Conjunction of ferric ion with chloride ion facilitated zero-valent copper/air system to eliminate paracetamol: Mechanistic insights and performance evaluation

Zero-valent copper/air process was studied in degrading contaminants owing to in-site generation of hydrogen peroxide and reactive oxygen species, while its oxidation efficacy was restrained by the dismutation of cuprous ion. In this study, when the dosages of paracetamol, ferric ion, chloride ion and zero-valent copper were respectively 10 μM, 40 μM, 2 mM and 0.2 g/L at pH 3.0, the paracetamol elimination was greatly enhanced and increased from 9.2% to 76.5% within 30 min with adding both ferric ion and chloride ion in the zero-valent copper/air process. Hydroxyl radical and reactive chlorine species were identified as the dominant reactive oxygen species, and the contribution rates of hydroxyl radical and reactive chlorine species to eliminating paracetamol were respectively 68.2% and 28.9%. In the proposed system, zero-valent copper and cuprous ion expedited the ferric/ferrous circulation, conducing to the production of reactive oxygen species. Moreover, chloride ion coupled with cuprous ion producing the cuprous chloride complexes, and chloride ion contributed to the comproportionation between zero-valent copper with cupric ion to form cuprous chloride, receding the dismutation of cuprous ion and contributing to the formation of hydrogen peroxide and reactive oxygen species. When zero-valent copper reused for three times in the proposed system, the degradation of paracetamol reached 62%. After we increased the end pH to > 7.0 and leaching, the total copper of reaction solution was under 0.85 mg/L and the acute toxicity had no insignificant increase for discharge water. The study provided a new idea to enhance zero-valent copper/air system for the purification of pollutants.