Personal Research Database

Full Text: W\Wat Res38, 1586.pdf

Abstract: This paper reports a study into the deployment of a metal adsorbent in situ to estimate bioavailable Cd(II) in marine waters. Eight adsorbents were screened in the laboratory to test their ability to accumulate Cd(II) from deionised water and artificial seawater, and an oxidised activated carbon was selected for further investigation. The adsorption isotherm at Cd(II) concentrations 0.16–38 g l^-1 and at salinity 15 followed the Freundlich equation. The adsorbent was contained in nylon bags (pore size 35 m) and dialysis tubes (membrane pore size 2 nm) to produce deployable devices and to investigate the effect of housing material on Cd(II) accumulation. The devices were tested in the laboratory and deployed at four field sites for up to 3 weeks. The adsorbent in the nylon bags reached equilibrium towards the end of this period and the measured contents were in good agreement with expected contents predicted from known seawater Cd(II) concentrations and the adsorption isotherm. The dialysis tubes accumulated significantly lower amounts of Cd(II) than the nylon bags, probably due to an initial lag as Cd(II) diffused into the dialysis bag and due to biofouling which reduced diffusion. The relationship between concentrations of Cd(II) accumulated by the mussels (indicating the bioavailable Cd(II) fraction) and the devices at different field sites could be described by the Freundlich model. The goodness of fit of this relationship was better for the dialysis tubes than the nylon bags. The adsorbent in the nylon bags may have collected small particles from seawater which affected the Cd(II) analysis. Both devices demonstrate potential as indicators of the relative bioavailable fraction of Cd(II) to Mytilus edulis in marine waters.

Keywords: Bioaccumulation, Cd(II), Carbon, Mytilus Edulis, Adsorbent

Nakagawa, K., Namba, A., Mukai, S.R., Tamon, H., Ariyadejwanich, P. and Tanthapanichakoon, W. (2004), Adsorption of phenol and reactive dye from aqueous solution on activated carbons derived from solid wastes. Water Research, 38 (7), 1791-1798.

Full Text: W\Wat Res38, 1791.pdf

Abstract: Activated carbons were produced from several solid wastes, namely, waste PET, waste tires, refuse derived fuel and wastes generated during lactic acid fermentation from garbage. Activated carbons having various pore size distributions were obtained by the conventional steam-activation method and via the pre-treatment method (i.e., mixture of raw materials with a metal salt, carbonization and acid treatment prior to steam-activation) that was proposed by the authors. The liquid-phase adsorption characteristics of organic compounds from aqueous solution on the activated carbons were determined to confirm the applicability of these carbons, where phenol and a reactive dye, Black5, were employed as representative adsorbates. The hydrophobic surface of the carbons prepared was also confirmed by water vapor adsorption. The characteristics of a typical commercial activated carbon were also measured and compared. It was found that the activated carbons with plentiful mesopores prepared from PET and waste tires had quite high adsorption capacity for large molecules. Therefore they are useful for wastewater treatment, especially, for removal of bulky adsorbates.

Keywords: Adsorption, Activated Carbon, Activation, Mesopores, Pore Size Distribution, Solid Wastes, Liquid-Phase Adsorption

Perić, J., Trgo, M. and Vukojević Medvidović, N. (2004), Removal of zinc, copper and lead by natural zeolite: A comparison of adsorption isotherms. Water Research, 38 (7), 1893-1899.

Full Text: W\Wat Res38, 1893.pdf

Abstract: An uptake of zinc (Zn), copper (Cu), and lead (Pb) from aqueous solutions by ion exchange on natural zeolitic tuff has been studied. The Croatian zeolite clinoptilolite from the Donje Jesenje deposit has been used as a natural ion exchanger. The efficiency of removal is higher for Pb and Cu than for Zn ions. Measured concentrations of Si in the liquid phase identify the detachment of the aluminosilicate structure during ion exchange in the presence of H⁺ and OH^- ions. The adsorption isotherm equations; Langmuir–Freundlich, Redlich–Petersen, Toth, Dubinin–Radushkevich, modified Dubinin–Radushkevich, and Lineweawer–Burk were derived from the basic empirical equations, and used for calculation of ion exchange parameters. The best fitting of experimental results to the proposed isotherms was observed in models that assume that ionic species bind first at energetically most favorable sites, with multi-layer adsorption taking place subsequently.

Keywords: Zinc, Copper, Lead, Natural Zeolite, Adsorption Models

? Werker, A.G. and Hall, E.R. (2004), Development and application of a quasi-static Langmuir isotherm for modelling selected resin acid fate in pulp mill wastewater treatment. Water Research, 38 (8), 1995-2008.

