高铁酸钾-次氯酸钠联用对卤乙腈生成控制

Control of haloacetonitrile formation by potassium ferrate and sodiumhypochlorite

为有效控制饮用水中氯消毒产生的有毒副产物卤乙腈,以天冬氨酸、谷氨酸、酪氨酸为前体物,研究不同前体物对四种卤乙腈生成能力及K_(2)FeO_(4)和NaClO单独、联合投加对其控制效果的影响.结果表明:氯处理不同前体物均生成四种卤乙腈,但生成量存在差异;而增加初始氯质量浓度能提升溴代与氯化反应,导致反应产物由DCAN(二氯乙腈)和BCAN(溴氯乙腈)向TCAN(三氯乙腈)和DBAN(二溴乙腈)转变.此外通过K_(2)FeO_(4)和NaClO联用试验发现:当不同投加顺序的投加间隔分别控制为10,60 min时,与单独加氯相比,四种卤乙腈生成减少近70%;在同时投加工艺中,当铁氯投加比为30∶1时,对卤乙腈最终生成控制效果最好,分别降低81.14%,94.25%,96.68%和89.55%,其原因为ClO-和K_(2)FeO_(4)分解产生的原子态氧通过提升不同价态铁的稳定性而增加卤乙腈的去除率.

In order to effectively control haloacetonitrile,a toxic by-product of chlorine disinfection in drinking water,aspartic acid,glutamic acid and tyrosine were used as precursors to study the effects of different precursors on the formation ability of four haloacetonitrile and the control effect of K_(2)FeO_(4) and NaClO alone and jointly.Results showed that four kinds of haloacetonitriles are produced from different precursors treated with chlorine,but the amount of haloacetonitrile is different;increasing the initial chlorine concentration can improve the bromination and chlorination reaction,resulting in the transformation of reaction products from DCAN(dichloroacetonitrile)and BCAN(bromine acetonitrile)to TCAN(trichloroacetonitrile)and DBAN(dibromoace-tonitrile).In addition,through the combined experiment of K_(2)FeO_(4) and NaCIO,it was found that when the dosing intervals of different dosing sequences were controlled to 10 and 60 min respectively,the generation of four haloacetonitrile was reduced by nearly 70%compared with that of chlorination alone;in the simultaneous dosing process,when the iron and chlorine dosing ratio is 30:1,the control effect on the final formation of haloacetonitrile is the best,reducing by 81.14%,94.25%,96.68%and 89.55%,respectively.The reason is that the atomic oxygen produced by the decomposition of CIO and K_(2)FeO_(4) increases the removal rate of haloacetonitrile by improving the stability of different valence iron.