals with the development of a clean and safe process for water pollution remediation. We have synthesized a magnetic adsorbent in order to develop a solid-phase extraction process assisted by a magnetic field. To follow an ‘ecoconception’ approach, magnetic beads containing magnetic nanoparticles and activated carbon are prepared with a biopolymer extracted from algae, sodium alginate. The use of renewable bioresources of low cost and those disposable in large amount allows the development of a product with a low impact on the environment. The adsorption properties of activated carbon and magnetic properties of iron oxide nanoparticles are combined to produce an interesting magnetic composite. Synthesis and characterization of the magnetic beads have been reported. Their adsorption capacity was investigated by measuring the removal of two dyes (methylene blue and methyl orange) of different charges from aqueous solutions. The efficiency of the beads has been compared with that of non-encapsulated activated carbon. The effects of initial dye concentration, pH and calcium content of the beads have been studied. Adsorption kinetics experiments have been carried out and the data have been well fitted by a pseudo-second-order equation. (c) 2007 Elsevier Ltd. All rights reserved.

Keywords: Acid, Activated Carbon, Activated Carbon, Adsorbent, Adsorption, Adsorption Kinetics, Alginate, Alginate Bead, Aqueous Solutions, Calcium, Calcium Alginate, Capacity, Carbon, Characterization, Composite, Cost, Development, Dye, Dyes, Efficiency, Environment, Experiments, Ferrofluid, Gels, Heavy-Metal Removal, Immobilization, Iron, Iron Oxide, Kinetics, Magnetic, Magnetic Beads, Magnetic Field, Magnetic Nanoparticles, Magnetic Properties, Matrices, Methylene Blue, Microparticles, Nanoparticles, Oxide, P-Nitrophenol, pH, Pollution, Remediation, Removal, Rights, Water, Water Pollution

? Goh, K.H., Lim, T.T. and Dong, Z. (2008), Application of layered double hydroxides for removal of oxyanions: A review. Water Research, 42 (6-7), 1343-1368.

Full Text: 2008\Wat Res42, 1343.pdf

Abstract: Layered double hydroxides (LDHs) are lamellar mixed hydroxides containing positively charged main layers and undergoing anion exchange chemistry. In recent years, many studies have been devoted to investigating the ability of LDHs to remove harmful oxyanions such as arsenate, chromate, phosphate, etc. from contaminated waters by both surface adsorption and anion exchange of the oxyanions for interlayer anions in the LDH structure. This review article provides an overview of the LDH synthesis methods, the LDH characterization techniques, and the recent advancement that has been achieved in oxyanion removal using LDHs, highlighting areas of consensus and currently unresolved issues. Experimental studies relating to the sorption behaviors of LDHs with various oxyanions, and the kinetic models adopted to explain the adsorption rate of oxyanions from aqueous solution onto LDHs, have been comprehensively reviewed. This review discusses several key factors such as pH, competitive anions, temperature, etc., that influence the oxyanion adsorption on LDHs. The reusability of LDHs is discussed and some mechanistic studies of oxyanion adsorption on LDHs are highlighted. The sorption capacities of LDHs for various oxyanions are also compared with those of other adsorbents. In addition, this review critically identifies the shortcomings in current research on LDHs, such as the common weaknesses in the adopted methodology, discrepancies among reported results and ambiguous conclusions. Possible improvement of LDHs and potential areas for future application of LDHs are also proposed. (c) 2007 Elsevier Ltd. All rights reserved.

Keywords: Adsorption, Aluminum-Oxide, Anion Exchange, Aqueous-Solutions, Calcined Mg-Al-Co3 Hydrotalcite, Characterization, Chromate, Clay Anion-Exchangers, Hydrotalcite, Hydrotalcite-Like Compounds, Ion-Exchange Properties, Kinetic Models, Layered Double Hydroxides (LDHS), Methodology, Mixed Oxides, Overview, Oxyanions, pH, Phosphate, Removal, Research, Review, Sorption, Synthetic Hydrotalcite, Waste-Water, X-Ray-Diffraction

? Boyer, T.H., Miller, C.T. and Singer, P.C. (2008), Modeling the removal of dissolved organic carbon by ion exchange in a completely mixed flow reactor. Water Research, 42 (8-9), 1897-1906.

