Octagon (HMX) is a typical organic pollutant of explosives in the surrounding environments of military factories, and it is widely regarded as a carcinogen which may enter the human body through wastewater and atmospheric exposure, resulting in potential health risks. Therefore, this paper studies the degradation of HMX by electrochemical oxidation. In this study, an electrochemical system was built using a copper plate as the cathode and a Ti/PbO2 electrode as the anode. The effects of various process variables, such as the initial pH value, the current density, and the distance between the electrodes, were investigated in relation to HMX degradation. Following this, performance optimization and intermediate analysis were carried out, along with an estimation of the energy consumption of HMX deterioration in various operating situations. The experimental results in this paper show that when the electrolyte concentration is 0.25 mol/L, the current density is 70 mA/cm2, the electrode spacing is 1.0 cm, and the initial pH is 5.0. Electrochemical oxidation has a better treatment efficiency for pollutants, and the removal rate reaches 81.2%. The findings of kinetic research reveal that the electrochemical oxidation degradation process of HMX follows quasi-first-order kinetics, and protein stress and Deoxyribo Nucleic Acid (DNA) loss stress are significantly different from other stress types throughout the whole degradation process. HMX degradation solution causes damage to protein transcription or expression. However, some genes of oxidative stress are continuously up-regulated, because H2O2 and OH produced by electrochemical oxidation cause a strong response to oxidative stress in cells. The research findings in this report offer crucial guidance and suggestions for the industrialization of HMX wastewater treatment.
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.
Complex and high levels of various pollutants in high-strength wastewaters hinder efficient and stable biological nutrient removal. In this study, the changes in pollutant removal performance and microbial community structure in a laboratory-scale anaerobic/aerobic sequencing batch reactor (SBR) treating simulated pre-fermented high-strength wastewater were investigated under different influent loading conditions. The results showed that when the influent chemical oxygen demand (COD), total nitrogen (TN), and orthophosphate (PO43−-P) concentrations in the SBR increased to 983, 56, and 20 mg/L, respectively, the COD removal efficiency was maintained above 85%, the TN removal efficiency was 64.5%, and the PO43−-P removal efficiency increased from 78.3% to 97.5%. Partial nitrification with simultaneous accumulation of ammonia (NH4+-N) and nitrite (NO2−-N) was observed, which may be related to the effect of high influent load on ammonia- and nitrite-oxidising bacteria. The biological phosphorus removal activity was higher when propionate was used as the carbon source instead of acetate. The relative abundance of glycogen accumulating organisms (GAOs) increased significantly with the increase in organic load, while Tetrasphaera was the consistently dominant polyphosphate accumulating organism (PAO) in the reactor. Under high organic loading conditions, there was no significant PAO–GAO competition in the reactor, thus the phosphorus removal performance was not affected.
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