Personal Research Database

Full Text: W\Wat Res34, 216.pdf

Abstract: This laboratory experiment systematically examines As speciation and solubility in sewage sludge suspensions as affected by pH and redox potential (Eh). Under oxidizing conditions, As solubility was low with the major portion of soluble As present as organic species; dimethylarsinic acid (DMAA) was always the dominant organic species. Under moderately reducing conditions (0-100 mV), arsenite a as the major inorganic As species in solution and As solubility significantly increased due to dissolution of iron oxyhydroxides. Upon reduction to -250 mV, As solubility was controlled by the formation of insoluble sulfides and as a result soluble As contents dramatically decreased as compared to levels measured at 0 mV. Speciation was drastically influenced by pH. Soluble As was maximum at a neutral pH value and decreased under both more acidic and alkaline concentrations. At pH 5.0, inorganic species were the dominant forms in solution, however, at pH 6.5, organic species were the major soluble forms. Alkaline conditions (pH 8.0) resulted in similar concentrations of soluble inorganic and organic As species. Arsenic biomethylation was measured at pH 6.5 and 8.0, but was drastically restricted at pH 5.0. (C) 1999 Elsevier Science Ltd. Ail rights reserved.

Keywords: Arsenic Speciation, Sewage Sludge, Redox Potential, Soil Amendment, Soil, Speciation, Selenium, Sediment, Adsorption, Reduction, Sorption, Cadmium, Water, Zinc

Tanaka, K., Padermpole, K. and Hisanaga, T. (2000), Photocatalytic degradation of commercial azo dyes. Water Research, 34 (1), 327-333.

Full Text: W\Wat Res34, 327.pdf

Abstract: Seven azo dyes were photocatalytically degraded in TiO₂ suspension. Their degradation rates were compared with disappearance and TOC elimination rates. It was demonstrated that diazo dye is less degradable than monoazo and the order of photocatalytic degradation rates was in approximate agreement with that of ozonation rates cited from literature. Major intermediates identified are aromatic amine, phenolic compounds and several organic acids. It was indicated from this study that in the photocatalytic degradation of azo dye the disappearance proceeds through both oxidation and reduction, whereas TOC is eliminated predominantly by oxidation. (C) 1999 Elsevier Science Ltd. All rights reserved.

Keywords: Azo Dye, Titanium Dioxide, Intermediate Products, Organic Acid, Waste-Water, TiO₂, Acid, Decolorization, Photochemistry, Suspensions, Oxidation, Reduction, Sediment, Kinetics

Hong, H.B., Hwang, S.H. and Chang, Y.S. (2000), Biosorption of 1,2,3,4-tetrachlorodibenzo-p-dioxin and polychlorinated dibenzofurans by Bacillus pumilus. Water Research, 34 (1), 349-353.

Full Text: W\Wat Res34, 349.pdf

Abstract: Microbial adsorption of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) and various polychlorinated dibenzofurans (PCDFs) was investigated in an effort to determine the significance of microorganisms as potential agents in transferring the molecules in the environment. The microorganisms used in this study were cultivated under low nutrient conditions for 2 months. The increase and decrease of 1,2,3,4-TCDD and PCDFs in the samples were measured by GC/MS. The peak of dibenzofuran (DBF), added as an internal standard, was compared with the peaks of 1,2,3,4-TCDD and PCDFs. The results showed that the dead biomass of microorganisms could remove these molecules from the medium more effectively than live cells. The subsequent studies suggested that the removal of the molecules be concerned with the unknown biocompound(s) of which secretion is pronounced at high temperature. UV-VIS spectrometry was used to monitor the change in the concentration of biocompound(s). (C) 1999 Elsevier Science Ltd. All rights reserved.

