College of Civil Engineering, Zhejiang University of Technology, Hangzhou 310023, China.
College of Civil Engineering, Zhejiang University of Technology, Hangzhou 310023, China.
Sci Total Environ. 2022 Feb 1;806(Pt 1):150379. doi: 10.1016/j.scitotenv.2021.150379. Epub 2021 Sep 20.
Organoarsenic contaminants existing in water body threat human health and ecological environment due to insufficient bifunctional treatment technologies for organoarsenic degradation and inorganic arsenic immobilization. In order to safely and efficiently treat organoarsenic contaminants discharged into the aquatic environment, Co-Mn-Fe layered double hydroxide (CoMnFe-LDH) and Co-Mn-Fe layered double oxide (CoMnFe-LDO) were fabricated and employed as peroxymonosulfate (PMS) activator for organoarsenic degradation and inorganic arsenic immobilization, and p-arsanilic acid (p-ASA) was selected as target pollutant. Results demonstrated that the satisfactory removal of p-ASA (100.0%) in both CoMnFe-LDH/PMS and CoMnFe-LDO/PMS systems was obtained within 30 min, and substantial inorganic arsenic adsorption could be achieved (below 0.5 mg/L) in two systems with converting major inorganic arsenic species to arsenate. As XPS, ESR and quenching experiment revealed, the existence and generation of surface-bound radicals in two systems were identified. Based on density functional theory calculation and XPS analysis, the catalytic mechanism of CoMnFe-LDO/PMS system that PMS could be activated via direct electron transfer from adsorbed p-ASA was clarified, which differed from PMS activation via coupling with surface hydroxyl groups in CoMnFe-LDH/PMS system. Catalytic performance assessment under various critical operation parameters indicated that CoMnFe-LDH presented more stable ability of p-ASA removal in a wide pH range and complex aquatic environment. The recycle experiment demonstrated the excellent stability and reusability of CoMnFe-LDH(LDO). Besides, seven degradation products of p-ASA in CoMnFe-LDH/PMS system including phenolic compounds, azophenylarsonic acid, nitrobenzene and benzoquinne were identified by UV-Vis spectra and LC-TOF-MS analysis, and the corresponding degradation pathway was proposed. In summary, compared to CoMnFe-LDO/PMS, CoMnFe-LDH/PMS holds great promise for the development of an oxidation-adsorption process for efficient control of organoarsenic pollutant.
水体中存在的有机砷污染物由于缺乏对有机砷降解和无机砷固定的双功能处理技术，对人类健康和生态环境构成威胁。为了安全有效地处理排放到水环境中的有机砷污染物，制备了 Co-Mn-Fe 层状双氢氧化物（CoMnFe-LDH）和 Co-Mn-Fe 层状双氧化物（CoMnFe-LDO），并将其用作过一硫酸盐（PMS）的活化剂，用于有机砷降解和无机砷固定，选择对氨基苯砷酸（p-ASA）作为目标污染物。结果表明，在 CoMnFe-LDH/PMS 和 CoMnFe-LDO/PMS 体系中，p-ASA（100.0%）在 30 min 内得到了令人满意的去除，并且在两个体系中都可以实现大量的无机砷吸附（低于 0.5 mg/L），主要的无机砷形态转化为砷酸盐。XPS、ESR 和猝灭实验表明，两个体系中均存在表面结合自由基的生成。基于密度泛函理论计算和 XPS 分析，阐明了 CoMnFe-LDO/PMS 体系中 PMS 通过吸附的 p-ASA 的直接电子转移而被激活的催化机制，这与 CoMnFe-LDH/PMS 体系中通过与表面羟基偶联而激活 PMS 的机制不同。在各种关键操作参数下的催化性能评估表明，CoMnFe-LDH 在较宽的 pH 范围和复杂的水相环境中具有更稳定的去除 p-ASA 的能力。循环实验表明，CoMnFe-LDH（LDO）具有优异的稳定性和可重复使用性。此外，通过 UV-Vis 光谱和 LC-TOF-MS 分析，在 CoMnFe-LDH/PMS 体系中鉴定了 p-ASA 的七种降解产物，包括酚类化合物、偶氮苯砷酸、硝基苯和苯醌，并提出了相应的降解途径。总之，与 CoMnFe-LDO/PMS 相比，CoMnFe-LDH/PMS 为开发高效控制有机砷污染物的氧化-吸附工艺提供了广阔的前景。
