Personal Research Database

Full Text: 2006\Wat Res40, 2201.pdf

Abstract: Phosphate and phosphonates are both strongly adsorbed onto mineral surfaces and their removal during wastewater treatment is mainly due to adsorptive processes. We have conducted experiments to study the mutual influence of phosphate and six different phosphonates on each other in buffered medium at pH 7.2. We have used phosphonates having one to five phosphonic acid groups (HMP, IDMP, HEDP, NTMP, EDTMP and DTPMP). The presence of phosphonates suppressed the adsorption of phosphate. The monophosphonate HMP had the smallest and the polyphosphonates the largest effect on phosphate adsorption. The presence of phosphate lowered phosphonate adsorption. The competition in the multicomponent system can reasonably well be predicted using a surface complexation model developed for single component systems. The competitive model only failed in systems containing the polyphosphonate DTPMP. With this approach we can predict the behavior of both compounds during wastewater treatment. The calculations show that phosphonates have a small effect on phosphate adsorption at the actual concentrations in observed wastewater. Adsorption of low concentrations of phosphonates was calculated to be significantly reduced by phosphate concentrations as observed in wastewater.

Keywords: Phosphate, Phosphonates, Competition, Adsorption, Iron Oxides, Water, Water Treatment

? Smičiklas, I., Dimović, S., Plećaš, I. and Mitrić, M. (2006), Removal of Co²⁺ from aqueous solutions by hydroxyapatite. Water Research, 40 (12), 2267-2274.

Full Text: 2006\Wat Res40, 2267.pdf

Abstract: A study on the removal of cobalt ions from aqueous solutions by synthetic hydroxyapatite was conducted in batch conditions. The influence of different sorption parameters, such as: initial metal concentration, equilibration time, solution pH and presence of EDTA on the amount of Co²⁺ sorbed was studied and discussed. The sorption process followed pseudo-second-order kinetics with necessary time of 24 h to reach equilibrium. Cobalt uptake was quantitatively evaluated using the Langmuir and Dubinin–Kaganer–Radushkevich (DKR) model. The Langmuir adsorption isotherm constant corresponding to adsorption capacity, X_m, was found to be 20.92 mg/g. Sorption of Co²⁺ is constant in the initial pH range 4–8, because HAP surface buffers these solutions to the constant final pH value of 5.1. In the presence of EDTA, sorption of Co²⁺ decreases due to formation of complex with lower sorption affinities. Cobalt desorption depends on the composition of the extracting solution. The desorbed amount of cobalt decreased continuously with increasing pH, and increased with increasing Ca²⁺ concentration in leaching solution.

Keywords: Hydroxyapatite, Cobalt Removal, Equilibrium Isotherm, Kinetics, pH, Desorption

? Southichak, B., Nakano, K., Nomura, M., Chiba, N. and Nishimura, O. (2006), Phragmites australis: A novel biosorbent for the removal of heavy metals from aqueous solution. Water Research, 40 (12), 2295-2302.

Full Text: 2006\Wat Res40, 2295.pdf

Abstract: Reed (Phragmites australis), a commonly used macrophyte in the wetlands constructed for water purification, was investigated as a new biosorbent for the removal of Cu²⁺, Cd²⁺, Ni²⁺, Pb²⁺ and Zn²⁺ from aqueous solution. The metal adsorption capacity of reed biomass was improved significantly by water-wash, base- and acid-treatment. The maximum sorption of NaOH-pretreated reed biomass was observed near neutral pH for Cu²⁺, Cd²⁺, Ni²⁺ and Zn²⁺, while that for Pb²⁺ was from an acidic range of pH 4.0 or higher. The maximum metal adsorption capacity on a molar basis assumed by Langmuir model was in the order of Cu²⁺>Ni²⁺>Cd²⁺>Zn²⁺>Pb²⁺. Reed biosorbent showed a very high adsorption affinity value, which helps predict its high ability to adsorb heavy metals at low concentration. Desorption of heavy metals and regeneration of the biosorbent was attained simultaneously by acid elution. Even after three cycles of adsorption-elution, the adsorption capacity was regained completely and the desorption efficiency of metal was maintained at around 90%.

