Pseudocapacitive MXene@Fe-TA ternary mediator enhances denitrification via optimized electron transfer and microbial regulation in wastewater treatment

Abstract

Inefficient electron transfer is one of the main challenges in practical denitrification applications. To address this issue, a novel ternary mediator functional material (Mxene@Fe-TA) was successfully synthesized, which exhibited pseudocapacitive properties to facilitate electron mediation and distribution. Batch experiments revealed that 50 mg/L MXene@Fe-TA achieved 2.04-fold nitrate degradation. This superior performance originated from three integrated mechanisms: (1) MXene@Fe-TA served as a pseudocapacitor, which stored electrons from substrate metabolism by electrochemical structure; (2) it fostered a microenvironment that selectively enriched electroactive bacteria (EAB), which boosted secretion of redox-active substances to accelerate extracellular electron transfer (EET); and (3) the battery function of MXene@Fe-TA facilitated the stored electrons flowed directionally to denitrification, thereby optimizing energy utilization and reducing metabolic demands. This study introduced an innovative strategy for denitrification and guided the design of multifunctional materials to improve the efficiency of biological wastewater treatment.