Personal Research Database

Full Text: W\Wat Res39, 2549.pdf

Abstract: An experimental investigation was made to study the effects of chemical coupling of flocculation and adsorption with photocatalysis in treating persistent organic pollutants in wastewater. The photocatalysis alone showed initial reverse reaction when titanium oxide (TiO₂) was used in catalysis. The effect of the pretreatment of adsorption with powdered activated carbon (PAC) on photocatalysis was studied. The results showed that PAC adsorption followed by photocatalysis was not effective in alleviating reverse reaction. On the other hand, when PAC and TiO₂ were added simultaneously, the reverse reaction was eliminated. Further, the organic removal was also improved by simultaneous PAC and TiO₂ additions. When flocculation with ferric chloride (FeCl₃) was used as pretreatment, the organic removal efficiency was superior. The initial reverse reaction was also eliminated/minimized. However, inadequate doses of FeCl₃ (less than 30 mg l⁻¹) resulted in initial reverse reaction and inferior DOC removal.

Keywords: Activated Carbon, Chemical Coupling, FeCl₃ Flocculation, Molecular Weight Distribution, Organic Matter, Photocatalysis, Reverse Reaction, Wastewater

? Maity, S., Chakravarty, S., Bhattacharjee, S. and Roy, B.C. (2005), A study on arsenic adsorption on polymetallic sea nodule in aqueous medium. Water Research, 39 (12), 2579-2590.

Full Text: W\Wat Res39, 2579.pdf

Abstract: A detailed study on As(III) and As(V) adsorption on polymetallic sea nodule in aqueous medium has been reported. Elemental composition of sea nodule comprises primarily, iron, manganese and silicon with trace quantities of aluminium, copper, cobalt and nickel. As(V) adsorption on sea nodule is dependent on pH while As(III) is insensitive to it. Adsorption data broadly follow Langmuir isotherm. Kinetic data follow a pseudo-second-order model for both As(III) and As(V). Arsenic loading on sea nodule is dependent on initial arsenic concentration. Optimum As(III) loading is 0.74 mg/g at 0.34 mg/L and for As(V) it is 0.74 mg/g at 0.78 mg/L. As(III) adsorption is broadly independent of ionic environment. Except for PO₄³⁻, As(III) adsorption is not influenced by anions but cations influence it significantly. As(V) adsorption, on the other hand, is influenced by anions and not by cations. Experimental evidence indicates an inner sphere complex for As(III) and partial inner and partial outer sphere complex for As(V). Both As(III) and As(V) adsorptions are marked with very little desorption in the pH range of 2–10. Sea nodule can speciate As(III) and As(V) in groundwater at or above pH 6. Sea nodule was successfully tested as an adsorbent for the removal of arsenic from six contaminated groundwater samples of West Bengal, India, containing arsenic in the range 0.04–0.18 mg/L.

Keywords: Adsorption, As(III), As(V), Sea Nodule, Aqueous Medium

? Ju, D. and Young, T.M. (2005), The influence of the rigidity of geosorbent organic matter on non-ideal sorption behaviors of chlorinated benzenes. Water Research, 39 (12), 2599-2610.

Full Text: W\Wat Res39, 2599.pdf

Abstract: This study focused on evaluating the influence of the rigidity of natural organic matter (NOM) associated with four natural geosorbents in controlling the non-ideal sorption behaviors of five chlorinated benzenes. Single solute sorption isotherms for each sorbate/sorbent combination were modeled and interpreted by the Freundlich sorption isotherm and the adsorption-partitioning model based on Polanyi–Manes theory (PM model). ‘Rigid’ organic matter was operationally quantified as the fraction of carbon resistant to wet chemical oxidation (hard carbon) or thermal oxidation (soot carbon); atomic H/O ratios indicated a close correlation between the degree of reduction of the NOM and its rigidity. Sorbents with larger rigid carbon fractions had more non-linear sorption isotherms and higher organic carbon (OC) normalized sorption affinities. The size of the PM hole filling domain for a given sorbent was closely correlated with the extent to which the sorbent’s affinity for chlorobenzenes exceeded predictions from a linear free energy relationship. Loss of some portions of the rigid character of the NOM domain due to the penetration of sorbate molecules (plasticization) was discussed as a possible contributor to the non-ideal sorption behaviors observed in this study. The existence of a permanently rigid NOM domain, not subject to plasticization under environmental conditions, was postulated as an additional factor determining the observed sorption behavior.

