Removal of Leishman stain from aqueous solutions using natural clay of Qulapalk area of Kurdistan region of Iraq

Abstract

Clay sample of Qulapalk – Sulaimani of Kurdistan region of Iraq was analyzed for its chemical composition and mineralogy. Calcite (a non-clay mineral) was a major constituent of the sample (34%). The main clay mineral was smectite as depicted by X-ray diffraction patterns of the oriented slides. Adsorption of Leishman stain from aqueous solution onto the natural clay sample was studied in batch system. The effect of operational conditions like initial pH, adsorbent dose, contact time and temperature were studied. The pseudo second order kinetic model fitted well in correlation to the experimental results. The rate of the adsorption process was found to follow the pseudo second-order kinetics, which was found to be increased with the increase of temperature. The activation parameters Ea, ΔH∗ and ΔS∗ were found to be 37.94 kJ mol−1, 35.34 kJ mol−1 and 148.02 J mol−1 K−1 respectively. The sorption isotherm fitted to both Freundlich and Langmuir isotherm models. High adsorption capacity was recorded for the current natural clay (455.37 mg/g) toward methylene blue. Equilibrium thermodynamic parameters ΔH°, ΔS° and ΔG° indicated that the adsorption processes was spontaneous and endothermic in nature.