Yasemin Bulut

Removal of heavy metals from aqueous solution by sawdust adsorption

The adsorption of lead, cadmium and nicel from aqueous solution by sawdust of walnut was investigated. The effect of contact time, initial metal ion concentration and temperature on metal ions removal has been studied. The equilibrium time was found to be of the order of 60 min. Kinetics fit pseudo first-order, second-order and intraparticle diffusion models, hence adsorption rate constants were calculated. The adsorption data of metal ions at temperatures of 25, 45 and 60 degrees C have been described by the Freundlich and Langmuir isotherm models. The thermodynamic parameters such as energy, entropy and enthalpy changes for the adsorption of heavy metal ions have also been computed and discussed. Ion exchange is probably one of the major adsorption mechanisms for binding divalent metal ions to the walnut sawdust. The selectivity order of the adsorbent is Pb(II) approximately Cd(II)>Ni(II). From these results, it can be concluded that the sawdust of walnut could be a good adsorbent for the metal ions from aqueous solutions.

Equilibrium and thermodynamic studies on biosorption of Pb(II) onto Candida albicans biomass.

Biosorption of Pb(II) ions from aqueous solutions was studied in a batch system by using Candida albicans. The optimum conditions of biosorption were determined by investigating the initial metal ion concentration, contact time, temperature, biosorbent dose and pH. The extent of metal ion removed increased with increasing contact time, initial metal ion concentration and temperature. Biosorption equilibrium time was observed in 30min. The Freundlich and Langmuir adsorption models were used for the mathematical description of biosorption equilibrium and isotherm constants were also evaluated. The maximum biosorption capacity of Pb(II) on C. albicans was determined as 828.50+/-1.05, 831.26+/-1.30 and 833.33+/-1.12mgg(-1), respectively, at different temperatures (25, 35 and 45 degrees C). Biosorption showed pseudo second-order rate kinetics at different initial concentration of Pb(II) and different temperatures. The activation energy of the biosorption (Ea) was estimated as 59.04kJmol(-1) from Arrhenius equation. Using the equilibrium constant value obtained at different temperatures, the thermodynamic properties of the biosorption (DeltaG degrees , DeltaH degrees and DeltaS degrees ) were also determined. The results showed that biosorption of Pb(II) ions on C. albicans were endothermic and spontaneous. The optimum initial pH for Pb(II) was determined as pH 5.0. FTIR spectral analysis of Pb(II) adsorbed and unadsorbed C. albicans biomass was also discussed.

Adsorption of Methylene Blue from Aqueous Solution by Crosslinked Chitosan/Bentonite Composite

This article reports the application of a crosslinked chitosan/bentonite composite as adsorbent for the removal of a cationic dye, methylene blue (MB), from aqueous solution. Batch experiments were conducted to study the effects of contact time, initial concentration of adsorbate (50–200 mg L−1), temperature (298–313 K), agitation speed (90–150 rpm), and pH (2–10) on adsorption. The equilibrium experimental data were analyzed by the Freundlich and Langmuir models. The kinetic data obtained with different initial concentration and temperature were analyzed using a pseudo-first-order, pseudo-second-order, and intraparticle diffusion equations. Maximum adsorption capacity (Q m) was calculated at different temperatures (298, 308, and 313 K) as 95.24, 97.09, and 142.86 mg g−1, respectively. The results showed that this novel adsorbent had a high adsorption capacity, making it suitable for use in the treatment MB-enriched wastewater.

Removal of methylene blue from aqueous solutions onto Bacillus subtilis: determination of kinetic and equilibrium parameters

AbstractIn the present study, Bacillus subtilis, a Gram-positive bacteria, was used in dried biomass form as biosorbent for removal of methylene blue (MB) from aqueous solutions. Batch adsorption tests were performed at different contact times, temperatures, pH, adsorbent doses, and initial dye concentration. The adsorption isotherms are described by means of the Langmuir and Freundlich isotherms. It was found that the Langmuir equation fit better than the Freundlich equation. Maximum biosorption capacity was found to be 169.49, 178.57, and 181.82 mg g−1 at 298, 308, and 318 K, respectively. The adsorption kinetics of MB could be described by the pseudo-second-order reaction model. The activation energy of the biosorption (Ea) was determined as 11.30 kJ mol−1 at initial concentration of 50 mg L−1. Free energy of adsorption (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) changes were calculated to predict the nature of adsorption. The estimated values for ΔG° were −21.22, −22.02, and −23.01 kJ mol−1 at 298, 308, ...

Removal of Methylene Blue from Aqueous Solution by Crosslinked Chitosan-g-Poly(Acrylic Acid)/Bentonite Composite

A new crosslinked chitosan-g-poly (acrylic acid)/bentonite composite (CS-g-PAA/BT) was prepared and used for the removal of methylene blue (MB). CS-g-PAA/BT was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The water absorbency for CS-g-PAA/BT was found to be 93 and 50 g H2Og−1 in distilled water and 0.2% NaCl, respectively. The results showed that the adsorption of the MB on the CS-g-PAA/BT was effected by the initial dye concentration, the initial pH value, as well as the temperature. Both kinetics and thermodynamic parameters of the adsorption process were estimated. These data indicated an endothermic spontaneous adsorption process that kinetically followed the second-order adsorption process. Equilibrium experiments fitted well the Langmuir isotherm model, and the maximum monolayer adsorption capacity for the MB was 2000–2500 mg g−1 at 298–313 K. The results of this study implied that CS-g-PAA/BT can be used a promising adsorbent for the removal of MB from wastewater.

Adsorption of Ni(II) from aqueous solution by Bacillus subtilis

Abstract This work reports the application of Bacillus subtilis as adsorbent for the removal of Ni(II) from aqueous solution. Batch experiments were conducted to study the effects of several parameters such as, contact time, initial concentration of adsorbate (25–200 mg L−1), temperature (298–318 K), and adsorbent dose (0.05–0.4 g) on Ni(II) adsorption. Equilibrium adsorption isotherms and kinetics were also investigated. The equilibrium experimental data were analyzed by Freundlich and Langmuir models. The kinetic data obtained with different initial concentration and temperature were analyzed using a pseudo-first-order, pseudo-second-order, and intraparticle diffusion equations. The results showed that this novel adsorbent had a high adsorption capacity, making it suitable for use in the treatment of Ni(II)-enriched wastewater.