Keywords: Isotherm Model, Equilibrium, Hard Carbon, Soot Carbon, Non-Linear Sorption

? Mysore, D., Viraraghavan, T. and Jin, Y.C. (2005), Treatment of oily waters using vermiculite. Water Research, 39 (12), 2643-2653.

Full Text: 2005\Wat Res39, 2643.pdf

Abstract: The main objective of this study was to examine the removal of oil from water by expanded and hydrophobized vermiculite. A pH of 9 showed a higher removal efficiency of oil by vermiculite. Oil removal efficiencies at pH 9 were found to be 79%, 93%, 90%, 57% for standard mineral oil (SMO), Canola oil (CO), Kutwell oil (KUT45), refinery effluent (RE), respectively, in the case of expanded vermiculite, and 56%, 58%, 47%, 43% for SMO, CO, KUT45 and RE, respectively, for hydrophobized vermiculite. Kinetic data satisfied both the Lagergren and Ho models. Equilibrium studies showed that the Langmuir isotherm was the best-fit isotherm for oil removal by both expanded and hydrophobized vermiculite. The data showed a higher adsorptive capacity by the expanded vermiculite compared to the hydrophobized vermiculite. Desorption studies showed that the expanded vermiculite did not desorb oil to the same extent compared to hydrophobized vermiculite. The Freundlich isotherm was the best-fit model for desorption. Expanded vermiculite showed better retention than hydrophobic vermiculite. The results showed that the expanded vermiculite had a greater affinity for oil than hydrophobized vermiculite. (c) 2005 Elsevier Ltd. All rights reserved.

Keywords: Expanded Vermiculite, Hydrophobized Vermiculite, Sorption, Desorption, Isotherms, Oil Retention, Oil-In-Water Emulsions, Adsorption, Removal, Bentonite, Pore

? McCullagh, C. and Saunders, G.C. (2005), Enhanced adsorption of Cd(II) on a hydrous Al(III) floc in the presence of a modified form of polyethylenimine. Water Research, 39 (13), 2799-2806.

Full Text: W\Wat Res39, 2799.pdf

Abstract: A polymer modified with succinic anhydride has been investigated for the adsorption of cadmium(II) on a freshly precipitated aluminium(III) hydroxide floc. The proportion of chelate attached to the polymer is varied to determine the relationship between carboxyl and amino groups on the polyelectrolyte, in terms of enhanced adsorption of cadmium(II) on a hydrous aluminium floc. The presence of polyelectrolyte enhanced the adsorption of 3.3 ppm Cd(II) on a 333 ppm Al(III) floc at every concentration of polyelectrolyte investigated. The proportion of succinic anhydride attached to the polymer had an impact on the increased adsorption of Cd(II) on an Al(III) floc observed. A decreasing proportion of succinic anhydride to polymer resulted in a decrease in the amount of cadmium adsorbed on the floc. Above pH 8, a decrease in the % Cd(II) adsorbed on the floc and % Al(III) retained within the floc decreases with the presence of polyelectrolyte as a result of the formation of soluble Cd–Polyethylenimine-succinic acid (PEISA) complexes. When the Al–PEISA combination was applied to a complex matrix where Cd(II), Cu(II) and Ni(II) ions competed for adsorption, enhanced adsorption was observed for Cd(II) and Ni(II). At pH 7, dissolution of the floc observed with the addition of discrete chelates was not observed with the addition of polyelectrolytes.

