Contact-electro-catalysis for efficient hexavalent chromium reduction under ambient conditions

Ultrasound-driven polytetrafluoroethylene contact-electro-catalysis reduces Cr(VI) to Cr(III). • PTFE contact-electro-catalysis enables generation of e − , •O 2 − , •OH and H 2 O 2 . • The PTFE contact-electro-catalytic system exhibits strong tolerance toward coexisting ions. • Contact-electro-catalysis decreases the biological toxicity of chromium. Efficient conversion of highly toxic hexavalent chromium (Cr(VI)) into low-toxicity trivalent chromium (Cr(III)) is of critical importance for mitigating environmental risks associated with chromium-containing wastewater. Here, we report an ultrasound-driven contact-electro-catalysis (CEC) process using commercial polytetrafluoroethylene (PTFE) as an efficient catalyst for Cr(VI) reduction. The PTFE CEC system achieved >99% Cr(VI) removal within 30 min under ambient conditions, and bioassays with Microcystis aeruginosa and wheat seedlings confirmed a marked decrease in ecotoxicity. Mechanistic studies revealed that PTFE continuously generated energetic electrons, superoxide radicals, and hydrogen peroxide during ultrasonication, which synergistically mediated the selective conversion of Cr(VI) to Cr(III). The system exhibited high tolerance to coexisting ions and maintained >90% removal efficiency in real water samples and > 95% activity after use in 27 cycles. Unlike conventional approaches, this strategy does not require sacrificial agents, engineered catalysts, or a controlled atmosphere. These findings demonstrate ultrasound-driven PTFE CEC is a green and efficient solution for treatment of Cr(VI)-contaminated wastewater. Download: Download high-res image (87KB) Download: Download full-size image