A. Safa Özcan

Adsorption of acid dyes from aqueous solutions onto acid-activated bentonite

The adsorption of two dyes, namely, Acid Red 57 (AR57) and Acid Blue 294 (AB294), onto acid-activated bentonite in aqueous solution was studied in a batch system with respect to contact time, pH, and temperature. Acidic pH was favorable for the adsorption of these dyes. The surface characterization of acid-activated bentonite was performed using the FTIR technique. The pseudo-first-order and pseudo-second-order kinetic models and the intraparticle diffusion model were used to describe the kinetic data and the rate constants were evaluated. The dynamic data fitted the pseudo-second-order kinetic model well and also followed the intraparticle diffusion model up to 90 min, but diffusion is not the only rate controlling step. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were determined. The Freundlich model agrees very well with experimental data. The activation energies of adsorption were also evaluated for the adsorption of AR57 and AB294 onto activated bentonite.

Adsorption of Acid Red 57 from aqueous solutions onto surfactant-modified sepiolite

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.

Adsorption of Acid Blue 193 from aqueous solutions onto DEDMA-sepiolite.

The adsorption of Acid Blue 193 (AB193) onto dodecylethyldimethylammonium (DEDMA)-sepiolite was investigated in aqueous solution in a batch system with respect to contact time, pH and temperature. The surface modification of DEDMA-sepiolite was examined by the FT-IR 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 with the pseudo-second-order kinetic model and also followed the simple external diffusion model up to initial 10 min and then by intraparticle diffusion model up to 75 min, whereas diffusion is not only the rate-controlling step. The adsorption capacities of natural sepiolite and DEDMA-sepiolite at pH 1.5 and 20 degrees C were (1.19 and 2.57) x 10(-4) mol g(-1), respectively. The above results indicate that DEDMA-sepiolite has around two times higher adsorption capacity than natural sepiolite. 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 Gibbs free energy, enthalpy and entropy of adsorption were also evaluated for the adsorption of AB193 onto DEDMA-sepiolite.

Adsorption of lead(II) ions onto 8-hydroxy quinoline-immobilized bentonite.

In this study, the immobilization of 8-hydroxy quinoline onto bentonite was carried out and it was then used to investigate the adsorption behavior of lead(II) ions from aqueous solutions. The changes of the parameters of pH, contact time, initial lead(II) ions concentration and temperature were tested in the adsorption experiments. The XRD, FTIR, elemental and thermal analyses were done to observe the immobilization of 8-hydroxy quinoline onto natural bentonite. The adsorption was well described by the Langmuir adsorption isotherm model at all studied temperatures. The maximum adsorption capacity was 142.94mgg(-1) from the Langmuir isotherm model at 50 degrees C. The thermodynamic parameters implied that the adsorption process is spontaneous and endothermic. The kinetic data indicate that the adsorption fits well with the pseudo-second-order kinetic model. 8-Hydroxy quinoline-immobilized bentonite can be used as well respective adsorbent for the removal of the heavy metal pollutants according to the results.

Adsorption of Acid Dyes from Aqueous Solutions onto Sepiolite

Abstract This research deals with an investigation of the adsorption of two acid dyes, namely Acid Red 57 (AR57) and Acid Blue 294 (AB294) onto sepiolite. Batch kinetics and isotherm studies were carried out. The results indicate that the adsorption of acid dyes obeys Freundlich isotherm and the second‐order kinetics model. In addition, the effectiveness of sepiolite on adsorption of AR57 and AB294 from aqueous solution was studied as a function of time, pH, and temperature. Thermodynamic parameters for the adsorption of dyes were calculated and are discussed. The maximum removals of acid dyes was observed around 90% and 75% at pH = 2 for AR57 and AB294, respectively.

Characterization of Punica granatum L. peels and quantitatively determination of its biosorption behavior towards lead(II) ions and Acid Blue 40.