Keywords: Waste Water Treatment, Polyelectrolytes, Flocs, Cadmium, Chelates

? Kamala, C.T., Chu, K.H., Chary, N.S., Pandey, P.K., Ramesh, S.L., Sastry, A.R.K.and Sekhar, K.C. (2005), Removal of arsenic(III) from aqueous solutions using fresh and immobilized plant biomass. Water Research, 39 (13), 2815-2826.

Full Text: W\Wat Res39, 2815.pdf

Abstract: The ability of Garcinia cambogia, an indigenous plant found in many parts of India, to remove trivalent arsenic from solution was assessed. Batch experiments were carried out to characterize the As(III) removal capability of fresh and immobilized biomass of G. cambogia. It was found that the kinetic property and uptake capacity of fresh biomass were significantly enhanced by the immobilization procedure. The uptake of As(III) by fresh and immobilized biomass was not greatly affected by solution pH with optimal biosorption occurring at around pH 6–8. The presence of common ions such as Ca and Mg at concentrations up to 100 mg/l had no effect on As(III) removal. However, the presence of Fe(III) at 100 mg/l caused a noticeable drop in the extent of As(III) removal but the effect was minimal when Fe(III) was present at 10 mg/l. The adsorption isotherms quantitatively predicted the extent of As(III) removal in groundwater samples collected from an arsenic-contaminated site in India. Immobilized biomass loaded with As(III) was amenable to efficient regeneration with NaOH solution. Column studies showed that immobilized biomass could be reused over five cycles of loading and elution. The excellent As(III) sequestering capability of fresh and immobilized G. cambogia biomass could lead to the development of a viable and cost-effective technology for arsenic removal in groundwater.

Keywords: Adsorption, Arsenic, Biosorption, Column, Immobilization, Plant Biomass

? Gibert, O., de Pablo, J., Cortina, J.L. and Ayora, C. (2005), Sorption studies of Zn(II) and Cu(II) onto vegetal compost used on reactive mixtures for in situ treatment of acid mine drainage. Water Research, 39 (13), 2827-2838.

Full Text: W\Wat Res39, 2827.pdf

Abstract: The efficiency of the sulphate reducing bacteria-based in situ treatment of acid mine drainage is often limited by the low degradability of the current carbon sources, typically complex plant-derived materials. In such non-sulphate-reducing conditions, field and laboratory experiences have shown that mechanisms other than sulphide precipitation should be considered in the metal removal, i.e. metal (oxy)hydroxides precipitation, co-precipitation with these precipitates, and sorption onto the organic matter.

The focus of the present paper was to present some laboratory data highlighting the Zn and Cu sorption on vegetal compost and to develop a general and simple model for the prediction of their distribution in organic-based passive remediation systems. The model considers two kinds of sorption sites (>SO₂H₂) and the existence of monodentate and bidentate metal-binding reactions, and it assumes that only free M²⁺ species can sorb onto the compost surface. The acid–base properties of the compost were studied by means of potentiometric titrations in order to identify the nature of the involved surface functional groups and their density. The distribution coefficient (K_D) for both Zn and Cu were determined from batch experiments as a function of pH and metal concentration. The model yielded the predominant surface complexes at the experimental conditions, being >SO₂Zn for Zn and >SO₂HCu⁺ and (>SO₂H)₂Cu for Cu, with log K_M values of −2.10, 3.36 and 4.65, respectively. The results presented in this study have demonstrated that the proposed model provides a good description of the sorption process of Zn and Cu onto the vegetal compost used in these experiments.

Keywords: Metal Sorption, Zn(II) and Cu(II), Acid Mine Drainage, Natural Organic Compost, Passive Remediation, Surface Complexation

? Hellerich, L.A. and Nikolaidis, N.P. (2005), Studies of hexavalent chromium attenuation in redox variable soils obtained from a sandy to sub-wetland groundwater environment. Water Research, 39 (13), 2851-2868.