Full Text: W\Wat Res38, 1995.pdf

Abstract: Resin acids are pulp mill effluent contaminants that exhibit significant solubility, diffusivity, and surfactancy changes with pH within the range typically used for biological treatment. Such physical-chemical property changes which can influence removal during biological wastewater treatment, can be characterized by dynamic surface tension measurements. Dynamic surface tension measurements were made by the maximum bubble pressure method during batch treatment of selected resin acids in pulp mill effluent. Interpretation of dynamic surface tension data was made through the framework of a quasi-static Langmuir isotherm model that was derived as part of this investigation. The results suggested that under acidic conditions, resin acids form associations with other dissolved organic matter contained in pulp mill effluent, while under alkaline conditions, they behave as relatively soluble surfactants. A resin acid residuum, or threshold concentration, has been found to increase under acidic growth conditions. This residuum increase corresponded to an inferred reduction in resin acid bioavailability that was suggested from the isotherm modelling. The development of quasi-static isotherm adsorption models has application in computer simulation for design of adsorption based unit processes, and could potentially be utilized as an informative treatment process monitor. (C) 2004 Elsevier Ltd. All rights reserved.

Keywords: Adsorption Kinetics, Langmuir Isotherm, Contaminant Fate, Dynamic Surface Tension, Maximum Bubble Pressure, Wastewater Treatment, Dynamic Surface-Tension, Bubble Pressure Method, Biological Treatment, Dehydroabietic Acid, Effluent, Detoxification, Mechanisms, Parameters, Kinetics, Removal

Faria, P.C.C., Órfão, J.J.M. and Pereira, M.F.R. (2004), Adsorption of anionic and cationic dyes on activated carbons with different surface chemistries. Water Research, 38 (8), 2043-2052.

Full Text: W\Wat Res38, 2043.pdf

Abstract: The influence of the surface chemical groups of an activated carbon on the removal of different classes of dyes is evaluated. Starting from the same material (NORIT GAC 1240 PLUS), the following treatments were carried out in order to produce a series of samples with different surface chemical properties but with no major differences in their textural properties: oxidation in the liquid phase with 6 M HNO₃ and 10 M H₂O₂ (acid materials) and heat treatment at 700°C in H₂ or N₂ flow (basic materials). The specific micropores volume and mesopores surface area of the materials were obtained from N₂ adsorption equilibrium isotherms at 77 K. The surface chemistry was characterised by temperature programmed desorption, by the determination of the point of zero charge (pH_pzc) and by the evaluation of the acidity/basicity of the samples. Elemental and proximate analyses were also carried out.

Equilibrium isotherms of selected dyes (an acid, a basic and a reactive dye) on the mentioned samples were obtained and the results discussed in relation to their surface chemistry. In general, the Langmuir model provided the best fit for the adsorption data.

It is shown that the surface chemistry of the activated carbon plays a key role in dye adsorption performance. The basic sample obtained by thermal treatment under H₂ flow at 700°C is the best material for the adsorption of all the tested dyes.

Keywords: Activated Carbon, Surface Chemistry, Wastewater, Decolourisation, Dyes, Adsorption

Ladeira, A.C.Q. and Ciminelli, V.S.T. (2004), Adsorption and desorption of arsenic on an oxisol and its constituents. Water Research, 38 (8), 2087-2094.

Full Text: W\Wat Res38, 2087.pdf

Abstract: The present work investigates the adsorption and mobility (desorption) of As(III) and As(V) on an oxisol, and its main mineral constituents, as part of a broader project aimed at selecting a soil liner to be used in tailings dams at a sulfidic gold ore plant. Emphasis was given to a quantitative comparison of As mobility––here assessed by the amount of As leached from the loaded samples––under different experimental conditions. From among the soil constituents, goethite was the most efficient adsorbent with regard to arsenic adsorption, 12.4 mg g^-1 for As(V) and 7.5 mg g^-1 for As(III), respectively. Gibbsite also presented a relevant adsorption capacity (4.6 mg g^-1 for As(V) and 3.3 mg g^-1 for As(III)); adsorption on kaolinite was negligible (<0.23 mg g^-1 for As(V) and As(III)). Desorption of the arsenic was shown to vary largely with the arsenic oxidation state, the adsorbents and the leaching solutions. While only 1–2% max. of As(V) was released from the loaded samples, leaching the A(III) reached 32%, the highest values corresponding to the solutions containing sulfate ions. Oxisol and goethite were superior to gibbsite with respect to As immobilization. Adsorption and mobility were also discussed with the help of electrophoretic mobility and isoelectric points (IEP) determined prior and following arsenic adsorption on goethite and gibbsite. The results indicated that As(V) is mainly adsorbed as an inner sphere complex. As(III) may be adsorbed as an inner or an outer neutral complex.

