Personal Research Database

Full Text: W\Wat Res39, 630.pdf

Abstract: Fine powder adsorbents or catalysts often show better adsorptive or catalytic properties, but they encounter the difficulties of separation and recovery in application. In this study, four inexpensive magnetic powder MnO–Fe₂O₃ composites used as adsorbent–catalyst materials were prepared and characterized. These materials could be recovered efficiently by a magnetic separation method. Their adsorptive properties for the removal of an azo-dye, acid red B (ARB), from water and the regeneration of adsorbents containing ARB by catalytic combustion was studied. These powder adsorbents showed excellent adsorption towards ARB under acidic conditions. A very fast adsorption rate was observed and could be well described by a pseudo-second-order kinetics model. The adsorption capacity increased with increasing Fe content and surface area of the adsorbent, and the highest adsorption capacity of 105.3 mg/g was obtained at pH 3.5. The adsorption was not affected by the presence of Cl⁻, but was significantly affected by SO₄²⁻. The adsorbent containing ARB can be regenerated by catalytic combustion of adsorbed ARB at 400 °C in air. Laboratory experiments demonstrated that this material is reusable.

Keywords: MnO–Fe₂O₃ Composite, Adsorption, Catalytic Combustion, Acid Red B

Yan, W.L. and Bai, R. (2005), Adsorption of lead and humic acid on chitosan hydrogel beads. Water Research, 39 (4), 688-698.

Full Text: W\Wat Res39, 688.pdf

Abstract: Chitosan hydrogel beads were studied for the adsorption of lead ions and humic acid from aqueous solutions to examine the adsorption behaviors and mechanisms. The experiments were carried out at room temperature with solution pH ranging from 5 to 7.5 (in near neutral pH range). Three types of batch adsorption experiments, including single species adsorption, sequential adsorption of one species after another and co-adsorption of both species, were investigated. The results show that: (1) adsorption of either species mainly results from the complexations between adsorbate and functional groups at the surface of the hydrogel beads; (2) previously adsorbed species can either act as additional binding sites for, or occupy the same binding sites as the subsequent species to be adsorbed, resulting in enhanced or retarded adsorption of the subsequent species; and (3) for co-adsorption, metal-organic interactions play a very important role in determining the extent of adsorption. It is concluded that multi-species adsorption can be significantly affected by adsorbate interactions and the understanding of these interactions needs great attention in adsorption study in the future.

Keywords: Chitosan Hydrogel Beads, Adsorption, Lead, Humic Acid, Interactions

Petrus, R. and Warchoł, J.K. (2005), Heavy metal removal by clinoptilolite. An equilibrium study in multi-component systems. Water Research, 39 (5), 819-830.

Full Text: W\Wat Res39, 819.pdf

Abstract: Ternary and quaternary ion-exchange equilibria have been studied between heavy metal solution (Pb²⁺, Cd²⁺, Cu²⁺) and Na-form of clinoptilolite. The value of the ion-exchange equilibrium constant was estimated using the Langmuir, Competitive Langmuir, and thermodynamic sorption models. For each isotherm, calculations were done taking into account the concentration of ions in both phases. Additionally, for the thermodynamic isotherm, two other cases were considered: activity of ions in the liquid phase and concentration in the solid phase; activity of ions in both phases. The activity coefficients of ions in the liquid phase were determined using Pitzer’s model; activity coefficients in the solid phase were estimated by Wilson’s model. It was found that the exchange capacity for a given M²⁺ is not constant and differs in one- or multi-component systems. The results show that the equilibrium model based on the law of mass action, which considers nonideal behavior of both phases, allows one to achieve the best approach to the real multi-component equilibrium data in all studied systems.

Keywords: Clinoptilolite, Ion-Exchange, Heavy Metals Removal, Equilibrium Models, Sorption

Zhang, S.J., Yu, H.Q. and Zhao, Y. (2005), Kinetic modeling of the radiolytic degradation of Acid Orange 7 in aqueous solutions. Water Research, 39 (5), 839-846.

