Physical Chemistry

Dodecyltrimethylammonium bromide-modified bentonite (DTMA–bentonite) was prepared and tested as an adsorbent for an acid dye (Acid Blue 193, AB193) removal from aqueous solution in comparison with Na–bentonite. The effect of various experimental parameters was ...

The adsorption of nitrate ions onto clay minerals has not been given much attention, possibly because clay surfaces are negatively charged. In order to increase the positive charge on the surface, sepiolite was modified in the present studies by treatment with dodecylethyldimethylammonium (DEDMA) bromide. After such modification, it was found that the maximum amount of nitrate ion adsorbed occurred at a pH value of 2.0.The chemical composition of natural sepiolite was determined by EDX methods and surface characterization of both natural and modified sepiolite samples was undertaken using FT-IR spectroscopic techniques. The adsorption of nitrate ions onto these adsorbents was determined by ion chromatography. The kinetic parameters of the adsorption process were calculated and it was shown that the reaction kinetic data could be fitted using the pseudo-second-order rate model. The calculated results indicate that both natural and surfactant-modified sepiolite are effective sorbents ...

Equilibrium, kinetics and thermodynamic studies on the removal of Acid Red 57 (AR57) by biosorption onto dried Cephalosporium aphidicola (C. aphidicola) cells have been investigated in a batch system with respect to pH, contact time and temperature. The ...

Biosorption of lead(II) onto Cephalosporium aphidicola was examined and the effects of pH, contact time, biosorbent and lead(II) concentrations and temperature on biosorption were investigated. The nature of the possible cell and metal ion interactions was examined by ...

Neurospora crassa (the common pink bread mould) is a filamentous ascomycete19 and its cell wall consists of randomly disposed skeletal microfibrils of chitin, an amorphous matrix of β-glucans and protein containing a high percentage of the amides of aspartic and glutamic acid. A ...

Polypyrrole (PPy) and overoxidized polypyrrole (OPPy) films were used as a potentiometric detector in ion chromatography, in order to determine some anions and cations in water samples. Electrodeposition of PPy film was performed by constant potential at +0.80 V (vs. Ag/AgCl) in an aqueous solution containing 0.1 M pyrrole and 0.2 M sodium nitrate. The overoxidation of PPy film was carried out in 0.1 M NaOH solution by cycling the potential between +0.80 and +1.20 V at 50 mV s −1. The PPy film exhibited good sensitivity toward, especially, fluoride and chloride ions. The lowest detection limit (3σ) observed was 10 −8 M for fluoride with PPy detector. This is the first study using OPPy electrode for the potentiometric detection of both monovalent and divalent cations in literature. The correlation coefficients obtained from the calibration curves were 0.947-0.991 for anions and 0.998-0.999 for cations. The response of ions at the PPy and OPPy electrodes maintained over 90-94% of the original value for 45 and 30 days, respectively. It can be concluded from the observed data that these electrodes can be used as an alternative detector materials to analyse anions and cations in the water samples by ion chromatography.

Biosorption of lead(II) ions onto Phaseolus vulgaris L. waste was investigated with the variation in the parameters of pH, contact time, biosorbent and lead(II) concentrations and temperatures. The nature of the possible biosorbent and metal ion interactions was examined by the FTIR technique. The lead(II) biosorption equilibrium was attained within 20 min. Biosorption of lead(II) ions onto P. vulgaris L. waste followed by the Langmuir and Dubinin-Radushkevich isotherm models. Maximum biosorption capacity (q max) of biosorbent for lead(II) ions was 2.064×10 !4 mol g !1 or 42.77 mg g !1 at 20EC. Thermodynamic parameters such as the changes of free energy, enthalpy and entropy were also evaluated for the biosorption of lead(II) ions onto P. vulgaris L. waste. It was indicated that the biosorption of lead(II) ions onto P. vulgaris L. waste is a spontaneous endothermic process.

In the present study a low-cost waste biomass derived from canned food plant, was tested for its ability to remove reactive textile dye from aqueous solutions. The batch biosorption experiments were carried out at various pH, biosorbent dosage, contact time and temperature. Optimum decolorization was observed at pH 2.0 and 1.6 g dm − 3 of biomass dosage within 20 min. The first-order and the pseudo-second-order kinetics were investigated for the biosorption system. The applicability of the Langmuir and Freundlich isotherm models was examined. The thermodynamic parameters for the biosorption were also calculated. The experimental results in this study indicated that this low-cost biomaterial was an attractive candidate for the removal of textile dye Reactive Red 198 (RR198) from aqueous solutions.