Keywords: Arsenic Mobility, Oxisol, Adsorption, Desorp

Basar, C.A., Karagunduz, A., Cakici, A. and Keskinler, B. (2004), Removal of surfactants by powdered activated carbon and microfiltration. Water Research, 38 (8), 2117-2124.

Full Text: W\Wat Res38, 2117.pdf

Abstract: Direct and indirect releases of large quantities of surfactants to the environment may result in serious health and environmental problems. Therefore, surfactants should be removed from water before release to the environment or delivery for public use. Using powdered activated carbon (PAC) as adsorbent and separating particles with a membrane may be an effective technique to remove surfactants. In this study, the removal of surfactants by microfiltration and PAC was investigated and the influences of the operating parameters on the effectiveness on microfiltration were determined. An anionic (LABS) and a cationic surfactant (CTAB) were selected for the experiments. A series of batch experiments were performed to determine the sorption isotherms of surfactants to PAC. Then microfiltration experiments were carried out. The results showed that formation of secondary membrane on the surface and, within the pores of the membrane, increased the retention of surfactants significantly. Increase in transmembrane pressure and pore size of the membrane decreased the rejection rates, but increase in cross-flow velocity increased the rejection rate. Temperature had no apparent affect on the efficiency of surfactant removal. Presence of electrolyte had different effects on CTAB and LABS. The rejection rates of CTAB significantly increased when the concentration of NaCl increased; however, a slight decrease was observed in the rejection rate of LABS at the same conditions.

Keywords: Powdered Activated Carbon, Surfactant, Membrane, Microfiltration

Hanzlík, J., Jehlička, J., Šebek, O. Weishauptová, Z. and Machovič, V. (2004), Multi-component adsorption of Ag(I), Cd(II) and Cu(II) by natural carbonaceous materials. Water Research, 38 (8), 2178-2184.

Full Text: W\Wat Res38, 2178.pdf

Abstract: Adsorption of silver, cadmium and copper from aqueous solutions by natural carbonaceous materials was investigated. The studied series of natural materials (spruce wood, pine bark, cork, peat, fusinite, lignite, oxidised lignite, bituminous coal and anthracite) was extended to include industrial carbon-rich materials: coke, activated carbon F-400 and Multisorb™100. Adsorption was tested on a single-component system and on the binary and ternary mixtures. All the materials used differ in their ability to adsorb selected metals. The adsorption of metals is significantly affected by the presence of other ions in solution. Total metal uptake was considerably higher in a mixture than single-ion adsorption. Chemical reactions, such as precipitation and reduction of metallic silver, play a role in metal uptake by bituminous coal, coke and activated carbon.

Keywords: Activated Carbon, Adsorption, Aqueous-Solution, Cadmium, Cadmium, Coal, Competitive Adsorption, Copper, Copper, Equilibrium, Ions, Lignite, Metal-Cations, Natural Materials, Peat, Removal, Silver, Sorption, Wood

? Jensen-Spaulding, A., Cabral, K., Shuler, M.L. and Lion, L.W. (2004), Predicting the rate and extent of cadmium and copper desorption from soils in the presence of bacterial extracellular polymer. Water Research, 38 (9), 2231-2240.

Full Text: 2004\Wat Res38, 2231.pdf

Abstract: The movement of cationic transition metals through the subsurface is strongly retarded by sorption to the porous media. However, dissolved organic ligands can compete with soil surfaces by providing binding sites for metals in solution. An extracellular polymer produced by a bacterium isolated from soil was used in this study to observe and model the influence of a naturally occurring ligand on the release of adsorbed metals from two test soils. Experimental results show that the presence of dissolved extracellular polymer enhanced the rate and extent of desorptive release of soil-bound cadmium and copper. A kinetic model that uses a gamma distribution of rate constants to account for the physical and chemical heterogeneity of the soil matrix was employed to describe the release of cadmium and copper in batch experiments. Model parameters describing soil, metal and extracellular polymer interactions were obtained through separate experiments. With these parameters the model successfully predicted the influence of dissolved polymer on the rate and extent of release of cadmium and copper from soil in independent batch experiments. These results suggest that the presence of natural metal-binding ligands such as bacterial extracellular polymers can act to increase the driving force for desorption by lowering the aqueous concentration of free unbound metals in solution. (C) 2004 Elsevier Ltd. All rights reserved.

