In this study, sodium tripolyphosphate (STPP) was used to promote the removal of organic pollutants in a zero-valent copper (ZVC)/O2 system under neutral conditions for the first time. 20 mg/L p-nitrophenol (PNP) can be completely decomposed within 120 min in the ZVC/O2/STPP system. The PNP degradation process followed pseudo-first-order kinetics and the degradation rate of PNP gradually increased upon the decreasing ZVC particle size. The optimal pH of the reaction system was 5.0. Our mechanism investigation showed that Cu+ generated by ZVC corrosion was the main reducing agent for the activation of O2 to produce ROS. ·OH was identified as the only ROS formed during the degradation of PNP and its production pathway was the double-electron activation of O2 (O2→H2O2→·OH). In this process, STPP did not only promote the release of Cu+ through its complexation, but also promoted the production of ·OH by reducing the redox potential of Cu2+/Cu+. In addition, we could initiate and terminate the reaction by controlling the pH. At pH < 8.1, ZVC/O2/STPP could continuously degrade organic pollutants; at pH > 8.1, the reaction was terminated. STPP was recycled to continuously promote the corrosion of ZVC and O2 activation as long as the pH was <8.1. This study provided a new and efficient way for O2 activation and organic contaminants removal.
Keywords: Oxygen activation; Sodium tripolyphosphate; Zero valent copper corrosion; pH control.
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