Full Text: 2008\Wat Res42, 1897.pdf

Abstract: A mathematical model was developed to describe removal of dissolved organic carbon (DOC) by a macroporous, strong-base anion exchange resin in a completely mixed flow reactor with resin recycle and partial resin regeneration. The two-scale model consisted of a microscale model describing the uptake of DOC by the resin coupled with a macroscale model describing the continuous-flow process. Equilibrium and kinetic parameters were estimated from batch laboratory experiments. The model was validated using continuous-flow data from two pilot plant studies. Model predictions were found to be in good agreement with the observed pilot plant data. (C) 2007 Elsevier Ltd. All rights reserved.

Keywords: Batch Stirred-Tank, Diffusion-Coefficient, Dissolved Organic Carbon, Distributions, Equilibrium, Finite-Element Method, Fractionation, Magnetic Ion Exchange, Mathematical Model, Matter, Model, Modeling, Natural Organic Matter, Plant, Precursors, Protein Adsorption, Regeneration, Removal, Sorption, Spectroscopy, Two-Scale Modeling, Uptake, Water

? Ahn, S., Werner, D. and Luthy, R.G. (2008), Modeling PAH mass transfer in a slurry of contaminated soil or sediment amended with organic sorbents. Water Research, 42 (12), 2931-2942.

Full Text: 2008\Wat Res42, 2931.pdf

Abstract: A three-compartment kinetic partitioning model was employed to assess contaminant mass transfer and intraparticle diffusion in systems comprising dense slurries of polluted soil or aquifer sediment with or without sorbent amendments to sequester polycyclic aromatic hydrocarbons (PAHs). The model was applied to simulate temporal changes in aqueous and particle-bound PAH concentrations comparing different pollution sources (heavy oil or tar sludge) and various sorbent amendments (polyoxymethylene (POM), coke breeze, and activated carbon). For the model evaluation, all the parameters needed were directly measured from a series of experiments, allowing full calibration and verification of model predictions without parameter fitting. The numerical model reproduced two separate laboratory-scale experiments reasonably: PAH uptake in POM beads and PAH uptake by semipermeable membrane devices. PAH mass transfer was then simulated for various scenarios, considering different sorbent doses and mass transfer rates as well as biodegradation. Such model predictions provide a quick assessment tool for identifying mass transfer limitations during washing, stabilization, or bioslurry treatments of polluted soil or sediment in mixed systems. It appears that PAHs would be readily released from materials contaminated by small oil droplets, but not tar decanter sludge. Released PAHs would be sequestered rapidly by activated carbon amendment but to a much lesser extent by coke breeze. If sorbing black carbon is present in the slurries, POM pellets would not be effective as a sequestration amendment. High first-order biodegradation rates in the free aqueous phase, e.g., in the order of 0.001 s(-1) for phenanthrene, would be required to compete effectively with adsorption and mass transfer for strong sorbents. (C) 2008 Elsevier Ltd. All rights reserved.

Keywords: Activated Carbon, Activated Carbon, Adsorption, Assessment, Bioavailability, Diffusion, Equilibrium, Evaluation, Impacts, In-Situ Sequestration, Intraparticle Diffusion, Marine-Sediments, Mass Transfer, Matter, Model, Modeling, PAHs, Phenanthrene Sorption, Polychlorinated-Biphenyls, Polycyclic Aromatic Hydrocarbons, Polycyclic Aromatic-Hydrocarbons, Polyoxymethylene, Polyoxymethylene, Slurry System, Sorbent, Uptake

? Francesca, P., Sara, M. and Luigi, T. (2008), New biosorbent materials for heavy metal removal: Product development guided by active site characterization. Water Research, 42 (12), 2953-2962.

Full Text: 2008\Wat Res42, 2953.pdf

Abstract: Olive pomace wastes were used as precursors for the development of new biosorbents for heavy metals. Thermal and/or chemical treatments were addressed in terms of their effects on functional group properties and copper removal. Product development was guided by experimental characterization (potentiometric titrations, IR spectra, copper biosorption, total surface area) and theoretical modeling of acid-base properties. Olive pomace was characterized by negative charge due to dissociation of two weakly acidic sites (carboxylic and phenolic). After thermal treatment, a char-like material was obtained characterized by basic sites with positive charge in the acidic pH range. Copper biosorption properties of this material were improved with respect to olive pomace due to the binding ability of pyrone-like sites. Both native and carbonized olive pomace samples were chemically treated by HNO3. Experimental tests were performed according to factorial designs and analysis of variance was used to evaluate significant effects on copper removal of both oxidant concentration and temperature. Chemical treatment by HNO3 Of carbonized material developed negatively charged groups in the acidic pH range (carboxylic groups), but presented a decreased copper removal. Chemical treatment by HNO3 of olive pomace without carbonization gave biosorbents with acid-base properties similar to those of native olive pomace, but with a significant increase of copper biosorption. Specific carboxylic-copper interactions indicated by IR spectra and increased surface area due to chemical treatment were simultaneously responsible for such improvement. (C) 2008 Elsevier Ltd. All rights reserved.