Full Text: W\Wat Res39, 839.pdf

Abstract: The degradation of Acid Orange 7 (AO7) in aqueous solutions induced by γ-ray irradiation was investigated in terms of both the disappearance of parent molecule (decoloration) and the degree of mineralization. The disappearance of AO7 followed pseudo first-order kinetics, whereas its mineralization could be described by zero-order kinetics. The pseudo first-order degradation rate constants were found to be proportional to irradiation dose rates and the reciprocals of initial AO7 concentrations. Based on the experimental results and a reaction analysis on the steady-state radiolysis of aerated aqueous solutions, a kinetic model was developed for describing the radiolytic degradation of AO7. Moreover, with this kinetic model, the reaction rate constants of e_aq⁻ and H· with AO7 were estimated as 3.0×10⁹ and 8.4×10⁹×L mol⁻¹ s⁻¹, respectively. Taking the relative contributions of oxidative and reductive species to AO7 degradation into account, oxidative radiolysis proved to be a better approach for the degradation of AO7.

Keywords: AO7, Degradation, Radiolysis, Kinetic, Modeling

Khraisheh, M.A.M., Al-Ghouti, M.A., Allen, S.J. and Ahmad, M.N. (2005), Effect of OH and silanol groups in the removal of dyes from aqueous solution using diatomite. Water Research, 39 (5), 922-932.

Full Text: W\Wat Res39, 922.pdf

Abstract: The removal of methylene blue, reactive black (C-NN), and reactive yellow (MI-2RN) from aqueous solution by calcined and raw diatomite at 980 °C was studied. These studies demonstrated the importance of the various functional groups on the mechanism of adsorption. The role of pore size distribution in the dye adsorption studies was also investigated. The adsorption isotherms were pH dependent. Henry and Freundlich adsorption isotherms were used to model the adsorption behavior and experimental results for all dyes used exhibited heterogeneous surface binding. The removal of the ionisable functional groups increased the pH_ZPC value from 5.4 to 7.7, while FTIR, SEM and XRD analysis showed a remarkable decrease of the characteristic Si–OH peaks after calcinations at 980 °C. The removal of hydroxyl groups from the surface of diatomite lead to a decrease in the adsorption. It was evident from pH and infrared spectra results that mechanisms of methylene blue and reactive yellow adsorption differed from that of reactive black. Accordingly, adsorption on the external surface by n–π interaction between the π system of the RB and the electron lone pairs of the oxygen atoms of siloxane group and columbic attraction between the dye and the surface of calcined diatomite was proposed as a possible adsorption mechanism.

Keywords: Diatomite, Calcined Diatomite, Adsorption, Reactive and Basic Dyes, Methylene Blue, Textile Wastewater

Amiri, F., Börnick, H. and Worch, E. (2005), Sorption of phenols onto sandy aquifer material: the effect of dissolved organic matter (DOM). Water Research, 39 (5), 933-941.

Full Text: W\Wat Res39, 933.pdf

Abstract: The influence of dissolved organic matter (DOM) on the sorption of four phenols, 2,4,6-trichlorophenol (2,4,6-TCP), pentachlorophenol (PCP), 2,4-dinitrophenol (2,4-DNP) and 2-methyl-4,6-dinitrophenol (2-M-4,6-DNP), onto sandy aquifer material at different pH values was investigated using flow through column experiments.

The pH-dependent sorption of the chlorinated phenols 2,4,6-TCP and PCP was not significantly affected by DOM (measured as dissolved organic carbon, DOC), whereas in the case of nitrophenols a significant lower retardation was found, depending on the DOC concentration and pH value of the aqueous solution. Sorption decreases with increasing DOC concentration, which indicates a binding of these compounds by DOM. The degree of sorption reduction depends on the pH value and increases with increasing fraction of neutral species. The different behaviour of nitrophenols in comparison to the chlorophenols is assumed to be a result of specific charge-transfer interactions.

A combined sorption and complex formation model was used to describe the effect of pH and DOC concentration on the sorption of nitrophenols onto aquifer material and to estimate binding coefficients of neutral nitrophenols on DOM.

Keywords: Sorption, Hydrophobic Ionic Organic Compounds (HIOCs), pH effEct, Dissolved Organic Matter (DOM), DOC, Complex Formation

? Logan, B.E., Murano, C., Scott, K., Gray, N.D. and Head, I.M. (2005), Electricity generation from cysteine in a microbial fuel cell. Water Research, 39 (5), 942-952.

