Efficient electrosynthesis of HO2- from air for sulfide control in sewers

Abstract

Electrochemically in-situ generation of oxygen and caustic soda is promising for sulfide management while suffers from scaling, poor inactivating capacity, hydrogen release and ammonia escape. In this study, the four-compartment electrochemical cell efficiently captured oxygen molecules from the air chamber to produce HO2- without generating toxic by-products. Meanwhile, the catalyst layer surface of PTFE/CB-GDE maintained a relatively balanced gas-liquid micro-environment, enabling the formation of enduring solid-liquid-gas interfaces for efficient HO2- electrosynthesis. A dramatic increase in HO2- generation rate from 453.3mgL-1 h-1 to 575.4mgL-1 h-1 was attained by advancement in operation parameters design (flow channels, electrolyte types, flow rates and circulation types). Stability testing resulted in the HO2- generation rate over 15gL-1 and the current efficiency (CE) exceeding 85%, indicating a robust stable operational capacity. Furthermore, after 120mgL-1 HO2- treatment, an increase of 11.1% in necrotic and apoptotic cells in the sewer biofilm was observed, higher than that achieved with the addition of NaOH, H2O2 method. The in-situ electrosynthesis strategy for HO2- represents a significance toward the practical implementation of sulfide abatement in sewers, holding the potential to treat various sulfide-containing wastewater. Environmental ImplicationSulfur-containing substances in sewers frequently incur unpleasant odors, corrosion-related economic loss, and potential human health concerns. Sulfides emit a potent offensive odor at lower concentrations and exhibits varying degrees of toxicity at higher concentrations, incurring potential chronic damage to the human body and even acute poisoning. Therefore, sulfur-containing substances in sewers are considered as "hazardous materials." This study would provide a theoretical basis for control of sulfide in sewer systems by environmentally friendly in-situ HO2- and oxygen production. It facilitates addressing environmental challenges arising from sulfur-containing substances in sewage systems.