Keywords: Biosorption, Heavy Metals, Phragmites Australis, Reed Biomass, Wetlands

? Tyrovola, K., Nikolaidis, N.P., Veranis, N., Kallithrakas-Kontos, N. and Koulouridakis, P.E. (2006), Arsenic removal from geothermal waters with zero-valent iron—Effect of temperature, phosphate and nitrate. Water Research, 40 (12), 2375-2386.

Full Text: 2006\Wat Res40, 2375.pdf

Abstract: Field column studies and laboratory batch experiments were conducted in order to assess the performance of zero-valent iron in removing arsenic from geothermal waters in agricultural regions where phosphates and nitrates were present. A field pilot study demonstrated that iron filings could remove arsenic, phosphate and nitrate from water. In addition, batch studies were performed to evaluate the effect of temperature, phosphate and nitrate on As(III) and As(V) removal rates. All batch experiments were conducted at three temperatures (20, 30 and 40 °C). Pseudo-first-order reaction rate constants were calculated for As(III), As(V), phosphate, nitrate and ammonia for all temperatures. As(V) exhibited greater removal rates than As(III). The presence of phosphate and nitrate decreased the rates of arsenic removal. The temperature of the water played a dominant role on the kinetics of arsenic, phosphate and nitrate removal. Nitrate reduction resulted in the formation of nitrite and ammonia. In addition, the activation energy, E_act, and the constant temperature coefficient, θ were determined for each removal process.

Keywords: Geothermal, Zero-valent iron, Arsenic, Phosphate, Nitrate

? Marshall, W.E. and Wartelle, L.H. (2006), Chromate (CrO₄²⁻) and copper (Cu²⁺) adsorption by dual-functional ion exchange resins made from agricultural by-products. Water Research, 40 (13), 2541-2548.

Full Text: 2006\Wat Res40, 2541.pdf

Abstract: Ion exchange resins commonly have a single functionality for either cations or anions. Resins that have a dual functionality for both cations and anions are uncommon. The objective of this study was to create dual-functional ion exchange resins derived from soybean hulls, sugarcane bagasse and corn stover. Dual-functional resins were prepared by two separate two-step processes. In the first two-step process, by-products were reacted with a solution of citric acid in order to impart additional negative charge, and then reacted with the cross-linking reagent dimethyloldihydroxyethylene urea (DMDHEU) and a quaternary amine (choline chloride) to add positive charge to the lignocellulosic material. In the second two-step process, the order of reaction was reversed, with positive charge added first, followed by the addition of negative charge. These combined reactions added both cationic and anionic character to the by-products as evidenced by the increased removal from solution of copper (Cu²⁺) cation and the chromate (CrO₄²⁻) anion compared to unmodified by-products. The order of reaction appeared to slightly favor the functionality that was added last. That is, if negative charge was added last, the resulting resin sequestered more copper ion than a comparable resin where the negative charge was added first and vice-versa. Cu²⁺ and CrO₄²⁻ were used as marker ions in a solution that contained both competing cations and anions. The dual-functional resins adsorbed as much as or more of the marker ions compared to commercial cation or anion exchange resins used for comparison. None of the commercial resins exhibited dual-functional properties to the same extent as the by-product-based resins.

Keywords: Chromate Ion Adsorption, Copper Ion Adsorption, Dual-Functional Ion Exchange Resin, Agricultural By-Product

? Al-Degs, Y.S., El-Barghouthi, M.I., Issa, A.A., Khraisheh, M.A. and Walker, G.M. (2006), Sorption of Zn(II), Pb(II), and Co(II) using natural sorbents: Equilibrium and kinetic studies. Water Research, 40 (14), 2645-2658.