Keywords: Olive Pomace, Biosorption, Potentiometric Titration, Modeling, IR Spectra, Aqueous-Solutions, Olive Stones, Waste-Water, Solid Residue, Carbon, Biosorption, Ions, Surface, Sorption, Biomass

? Yu, Q., Deng, S.B. and Yu, G. (2008), Selective removal of perfluorooctane sulfonate from aqueous solution using chitosan-based molecularly imprinted polymer adsorbents. Water Research, 42 (12), 3089-3097.

Full Text: 2008\Wat Res42, 3089.pdf

Abstract: Perfluorooctane sulfonate (PFOS) pollution in aqueous environment is a problem of global concern. A novel chitosan-based molecularly imprinted polymer (MIP) was prepared by crosslinking with epichlorohydrin (ECH) in the presence of PFOS as the template. During the preparation of the MIP adsorbents, the template amount and crosslinking agents significantly affected the imprinting effect. The optimized MIP adsorbents had a sorption amount of 560 mol g^-1 for PFOS, while the sorption amount of the non-imprinted polymer (NIP) was only 258 molg^-1. The sorption behaviors of the MIP adsorbents including sorption kinetics, isotherms, effect of pH, ionic strength and selective sorption were investigated in detail. Sorption experimental results showed that the MIP adsorbents had good selectivity for PFOS, while other anionic contaminants with different structure had little influence on the sorption of the target PFOS. It was found that the electrostatic interaction played an important role in recognizing the target compound in the sorption process. Additionally, the MIP adsorbents could be used at least five times without any loss in sorption capacity. The chitosan-based MIP adsorbents may find potential application in water or wastewater treatment for the selective removal of PFOS. (c) 2008 Elsevier Ltd. All rights reserved.

Keywords: PFOS, Chitosan, Selective Adsorption, MIP Adsorbent, Electrostatic Interaction, Perfluorinated Surfactants, Mass-Spectrometry, Adsorption, Water, Sorption, Decomposition, Environment, Kinetics, Beads, Acid

? Banerjee, K., Amy, G.L., Prevost, M., Nour, S., Jekel, M., Gallagher, P.M. and Blumenschein, C.D. (2008), Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH). Water Research, 42 (13), 3371-3378.

Full Text: 2008\Wat Res42, 3371.pdf

Abstract: Relatively limited information is available regarding the impacts of temperature on the adsorption kinetics and equilibrium capacities of granular ferric hydroxide (GFH) for arsenic M and arsenic(III) in an aqueous solution. In general, very little information is available on the kinetics and thermodynamic aspects of adsorption of arsenic compounds onto other iron oxide-based adsorbents as well. In order to gain an understanding of the adsorption process kinetics, a detailed study was conducted in a controlled batch system. The effects of temperature and pH on the adsorption rates of arsenic(V) and arsenic(III) were investigated. Reaction rate constants were calculated at pH levels of 6.5 and 7.5. Rate data are best described by a pseudo first-order kinetic model at each temperature and pH condition studied. At lower pH values, arsenic(V) exhibits greater removal rates than arsenic(III). An increase in temperature increases the overall adsorption reaction rate constant values for both arsenic M and arsenic(III). An examination of thermodynamic parameters shows that the adsorption of arsenic M as well as arsenic(III) by GFH is an endothermic process and is spontaneous at the specific temperatures investigated. (c) 2008 Elsevier Ltd. All rights reserved.

Keywords: Arsenic, Adsorption, Kinetics, Iron Oxide, Granular Ferric Hydroxide, Drinking-Water, Removal, Goethite, Soils, Iron, Ferrihydrite, Temperature, Groundwater, Phosphate, Sorption

? Zhang, N., Lin, L.S. and Gang, D.C. (2008), Adsorptive selenite removal from water using iron-coated GAC adsorbents. Water Research, 42 (14), 3809-3816.