Keywords: Biosorption, 1,2,3,4-TCDD, PCDF, Bacillus Pumilus, Biomass

Dong, D.M., Nelson, Y.M., Lion, L.W., Shuler, M.L. and Ghiorse, W.C. (2000), Adsorption of Pb and Cd onto metal oxides and organic material in natural surface coatings as determined by selective extractions: New evidence for the importance of Mn and Fe oxides. Water Research, 34 (2), 427-436.

Full Text: W\Wat Res34, 427.pdf

Abstract: Surface coatings (biofilms and associated minerals) were collected on glass slides in the oxic surface waters of Cayuga Lake (New York State, U.S.A.) and were used to evaluate the relative contributions of Fe, Mn and Al oxides and organic material to total observed Pb and Cd adsorption by the surface coating materials. Several alternative selective extraction techniques were evaluated with respect to both selectivity and alteration of the residual unextracted material. Pb and Cd adsorption was measured under controlled laboratory conditions (mineral salts solution with defined metal speciation, ionic strength 0.05 M, 25°C and pH 6.0) before and after extractions to determine by difference the adsorptive properties of the extracted component(s). Hydroxylamine hydrochloride (0.01 M NH₂OH . HCl + 0.01 M HNO₃) was used to selectively remove Mn oxides; sodium dithionite (0.3 M Na₂S₂O₄) was used to remove Mn and Fe oxides, and 10% oxalic acid was used to remove metal oxides and organic materials. Several other extractants were evaluated, but preliminary experiments indicated that they were not suitable for these experiments because of undesirable alterations of the residual, unextracted material. The selected extraction methods removed target components with efficiencies between 71 and 83%, but significant amounts of metal oxides and organic materials other than the target components were also removed by the extractants (up to 39%). Nonlinear regression analysis of the observed Pb and Cd adsorption based on the assumption of additive Langmuir adsorption isotherms was used to estimate the relative contributions of each surface coating constituent to total Pb and Cd binding of the biofilms. Adsorption of Cd to the lake biofilms was dominated by Fe oxides, with lesser roles attributed to adsorption by Mn and Al oxides and organic material. Adsorption of Pb was dominated by Mn oxides, with lesser roles indicated for adsorption to Fe oxides and organic material, and the estimated contribution of Al oxides to Pb adsorption was insignificant. The fitted Pb adsorption isotherm for Fe oxides was in excellent agreement with those obtained through direct experiments and reported in independent investigations. The estimated Pb distribution between surface coating components also agreed well with that previously predicted by an additive adsorption model based on Pb adsorption isotherms for laboratory surrogates for Mn, Fe and Al oxides and defined biological components, (C) 1999 Elsevier Science Ltd. All rights reserved.

Keywords: Selective Extraction, Adsorption, Lead, Cadmium, Iron Oxide, Manganese Oxide, Trace-Metals, Lake-Sediments, Fresh-Waters, Iron, Manganese, Matter, Lead, Environment, Particles, Goethite

Morlay, C., Cromer, M. and Vittori, O. (2000), The removal of copper(II) and nickel(II) from dilute aqueous solution by a synthetic flocculant: A polarographic study of the complexation with a high molecular weight poly(acrylic acid) for different pH values. Water Research, 34 (2), 455-462.

Full Text: W\Wat Res34, 455.pdf

Abstract: The aim of this work was to assess the possible removal of copper(II) or nickel(II) from dilute aqueous solution by a synthetic flocculant used in the water treatment field. The copper(II) or nickel(II) complex formation with the 3×10⁶ g mol^-1 average molecular weight poly(acrylic acid) (PAA 3×10⁶) was examined at pH 6.0, 5.0 and 4.0 successively using differential pulse polarography as an investigation mean. The complexing capacity Cc of the polyacid towards copper(II) at pH 6.0 was estimated to be 5.8 mmol Cu(II)/g PAA 3×10⁶ in the operative conditions considered here (NaNO₃ 0.1 mol l^-1; 25°C). The conditional stability constant of the PAA 3×10⁶/copper(II) complex species was determined using the method proposed by assuming that only the 1: 1 complex species was formed: log K’ = 5.2±0.2 at pH 6.0. Both values decreased with the pH of the aqueous medium. Whatever the pn considered, all the values of Cc and log K’ obtained with nickel(II) were significantly lower than these obtained with copper(II); this confirmed the conclusions of the previous potentiometric study of the PAA 3×10⁶complexation properties (). (C) 1999 Elsevier Science Ltd. All rights reserved.