Full Text: 2005\Wat Res39, 942.pdf

Abstract: In a microbial fuel cell (MFC), power can be generated from the oxidation of organic matter by bacteria at the anode, with reduction of oxygen at the cathode. Proton exchange membranes used in MFCs are permeable to oxygen, resulting in the diffusion of oxygen into the anode chamber. This could either lower power generation by obligate anaerobes or result in the loss in electron donor from aerobic respiration by facultative or other aerobic bacteria. In order to maintain anaerobic conditions in conventional anaerobic laboratory cultures, chemical oxygen scavengers such as cysteine are commonly used. It is shown here that cysteine can serve as a substrate for electricity generation by bacteria in a MFC. A two-chamber MFC containing a proton exchange membrane was inoculated with an anaerobic marine sediment. Over a period of a few weeks, electricity generation gradually increased to a maximum power density of 19 mW/m² (700 or 100 resistor; 385 mg/L of cysteine). Power output increased to 39 mW/m² when cysteine concentrations were increased up to 770 mg/L (493 resistor). The use of a more active cathode with Pt- or Pt–Ru, increased the maximum power from 19 to 33 mW/m² demonstrating that cathode efficiency limited power generation. Power was always immediately generated upon addition of fresh medium, but initial power levels consistently increased by ca. 30% during the first 24 h. Electron recovery as electricity was 14% based on complete cysteine oxidation, with an additional 14% (28% total) potentially lost to oxygen diffusion through the proton exchange membrane. 16S rRNA-based analysis of the biofilm on the anode of the MFC indicated that the predominant organisms were Shewanella spp. closely related to Shewanella affinis (37% of 16S rRNA gene sequences recovered in clone libraries).

Keywords: Bacteria, Biofuel Cell, Microbial Fuel Cell, Electricity, Power Output, Shewanella, Fuel Cell

Vaughan, Jr., R.L. and Reed, B.E. (2005), Modeling As(V) removal by a iron oxide impregnated activated carbon using the surface complexation approach. 39 (6), 1005-1014.

Full Text: W\Wat Res39, 1005.pdf

Abstract: The objective of this research was to model As(V) removal onto a iron oxide impregnated activated carbon (FeAC) using the surface complexation model (SCM) approach. As(V) removal by FeAC was due to the impregnated Fe oxide, not the base carbon material and was a strong function of pH. The two-monoprotic site-triple layer model adequately described As(V) removal using 2 fitting parameters compared with the 3 parameters needed for the diprotic site model. This, along with a better representation of the recognized As(V) removal mechanism (ligand exchange with −OH) as well as the acid–base behavior makes the two-monoprotic approach the better model for As(V) removal by the impregnated iron oxide although the diprotic model was able to describe the pH dependent removal of As(V). Both models were also able to predict As(V) removal at different adsorbent/adsorbate ratios using K_As determined from a single FeAC adsorption experiment. Thus, fewer adsorption experiments are required in order to model As(V) removal in equilibrium and column systems. The results described in this work will be used as a foundation in developing a dynamic model to predict As(V) adsorption in a fixed-bed adsorber.

Keywords: Arsenic, Modeling, Iron Oxide, Impregnated Carbon

Faghihian, H. and Bowman, R.S. (2005), Adsorption of chromate by clinoptilolite exchanged with various metal cations. Water Research, 39 (6), 1099-1104.

Full Text: W\Wat Res39, 1099.pdf

Abstract: Unmodified zeolite surfaces show no affinity for anions, due to the fact that zeolites are negatively charged. Thus, adsorption of anions by zeolites has not been given much attention. In this work, after modification of clinoptilolite by different cations, the mineral was found to adsorb a considerable amount of the divalent anion chromate. Chromate adsorption was proportional to the K_sp of the chromate precipitate and the amount of the exchangeable cation. The amount of chromate adsorbed was maximized when the Pb-exchanged form was used. Chromate desorption in deionized water indicated that between 2.50% and 18.60% of the adsorbed chromate was released depending upon the exchangeable cation. Some of the exchanged forms are candidate materials for adsorption and immobilization of chromate.

Keywords: Zeolites, Adsorption, Chromate

Lu, C., Chung, Y.L. and Chang, K.F. (2005), Adsorption of trihalomethanes from water with carbon nanotubes. Water Research, 39 (6), 1183-1189.

Full Text: W\Wat Res39, 1183.pdf

Abstract: Commercial carbon nanotubes (CNTs) were purified by acid solution and were employed as adsorbents to study adsorption of trihalomethanes (THMs) from water. The properties of CNTs such as purity, structure and nature of the surface were greatly improved after acid treatment which made CNTs become more hydrophilic and suitable for adsorption of low molecular weight and relatively polar THM molecules. The adsorption of THMs onto CNTs fluctuates very little in the pH range 3–7, but decreases with pH value as pH exceeds 7. A comparative study between CNTs and powdered activated carbon (PAC) for adsorption of THMs from water was also conducted. The short time needed to reach equilibrium as well as the high adsorption capacity of CHCl₃, which accounts for a significant portion of THMs in the chlorinated drinking water, suggests that CNTs possess highly potential applications for THMs removal from water.