Full Text: 2008\Wat Res42, 3809.pdf

Abstract: Removal of selenite from aqueous phase using iron-coated granular activated carbons (GAC) was investigated in this study. Five different types of GAC were used for iron coating by oxidizing ferrous chloride with sodium hypochlorite and the iron-coated GAC (Fe-GAC) were tested for selenite removal. Nitrogen adsorption-desorption analyses indicated that Brunauer-Emmett-Teller (BET) specific surface area, pore size, and pore volume decreased with the iron coating. The Darco 12 x 20 GAC was shown to be the most effective adsorbent among the five tested GACs after iron coating. Among the different concentrations used for iron coating, the Darco 12 x 20 GAC coated with 0.1 M ferrous chloride achieved the highest selenite removal (97.3%). High removal efficiency of selenite occurred in a wide range of pH (i.e., 2-8), but the efficiency decreased when pH was higher than 8. Adsorption kinetics showed that selenite removal efficiency reached more than 90% after 6-h adsorption for initial selenium concentration of 2 mg/L and equilibrium was obtained after 48 h. A pseudo-second-order kinetic model was found to characterize the adsorption kinetics well for all the initial selenium concentrations and temperatures tested (R-2 >= 0.9969). Three temperatures (25, 35, 45 degrees C) were used to examine temperature effect on the adsorption behavior of the Fe-GAC with initial selenium concentration of 1 mg/L. Activation energy was calculated to be 30.42 kJ/mol. Adsorption isotherms for initial selenium concentration of 2 mg/L at various temperatures and ionic strengths were developed and the data generally fit the Langmuir model well (R-2 >= 0.994). The adsorption capacity reached as high as 2.50 mg-Se/g-adsorbent at equilibrium for initial concentration of 2 mg/L at 25 degrees C. The Gibbs free energy was determined to be negative, indicating the spontaneous nature of the adsorption reaction. Oxyanion competitive adsorption showed that sulfate (0.1-5 mM) barely affected selenite adsorption. Other anions (phosphate, silicate and carbonate) impact selenite adsorption to various degrees with phosphate completely excluded selenite adsorption at 5 mM. The possible adsorption mechanisms were discussed. (C) 2008 Elsevier Ltd. All rights reserved.

Keywords: Activated Carbons, Adsorbent, Adsorption, Adsorption Isotherm, Adsorption Isotherms, Adsorption Kinetics, Adsorption-Desorption, Anion Adsorption, Behavior, Capacity, Carbons, Energy, Equilibrium, GAC, Gibbs Free Energy, Hydroxides, Impact, Iron, Iron-Coated GAC, Isotherms, Kinetics, Langmuir Model, Model, Oxide-Solution Interfaces, pH, Phosphate, Pseudo-Second-Order, Removal, Selenite Removal, Sodium Hypochlorite, Soil

? McCuen, R.H. and Surbeck, C.Q. (2008), An alternative to specious linearization of environmental models. Water Research, 42 (15), 4033-4040.

Full Text: 2008\Wat Res42, 4033.pdf

Abstract: The solution of a number of environmental models is incorrectly obtained by linearizing a nonlinear analytical solution. The linearization can yield a model that includes a common variable on both sides of the equal sign (i.e., ratio analysis), which in calibration causes highly inflated goodness-of-fit statistics. These specious practices continue likely because of tradition, i.e., “that is the way it is done”. Goodness-of-fit statistics that result from these erroneous practices do not accurately reflect the actual prediction accuracy of the model. Additionally, the linearly calibrated coefficients can be poor estimators of the true coefficients. The goal of this paper is to demonstrate the pitfalls of models based on ratio analyses. Several environmental models are used to demonstrate the erroneous procedure. Monte Carlo simulation is used to show the distribution of the true correlation coefficient and compare it to the distribution that results from the erroneous linearization. Linearization can produce correlation coefficients above 0.9 when the actual correlation is near 0. Nonlinear least squares algorithms can be used to more accurately fit nonlinear data to nonlinear models. (C) 2008 Elsevier Ltd. All rights reserved.

Keywords: Modeling, Ratio Correlation, Linearization, Specious Correlation, Spurious Correlation, Monte Carlo Analysis, Nonlinear Least Squares, Monod, Michaelis-Menten, Sludge Filtration, Adsorption, Sediment Rating Curve

? Canterino, M., Di Somma, I., Marotta, R. and Andreozzi, R. (2008), Kinetic investigation of Cu(II) ions photoreduction in presence of titanium dioxide and formic acid. Water Research, 42 (17), 4498-4506.