Keywords: Poly(Acrylic Acid), Flocculant, Copper(II), Nickel(II), Complexation, Polarography, Natural Ionic Polysaccharides, Stripping Voltammetry, Metal Speciation, Waters, Binding

Tan, B.H., Teng, T.T. and Omar, A.K.M. (2000), Removal of dyes and industrial dye wastes by magnesium chloride. Water Research, 34 (2), 597-601.

Full Text: W\Wat Res34, 597.pdf

Abstract: Magnesium chloride, as compared to alum and polyaluminium chloride (PAC) is a less commonly used coagulant in the field of wastewater treatment, with a cost in between alum and PAC. It has been used in this study as a coagulant to investigate the effectiveness in the chemical precipitation method for the removal of colouring matters. The colour concentration of dye solutions was measured by visible spectrophotometry. Parameters such as the effect of pH, the effect of coagulant and coagulant aid dosages and the effect of different coagulants have been studied. The results show that MgCl₂ is capable of removing more than 90% of the colouring material at a pH of 11 and a dose of 4 g MgCl₂/l of dye solution. MgCl₂ is shown to be more effective in removing reactive dye than alum and PAC in terms of settling time and amount of alkalinity required. Optimal operating conditions such as pH value. coagulant dose and effect of polyelectrolyte have been determined. Wastewaters of a dyeing and printing mill on different days have been treated by MgCl₂ aqueous solution in bench scale. The treatment of the industrial waste has shown a reduction of 88% in COD and 95% of suspended solids.

Keywords: Aqueous-Solutions, Activated Carbon, Adsorption, Water, Coagulation, Effluents, Dyestuffs, Chemical Coagulation, Colour Reduction, Textile Waste Effluent

Notes: highly cited

Ho, Y.S. and McKay, G. (2000), The kinetics of sorption of divalent metal ions onto sphagnum moss peat. Water Research, 34 (3), 735-742.

Full Text: W\Wat Res34, 735.pdf

Abstract: A pseudo-second order rate equation describing the kinetics of sorption of divalent metal ions onto sphagnum moss peat at different initial metal ion concentrations and pear doses has been developed. The kinetics of sorption were followed based on the amounts of metalsorbed at various time intervals. Results show that sorption (chemical bonding) might be rate-limiting in the sorption of divalent metal ions onto peat during agitated batch contact time experiments. The rate constant, the equilibrium sorption capacity and the initial sorption rate were calculated. From these parameters, an empirical model for predicting the sorption capacity of metal ions sorbed was derived.

Keywords: Capacity, Copper, Elsevier, Equilibrium, Hong Kong, Kinetics, Kinetics And Sorption, Lead, Metal, Metal Ions, Model, Nickel, Peat, Peat, Pseudo Second Order, Pseudo-Second Order, Pseudo-Second-Order, Removal, Science, Sorption, Water

Ito, A., Umita, T., Aizawa, J., Takachi, T. and Morinaga, K. (2000), Removal of heavy metals from anaerobically digested sewage sludge by a new chemical method using ferric sulfate. Water Research, 34 (3), 751-758.

