Efficient and stable copper tungstate catalyst for water treatment with peroxymonosulfate: Effect of synthetic pH, primary oxidant, and practical feasibility.

In this study, copper tungstate (CuWO₄) nanoparticles, which are highly efficient and stable catalysts for water treatment, were synthesized via a hydrothermal method under various pH conditions. CuWO₄ synthesized at pH 10 (CuWO₄@10) exhibited the highest degradation efficiency and the lowest metal ion leaching. In the presence of CuWO₄@10 (0.5 g/L) and peroxymonosulfate (PMS, 1 mM), 4-chlorophenol (4-CP, 100 μM) was completely degraded within 5 min, and the total metal ion leaching concentration after 4 h was only 10.2 μM. The catalytic activity of CuWO₄ for 4-CP degradation was 4.7-99.0 times greater than that of CuO catalysts. This enhanced performance is attributed to the presence of W, which increases the surface area and reduces charge transfer resistance. Based on the results of radical-quenching experiments, solvent exchange experiments, PMS decomposition measurements, electron paramagnetic resonance spectroscopy, and Raman spectroscopy, high-valent copper (Cu(III)) was identified as the primary oxidant responsible for degradation in the CuWO₄/PMS system. The CuWO₄/PMS system rapidly degraded various phenolic compounds, and its degradation efficiency remained consistent across repeated uses of the CuWO₄ catalyst. Degradation in groundwater also occurred efficiently in the CuWO₄/PMS system. This study provides valuable insights into the development of practical PMS-based water treatment processes.