Adsorption studies of Cr+6 onto low- cost apple juice industry waste from aqueous solution: Equilibrium, kinetics and thermodynamics

The potential use of apple pomace (AP) for the removal of Cr+6 ions from aqueous solution has been investigated under optimized conditions. The adsorption influencing parameters such as dose, pH, time and concentrations have been optimized. Langmuir, Freundlich and Temkin follow the adsorption data with r(2) = 0.99, 0.94 and 0.99, q(max) has been found to be 7.89, 8.94 and 1.49 mg/g, respectively. Langmuir isotherm data is further supported with R-(L)over dot value from 0.658 to. 0.088 from concentration range of 10-200 mg/L. The rate determining data follow pseudo-second order kinetics (r(2)=0.99-1) for removal of Cr+6 using AP. The value of Delta G degrees (-7668.6 to -8917.6 J/mol), Delta H degrees (3.503 KJ/mol/K) and Delta S degrees (22.95 J/mol) show that the adsorption process is found to be spontaneous, endothermic and increase in randomness during adsorption process is observed. One of the interesting aspects of adsorption study is reutilization of adsorbent in multiple cycles; AP show removal efficiency 78% of Cr+6 upto seven cycles. It reduces the operation cost and enhances the industrial application for the removal of the chromium from aqueous solution.