Full Text: W\Wat Res34, 751.pdf

Abstract: The removal of heavy metals from anaerobically digested sewage sludge was studied by using ferric sulfate. The addition of ferric sulfate to the sludge caused the acidification of the sludge and the elution of heavy metals from the sludge. The pH of the sludge decreased with an increase in the amount of iron added and with a decrease in the sludge concentration. At a sludge solid concentration of 2% (w/w), the sludge pH dropped below 3 and the elution percentage of cadmium, copper and zinc was more than 80% when the added amount of ferric iron was more than 1.5g per L of wet sludge. Furthermore, the method using ferric sulfate was compared with that using sulfuric acid at pH 3 in order to clarify the effect of ferric iron as an oxidation reagent on elution of heavy metals. Ferric iron eluted cadmium, copper and zinc more effectively than sulfuric acid. This effective elution of heavy metals was caused by the oxidation of the sludge solid by ferric iron added. From these results, it was concluded that ferric iron played a role to acidify the sludge and to oxidize metallic compounds in the sludge and this new chemical method was useful for the removal of heavy metals from anaerobically digested sewage sludge. (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Anaerobically Digested Sewage Sludge, Heavy Metals Removal, Ferric Sulfate, Sulfuric Acid, Sequential Selective Extraction Method, Kinetics

Lin, S.H. and Lai, C.L. (2000), Kinetic characteristics of textile wastewater ozonation in fluidized and fixed activated carbon beds. Water Research, 34 (3), 763-772.

Full Text: W\Wat Res34, 763.pdf

Abstract: This study was to investigate the ozone oxidation of textile wastewaters in a fluidized or fixed granular activated carbon (GAC) bed. Experiments were conducted to examine the effects of various operating variables on the treatment efficienies of the combined ozonation and activated carbon adsorption. Ozonation was found to provide very efficient regeneration of exhausted GAC in the reactor, avoiding the costly ex situ GAC regeneration. It was also observed that the GAC acts not only as an adsorbent, but also as a catalyst in promoting ozone oxidation. The combined ozonation and GAC adsorption offers strong synergistic effects on the textile wastewater treatment. A generalized kinetic model consisting of multiple steps of ozonation and adsorption was proposed in this work to represent the combined process. The proposed adsorption/ozonation/desorption mechanism and the generalized kinetic model were shown to describe very well the combined treatment process.

Keywords: Water, Reagent, Ozonation, GAC Adsorption, In Situ GAC Regeneration, Adsorption/Reaction Mechanism, Generalized Kinetic Model

Notes: highly cited

Al-Degs, Y., Khraisheh, M.A.M., Allen, S.J. and Ahmad, M.N. (2000), Effect of carbon surface chemistry on the removal of reactive dyes from textile effluent. Water Research, 34 (3), 927-935.

Full Text: W\Wat Res34, 927.pdf

Abstract: The removal efficiency of activated carbon Filtrasorb 400 (F-400) towards three highly used reactive dyes in the textile industry was investigated. In this work, the adsorption capacities for the anionic reactive dyes, namely; Remazol Reactive Yellow, Remazol Reactive Black and Remazol Reactive Red were determined. The adsorption capacity data showed a high removal ability for the three reactive dyes and a distinguished ability for R. Yellow. The high adsorption capacities for F-400 were attributed to the net positive surface charge during the adsorption process. Surface acidity, surface basicity, H⁺ and OH^-adsorption capacities and pH_ZPC for F-400 were estimated and compared with other reported values.

Keywords: Acidity, Activated Carbon, Activated Carbons, Adsorbents, Adsorption, Adsorption, Adsorption Capacity, Aqueous-Solutions, Capacity, Chitosan, Ions, Isotherms, Oxides, pH_ZPC, Process, Reactive Dyes, Titration, Wastewater

Meng, X.G., Bang, S. and Korfiatis, G.P. (2000), Effects of silicate, sulfate, and carbonate on arsenic removal by ferric chloride. Water Research, 34 (4), 1255-1261.