Full Text: 2005\Wat Res39, 2851.pdf

Abstract: Laboratory experiments were conducted to characterize and quantify the capacity and kinetics of the combined effects of natural attenuation processes, such as adsorption, reduction, and precipitation, for hexavalent chromium [Cr(VI)] in a variable geochemical (i.e. fraction of organic carbon [foc], redox) environment of glaciated soils. Equilibrium attenuation terms: linear sorption (K-d), estimated capacity, and non-linear Langmuir (K-L, Q) sorption parameters; varied over several orders of magnitude. The pseudo-first-order rate of disappearance of Cr(VI) from aqueous:soil slurries ranged from similar to 10(-5) to similar to 10(-1)/min. An operationally defined kinetic attenuation term, attenuation capacity (AC), describing the quantity of Cr(VI) disappearing from the slurries, ranged from 1.1 to similar to 12 mu g Cr(VI)/g soil/7 days. The linear K-d’s and estimated attenuation capacities were indirectly and directly related to increasing soil pH and foc, respectively. The AC values decreased and increased as a function of increasing soil pH and foc, respectively. The parameters determined in this work were used to evaluate the kinetics, capacity, and stability of chromium attenuation in the sub-wetland saturated soils in Hellerich (2004. A field, laboratory, and modeling study of natural attenuation processes affecting the fate and transport of hexavalent chromium in a redox variable groundwater environment. Ph.D. Dissertation, Department of Civil and Environmental Engineering, University of Connecticut-Storrs) using a statistical simulation framework. (c) 2005 Elsevier Ltd. All rights reserved.

Keywords: Adsorption, Aquifer Solids, Attenuation, Behavior, Capacity, Chromium, Cr(VI), Environment, Equilibrium, Groundwater, Hexavalent, Hexavalent Chromium, Iron, Kinetics, Mobility, Modeling, Natural, Oxidation, pH, Precipitation, Pseudo-First-Order, Redox, Reduction, Sorption, Statistical, System, University

? Wartelle, L.H. and Marshall, W.E. (2005), Chromate ion adsorption by agricultural by-products modified with dimethyloldihydroxyethylene urea and choline chloride. Water Research, 39 (13), 2869-2876.

Full Text: W\Wat Res39, 2869.pdf

Abstract: The use of cellulose-containing agricultural by-products modified with the cross-linking reagent dimethyloldihydroxyethylene urea (DMDHEU) and the quaternary amine, choline chloride, as anion exchange resins, has not been reported. The objective of the present study was to convert the readily available by-products, soybean hulls, sugarcane bagasse and corn stover to functional anion exchange resins using DMDHEU and choline chloride. Optimization of the modification method was achieved using soybean hulls as a substrate. The optimized method was additionally used to modify sugarcane bagasse and corn stover. Adsorption efficiency results with chromate ion showed that modification with both DMDHEU and choline chloride was required for the highest efficiencies. Adsorption capacities of the modified by-products were determined using chromate ion and found to be 1.97, 1.61 and 1.12 mmol/g for sugarcane bagasse, corn stover and soybean hulls, respectively. Competitive adsorption studies were conducted at 10 and 50 times US Environmental Protection Agency (US EPA) limits for arsenic, chromium and selenium in a simulated wastewater at pH 7. The results showed preferential adsorption of chromate ion over arsenate or selenate ion. Estimated product costs for the three resins ranged from $0.88/kg to $0.99/kg, which was considerably lower than the market costs for the two commercial anion exchange resins QA-52 and IRA-400 also used in this study. DMDHEU/choline chloride modification of the three by-products produced an anion exchange resin with a high capacity to adsorb chromate ion singly or competitively in the presence of other anions from aqueous solutions.

Keywords: Soybean Hulls, Sugarcane Bagasse, Corn Stover, Anion Exchange Resins, DMDHEU, Choline Chloride, Chromium, Arsenic, Selenium

? Genç-Fuhrman, H., Bregnhøj, H. and McConchie, D. (2005), Arsenate removal from water using sand–red mud columns. Water Research, 39 (13), 2944-2954.