Full Text: 2006\Wat Res40, 2635.pdf

Abstract: Natural Jordanian sorbent (consisting of primary minerals, i.e., quartz and aluminosilicates and secondary minerals, i.e., calcite and dolomite) was shown to be effective for removing Zn(II), Pb(II) and Co(II) from aqueous solution. The major mineral constitutions of the sorbent are calcite and quartz. Dolomite was present as minor mineral and palygorskite was present as trace mineral. The sorbent has microporous structure with a modest surface area of 14.4 m² g⁻¹. pH_zpc (pH of zero point charge) of the sorbent was estimated by alkaline–titration methods and a value of 9.5 was obtained. The sorption capacities of the metals were: 2.860, 0.320, 0.076 mmol cation g⁻¹ for Zn(II), Pb(II) and Co(II) at pH 6.5, 4.5 and 7.0, respectively. The shape of the experimental isotherm of Zn(II) was of a ‘L2’ type, while that of Pb(II) and Co(II) was of a ‘L1’ type according to Giles classification for isotherms. Sorption data of metals were described by Langmuir and Freundlich models over the entire concentration range. It was found that the mechanism of metal sorption was mainly due to precipitation of metal carbonate complexes. The overall sorption capacity decreased after acid treatment, as this decreased the extent of precipitation on calcite and dolomite. The effect of Zn(II) ions concentration on sorption kinetics was investigated. Kinetic data were accurately fitted to pseudo-first order and external diffusion models which indicated that sorption of Zn(II) occurred on the exterior surface of the sorbent and the contribution of internal diffusion mechanism was insignificant. Furthermore, the sorption rate of Zn(II) was found to be slow, where only 10–20% of the maximum capacity was utilized in the first 30 min of interaction.

Keywords: Adsorption, Adsorption, Aqueous, Bentonite, Bone Char, Cadmium Ions, Calcite, Calcium-Carbonate Surfaces, Capacity, Classification, Clay Minerals, Contribution, Diffusion, Dolomite, Elsevier, Equilibrium, External Diffusion, Freundlich, Heavy Metals, Heavy-Metals, Interaction, Isotherm, Isotherms, Kaolinite, Kinetic, Kinetics, Langmuir, Mechanism, Metal, Metals, Methods, Models, Natural Adsorbent, Pb(II), pH, Precipitation, Primary, Pseudo-First Order, Removal, Single-Component, Sorption, Sorption Kinetics, Surface Area, Treatment, Zinc, Zn(II)

? Jang, J.H., Dempsey, B.A. and Burgos, W.D. (2006), Solubility of schoepite: Comparison and selection of complexation constants for U(VI). Water Research, 40 (14), 2738-2746.

Full Text: 2006\Wat Res40, 2738.pdf

Abstract: Solubility of UO3.nH(2)O and sorption of U(VI) onto ferric (hydr)oxides were measured at pH 5.9, 6.8, and 7.8 at 10(-3.5) atm CO2 using reaction times up to 48 days. Precipitation was fastest in the presence of hydrous ferric oxide and slower with hematite or without an initial solid phase. Solubility after 48 days was statistically similar for low to intermediate initial supersaturation conditions and increased for the highest initial supers aturation. Schoepite was identified for low-to-intermediate initial conditions of supersaturation and was not found for the highest initial supersaturation. Predicted concentrations of monomeric and polymeric species differed considerably with the different suites of complexation constants, resulting in significant differences in predicted oxidation-reduction potential and mobility of U(VI) in groundwater. Solubilities for low to intermediate initial supersaturation were best represented using complexation constants from Langmuir, D. [1978. Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits. Geochim. Cosmochim. Acta 42, 547-569] and Iog*K-SP = 5.39 for schoepite, while solubilities for very high initial supersaturation were consistent with amorphous UO3 - nH(2)O. (c) 2006 Elsevier Ltd. All rights reserved.

