Octogen (HMX) is widely used as a high explosive and constituent in plastic explosives, nuclear devices, and rocket fuel. The direct discharge of wastewater generated during HMX production threatens the environment. In this study, we used the electrochemical oxidation (EO) method with a PbO₂-based anode to treat HMX wastewater and investigated its degradation performance, mechanism, and toxicity evolution under different conditions. The results showed that HMX treated by EO could achieve a removal efficiency of 81.2% within 180 min at a current density of 70 mA/cm², Na₂SO₄ concentration of 0.25 mol/L, interelectrode distance of 1.0 cm, and pH of 5.0. The degradation followed pseudo-first-order kinetics (R² > 0.93). The degradation pathways of HMX in the EO system have been proposed, including cathode reduction and indirect oxidation by •OH radicals. The molecular toxicity level (expressed as the transcriptional effect level index) of HMX wastewater first increased to 1.81 and then decreased to a non-toxic level during the degradation process. Protein and oxidative stress were the dominant stress categories, possibly because of the intermediates that evolved during HMX degradation. This study provides new insights into the electrochemical degradation mechanisms and molecular-level toxicity evolution during HMX degradation. It also serves as initial evidence for the potential of the EO-enabled method as an alternative for explosive wastewater treatment with high removal performance, low cost, and low environmental impact.

This study evaluated the degradation of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) in simulated wastewater using an iron-carbon (Fe-C) micro-electrolysis system. The treatment efficiency was systematically evaluated under varying initial pH, Fe dosage, and Fe/C mass ratios. Under the optimized operating conditions (initial pH of 4, Fe dosage of 70 g/L, and an Fe/C mass rat of 1:1), the system achieved a maximum HMX removal efficiency of 98.4%. Kinetic analysis indicated that the degradation process conformed to pseudo-first-order kinetics. Mechanistically, HMX removal was attributed to interfacial adsorption and co-precipitation via in situ generated Fe²⁺ and Fe³⁺ hydroxides, alongside reductive transformation mediated by Fe, Fe²⁺, and nascent hydrogen ([H]) evolved during the micro-electrolysis process. To assess the molecular toxicity evolution of the treated wastewater, a toxicogenomic assay was deployed to evaluate the molecular toxicity evolution of the treated wastewater matrix. The transcriptomic profiling revealed that DNA damage and oxidative stress were the predominant cellular stress responses induced by the wastewater. While the total toxic effect transcript index (TELI_total) exhibited a transient initial increase before steadily declining, the overall toxic potency remained within a relatively stable range throughout the treatment cycle. Ultimately, this study provides critical insights into process optimization and pathway elucidation, demonstrating that Fe-C micro-electrolysis is a promising and scalable pretreatment technology for the remediation of energetic compound-laden industrial effluents.