Full Text: W\Wat Res39, 2944.pdf

Abstract: This study describes experiments in which sorption filters, filled with chemically modified red mud (Bauxsol) or activated Bauxsol (AB) coated sand, are used to remove As(V) (arsenate) from water. Bauxsol-coated sand (BCS) and AB-coated sand (ABCS) are prepared by mixing Bauxsol or AB with wet sand and drying. Samples of the BCS and ABCS are also used in batch experiments to obtain isotherm data. The observed adsorption data fit the Langmuir model well, with adsorption maxima of 3.32 and 1.64 mg g⁻¹ at pH values of 4.5 and 7.1, respectively for BCS; and of 2.14 mg g⁻¹ for ABCS at a pH of 7.1. Test results show that higher arsenate adsorption capacities can be achieved for both BCS and ABCS when using the columns compared to results for batch experiments; the difference is greater for BCS. Additional batch tests, carried out for 21 days using BCS to explain the observed discrepancy, show that the equilibrium time previously used in batch experiments was too short because adsorption continued for at least 21 days and reached 87% after 21 days compared to only 35% obtained after 4 h. Fixed bed column tests, used to investigate the effects of flow rate and initial arsenate concentration indicate that the process is sensitive to both parameters, with lower flow rates (longer effective residence times in the columns) and initial arsenate concentrations providing better column performance. An examination of the combined effect of potential competing anions (i.e. silicate, phosphate, sulphate and bicarbonate) on the column performance showed that the presence of these anions in tap water slightly decreases arsenate removal. Each breakthrough curve is compared to the Thomas model, and it is found that the model may be applied to estimate the arsenate sorption capacity in columns filled with BCS and ABCS. The data obtained from both batch and column studies indicate that BCS and ABCS filtration could be effectively used to remove arsenate from water, with the latter being more efficient.

Keywords: Activated Bauxsol Coated Sand, Arsenate Removal, Batch Tests, Bauxsol Coated Sand, Column Tests, Thomas Model

Notes: highly cited

? Joss, A., Keller, E., Alder, A.C., Göbel, A., McArdell, C.S., Ternes, T. and Siegrist, H. (2005), Removal of pharmaceuticals and fragrances in biological wastewater treatment. Water Research, 39 (14), 3139-3152.

Full Text: 2005\Wat Res39, 3139.pdf

Abstract: The removal of seven pharmaceuticals and two fragrances in the biological units of various full-scale municipal wastewater treatment plants was studied. The observed removal of pharmaceuticals was mainly due to biological transformation and varied from insignificant (<10%, carbamazepine) to>90% (ibuprofen). However, no quantitative relationship between structure and activity can be set up for the biological transformation. Overall, it can be concluded that for compounds showing a sorption coefficient (K_d) of below 300 L kg⁻¹, sorption onto secondary sludge is not relevant and their transformation can consequently be assessed simply by comparing influent and effluent concentrations. The two fragrances (HHCB, AHTN) studied were mainly removed by sorption onto sludge. For the compounds studied, comparable transformation and sorption was seen for different reactor types (conventional activated sludge, membrane bioreactor and fixed bed reactor) as well as for sludge ages between 10 and 60–80 days and temperatures between 12 °C and 21 °C. However, some significant variations in the observed removal currently lack an explanation. The observed incoming daily load of iopromide and roxithromycin in medium-sized municipal wastewater treatment plants (up to 80,000 population equivalents) is generated by only a small number of patients: the consequences for representative 24 h composite sampling are discussed. Generally, the paper presents a method for setting up mass balances for micropollutants over entire wastewater treatment plants, including an estimation of the accuracy of the quantified fate (i.e. removal by sorption and biological transformation).