Full Text: W\Wat Res34, 1255.pdf

Abstract: Effects of silicate, sulfate, and carbonate on the removal of arsenite [As(III)] and arsenate [As(V)] by coprecipitation with ferric chloride were studied. Silicate significantly decreased As(III) removal when Si concentration was higher than 1 mg/l and the pH was greater than 5. The removal of As(V) was decreased moderately by silicate in 0.04 M KNO₃ solution. Addition of Ca²⁺ and Mg²⁺ to the KNO₃ solution reduced the adverse affect of silicate on As(V) removal. In the presence of 10 mg/l Si and at a pH of approximately 6.8, the adsorption capacity of ferric hydroxide for As(V) and As(III) was reduced from 864 and 116 µg/mg to 274 and 23 µg/mg Fe, respectively. Sulfate and carbonate had a negligible effect on the removal of As(III) and As(V). The triple layer model was used with site binding reactions to describe As(III) and As(V) removal by ferric hydroxide in the presence of silicate. The results obtained in the present study suggest that silicate in natural water can significantly decrease the efficiency of As(III) removal by coagulation treatment with ferric chloride. (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Arsenic, Coprecipitation, Adsorption, Coagulation, Silicate, Sulfate, Anions, Model, Amorphous Iron Oxyhydroxide, Oxide-Solution Interfaces, Metal-Ions, Surface-Ionization, Water Interface, Drinking-Water, Natural-Waters, Mixed Oxides, Adsorption, Complexation

Gupta, V.K., Srivastava, S.K. and Tyagi, R. (2000), Design parameters for the treatment of phenolic wastes by carbon columns (obtained from fertilizer waste material). Water Research, 34 (5), 1543-1550.

Full Text: W\Wat Res34, 1543.pdf

Abstract: The waste slurry generated in fertilizer plants in India has been converted into a cheap carbonaceous adsorbent material. The practical applicability of this product has been investigated in the column operations and the mass transfer kinetic approach has been successfully used for the determination of various parameters necessary for designing a fixed bed adsorber. The value of breakthrough capacity is more than the batch capacity. The total time (t_x) involved for the establishment of the primary adsorption zone (PAZ), the time (t) required for the movement of PAZ down its length, the fractional capacity (f), the length of (PAZ) primary adsorption zone (), and percentage saturation of column at break point have been evaluated for carbon columns for the removal of phenols viz., 2,4,6-trinitrophenol, 4-nitrophenol, 4-chlorophenol and 1,3-dihydroxybenzene. Studies have also been performed for the recovery of phenols and chemical regeneration of the spent column. It was observed that 70 mL of 5% w/w NaOH or 50 mL of acetone are sufficient for almost complete desorption of phenols. After regeneration with 1M HNO₃ the sorption capacity of the column is almost the same as that of virgin adsorbent material.

Keywords: Adsorption, Fertilizer Waste, Substituted Phenols, 2,4,6-Trinitrophenol, 4-Nitrophenol, 4-Chlorophenol, 1,3-Dihydroxybenzene, Column, Studies, Activated Carbon, Design Parameters

Notes: highly cited

Nam, S. and Tratnyek, P.G. (2000), Reduction of azo dyes with zero-valent iron. Water Research, 34 (6), 1837-1845.

Full Text: W\Wat Res34, 1837.pdf

Abstract: The reduction of azo dyes by zero-valent iron metal (Fe-0) at pH 7.0 in 10 mM HEPES buffer was studied in aqueous, anaerobic batch systems. Orange II was reduced by cleavage of the azo linkage, as evidenced by the production of sulfanilic acid (a substituted aniline). Adsorption of the dyes on iron particles was less than 4% of the initial concentration, and > 90% mass balance was achieved by summing aqueous concentrations of dye and product amine. All of the 9 azo dyes tested were reduced with first-order kinetics. The kinetics of decolorization at the lambda_max of each dye were rapid: a typical k _(obs) was 0.35±0.01 min^-1 for Orange II at 130 rpm on an orbital shaker, corresponding to a surface area normalized rate constant (k (SA)) of 0.21±0.01 Lm^-2min^-1. The rate of reduction of Crocein Orange G varied with initial dye concentration in a way that suggests saturation of surface sites on the Fe-0, and varied with the square-root of mixing rate (rpm) in a manner indicative of mass transfer limited kinetics. Correlation analysis using k_(obs) for all of the azo dyes, estimates of their diffusion coefficients, and calculated energies of their lowest unoccupied molecular orbitals (E-LUMO), gave no strong trends that could be used to derive structure-activity relationships. Using an authentic sample of wastewater from a dye manufacturing operation and construction-grade granular Fe-0, rapid decolorization was achieved that was consistent with reduction of azo dyes.