Keywords: Aquifer Material, Bacteria, Cadmium, Contaminated Soils, Copper, Desorption, Desorption Kinetics, Dissolved Organic-Matter, Driving, Extracellular Polymer, Gamma Distribution, Heavy-Metals, Lead, Metal, Metals, Microbial Polymers, Model, Movement, Natural, Phenanthrene, Porous-Media, Soil, Sorption, Transport, Water

Zheng, S.K., Yang, Z.F., Jo, D.H. and Park, Y.H. (2004), Removal of chlorophenols from groundwater by chitosan sorption. Water Research, 38 (9), 2314-2321.

Full Text: W\Wat Res38, 2314.pdf

Abstract: The equilibrium and kinetics of chlorophenol (CP) sorption by chitosan, poly D-glucosamine, were studied under simulated groundwater conditions. Lower temperature, from 25°C to 15°C and then 5°C, markedly decreased the adsorption rates by a factor of 30–53% and 7–22%. Comparison between two types of chitosan, flakes and highly swollen beads, demonstrated that the maximum pentachlorophenol (PCP) uptake capacities in Langmuir and Freundlich models depend on the specific surface area of the particle. Low temperature (5°C) significantly increased the PCP uptake capacity in comparison to higher temperatures (15°C and 25°C). PCP uptake capacity was halved at pH levels higher than 6.5, and NaCl concentrations greater than 1% blocked PCP sorption almost completely. Of five kinds of chlorophenols, i.e. 2,4,6-trichlorophenol (2,4,6-TCP), 3,4-dichlorophenol (3,4-DCP), 2,3-dichlorophenol (2,3-DCP), 2,6-dichlorophenol (2,6-DCP), 3-monochlorophenol (3-MCP), TCP had the maximum sorption efficiency on flake-type chitosan, followed by DCPs, and finally MCP (the three kinds of DCP, with the same elemental compositions, achieved similar sorption performances).

Keywords: Chlorophenol, Chitosan, Sorption, Groundwater, Salinity, Low–Temperature

Deng, S.B. and Bai, R.B. (2004), Removal of trivalent and hexavalent chromium with aminated polyacrylonitrile fibers: Performance and mechanisms. Water Research, 38 (9), 2423-2431.

Full Text: W\Wat Res38, 2423.pdf

Abstract: Aminated polyacrylonitrile fibers (APANFs) were prepared and used as an adsorbent in a series of batch adsorption experiments for the removal of Cr(III) and Cr(VI) species from aqueous solutions of different pH values. The results show that significant amounts of Cr(III) or Cr(VI) species can be adsorbed by the APANFs, although the adsorption performances was greatly dependent upon the solution pH values. In general, the amounts of adsorption for Cr(III) species increased whereas that for Cr(VI) decreased with the increase of the solution pH values, which suggests that different adsorption mechanisms dominated the removal of Cr(III) or Cr(VI) species on the APANFs. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy revealed that the adsorption of Cr(III) species on the APANFs was largely attributed to the formation of surface complexes between the nitrogen atoms on the APANFs and the Cr(III) species adsorbed, but the adsorption of Cr(VI) species on the APANFs was more likely effected through the formation of hydrogen bonds at high solution pH values or through both electrostatic attraction and surface complexation at low solution pH values. It was found that the Cr(VI)-adsorbed APANFs can be effectively regenerated in a basic solution and be reused almost without any loss of the adsorption capacity, while the Cr(III)-adsorbed APANFs needed to be regenerated in an acidic solution and the regeneration appeared to be less effective.

Keywords: Aminated Polyacrylonitrile Fibers (APANFs), Chromium Adsorption, FTIR and XPS Analyses, Adsorption Mechanisms, Surface Interactions

? Jeon, B.H., Dempsey, B.A., Burgos, W.D., Royer, R.A. and Roden, E.E. (2004), Modeling the sorption kinetics of divalent metal ions to hematite. Water Research, 38 (10), 2499-2504.

Full Text: W\Wat Res38, 2499.pdf

Abstract: The sorption kinetics of the divalent metals Zn, Co, Ni, and Cd to hematite were studied in single sorbate systems with high sorbate/sorbent ratios (from 1.67 to 3.33 mol sorbate/mol sorption sites) in 10 mM Na-piperazine N,N’-bis 2-ethane sulfonic acid (Na-PIPES) solution at pH 6.8. The experimental data showed a rapid initial sorption (half-time about 1 min) followed by slower sorption that continued for 1–5 days. The sequence of fast to slow sorption kinetics was modeled by slow inner-sphere (IS) complexation in equilibrium with outer-sphere (OS) complexes. Although the OS reaction was fast and considered to be in equilibrium, the extent of OS complexation changed over time due to increased surface potential from the IS complexes. For example, the model showed that the dimensionless OS complexation function, Kos, decreased from 0.014 initially to 0.0016 at steady state due to sorption of 4×10⁻⁵ M Zn(II) to 2 g L⁻¹ hematite. Sorption rate constants, kads, for the various divalent metals ranged from 6.1 to 82.5 M⁻¹ s⁻¹. Desorption rate constants, kdes, ranged from 5.2×10⁻⁷ to 6.7×10⁻⁵ s⁻¹. This study suggests that the conversion from OS to IS complex was the rate-determining step for the sorption of divalent metals on crystalline adsorbents.

