Search

In this study, single and competitive sorption of Pb(II), Cd(II), Cu(II), and Ni(II) ions onto vermiculite were studied. Preliminary examination revealed that vermiculite possesses low bulk density (279kg/m3), a high cation exchange capacity (41.3meq/100g), water holding capacity (62.5%), and air-filled porosity (5.8%). The pH edge experiments indicated that the uptake capacity of vermiculite improved with enhancement in pH and highest value was detected at pH 5. Fourier transform IR spectroscopy along with scanning electron microscopy and energy dispersive X-ray spectroscopy confirmed changes in the sorbent functionality after metal sorption, and the results were in agreement with metal removal studies. It was observed by isotherm experiments that vermiculite was capable of sorbing 0.238, 0.099, 0.199 and 0.115mmol/g of Pb(II), Cd(II), Cu(II) and Ni(II), respectively, according to the Langmuir model. The reaction was rapid and the kinetic experimental data were successfully modelled using the pseudo-first order model. Quaternary biosorption experimental results revealed that severe competition exists between metal ions during the sorption onto vermiculite surface and it was inferred that the total metal uptake was distributed among four elements. � 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An eco-friendly and inexpensive technique for wastewater treatment originated from inductively coupled plasma-optical emission spectrometry (ICP-OES) is presented within this paper. The proposed process comprised of loading waste crab shells in packed column for adsorption of heavy metal ions, followed by desorption using 0.01 M HCl. An exhaustive physical and chemical characterization of ICP-OES wastewater revealed the complex nature of effluent, including the presence of 15 different metals and metalloid under strong acidic condition (pH 1.3). Based on the preliminary batch experiments, it was identified that solution pH played a major role in metal sequestration by crab shell with pH 3.5 identified as optimum pH. Rapid metal biosorption kinetics along with complete desorption and subsequent reuse for three cycles was possible with crab shell-based treatment process. Continuous flow-through column experiments confirmed the high performance of crab shell towards multiple metal ions with the column able to operate for 22 h at a flow rate of 10 mL/min before outlet concentration of arsenic reached 0.25 times of its inlet concentration. Other metal ions such as Cu, Cd, Co, Cr, Pb, Ni, Zn, Mn, Al, and Fe were only in trace levels in the treated water until 22 h. The performance of the treatment process was compared with trade effluent discharge standards, and the process flow diagram along with cost analysis was suggested.

The ability of green algal biomass of Ulva sp. to biosorb Cr(III) and Mn(II) from single- and binary- solute systems was investigated. Experimental results showed that pH 4.5 resulted in highest metal uptake by Ulva sp. biomass. Determined levels of maximum biosorption capacities were 2.89 and 1.07 mmol g−1 for Cr(III) and Mn(II), respectively, during single-solute systems. Isotherms were modeled using the Langmuir, Freundlich, and Redlich-Peterson models with the later able to describe the biosorption isotherms with high correlation coefficients and low % error values. The removal kinetics were described using pseudo -first and -second order models. Desorption was possible using 0.01 M HCl and with this elutant, Ulva sp. biomass was reused for three cycles of sorption-desorption. Experiments with binary metal solutions showed that Ulva sp. biomass preferred Cr(III) (2.03 mmol g−1) compared to Mn(II) (0.34 mmol g−1) at pH 4.5. Binary isotherms were described using the extended Langmuir, Freundlich, and Redlich-Peterson models incorporated with interaction factor. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 147–153, 2014

