Equilibrium, thermodynamic and kinetic study for potassium permanganate adsorption by Neem leaves powder

Zinc chloride (ZnCl 2 ) was used for modification of the adsorptive properties of Neem leaves powder. Fourier-transforms infrared spectroscopy, and Brunauer-Emmett-Teller surface analyzer were applied to investigate the physical and chemical properties of the prepared sample. It was found that the surface area, density, average pore width, pore volume and pH ZPC of the modified adsorbent are 58.6 m 2 g -1 , 0.7 g cc -1 , 13.8 , 0.106 cm 3 g -1 and 6.8, respectively. Adsorption of potassium permanganate (KMnO 4 ) by this adsorbent was also examined. The effects of pH, adsorbate initial concentration, time and temperature were also investigated. The real experimental conditions were observed to be pH of 7, KMnO 4 concentration of 1,000 mg L -1 , 120 min contact time and temperature of 55C. Kinetic experimental data in the case of diluted and concentrated solutions were described well by the kinetic models of second-order and first-order. Langmuir, Freundlich, and Temkin isotherm models were applied. It was observed that the model of Langmuir was the best for describing the equilibrium data. 775.19, 925.93, and 1,066.79 mg g -1 was the adsorption capacities at 25C, 40C, and 55C, respectively. Thermodynamic parameters designate that the adsorption obtained in this research is an endothermic and spontaneous process.