In this work, we have explored for the first time the potential application of trace‐Fe(III)/chlorine system as an innovative oxidation technology for the degradation of persistent textile dyes. Fe(III)/chlorine combination improved the dye removal by ~40% within 30 s, as compared with chlorination alone, mainly through a radical pathway induced by the catalytic activation of chlorine in the presence of Fe(III). A chemical probe method was used for identifying the main reactive species. Cl₂^●− was found to be the key species responsible of huge abatement of dyes in the Fe(III)/chlorine system, whereas ^●OH and Cl^● can participate with only ~5% in the overall removal efficiency. At pH 3, 77% of reactive green 12 (RG12) was removed after 30 s, and then the removal efficiency diminished to 60% at pH 4, 20% at pH 5, and ~10% at pH 6 and 7. However, the best implication of free radicals was achieved at pH 4, at which the degradation rate was 3.3 time higher than that of chlorination alone. The dye removal efficiency increased with an increase in chlorine and iron loads up to certain optimums, but detrimental effect was observed at higher dosage levels. An increase in the solution temperature notably accelerated the removal yield (i.e., 81% of RG12 was removed at 50°C against 67% at 30°C and 57% at 10°C). NO₂⁻ and HSO₃⁻ as well as the cationic surfactant Adogen 464 showed strongest inhibiting effect on the performance of the process. Based on these findings, the Fe(III)/chlorine process is highly efficient in removing dyes from wastewaters.

中文翻译：

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Fe（III）在弱酸性条件下通过氯催化的持久性纺织品染料降解：Cl2-自由基在降解过程以及矿物和有机竞争者的影响中的关键作用

在这项工作中，我们首次探索了痕量Fe（III）/氯系统作为一种创新的氧化技术用于降解持久性纺织染料的潜在应用。与单独氯化相比，Fe（III）/氯的组合在30 s内可将染料去除率提高约40％，这主要是通过在Fe（III）存在下由氯催化活化引起的自由基途径进行的。化学探针法用于鉴定主要反应物种。在Fe（III）/氯系统中，发现Cl ₂ ^●-是导致大量减少染料的关键物质，而^● OH和Cl ^●只能以约5％的总去除效率参与。在pH 3下，30 s后去除了77％的反应性绿色12（RG12），然后去除效率在pH 4下降低至60％，在pH 5下降低至20％，在pH 6和7下降低至〜10％。最佳的自由基含义是在pH 4下实现的，在该pH下，降解速率比单独氯化的降解速率高3.3倍。染料去除效率随着氯和铁含量的增加达到一定的最佳值而增加，但是在较高的剂量水平下观察到有害的作用。溶液温度的升高显着加快了去除率（即，RG50在50°C下的去除率为81％，而30°C下的67％和10°C下的57％）被去除。NO ₂ ^-和HSO ₃ ^-阳离子表面活性剂Adogen 464对该工艺的性能表现出最强的抑制作用。基于这些发现，Fe（III）/氯工艺可高效去除废水中的染料。