Synergizing Fenton oxidation and in-situ coagulation over a wide pH range for the simultaneous removal of multiple pollutants

Abstract

Efficient removal of multiple pollutants from discharged antibiotic wastewater effluents by a single processing unit is highly desirable, yet challenging. In this study, intrinsically synergizing Fenton oxidation and in-situ coagulation were achieved in the tannic acid (TA)/Fe(III)/H2O2 process, demonstrating the simultaneous removal of multiple pollutants over a wide pH range. Under the optimal conditions (TA/Fe(III)/H2O2 = 25 mg/L/0.1 mM/0.5 mM), 95.43 % of SMR and 98.41 % of turbidity were simultaneously removed at pH = 7. Moreover, the applicability of this process was validated by treating a spiked actual secondary effluent. Compared with polymer ferric sulphate coagulation and conventional Fe(II)/H2O2 Fenton, TA/Fe(III)/H2O2 process exhibited significantly enhanced removal performance in terms of SMR, COD, UV254 and turbidity without any pH adjustment. The mechanism analysis revealed that the introduction of TA can not only promote the iron redox cycle for the production of ∙OH, but also neutralize the charge for the generation of the porous flocs. Due to the bridging of TA, the synergy of Fenton oxidation and in-situ coagulation was achieved in a single processing unit. Finally, the synergy mechanism proposed that a four-step process sequentially proceeded during the treatment. This study may provide new insights into the simultaneous removal of multiple pollutants in the advanced treatment of refractory industrial wastewater.