In this study, a waste biomass of Punica granatum L. (P. granatum L.) peels was firstly characterized by means of Brunauer-Emmett-Teller (BET) surface area, elemental analysis, FT-IR, thermogravimetric (TG) analysis and zeta potential measurement techniques. FT-IR results indicated that the mechanism involved in the biosorption of lead(II) ions and AB40 onto biosorbent was mainly attributed to lead(II) ions and dye binding of amino, carboxylic, hydroxyl and carbonyl groups. The biosorption abilities of P. granatum L. peels for lead(II) ions and Acid Blue 40 (AB40) were then investigated. Biosorption equilibrium and kinetic data fit well by the Langmuir isotherm and the pseudo-second-order kinetic models, respectively. The maximum biosorption capacities were 193.9 mg g(-1) for lead(II) ions and 138.1 mg g(-1) for AB40. Biosorption processes were spontaneous and endothermic in nature according to the thermodynamic results and the equilibrium was attained within 50 min. The validity of used kinetic models in this study can be quantitatively checked by using a normalized standard deviation Δq(%). Finally, the biosorption procedure was adopted to treat the real and simulated wastewaters including several metal salts and dyes. The wastewater applications have shown that the biosorbent indicated a reasonable biosorption capability to remove lead(II) ions (98.07%) and AB40 (94.76%) from industrial wastewaters.

Utilization of the Phaseolus vulgaris L. Waste biomass for decolorization of the textile dye Acid Red 57: determination of equilibrium, kinetic and thermodynamic parameters.

In the present study, biosorption of Acid Red 57 (AR57) onto a waste biomass of Phaseolus vulgaris L. was investigated by varying pH, contact time, biosorbent concentration and temperature, to determine the equilibrium, thermodynamic and kinetic parameters. The AR57 biosorption was fast, and equilibrium was attained within 20 min. Biosorption equilibrium data fit the Langmuir isotherm model well with high correlation coefficients. According to Langmuir isotherm model the maximum biosorption capacity of Phaseolus vulgaris L. for AR57 dye was determined as 4.09 × 10− 4 mol g− 1 or 215.13 mg g− 1 at 20°C. The thermodynamic parameters (Gibbs free energy, enthalpy and entropy) for the biosorption of AR57 were indicated that the biosorption was spontaneous and exothermic in nature. The pseudo-second-order kinetic model agrees well with the dynamic behavior of the biosorption of AR57 onto P. vulgaris L., under various temperatures. The removal efficiency of the biomass was also examined in real textile wastewater.

Adsorption Potential of Lead(II) Ions from Aqueous Solutions onto Capsicum annuum Seeds

Abstract The purpose of this work was to evaluate the adsorption potential of Capsicum annuum seeds, in a batch system for the removal of lead(II) ions from aqueous solutions. The experimental results showed that this agricultural by‐product was effective in removing lead(II) ions. The FT‐IR analysis indicated that the mechanism involved in adsorption of lead(II) ions by seeds of C. annuum was mainly attributed to lead(II) binding of amino and hydroxyl groups. Adsorption equilibrium approached within 40 min. The adsorption data fitted well to the Langmuir isotherm model. The maximum adsorption capacity (q max) was 1.87×10−4 mol g−1. Pseudo‐second‐order kinetic model was applicable to all the adsorption data over the entire time range. The thermodynamic parameters indicated that the adsorption process is spontaneous since Gibbs free energy values are negative, which are between −26.92 and −30.77 kJ mol−1 at the temperature range of 20–50°C.

Adsorption of Acid Yellow 99 onto DEDMA-sepiolite from aqueous solutions

The adsorption of Acid Yellow 99 (AY99) onto dodecylethyldimethylammonium (DEDMA)-sepiolite was investigated in aqueous solution in a batch system with respect to pH, contact time and temperature. The surface modification of DEDMA-sepiolite was examined by the FTIR technique. The experimental data fitted very well with the pseudo-second-order kinetic model with the correlation coefficients above 0.985. The Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption isotherm models agree well with experimental data. The Langmuir-isotherm constant (KL) was used to evaluate the thermodynamic parameters for the adsorption of AY99 onto DEDMA-sepiolite.

Capacity of activated carbon derived from peach stones by K2CO3 in the removal of acid, reactive, and direct dyes from aqueous solution.

The present research deals with the production of activated carbon by chemical activation using peach stones and its adsorption behavior. The prepared activated carbon was used for the adsorption of three kinds of textile dyes, acid, reactive, and direct dyes, from aqueous solution. The results indicated that the overall adsorption process followed the pseudo-second-order kinetic model. The equilibrium data were found to be well represented by the Langmuir adsorption isotherm model. The calculated adsorption capacities for Reactive Orange 16, Acid Yellow 11, and Direct Red 23 onto activated carbon were 667, 539, and 427 mg g−1 at 50°C , respectively. Thermodynamic parameters, such as ΔG° , ΔH° , and ΔS° , were also calculated and indicated that the adsorption of dyes onto activated carbon was spontaneous and endothermic in nature.