Chalcopyrite-activated sodium percarbonate oxidation for sludge dewaterability enhancement: Synergetic roles of •OH and 1O2

Abstract

Efficient dewatering of sewage sludge is an energy- and carbon-saving procedure of sludge treatment in wastewater treatment facilities. Due to the limiting factors of hydrophilic extracellular polymeric substances, it is crucial to weaken the water-holding capacity and hydrophilicity for high-performance sludge-water separation. The current study successfully put forward a combination process of chalcopyrite + sodium percarbonate (SPC) to proficiently facilitate sludge dewaterability. Results showed that after the optimized treatment, the water removal efficiency augmented from 51.3 to 94.9%, while the water content of sludge cake declined from 90.1 to 52.0 wt%. Mechanism investigation demonstrated that the chalcopyrite + SPC system could consecutively generate reactive oxygen species via strong Fe3+/Fe2+ and Cu2+/Cu+ conversion cycles. The dominant reactive radical •OH and non-radical 1O2 could effectively degrade the macromolecular EPS into low-molecular biopolymers, decrease the high-polarity hydrophilic protein secondary structure and amino acids, and further reduce water-holding interfacial affinity. Afterward, the electrostatic force and interfacial free energy were decreased and turned out to enhance self-flocculation and flowability. Accordingly, bound water reduction and sludge-water separation efficiency were promoted. Furthermore, the chalcopyrite + SPC system could be viewed as a surrogate to Fenton/Fenton-like strategies for sludge dewaterability with economic advantage and low environmental risk. These findings inspire the application prospect of the chalcopyrite + SPC conditioning technique, which expects to save energy and reduce carbon emissions.