Wei Yunmei, Song Peng, Wen Yi, Liao Qin, Du Xiaoqi, Chen Lianying, Liang Jialiang, Long Gang, Shimaoka Takayuki
Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing, 400045, PR China.
Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing, 400045, PR China.
Water Res. 2025 Jan 1;268(Pt A):122656. doi: 10.1016/j.watres.2024.122656. Epub 2024 Oct 19.
Persulfate-based advanced oxidation processes (PS-based AOPs), characterized by the coexistence of SO₄•⁻ and HO•, have been proven effective in treating a series of cyanide-bearing pollutants. However, the mechanisms of these reactive species in the degradation of cyanides, especially metal-cyanide complexes, remain unclear or contradictory. The degradation behavior of representative cyanides (including potassium cyanide and potassium ferricyanide) at different pH conditions (2, 7 and 12) in thermally activated persulfate system (T = 60 °C) was explored, and the roles of SO₄•⁻ and HO• in cyanide degradation were explored by leveraging the distinct characteristics of reactive species under different pH conditions. The study found that both HO• and SO₄•⁻ can react with free cyanide (CN⁻ and HCN). However, the reaction barrier between CN⁻ and HO• is lower than that between HCN and SO₄•⁻, resulting in a higher removal rate of free cyanide under alkaline conditions compared to acidic and neutral conditions. For complexed cyanide, the complex bonds in ferricyanide were completely broken within 24 h by thermally activated persulfate at pH 2, releasing free cyanide, indicating the effectiveness of SO₄•⁻ in breaking the Fe-C bonds in ferricyanide. In contrast, ferricyanide was barely decomposed at pH 12, implying the inefficacy of HO• in breaking the Fe-C bonds. This study also innovatively found that SO₄•⁻ breaks the Fe-C bonds by oxidizing Fe(Ⅲ) in ferricyanide to Fe(Ⅳ) or Fe(Ⅴ), releasing CN⁻, which is then converted to CNO⁻ by SO₄•⁻ and HO•. CNO⁻ is further mineralized to NO₃⁻, NH₄⁺, and N₂ through hydrolysis or oxidation reactions. This research clarifies, for the first time, the activity of SO₄•⁻ and HO• toward cyanide degradation in PS-based AOPs.
基于过硫酸盐的高级氧化工艺（PS基AOPs）以硫酸根自由基（SO₄•⁻）和羟基自由基（HO•）共存为特征，已被证明在处理一系列含氰污染物方面有效。然而，这些活性物种在氰化物降解中的作用机制，尤其是金属氰化物配合物的降解机制，仍不明确或存在矛盾。本研究探索了在热活化过硫酸盐体系（T = 60 °C）中，代表性氰化物（包括氰化钾和铁氰化钾）在不同pH条件（2、7和12）下的降解行为，并利用不同pH条件下活性物种的独特特性，探究了SO₄•⁻和HO•在氰化物降解中的作用。研究发现，HO•和SO₄•⁻均可与游离氰化物（CN⁻和HCN）发生反应。然而，CN⁻与HO•之间的反应势垒低于HCN与SO₄•⁻之间的反应势垒，导致碱性条件下游离氰化物的去除率高于酸性和中性条件。对于络合氰化物，在pH为2时，热活化过硫酸盐可在24小时内完全破坏铁氰化物中的络合键，释放出游离氰化物，表明SO₄•⁻在破坏铁氰化物中的Fe-C键方面具有有效性。相比之下，在pH为12时，铁氰化物几乎不分解，这意味着HO•在破坏Fe-C键方面无效。本研究还创新性地发现，SO₄•⁻通过将铁氰化物中的Fe(Ⅲ)氧化为Fe(Ⅳ)或Fe(Ⅴ)来破坏Fe-C键，释放出CN⁻，然后CN⁻被SO₄•⁻和HO•转化为CNO⁻。CNO⁻通过水解或氧化反应进一步矿化为NO₃⁻、NH₄⁺和N₂。本研究首次阐明了PS基AOPs中SO₄•⁻和HO•对氰化物降解的活性。