Keywords: Divalent Metal Ions, Hematite; Slow Sorption Kinetics, Modeling

? Huang, Y.H. and Zhang, T.C. (2004), Effects of low pH on nitrate reduction by iron powder. Water Research, 38 (11), 2631-2642.

Full Text: 2004\Wat Res38, 2631.pdf

Abstract: The effect of low pH (2-4.5) on nitrate reduction in an iron/nitrate/water system was investigated through batch experiments conducted in a pH-stat. The results showed that nitrate could be rapidly reduced to ammonium at pH 24.5. A black coating, consisted of both Fe(II) and Fe(III), was formed on the surface of iron grains as an iron corrosion product. X-ray diffractometry indicated that the black coating was poorly crystalline, and its spectrum could not be matched with commonly known iron oxides/hydroxides/oxide hydroxides or green rust I/II. The black coating does not inhibit the reactivity of Fe-0 (at least at pH < 3). The black coating was unstable and evolved with time into other oxides under certain conditions. A kinetic model incorporating the effects of pH on nitrate reduction and Langrymuir adsorption of nitrate was proposed, and the parameters were estimated by nonlinear curve fitting. Based on this model, the two major effects of pH on the kinetics of nitrate reduction are that: (a) H+ ions directly participate in the redox reaction of nitrate reduction following first-order kinetics; and (b) H+ ions affect the nitrate adsorption onto reactive sites. (C) 2004 Elsevier Ltd. All rights reserved.

Keywords: Adsorption, Corrosion, I, II, Ions, Iron, Iron Corrosion, Iron Oxides, Kinetics, Kinetics, Metal, Model, Nitrate, Oxide, pH, Redox, Water, Zero-Valent Iron, Zerovalent Iron

Zhou, D., Zhang, L.N., Zhou, J.P. and Guo, S.L. (2004), Cellulose/chitin beads for adsorption of heavy metals in aqueous solution. Water Research, 38 (11), 2643-2650.

Full Text: W\Wat Res38, 2643.pdf

Abstract: We successfully prepared the biodegradable cellulose/chitin beads by coagulating a blend of cellulose and chitin in 6 wt% NaOH/5 wt% thiourea aqueous solution with 5 % H₂SO₄ as coagulant, and investigated the adsorption of heavy metals (Pb²⁺, Cd²⁺, Cu²⁺) from an aqueous solution on the beads by atomic absorption spectrophotometer. Batch adsorption experiments were carried out as a function of ion concentrations, initial pH, ionic strength, temperature, 21 adsorption time and desorption time. The results revealed that the cellulose/chitin beads could adsorb effectively Pb Cd²⁺ and Cu²⁺ ions, and the uptakes of Pb²⁺ Cd²⁺ and ions on cellulose/chitin beads were 0.33 mmol/g at pH(0) 4 0.32 mmol/g at pH(0) 5 and 0.30 mmol/g at pH(0) 4, respectively. Experimental results also showed that the adsorption of these heavy metals was selective to be in the order of Pb²⁺ > Cd²⁺ > Cu²⁺ in a low ion concentration solution. The adsorption equilibrium time of these heavy metals on beads was 4-5 h, but the desorption time was 5-15 min. Moreover, these beads could be regenerated up to about 98% by treating with 1 mol/L HCl aqueous solution. The mechanisms for the removal of free heavy metal ions by cellulose/chitin beads was based on mainly complexation adsorption model, as well as a affinity of hydroxyl groups of the materials on metals. Therefore, we developed new environment-friendly beads prepared by a simple produce process for removal and recovery of heavy metals. (C) 2004 Elsevier Ltd. All rights reserved.

Keywords: Cellulose/Chitin Bead, Adsorption, Heavy Metal, Removal, Chitin, Biosorption, Ions, Chitosan, Biomass, Lead, Equilibrium, Copper(II), Membrane

Nakajima, A. and Baba, Y. (2004), Mechanism of hexavalent chromium adsorption by persimmon tannin gel. Water Research,