Full Text: 2008\Wat Res42, 4498.pdf

Abstract: The photoreduction of Cu(II) in presence of an organic species as sacrificial agent has been investigated by many research groups but some controversial results are reported in literature. In this work, the photoreduction process of Cu(II) in presence of formic acid is investigated aiming at clarifying the reaction mechanism and assess the reaction kinetics. The effect of operating conditions such as TiO2 load, initial concentration of sacrificial agent, pH and ionic strength was studied. The results of the work are: (1) the system reactivity does not depend neither on pH (in the range 2.0-3.5) nor on ionic strength of the solution; (2) formic acid is adsorbed on TiO2 surface; (3) the nature of anionic species can influence the Cu(II) photoreduction (e.g. the addition of sulphate or phosphates reduces the reaction rates); and (4) FA can be completely mineralized during this photoxidation process; for example, this is observed for a TiO2 load of 0.1 g/L after a reaction time of about 240 min. A simplified kinetic model is developed to describe the behavior of the system and validated by analysing the data collected during the experimental work. (C) 2008 Elsevier Ltd. All rights reserved.

Keywords: Adsorption, Aqueous Suspensions, Behavior, Copper, Copper Ions, Cu(II), Deposition, FA, Formic Acid, Heavy-Metal, Ions, Kinetic, Kinetics, Literature, Mechanism, Metal-Ions, Model, pH, Photocatalytic Degradation, Photoreduction, Reduction, Research, Sacrificial Agent, Strength, TiO₂, Waste-Water

? Li, K., Hokanson, D.R., Crittenden, J.C., Trussell, R.R. and Minakata, D. (2008), Evaluating UV/H₂O₂ processes for methyl tert-butyl ether and tertiary butyl alcohol removal: Effect of pretreatment options and light sources. Water Research, 42 (20), 5045-5053.

Full Text: 2008\Wat Res42, 5045.pdf

Abstract: In this paper, we evaluate the efficiency of UV/H(2)O(2) process to remove methyl tert-butyl ether (MtBE) and tertiary butyl alcohol (tBA) from a drinking water source. Kinetic models were used to evaluate the removal efficiency of the UV/H(2)O(2) technologies with different pretreatment options and light sources. Two commercial UV light sources, i.e. low pressure, high intensity lamps and medium pressure, high intensity lamps, were evaluated. The following pretreatment alternatives were evaluated: (1) ion exchange softening with seawater regeneration (NaIX); (2) Pellet Softening; (3) weak acid ion exchange (WAIX); and (4) high pH lime softening followed by reverse osmosis (RO). The presence or absence of a dealkalization step prior to the UV/H(2)O(2) Advanced Oxidation Process (AOP) was also evaluated for each pretreatment possibility. Pretreatment has a significant impact on the performance of UV/H(2)O(2) process. The NaIX with dealkalization was shown to be the most cost effective. The electrical energy per order (EEO) values for MtBE and tBA using low pressure high output UV lamps (LPUV) and 10 mg/L H(2)O(2) are 0.77 and 3.0 kWh/kgal-order, or 0.20 and 0.79 kWh/m(3)-order, respectively. For medium pressure UV high output lamps (MPUV), EEO values for MtBE and tBA are 4.6 and 15 kWh/kgal-order, or 1.2 and 4.0 kWh/m(3)-order, for the same H(2)O(2) dosage. (C) 2008 Elsevier Ltd. All rights reserved.

Keywords: Adsorption, Alcohol, Bromate Formation, Chlorine, Degradation, Drinking Water, Electrical Energy Per Order, Energy, Hydroxyl Radical, Hydroxyl Radicals, Impact, Kinetic, Kinetic Models, Low Pressure UV System, Medium Pressure UV System, Methyl Tert-Butyl Ether, Molecular Ozone, Oxidation, Ozonation, Pathways, Peroxide, pH, Pressure, Regeneration, Removal, Tertiary Butyl Alcohol, Ultraviolet Light, Hydrogen Peroxide Process

? Upadhyayula, V.K.K., Deng, S.G., Smith, G.B. and Mitchell, M.C. (2009), Adsorption of Bacillus subtilis on single-walled carbon nanotube aggregates, activated carbon and NanoCeram (TM). Water Research,