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In 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−1at 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−1at 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−1at 298, 308, and 318 K, respectively. The enthalpy changes and entropy of adsorption were 5.47 kJ mol−1and 89.43 Jmol−1, respectively. The experimental data obtained in the present study indicate that B. subtilisis a suitable and inexpensive adsorbent which can be used for dye removal in wastewater treatment processes.

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−1at 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−1at 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−1at 298, 308, and 318 K, respectively. The enthalpy changes and entropy of adsorption were 5.47 kJ mol−1and 89.43 Jmol−1, respectively. The experimental data obtained in the present study indicate that B. subtilisis a suitable and inexpensive adsorbent which can be used for dye removal in wastewater treatment processes.

The antimicrobial activity of the ethanol extract of resins obtained from the roots and stems of Cedrus libaniand Abies ciliciahas been studied, using the disc diffusion method. The results obtained indicate that crude extracts of the resins of both plants are highly efficient in preventing the growth of microorganisms.