A comprehensive study (kinetic, thermodynamic and equilibrium) of arsenic (V) adsorption using KMnO4 modified clinoptilolite

The sorption of As(V) on manganese oxide coated zeolite (MOCZ) was investigated through batch study to explore the feasibility of removing arsenic from groundwater. MOCZ was characterized by scanning electron microscopy, XRD, FTIR spectroscopy, and point of zero charge (pH PZC ) measurements. The effects of process parameters such as contact time, adsorbent size, temperature and pH were investigated. Arsenic detection was carried out by atomic fluorescence spectrometer. Arsenate adsorption onto MOCZ followed the pseudo-second-order kinetic model with a correlation coefficient more than 0.99. Optimum removal of arsenate occurred within pH range of 6–10. The equilibrium data were analyzed by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. The maximum adsorption capacity calculated from the Langmuir and D-R models was 151 and 152.8 μg g−1, respectively, at 38 °C. The activation energy of adsorption (E a ) was found to be 3.68 kj mol−1, suggesting that the adsorption process may be physical sorption. Thermodynamic parameters: ΔH o , was 1.181 kj mol−1; ΔS o , was −0.29 kj mol−1, while the values of ΔG o were −83.9, −86.7 and 89.8 kj mol−1 at 18, 28 and 38, respectively, suggesting endothermic and spontaneous process and a rise in temperature favoring the adsorption