Biodegradation of naphthalene by Micrococcus sp., isolated from the effluent of an activated sludge plant, was studied. The effects of pH (5–8), glucose concentration (100–1000 mg/L) and inoculum concentrations (1–5%) on the growth and naphthalene degradation potential of Micrococcus sp. were investigated. Maximum naphthalene degradation and subsequent high microbial growth were observed at optimum pH (pH 7), glucose concentration (500 mg/L) and inoculum concentration (3%). To investigate the maximum naphthalene tolerance potential of Micrococcus sp., very high concentrations of naphthalene (500–5000 mg/L) were used in the presence of non-ionic surfactants. The examined surfactants (Triton X-100 and Tween-80) increased the bioavailability of naphthalene to the microbes and Complete naphthalene degradation by Micrococcus sp. was observed at an initial naphthalene concentration of 500 mg/L. However, the degradation potential decreases as the naphthalene concentration increases. Very high naphthalene concentrations also affected the growth of microbes and the corresponding substrate inhibition kinetics was described using four models (Haldane, Webb, Edward and Aiba). Based on correlation coefficient and percentage error values, all four substrate kinetic models were able to describe the dynamic behavior of naphthalene biodegradation by Micrococcus sp.

A marine brown alga, Sargassum polycystum, showed high-chromium biosorption capacity in batch and column mode of operation. The biosorbent performance was strongly influenced by equilibrium solution pH, with pH 2 as optimal condition for Cr biosorption. Isotherm experiments revealed that S. polycystum possessed a maximum chromium uptake of 69.4 mg/g at pH 2. The pseudo-second order model was found to describe the chromium kinetic biosorption data with high-correlation coefficients compared with pseudo-first order model. Various thermodynamic parameters, such as ΔG°, ΔH°, and ΔS°, were calculated, indicating that the present system was a spontaneous and endothermic process. A packed column was used to study the continuous chromium biosorption performance of S. polycystum. The biosorbent performance was evaluated at different bed heights (15–25 cm) and flow rates (5–15 mL/min). Favorable conditions for Cr biosorption were observed at the highest bed height (25 cm) and lowest flow rate (5 mL/min); at which the Cr uptake and percent removal were recorded as 29.1 mg/g and 63.3%, respectively. Mathematical modeling of column experimental data was performed, using nonlinear forms of the Thomas and modified-dose-response models; with the latter able to describe the breakthrough curves with high-correlation coefficients. © 2010 American Institute of Chemical Engineers Environ Prog, 2010

The biosorption of basic dyes, rhodamine B (RMB) and methylene blue (MB), using Azolla filiculoides was investigated in a batch reactor and in a fixed-bed column. Biosorption isotherms revealed that pH 5 was the optimum condition for maximum biosorption of both basic dyes. Sorption isotherm data were fitted with Langmuir, Freundlich, Redlich–Peterson and Sips models. A maximum uptake of 166.7 and 91.8 mg/g was observed for MB and RMB, respectively, according to the Langmuir model. It was observed from the kinetic data that the biosorption process using A. filiculoides followed pseudo-second order kinetics. The ability of A. filiculoides to biosorb MB in a packed column was investigated, as well. Experiments conducted at different bed heights (15–25 cm) revealed that decrease in bed height resulted in inferior biosorption performance. At 25 cm, the A. filiculoides bed was capable of providing breakthrough at 76.2 h, with column uptake and removal efficiency of 80.2 mg/g and 84.9%, respectively. The Thomas model was successfully used to analyze the experimental data and the model parameters were evaluated. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd.

The present work investigated the biosorption of nickel from synthetic and electroplating industrial effluents using a green marine algae Ulva reticulata. Preliminary batch results imply that pH 4.5 was optimum for nickel uptake and the isotherm experiments conducted at this pH condition indicated that U. reticulata can biosorb 62.3 mg g -1 nickel ions from synthetic solutions, according to the Langmuir model. Desorption was effective and practical using 0.1 M CaCl 2 (pH 2.5, HCl) and the biomass was regenerated and reused for three cycles. Continuous biosorption experiments were performed in an upflow packed column (2 cm I.D and 35 cm height). Among the two electroplating effluents used, effluent-1 is characterized by excess co-ions and high nickel ion content. This influenced the column nickel uptake with U. reticulata exhibiting 52.1 mg g -1 in the case of effluent-1 compared to 56.5 mg g -1 in the case of synthetic solution. On the other hand U. reticulata performed well in effluent-2 with uptakes of 53.3 and 54.3 mg g -1 for effluent-2 and synthetic solution, respectively. Mathematical modeling of column experimental data was performed using nonlinear forms of the Thomas- and modified dose-response models, with the latter able to simulate breakthrough curves with high correlation coefficients.