Keywords: In-Situ Remediation, Metallic Iron, Polychlorinated-Biphenyls, Water System, Ground-Water, Dechlorination, Nitrate, Kinetics, Transformation, Decolorization, Iron Metal, Decolorization, Kinetics, Mass Transport, Correlation Analysis

Kunz, A. and Jardim, W.F. (2000), Complexation and adsorption of copper in raw sewage. Water Research, 34 (7), 2061-2068.

Full Text: W\Wat Res34, 2061.pdf

Abstract: Competition between complexation and adsorption of copper was evaluated in raw sewage samples. Dissociation constants of filtered and non-filtered samples were calculated by linearization of potentiometric titration data using a modified Gran method. Sewage samples were also titrated with cupric ions at three different pH values using an ion selective electrode to quantify the effect of pH, ligand concentration, and particulates in the speciation of copper. Three titratable groups with pKa values of 4.45, 6.42, and 9.31 were detected in non-filtered samples. Changes in pH showed a marked effect in the concentration of free metal caused by the competition between copper and hydrogen ions for organic ligands present in raw sewage. Particulate matter as well as carbonate did not show a significant contribution to control copper speciation in the system. Assuming a two binding sites model, conditional stability constants (K’) of copper complexes were dependent on pH, showing values around log K’ (1) = 8.00 and log K’ (2) = 6.30 at pH 5.8, whereas at pH 7.8, these constants increased to log K’ (1) = 10.60 and log K’ (2) = 8.70 for filtered samples. Particulates caused small changes in K’ Values due to adsorption contribution, and this effect was minimized in diluted samples. Ligand concentrations varied between 5 and 10 µmoll^-1.

Keywords: Dissolved Organic-Matter, Metal Removal, Trace-Metals, River Water, Humic-Acid, Speciation, Bioavailability, Binding, Raw Sewage, Copper Speciation, Complexation, Adsorption, Dissociation Constants, Conditional Stability Constants

? Song, Z., Williams, C.J. and Edyvean, R.G.J. (2000), Sedimentation of tannery wastewater. Water Research, 34 (7), 2171-2176.

Full Text: 2000\Wat Res34, 2171.pdf

Abstract: Tannery wastewater is a powerful pollutant. It can cause severe environmental problems related to its high chemical oxygen demand (COD) together with elevated chrome concentration and deep colour content. The strength parameters employed are COD and suspended solids (SS). Chromium (III) is widely used as tanning agent in the leather industry, and is a significant source of environmental contamination. Tannery effluent containing chromium (III) salts have to be treated to reduce the chromium concentration in the final works effluent to below the value specified in the discharge consent conditions. The objective of this study is to investigate the pretreatment of a tannery wastewater, typified by the mixed effluent from tannery operations. The behaviour of plain settling is described. The results demonstrate 41.5% removal of total GOD, 83.2% removal of chromium and 76.1% removal of suspended solid after 3 h of plain settling. The sludge Volume was 28% of the volume of the mixed wastewater, (C) 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Tannery Wastewater, Sedimentation, Chromium, Plain Settling, COD, Suspended Solids, Industry, Sludge

Notes: highly cited

? Brillas, E., Calpe, J.C. and Casado, J. (2000), Mineralization of 2,4-D by advanced electrochemical oxidation processes. Water Research,