Iron recovery from acid mine drainage sludge as Fenton source for municipal wastewater treatment

Abstract

ABSTRACT Iron recovered from acid mine drainage (AMD) waters effluent and introduced as an advanced oxidation processes (AOPs) source, namely, Fenton reagent (FR) for municipal wastewater (MWW) treatment. Acid mine drainage-based Fenton reagent’s (AMD-FR) experiments were carried out in a lab-scale facility and various operating parameters such as reaction time, solution pH, AMD as the iron source dose and H2O2 concentration were investigated. Box–Behnken design was applied to optimise the multiple variables and a mathematical model was developed with a high correlation coefficient (R2 = 96%). The maximum Chemical Oxygen Demand (COD) removal reached 73% within 30 min of reaction time. Optimum AMD sludge introduced to the system was 41 mg/L and H2O2 of 398 mg/L at the optimum operating pH 2.7. Kinetic study of AMD-FR revealed that COD removal followed the second-order reaction kinetic model. Thermodynamic analysis of the results with positive values of enthalpy (∆H`) suggested the endothermic nature of the reaction. Positive Gibbs free energy of activation (∆G`) and negative entropy of activation (∆S`) values verified the non-spontaneous nature of the oxidation reaction with a low energy of activation barrier (55.59 kJmol−1).