Adsorption of copper ions onto Capsicum annuum (red pepper) seeds was investigated with the variation in the parameters of pH, contact time, adsorbent and copper(II) concentrations and temperature. The nature of the possible adsorbent and metal ion interactions was examined by the FTIR technique. The copper(II) adsorption equilibrium was attained within 60min. Adsorption of copper(II) ions onto C. annuum seeds

Biosorption of lead(II) onto Cephalosporium aphidicola was examined and the effects of pH, contact time, biosorbent and lead(II) concentrations and temperature on biosorption were investigated. The nature of the possible cell and metal ion interactions was examined by the FTIR technique. The lead(II) biosorption was fast and equilibrium was attained within 30min. It was found that the overall biosorption process

Biosorption of Acid Red 57 (AR57) on to Neurospora crassa was studied with variation of pH, contact time, biosorbent and dye concentrations and temperature to determine equilibrium and kinetic models. The AR57 biosorption was fast and equilibrium was attained within 40 min. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models were applied to experimental equilibrium data for AR57 biosorption at various temperatures. The equilibrium data fitted very well to all the equilibrium models in the studied concentration range of AR57. Maximum biosorption capacity (q max) of AR57 on to N. crassa was 2.16 × 10 −4 mol g −1 at 20 • C. The kinetics of biosorption of AR57 were analyzed and rate constants were derived. The overall biosorption process was best described by a pseudo-second-order kinetic model. The changes in Gibbs free energy, enthalpy and entropy of biosorption were also evaluated for the biosorption of AR57 on to N. crassa. The results indicate that the biosorption was spontaneous and exothermic in nature.

The adsorption of Acid Red 57 (AR57) onto calcined-alunite was examined in aqueous solution in a batch system with respect to contact time, pH and temperature. The first-order, pseudo-second-order kinetic and the intraparticle diffusion models were used to describe the kinetic data and the rate constants were evaluated. The experimental data fitted very well the pseudo-second-order kinetic model and also

The adsorption of Acid Red 57 (AR57) onto surfactant-modified sepiolite was investigated in aqueous solution in a batch system with respect to contact time, pH and temperature. The surface modification of surfactant-modified sepiolite was controlled using the FTIR technique. The pseudo-first-order, pseudo-second-order kinetic models and the intraparticle diffusion model were used to describe the kinetic data and the rate constants were evaluated. The experimental data fitted very well the pseudo-second-order kinetic model and also followed the intraparticle diffusion model up to 90 min, whereas diffusion is not only the rate controlling step. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were also determined. The Freundlich model agrees with experimental data well. The activation energy, change of free energy, enthalpy and entropy of adsorption were also evaluated for the adsorption of AR57 onto surfactant-modified sepiolite. The results indicate that surfactant-modified sepiolite could be employed as low-cost material for the removal of textile dyes from effluents.

The utilization of modified bentonite with a cationic surfactant (dodecyltrimethylammonium (DTMA) bromide) as an adsorbent was successfully carried out to remove a synthetic textile dye (Reactive Blue 19 (RB19)) by adsorption, from aqueous solutions. Batch studies were carried out to address various experimental parameters such as pH, contact time and temperature. The surface modification of bentonite with a surfactant was examined using the FTIR spectroscopic technique and elemental analysis. Effective pH for the adsorption of RB19 onto DTMA-bentonite was around 1.5. The Langmuir isotherm model was found to be the best to represent the equilibrium with experimental data. The maximum adsorption capacity (q max) has been found to be 3.30 × 10 −4 mol g −1 or 206.58 mg g −1. The thermodynamic study indicated that the adsorption of RB19 onto DTMA-bentonite was favored with the negative Gibbs free energy values. The pseudo-second-order rate equation was able to provide the best description of adsorption kinetics and the intraparticle diffusion model was also applicable up to 40 min for the adsorption of RB19 onto DTMA-bentonite.

Lead(II), copper(II) and many of other heavy metals cause to the environmental pollution, which is one of the major environmental problems in many countries. Several traditional techniques such as oxidation or reduction, solvent extraction, evaporation, ion exchange, filtration, reverse osmosis, related to the removal of heavy metals are available, but these techniques are very expensive and ineffective. One of the alternative methods of metal/heavy metals removal may be the adsorption process, which is lower cost and more feasible. The widely used adsorbent in the adsorption studies is activated carbon, which is a high surface area and high adsorption capacity towards to many of pollutants, but it shows disadvantages of high operating costs and problems with regeneration. This led to a search directed at developing low cost and locally available adsorbing materials such as clay minerals including montmorillonite, bentonite, sepiolite and smectite. For this respect, sepiolite is cho...