Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture and Rural Affairs of the People's Republic of China, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, People's Republic of China.
Environ Sci Technol. 2024 Sep 10;58(36):16225-16235. doi: 10.1021/acs.est.4c06158. Epub 2024 Aug 27.
In this study, we proposed a moderate oxidation strategy for accelerating the oxidative dissolution of zerovalent iron (ZVI) using sulfite (S(IV)), thereby improving the removal of As(V) and As(III). Results revealed that, in the presence of 2.0 mM S(IV), both As(V) and As(III) were selectively converted into scorodite at pH 3.0-7.0, while As(III) oxidation and As(V) immobilization were impressed over pH 8.0-10.0. Batch experiments, radical quenching experiments, and electron spin resonance (ESR) measurements demonstrated that ZVI initially boosted S(IV) activation to generate SO, OH, and protons, and in turn, ZVI was further oxidized more intensely by these radicals than by oxygen. Concurrently, substantial protons derived from S(IV) oxidation neutralized hydroxyls produced by ZVI oxidation, maintaining an acidic environment conducive to the generation of scorodite rather than iron (hydr)oxides. Characterizations of X-ray diffraction (XRD), Raman, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) confirmed that scorodite was formed in situ and then exfoliated from the surface of ZVI, and approximately 75% of ZVI could still be recovered, which contributed to efficient As removal in successive runs and real As-polluted wastewater. The application of S(IV) achieved a balance among ZVI reactivity improvement, As(V)/As(III) removal, and raw material consumption, making it a promising approach for addressing arsenic contamination in wastewater treatment.
在本研究中，我们提出了一种适度氧化策略，使用亚硫酸盐（S(IV)）来加速零价铁（ZVI）的氧化溶解，从而提高砷（V）和砷（III）的去除率。结果表明，在 2.0 mM S(IV)存在的情况下，在 pH 3.0-7.0 时，砷（V）和砷（III）被选择性地转化为硫砷铁矿，而在 pH 8.0-10.0 时，砷（III）氧化和砷（V）固定化效果显著。批量实验、自由基猝灭实验和电子自旋共振（ESR）测量表明，ZVI 最初促进 S(IV)的活化，生成 SO、OH 和质子，而这些自由基进一步氧化 ZVI 的强度比氧更高。同时，S(IV)氧化产生的大量质子中和了 ZVI 氧化产生的羟基，维持了有利于生成硫砷铁矿而不是铁（氢）氧化物的酸性环境。X 射线衍射（XRD）、拉曼、衰减全反射傅里叶变换红外（ATR-FTIR）、X 射线光电子能谱（XPS）、X 射线吸收精细结构（XAFS）、场发射扫描电子显微镜（FESEM）和高分辨率透射电子显微镜（HRTEM）的表征证实了硫砷铁矿是原位形成的，然后从 ZVI 表面剥落，大约 75%的 ZVI 仍可以回收，这有助于在连续运行和实际含砷废水处理中实现高效的砷去除。S(IV)的应用在提高 ZVI 反应性、去除砷（V）/砷（III）和消耗原材料之间取得了平衡，是解决废水处理中砷污染的一种很有前途的方法。