Procion Blue H-B (PBHB) was used as a model reactive dye for biosorption studies onto inactive/dead mycelial biomass of Panus fulvus. Process parameters like pH, contact time and temperature were optimized. pH 2, 150min of contact time and 35 ◦ C were found to be more favorable for maximum biosorption. Various two- and three-parameter isotherms were employed to understand the biosorption process. Among the various two-parameter isothermal models applied, the Langmuir isotherm showed the best fit and among the three- parameter isothermal models, the Khan, Redlich-Peterson, Sips and Toth isotherm models showed similar fits and only the Koble-Corrigan model showed a poor fit. In kinetic studies, pseudo-first-order model fitted better than pseudo-second-order model. Maximum desorption was observed in alkaline pH, which reveals the possibility of a chemisorption mechanism involved in the removal of PBHB. Among the various desorption media assessed, 70% (v/v) acetone showed complete desorption of the sorbate from the sorbent. Scanning electron microscopy images revealed the non-fibrous nature of the adsorbent. FT-IR studies showed the existence of amine groups in the sorbent which are the major adsorbent sites for reactive dyes.  2007 Society of Chemical Industry

An electrolytic process based on chlorine generation was adopted to treat wastewater containing textile dyes. In situ production of hypochlorous acid was achieved in an undivided electrolytic cell. The cell contained a graphite rod as the anode and a stainless steel sheet as the cathode. The generated chlorine reacts with water leading to the formation of hypochlorous acid and hydrochloric acid. The resultant hypochlorous acid, being an oxidising agent, oxidises the organic components present in the textile wastewater. In this study, the colour in wastewater containing Procion Navy and Procion Red dyes, was completely removed after 40 min of electrolysis at a constant current density of 39 mA/cm 2 (where the initial dye concentrations were 3700 and 3200 mg/l, respectively). In the case of the Procion Yellow and composite dyes, complete colour removal occurred after 50 min of electrolysis (with initial dye concentrations of 3500 mg/l). Even though colour removal occurred during the electrolysis process, it required up to 180 min of electrolysis to reduce the chemical oxygen demand values for the four dyes (Procion Navy, Red, Yellow and the composite) from the initial levels of 4520, 4200, 4170 and 4283 mg/l to 70, 45, 39 and 52 mg/l, respectively. This clearly indicates that the process removes both colour and organic components present in textile wastewater.

Ionic liquids (ILs) are low-melting organic salts that are being researched intensively as possible environmentally friendly replacements for volatile organic solvents. Despite their nonmeasurable vapor pressure, some quantities of ILs soon will be present in effluent discharges because solubility of ILs in water is small, but far from negligible. Therefore, it is important to understand how ILs will influence aquatic ecosystems. In the present study, the toxic effects of imidazolium-based ILs (1-butyl-3-methylimidazolium cation associated with bromide [BMIM] [Br] and tetrafluoroborate [BMIM] [BF4]) to the freshwater green alga Selenastrum capricornutum were investigated. Two approaches were followed to quantify toxicity of these compounds: Analyses of photosynthetic activity and cell proliferation. The obtained data showed that the relative declines of growth rates generally were more pronounced than those of photosynthetic activity. The ecotoxicity of a range of common organic solvents also was examined. It was revealed that both imidazolium-based ILs studied were some orders of magnitude more toxic than methanol, isopropanol, and dimethylformamide. In addition, with respect to IL incorporating perfluorinated anion, EC50 values (concentrations which lead to a 50% reduction of the exposed organisms relative to control) of the previously prepared stock solution were significantly lower compared to those of the freshly made one. This might be due to hydrolytic effects of [BMIM][BF4] leading to fluoride formation, which was confirmed by ion chromatography analysis. This indicates that, after ILs are discharged into the aqueous system, they can become more toxic than expected by laboratory data with fresh ILs.