Keywords: Chemical Speciation, CO2, Coprecipitation, Dioxouranium(VI), Equilibria, Goethite, Groundwater, Hydrolysis Constant, Kinetic Phosphorimetry, Minerals, pH, Solubility, Sorption, Surface Precipitation, Uranium, Uranium(VI) Adsorption, Uranyl, Uranyl

Notes: highly cited

? Nakada, N., Tanishima, T., Shinohara, H., Kiri, K. and Takada, H. (2006), Pharmaceutical chemicals and endocrine disrupters in municipal wastewater in Tokyo and their removal during activated sludge treatment. Water Research, 40 (17), 3297-3303.

Full Text: 2006\Wat Res40, 3297.pdf

Abstract: We measured six acidic analgesics or anti-inflammatories (aspirin, ibuprofen, naproxen, ketoprofen, fenoprofen, mefenamic acid), two phenolic antiseptics (thymol, triclosan), four amide pharmaceuticals (propyphenazone, crotamiton, carbamazepine, diethyltoluamide), three phenolic endocrine disrupting chemicals (nonylphenol, octylphenol, bisphenol A), and three natural estrogens (17 beta-estradiol, estrone, estriol) in 24-h composite samples of influents and secondary effluents collected seasonally from five municipal sewage treatment plants in Tokyo. Aspirin was most abundant in the influent, with an average concentration of 7300 ng/L (n = 16), followed by crotamiton (921 ng/L), ibuprofen (669 ng/L), triclosan (511 ng/L), and diethyltoluamide (503 ng/L). These concentrations were 1 order of magnitude lower than those reported in the USA and Europe. This can be ascribed to lower consumption of the pharmaceuticals in Japan. Aspirin, ibuprofen, and thymol were removed efficiently during primary+secondary treatment (> 90% efficiency). On the other hand, amide-type pharmaceuticals, ketoprofen, and naproxen showed poor removal (< 50% efficiency), which is probably due to their lower hydrophobicity (logK(ow)< 3). Because of the persistence of crotamiton during secondary treatment, crotamiton was most abundant among the target pharmaceuticals in the effluent. This is the first paper to report ubiquitous occurrence of crotamiton, a scabicide, in sewage. Because crotamiton is used worldwide and it is persistent during secondary treatment, it is a promising molecular marker of sewage and secondary effluent. (c) 2006 Elsevier Ltd. All rights reserved.

Keywords: Pharmaceuticals, Crotamiton, Sewage Treatment Plant, Activated Sludge Treatment, Endocrine Disrupting Chemicals, Removal Efficiency, Sewage-Treatment Plants, Estrogenic Compounds, Aquatic Environment, Behavior, Triclosan, Drugs, River, Fate, Micropollutants, Carbamazepine

? Gaspard, S., Altenor, S., Passe-Coutrin, N., Ouensanga, A. and Brouers, F. (2006), Parameters from a new kinetic equation to evaluate activated carbons efficiency for water treatment. Water Research, 40 (18), 3467-3477.

Full Text: 2006\Wat Res40, 3467.pdf

Abstract: The fractal dimension of some commercial activated carbon (AC) was determined in the micro-, meso- and macropore range using mercury porosimetry and N₂ adsorption data. We studied the kinetic of adsorption of phenol, tannic acid and melanoidin on those ACs. The typical concentration-time profiles obtained here could be very well fitted by a general fractal kinetics equation q(n,alpha)(t) = q(e)[1 -(1+ (n - 1)(t/tau(n,alpha))(alpha))(-1/(n-1))] deduced from recently new methods of analysis of reaction kinetics and relaxation. The parameter n is the reaction order, a is a fractional time index, qe measures the maximal quantity of solute adsorbed, and a ‘half-reaction time’, tau(1/2), can be calculated, which is the time necessary to reach half of the equilibrium. The adsorption process on AC is clearly a heterogeneous process, taking place at the liquid-solid boundary, and the diffusion process occurs in a complex matrix with a fractal architecture as demonstrated here. In fact, these systems belong to what has been called ‘complex systems’ and the fractal kinetic, which has been extensively applied to biophysics, can be a useful theoretical tool for study adsorption processes. (c) 2006 Elsevier Ltd. All rights reserved.