Keywords: Carbon Nanotubes, Adsorption, Trihalomethanes, pH Effect, Powdered Activated Carbon

? Zhou, A.M., Tang, H.X. and Wang, D.S. (2005), Phosphorus adsorption on natural sediments: Modeling and effects of pH and sediment composition. Water Research, 39 (7), 1245-1254.

Full Text: W\Wat Res39, 1245.pdf

Abstract: The classic Langmuir isotherm equation was modified to describe phosphorus (P) adsorption on P-polluted sediments. The P adsorption characteristics of six sediment samples from Chinese Taihu Lake were studied by short-term isotherm batch experiments and related to sediment composition. The maximum P adsorption capacities (PAC) and P-binding energy constant (k) were obtained by nonlinearly fitting sorption data using the modified Langmuir isotherm model. Native adsorbed exchangeable phosphorus (NAP), the zero equilibrium P concentration value (EPC₀), and partitioning coefficients (K_p) were subsequently calculated by corresponding formulae. K_p and PAC were linearly related to the contents of active Fe and Al in sediments by least squares regression analyses (R²≈0.9 for both).

The effect of pH in a wide range on adsorption process was investigated and H₂PO₄⁻ was presumed to be the preferential sorption species in overall sorption process. The fact that the amount of P sorbed and zeta potential of sediment particles have no necessary relationship reveals that a strong contribution to the P binding still comes from a ligand-exchange process on the Me–OH₂⁺ and Me–OH sites rather than electrostatic attraction. In addition, the influence of oxidation–reduction potential (ORP) was investigated and discussed and the dual nature of sediments as a pool or source of P in natural waters was evaluated in site T1–T4.

Keywords: Adsorption, Model, Sediment, NAP, Preferential Sorption Species, Taihu Lake

? Kim, Y.H. and Nakano, Y. (2005), Adsorption mechanism of palladium by redox within condensed-tannin gel. Water Research, 39 (7), 1324-1330.

Full Text: W\Wat Res39, 1324.pdf

Abstract: Condensed-tannin gel particles with polyhydroxyphenyl groups were synthesized as the adsorbent for the new recovery system of palladium (Pd), which was simple and generated little secondary waste in comparison with the conventional recovery processes. The properties of condensed-tannin gel particles for the Pd adsorption were examined in PdCl₂ aqueous solution and it was found that Pd(II) was adsorbed onto the tannin gel particles as a reduced metallic Pd through redox reaction mechanism: chloropalladium(II) species were reduced to Pd(0), while hydroxyl groups of condensed-tannin gel were oxidized during the adsorption. Additionally, it was observed that Pd(II) species containing fewer Cl, such as PdCl₂(H₂O)₂ and PdCl(H₂O)₃⁺, were more favorable for the adsorption than PdCl₃(H₂O)⁻ and PdCl₄²⁻. By utilizing such characteristics of tannin gel particles, it is expected that they can be applied to recover Pd efficiently and simply with low cost.

Keywords: Tannin, Gel, Palladium, Chloropalladium(II), Recovery, Redox

? Chen, J.S., Zhang, J.D., Xian, Y.Z., Ying, X.Y., Liu, M.C. and Jin, L.T. (2005), Preparation and application of TiO₂ photocatalytic sensor for chemical oxygen demand determination in water research. Water Research, 39 (7), 1340-1346.

Full Text: W\Wat Res39, 1340.pdf

Abstract: In this work, a TiO₂ photocatalytic sensor was prepared and utilized into flow injection analysis (FIA) for chemical oxygen demand (COD) determination. With a positive bias potential of 0.4 V (vs. Ag/AgCl) applied to the sensor and a 12-W quartz UV lamp illuminating it, photocurrent, due to the charge transfer at the interface of TiO₂ sensor and the passing solution, was recorded and its change (ΔI_Photo) caused by the detected sample was calculated to characterize the COD value of the sample. Under the optimizing conditions, the sensor responded linearly to the COD of d-glucose solution in the range of 0.5–235 mg/L, with a linear correlation coefficient of 0.9998. Its application in artificial wastewater analysis has achieved results in good agreement with those from the conventional dichromate method; meanwhile, the process requires no hypertoxic reagents and less analysis time, suggesting that it would be another appropriate method for COD determination in water assessment.

