Using FeS2 3D electrochemical treatment for the simultaneous removal of humid acid and nitrate from high-saline wastewater

Abstract

Highly saline industrial wastewaters pose significant challenges for effective post-biological treatment due to the presence of humic acid (HA) and nitrate, which can severely impede the efficiency of conventional purification processes. Despite these challenges, there is a notable lack of studies focusing on the simultaneous removal of HA and total nitrogen (TN). This study innovatively employed a three-dimensional FeS₂ particle electrode to address this gap, aiming to simultaneously remove TOC and TN from high-salinity waters. Through comprehensive investigation of performance and underlying mechanisms, we identified that reactive oxygen species, specifically hydroxyl radicals (•OH), superoxide anions (O₂•⁻), and singlet oxygen (¹O₂), played pivotal roles in the synergistic degradation of TOC and TN. Notably, our results demonstrated that an optimal initial NO₃^--N to HA ratio of 1:3 significantly enhanced the synergistic removal efficiency. Under optimal conditions, the removal rates of TOC, NO₃⁻-N and TN reached 92.2 %, 92.6 %, and 93.3 %, respectively. Additionally, the system showed good applicability in treating actual wastewater, achieving removal rates of 85.2 % for TOC, 99.7 % for NO₃⁻-N, and 88.4 % for TN. Post-treatment analysis revealed the formation of a stable core-shell structure (FeS₂@FeOOH) on the particle electrode, which not only maintained the integrity of the material but also facilitated its sustained use. These findings not only provide valuable scientific insights but also offer practical solutions to improve the biochemical treatment of high-salinity industrial wastewaters, paving the way for more efficient and sustainable water purification technologies.