Keywords: Fractal Kinetic, Activated Carbon, Adsorption, Fractal Dimension, Fractal Dimension, Noninteger Dimensions, Universal Relaxation, Adsorption-Isotherms, Surface-Diffusion, Porous Materials, Complex-Systems, Heterogeneity, Molecules, Solids

? Maliyekkal, S.M., Sharma, A.K. and Philip, L. (2006), Manganese-oxide-coated alumina: A promising sorbent for defluoridation of water. Water Research, 40 (19), 3497-3506.

Full Text: 2006\Wat Res40, 3497.pdf

Abstract: In this study, adsorption potential of a new sorbent manganese-oxide-coated alumina (MOCA) was investigated for defluoridation of drinking water using batch and continuous mode experiments. The effects of different parameters such as pH, initial fluoride concentration and co-existing ions (usually present in groundwater sample) were studied to understand the adsorption behavior of the sorbent under various conditions. Optimum removal of fluoride ions occurred in a pH range of 4-7. Results of the present study indicate that fluoride adsorption rate and adsorption capacity of MOCA are far superior to that of activated alumina (AA), which was used as the base material for MOCA preparation. The MOCA can be effectively regenerated using 2.5% NaOH as eluent. The Langmuir equilibrium model was found to be suitable for describing the fluoride sorption on AA and MOCA. The maximum fluoride uptake capacity for MOCA and AA was found to be 2.85 and 1.08 mg g^-1, respectively. The kinetic results showed that the fluoride sorption to MOCA followed pseudo-second-order kinetics with a correlation coefficient greater than 0.98. The fluoride sorption capacity at breakthrough point for both the adsorbents was greatly influenced by bed depth. A bed depth service time (BDST) approach was adopted to describe the continuous flow system. The batch and column studies demonstrated the superiority of MOCA over AA in removing fluoride from the drinking water system. (c) 2006 Elsevier Ltd. All rights reserved.

Keywords: Fluoride, Adsorption, Manganese-Oxide-Coated Alumina, Activated Alumina, Drinking Water, Fluoride Removal, Activated Alumina, Adsorption, Equilibrium, Sorption, Breakthrough, Diffusion, Earth, Mn, Fe

Notes: highly cited

? Adams, L.K., Lyon, D.Y. and Alvarez, P.J.J. (2006), Comparative eco-toxicity of nanoscale TiO₂, SiO₂, and ZnO water suspensions. Water Research, 40 (19), 3527-3532.

Full Text: 2006\Wat Res40, 3527.pdf

Abstract: The potential eco-toxicity of nanosized titanium dioxide (TiO2), silicon dioxide (SiO2), and zinc oxide (ZnO) water suspensions was investigated using Gram-positive Bacillus subtilis and Gram-negative Escherichia coli as test organisms. These three photosensitive nanomaterials were harmful to varying degrees, with antibacterial activity increasing with particle concentration. Antibacterial activity generally increased from SiO2 to TiO2 to ZnO, and B. subtilis was most susceptible to their effects. Advertised nanoparticle size did not correspond to true particle size. Apparently, aggregation produced similarly sized particles that had similar antibacterial activity at a given concentration. The presence of light was a significant factor under most conditions tested, presumably due to its role in promoting generation of reactive oxygen species (ROS). However, bacterial growth inhibition was also observed under dark conditions, indicating that undetermined mechanisms additional to photocatalytic ROS production were responsible for toxicity. These results highlight the need for caution during the use and disposal of such manufactured nanomaterials to prevent unintended environmental impacts, as well as the importance of further research on the mechanisms and factors that increase toxicity to enhance risk management. (c) 2006 Elsevier Ltd. All rights reserved.

Keywords: Antibacterial, Bacillus Subtilis, Escherichia Coli, Eco-Toxicity, Nanomaterials, Nanolitter, Photocatalysis, Titanium-Dioxide Particles, Escherichia-Coli, Photocatalytic Disinfection, Bactericidal Activity, Solar

? Qi, S.Y., Schideman, L., Marinas, B.J., Snoeyink, V.L. and Campos, C. (2007), Simplification of the IAST for activated carbon adsorption of trace organic compounds from natural water. Water Research, 41 (2), 440-448.

