The reductive detoxification of Cr(VI) by sulfite is known as the prevailing strategy and can be successfully implemented for the treatment of Cr(VI)-contaminated waters. However, this method inevitably faces the challenges of excessive consumption of sulfite due to the generations of highly oxidative OH and SO₄⁻ during the process of sulfite reducing Cr(VI). In this study, we find that a small quantity of thiocyanate (SCN) can catalytically enhance the process efficiency of Cr(VI) reduction by sulfite and effectively prevent the excessive consumption of sulfite. Specifically, when adding 5 μM SCN into 100 μM Cr(VI) + 600 μM sulfite reaction system at pH 3.5, Cr(VI) reduction amount and [sulfite]_oxidation/[Cr(VI)]_reduction ratio value are approximately 2 and 0.45, respectively, times those in the SCN-free case. The maximum Cr(VI) reduction amount can be achieved at an initial [SCN]/[Cr(VI)] molar ratio of 2.0. Electron spin resonance measurement, combined with the fluorescence spectrum detection, verifies that the process of sulfite reducing Cr(VI) mediated by SCN probably proceeds via the non-radical pathway, avoiding the formation of OH and SO₄⁻ under aerobic condition. In general, the groundbreaking findings is of great importance to designing the strategies for the in or ex situ detoxification of Cr(VI) in aqueous environment.

中文翻译：

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硫氰酸盐通过抑制活性氧的形成，在促进亚硫酸盐还原Cr（VI）的过程中的作用

亚硫酸盐对Cr（VI）的还原性解毒是一种流行的策略，可以成功地用于处理受Cr（VI）污染的水。然而，由于产生高氧化性，该方法不可避免地面临过度消耗亚硫酸盐的挑战。OH和SO ₄⁻在亚硫酸盐还原Cr（VI）过程中。在这项研究中，我们发现少量的硫氰酸盐（SCN）可以催化提高亚硫酸盐还原Cr（VI）的工艺效率，并有效防止亚硫酸盐的过度消耗。具体而言，在pH 3.5的100μMCr（VI）+ 600μM亚硫酸盐反应体系中添加5μMSCN时，Cr（VI）的还原量和[亚硫酸盐]_氧化/ [Cr（VI）]的_还原比率值分别约为无SCN情况下的2倍和0.45倍。最大的Cr（VI）还原量可以在初始[SCN] / [Cr（VI）]摩尔比为2.0时实现。电子自旋共振测量与荧光光谱检测相结合，验证了SCN介导的亚硫酸盐还原Cr（VI）的过程可能是通过非自由基途径进行的，从而避免了SCN的形成。OH和SO ₄⁻在有氧条件下。总的来说，开创性的发现对于设计在水环境中对Cr（VI）进行原位或非原位解毒的策略非常重要。