Kinetics, equilibrium, and thermodynamic studies of sulphate adsorption from aqueous solution using activated carbon derived from rice straw

In this study, the possibility of sulphate adsorption from a synthetic solution containing sodium sulphate was investigated using activated carbon derived from rice straw by ZnCl2 activation. The structural and morphological characteristics of rice straw and activated carbon were evaluated applying SEM, FTIR, and EDS techniques. Influence of various parameters such as agitation time, pH, temperature, sulphate concentration and adsorbent dose at 5 levels was also studied. The highest uptake of sulphate ions was determined as 56.49 mg/g (1.8 mg/g compared to adsorption by raw straw). Adsorption kinetics and sulphate adsorption equilibrium behaviour were studied. It was found that the adsorption process follows second-order kinetics model and Langmuir isotherm fits well the equilibrium data Delta G(0) was found to be -3.208, -3.230,-3.317,-3.372,-3.427 and -3.482 KJ/mol at 20, 25, 30, 35, 40, and 45 degrees C, respectively Delta S-0 and Delta H-0 of the adsorption were 10.95 J/K/mol and 0.001076 KJ/mol, respectively. The results further show that the adsorption process was a spontaneous and endothermic reaction and the activated carbon derived from rice straw by ZnCl2 chemical activation can be considered as an effective adsorbent for sulphate adsorption from the aqueous solutions.