Keywords: Photocatalytic Sensor, Chemical Oxygen Demand (COD), Titanium Dioxide (TiO₂), Flow Injection Analysis (FIA)

? Tanthapanichakoon, W., Ariyadejwanich, P., Japthong, P., Nakagawa, K., Mukai, S.R. and Tamon, H. (2005), Adsorption–desorption characteristics of phenol and reactive dyes from aqueous solution on mesoporous activated carbon prepared from waste tires. Water Research, 39 (7), 1347-1353.

Full Text: W\Wat Res39, 1347.pdf

Abstract: Liquid-phase adsorption–desorption characteristics and ethanol regeneration efficiency of an activated carbon prepared from waste tires and a commercial activated carbon were investigated. Water vapor adsorption experiments reveal that both activated carbons showed hydrophobic surface characteristics. Adsorption experiments reveal that the prepared activated carbon possessed comparable phenol adsorption capacity as the commercial one but clearly larger adsorption capacity of two reactive dyes, Black 5 and Red 31. It was ascertained that the prepared activated carbon exhibited less irreversible adsorption of phenol and the two dyes than its commercial counterpart. Moreover, ethanol regeneration efficiency of the prepared AC saturated with either dye was higher than that of the commercial AC. Because of its superior liquid-phase adsorption–desorption characteristics as well as higher ethanol regeneration efficiency, the prepared activated carbon is more suitable for wastewater treatment, especially for adsorbing similarly bulky adsorbates.

Keywords: Activated Carbon, Waste Tires, Adsorption, Desorption, Ethanol Regeneration, Porosity

? Athanasiadis, K. and Helmreich, B. (2005), Influence of chemical conditioning on the ion exchange capacity and on kinetic of zinc uptake by clinoptilolite. Water Research, 39 (8), 1527-1532.

Full Text: 2005\Wat Res39, 1527.pdf

Abstract: Aim of this study was to evaluate the feasibility of the use of clinoptilolite as a barrier material to eliminate heavy metals from roof runoff. The effect of chemical conditioning with 1 M NaCl solution upon the ion exchange capacity and on kinetic of zinc uptake by clinoptilolite has been investigated. According to the batch experiments the modified clinoptilolite has up to 100% higher sorption capacity, regarding Zn than the natural material. The pre-treatment of clinoptilolite results in an acceleration of the ion exchange process up to 40% regarding zinc. In order to define the reasons of this behaviour, both materials, modified and natural, were analysed for: (i) chemical composition, (ii) density, (iii) pore size distribution and (iv) zeta potential. The clogging of the pores, the charge of the grain surface, the pH of the initial metal solution and the ion metal concentration are the factors which are mainly affecting the ion exchange capacity and the rate of zinc uptake by clinoptilolite. (c) 2005 Elsevier Ltd. All rights reserved.

Keywords: Capacity, Clinoptilolite, Feasibility, Heavy Metals, Ion Exchange, Ion Exchange Capacity, Lead, Metal, Metals, Modified, Natural, pH, Pore Size Distribution, Removal, Roof Runoff, Runoff, Sorption, Uptake, Zeolites, Zeta Potential

? Pagnanelli, F., Mainelli, S., De Angelis, S. and Toro, L. (2005), Biosorption of protons and heavy metals onto olive pomace: Modelling of competition effects. Water Research, 39 (8), 1639-1651.

Full Text: W\Wat Res39, 1639.pdf

Abstract: Heavy metal biosorption onto solid wastes from olive oil production plants, olive pomace, has been investigated. Acid–base properties of the active sites of olive pomace were determined by potentiometric titrations and represented by a continuous model accounting for two main kinds of active sites. Competition among protons and heavy metals in solution was considered by performing biosorption tests at different equilibrium pH with single (Cu and Cd) and binary metal systems (Cu–Cd). Both Langmuir extensions and non-ideal competitive adsorption models (NICA models) can be used to represent experimental data of Cu and Cd biosorption in single metal systems at different equilibrium pH. Nevertheless only NICA models, accounting for site heterogeneity and non-ideal adsorption of the different species simultaneously present in solution, can adequately simulate the competition among Cu and Cd in binary metal systems by using the parameters fitted to single system data.

Keywords: Biosorption, Heavy Metals, Olive Pomace, Equilibrium Modeling, Binary Systems

? Quinlivan, P.A., Li, L. and Knappe, D.R.U. (2005), Effects of activated carbon characteristics on the simultaneous adsorption of aqueous organic micropollutants and natural organic matter. Water Research,