Treatment of dairy wastewater by commercial activated carbon and bagasse fly ash: Parametric, kinetic and equilibrium modelling, disposal studies

Present study reports treatment of synthetic dairy wastewater (SDW) in terms of chemical oxygen demand (COD) removal by means of adsorption onto activated carbon-commercial grade (ACC) and bagasse fly ash (BFA). Optimum conditions for SDW treatment were found to be: initial pH ≈ 4.8, adsorbent dose of 20 g/l for ACC and 10 g/l for BFA and contact time ≈8 h. Pseudo-second-order kinetic model was found to fit the kinetic data and Redlich–Peterson isotherm model was generally found to best represent the equilibrium data for SDW treatment by ACC and BFA. The change in entropy and enthalpy for SDW adsorption onto ACC and BFA were estimated as 125.85 kJ/mol K and 91.53 kJ/mol; and 25.71 kJ/mol K and 17.26 kJ/mol, respectively. The negative values of change in Gibbs free energy indicate the feasibility and spontaneous nature of the adsorptive treatment.