WS_(2)强化Fe^(2+)活化高碘酸盐降解酸性橙7的研究

WS_(2)promoted periodate activation by ferrous ions(Fe^(2+))for the degradation of acid orange 7

构建无机还原剂硫化钨(WS_(2))强化Fe^(2+)活化高碘酸盐(PI)体系,以典型有机染料酸性橙7(AO7)为模拟污染物,探究了Fe^(2+)浓度、PI浓度、WS_(2)浓度、pH值及水体常见共存阴离子对AO7去除过程的影响,并基于自由基淬灭与捕获实验(EPR)分析了体系中可能存在的活性氧化物种及其生成机制.结果表明:WS_(2)/Fe^(2+)/PI体系氧化去除AO7的效率远高于同等条件下单一Fe^(2+)/PI活化过程;在[Fe^(2+)]0=0.1 mmol·L^(-1)、[PI]0=0.5mmol·L^(-1)、[WS_(2)]_(0)=0.3 g·L^(-1)、初始pH为2.6条件下,AO7去除率在12 min内达到93.0%.实验中Fe^(2+)浓度、WS_(2)浓度与AO7去除率呈正相关,而PI浓度过高会抑制反应过程.通过动力学模型发现,WS_(2)浓度是体系高效产生活性物种去除有机物的主导控制条件.机理研究表明,WS_(2)的存在能加速Fe^(3+)还原,生成更多的Fe^(2+)持续参与PI活化反应;Fe(Ⅳ)、碘酸根自由基(IO_(3)·/IO_(4)·)和硫酸根自由基(SO_(4)^(·-))是WS_(2)/Fe^(2+)/PI体系中主要活性氧化物种,其中,SO_(4)^(·-)可能来源于WS_(2)表面硫物种(S_(2)^(4-)→SO_(3)^(2-)→SO_(4)^(·-))的迁移转化;而非自由基高价铁氧化途径为AO7降解的主导过程.

In this study,an inorganic reductant Tungsten Sulfide(WS_(2))was applied to enhance Fe^(2+)activated Periodate(PI)process for the degradation of a typical dye Acid Orange 7(AO7).The effects of Fe^(2+)dosage,PI dosage,WS_(2)dosage,initial pH(pH_(0))and common coexisting anions on the removal of AO7 were explored.Results show that the removal efficiency of AO7 in WS_(2)/Fe^(2+)/PI system is much higher than that in sole Fe^(2+)/PI process.Under the conditions of[Fe^(2+)]_(0)=0.1 mmol·L^(-1),[PI]0=0.5 mmol·L^(-1),[WS_(2)]0=0.3 g·L^(-1),pH_(0)=2.6,the removal efficiency of AO7 was 93.0%within 12 min.Specifically,Fe^(2+)dosage and WS_(2)dosage were positively correlated with the removal efficiency of AO7,while an increased concentration of PI would inhibit the removal of AO7.The kinetic models investigation verifies a key control role of WS_(2)dosage for the generation of active species during the WS_(2)/Fe^(2+)/PI process.Mechanistic studies indicate that the presence of WS_(2)can accelerate the reduction of Fe^(3+)for generating more Fe^(2+)to continuously participate in PI activation process.Based on the radical scavenging experiments and EPR techniques,high-valent iron(i.e.Fe(Ⅳ)),iodate radicals(IO_(3)•/IO_(4)•)and sulfate radicals(SO_(4)^(·-))are revealed to be the primary active oxidizing species responsible for the degradation of AO7 in the WS_(2)/Fe^(2+)/PI system.Besides,SO_(4)^(·-)might originate from the transformation of sulfur species(S_(2)4^(-)→SO_(3)^(2-)→SO_(4)^(·-)),and the nonradical high-valent iron oxidation pathway dominated the AO7 degradation.