Keywords: Degradation, Sorption, Municipal Wastewater, Membrane Bioreactor, Pharmaceuticals, Musk Fragrances

? Herrero, R., Lodeiro, P., Rey-Castro, C., Vilariño T. and Sastre de Vicente, M.E. (2005), Removal of inorganic mercury from aqueous solutions by biomass of the marine macroalga Cystoseira baccata. Water Research, 39 (14), 3199-3210.

Full Text: 2005\Wat Res39, 3199.pdf

Abstract: The ability of Cystoseira baccata algal biomass to remove Hg(II) from aqueous solutions is investigated. The mercury biosorption process is studied through batch experiments at 25 °C with regard to the influence of contact time, initial mercury concentration, solution pH, salinity and presence of several divalent cations. The acid–base properties of the alga are also studied, since they are related to the affinity for heavy metals. The studies of the pH effect on the metal uptake evidence a sharp increasing sorption up to a pH value around 7.0, which can be ascribed to changes both in the inorganic Hg(II) speciation and in the dissociation state of the acid algal sites. The sorption isotherms at constant pH show uptake values as high as 178 mg g⁻¹ (at pH 4.5) and 329 mg g⁻¹ (at pH 6.0). The studies of the salinity influence on the Hg(II) sorption capacity of the alga exhibit two opposite effects depending on the electrolyte added; an increase in concentration of nitrate salts (NaNO₃, KNO₃) slightly enhances the metal uptake, on the contrary, the addition of NaCl salt leads to a drop in the sorption. The addition of different divalent cations to the mercury solution, namely Ca²⁺, Mg²⁺, Zn²⁺, Cd²⁺, Pb²⁺ and Cu²⁺, reveals that their effect on the uptake process is negligible. Finally, the equilibrium sorption results are compared with predictions obtained from the application of a simple competitive chemical model, which involves a discrete proton binding constant and three additional constants for the binding of the main neutral inorganic Hg(II) complexes, Hg(Cl)₂, HgOHCl and Hg(OH)₂, to the algal surface sites.

Keywords: Cystoseira Baccata, Mercury, Adsorption, Marine Macroalga

? Rodgers, M., Healy, M.G. and Mulqueen, J. (2005), Organic carbon removal and nitrification of high strength wastewaters using stratified sand filters. Water Research, 39 (14), 3279-3286.

Full Text: 2005\Wat Res39, 3279.pdf

Abstract: The current practice of spray irrigation of dairy parlour wastewaters is laborious and time consuming. Intermittent sand filtration systems may offer an alternative to spray irrigation when designed to remove organic carbon, nitrogen, phosphorus, coliforms and viruses from such wastewaters to allow discharge of the final effluent directly into receiving waters without damage to the environment. In this study two instrumented stratified sand filter columns (0.425 and 0.9 m deep, and both 0.3 m in diameter) were intermittently loaded for 439 days with synthetic dairy parlour washings at a number of hydraulic and organic loading rates. At a biochemical oxygen demand (BOD) loading of 22 g m⁻² d⁻¹, over 92% of the BOD and suspended solids in the wastewater was removed in the two filters and nitrification was complete. The 0.9 m column had a sustained ability to adsorb the influent phosphorus during the study period; however, the phosphorus adsorption capacity of the 0.425 m column began to decrease after approximately 30 days. Biomass, comprising hydrated extracellular polymers (exopolymers) and living and dead cells, accumulated in the 0.9 m column; it was assessed by sodium bromide tracer studies and by variations in the sand volumetric water contents using time domain reflectometry (TDR). The biomass growth increased the retention time of the wastewater in the filter media, and occurred mainly at the top of the first sand layer. Intermittent stratified sand filters appear to offer an effective and sustainable treatment process for the removal of BOD from high-strength wastewaters, and for the complete nitrification of ammonium.

Keywords: Intermittent Sand Filtration, Organic Loading Rate, Volumetric Water Content, Adsorption Isotherm Test

? Wingenfelder, U., Nowack, B., Furrer, G. and Schulin, R. (2005), Adsorption of Pb and Cd by amine-modified zeolite. Water Research,