Environmental Remediation Potential of Ferrous Sulfate Waste as an Eco-Friendly Coagulant for the Removal of NH3-N and COD from the Rubber Processing Effluent

The present study was conducted to determine the potential of utilizing the FeSO₄·7H₂O waste from the titanium manufacturing industry as an effective coagulant for treating industrial effluent. In this study, the secondary rubber processing effluent (SRPE) was treated using ferrous sulfate (FeSO₄·7H₂O) waste from the titanium oxide manufacturing industry. The FeSO₄·7H₂O waste coagulation efficiency was evaluated on the elimination of ammoniacal nitrogen (NH₃-N) and chemical oxygen demand (COD) from SRPE. The central composite design (CCD) of experiments was employed to design the coagulation experiments with varying coagulation time, coagulant doses, and temperature. The coagulation experiments were optimized on the optimal elimination of NH₃-N and COD using response surface methodology (RSM). Results showed that coagulant doses and temperature significantly influenced NH₃-N and COD elimination from SRPE. The highest NH₃-N and COD removal obtained were 98.19% and 93.86%, respectively, at the optimized coagulation experimental conditions of coagulation time 70 min, coagulant doses 900 mg/L, and temperature 62 °C. The residual NH₃-N and COD in treated SPRE were found below the specified industrial effluent discharge limits set by DoE, Malaysia. Additionally, the sludge generated after coagulation of SRPE contains essential plant nutrients. The present study's finding showed that FeSO₄·7H₂O waste generated as an industrial byproduct in a titanium oxide manufacturing industry could be utilized as an eco-friendly coagulant in treating industrial effluent.