Full Text: 2007\Wat Res41, 440.pdf

Abstract: Recent studies have shown that the ideal adsorbed solution theory (IAST) coupled with the concept of equivalent background compound (EBC) can be simplified for describing trace organic compound adsorption from natural water, provided that the adsorbent surface loading is dominated by competing natural organic matter. The resulting simplified IAST has been used to reduce the complexity of kinetic models for various dynamic adsorption processes. In order to be correctly applied, however, the simplified IAST requires some additional clarification and a quantitative evaluation of the deviation caused by the simplifying assumption. In this study, we derive a simple equation that relates the relative deviation of the simplified IAST directly to the molar ratio of EBC and trace organic compound surface loadings and their Freundlich isotherm exponents. We then verify the simplified IAST using the original IAST and experimental isotherm data from the literature for trace organic compounds at various initial concentrations in natural water. By further assuming that the adsorbed amount of the EBC is substantially greater than what remains in solution, a new pseudo single-solute isotherm equation is derived and a simple relation is subsequently established between the carbon dose and the remaining trace compound concentration. The results show that the adsorption capacity and relative removal of a trace organic compound at any carbon dose can be estimated directly with the simple equations developed here and data from a single isotherm experiment for the target compound conducted in the natural water of interest. (c) 2006 Elsevier Ltd. All rights reserved.

Keywords: Activated Carbon, Adsorbent, Adsorption, Capacity, Chemicals, Competitive Adsorption, Competitive Adsorption, Contaminants, Evaluation, IAST, Interest, Isotherm, Kinetic Models, Literature, Matter, Model, Natural Organic Matter, Natural Water, Organic Compound, PAC, Prediction, Quantitative, Ratio, Removal, Theory, Verification

? Feo, J.C., Ordonez, E., Letek, M., Castro, M.A., Munoz, M.I., Gil, J.A., Mateos, L.M. and Aller, A.J. (2007), Retention of inorganic arsenic by coryneform mutant strains. Water Research, 41 (3), 531-542.

Full Text: 2007\Wat Res41, 531.pdf

Abstract: The natural resistance mechanisms of corynebacteria to respond to the environments containing high levels of arsenic were successfully adopted to develop inexpensive and selective extractants for submicrogram amounts of arsenic. Kinetic and equilibrium characteristics were evaluated, and a preliminary exploration of the capability of these strains to be used for arsenic speciation was also made in this work. Three kinetics models were used to fit the experimental data. It was found that the pseudo-first-order kinetics model was not quite adequate to describe the retention process, while the intraparticle diffusion and the pseudo-second-order kinetics models provide the best fits. The equilibrium isotherm showed that the retention of arsenic was consistent with the Langmuir equation and that the Freundlich and Dubinin-Radushkevich models provided poorer fits to the experimental data. The maximum effective retention capacity for arsenic was about 15.4ng As/mg biomass. The amount of arsenic retained was directly measured in the biomass by forward planning a slurry electrothermal atomic absorption spectrometric procedure. (c) 2006 Elsevier Ltd. All rights reserved.

Keywords: Absorption, Adsorption, Antimonite, Arsenate, Arsenic, Arsenite, Bacterial-Cells, Biomass, Capacity, Corynebacteria, Diffusion, Electrothermal Atomic Absorption, Equilibrium, Escherichia-Coli, Exploration, Freundlich, Inorganic, Isotherm, Kinetics, Kinetics, Kinetics Model, Langmuir, Langmuir Equation, Levels, Made, Mechanisms, Mercury, Model, Models, Mutant Strains, Natural, Planning, Resistance, Retention, Retention Capacity, Selective, Slurry, Slurry Sampling, Sorption, Speciation, Spectrometry, Toxicity

? Murphy, V., Hughes, H. and McLoughlin, P. (2007), Cu(II) binding by dried biomass of red, green and brown macroalgae. Water Research,