MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
Environ Int. 2019 Jun;127:730-741. doi: 10.1016/j.envint.2019.03.059. Epub 2019 Apr 16.
p-Arsanilic acid (p-ASA) and roxarsone (ROX) are two major phenylarsenic feed additives that are still widely used in many countries, and the land application of animal waste containing these compounds could introduce large quantities of arsenic into the environment. In this study, we proposed a treatment scheme for animal waste that involves leaching of p-ASA/ROX out of the manure first by water, then oxidation by ferrate (Fe(VI)) and removal of the arsenate released by in situ formed Fe(III) oxide-hydroxide. The effects of solution pH, dosage of Fe(VI), solution ionic strength, and matrix species on the treatment performance were systematically evaluated. Initial solution pH values of 4.1 and 2.0 were chosen for the oxidation of p-ASA and ROX, respectively, while efficient arsenate removal could be achieved with relatively small adjustment of the final solution pH (to 4.0). The pH-dependent second-order rate constants for the reactions between ferrate and p-ASA and ROX over the pH range of 2.0-12.0 were estimated to be 7.13 × 10-2.01 × 10 and 8.91 × 10-1.65 × 10 M s, respectively. The degradation pathways of p-ASA/ROX during ferrate oxidation were proposed based on the inorganic and organic intermediates identified. Depending on the levels of p-ASA/ROX, effective treatment could be achieved through flexible adjustment of the Fe(VI) dosage. p-ASA/ROX (10 mg-As/L) in swine manure leachate could be efficiently treated by ferrate oxidation within 5 min, with the overall arsenic removal efficiency higher than 99.2%. The treatment performance was barely affected by the presence of common ions (K, Ca, Na, Mg, SO, NO, and Cl), while humic acid, Mn, Ni, Fe, and Co inhibited p-ASA/ROX oxidation. The presence of PO and NH could accelerate the oxidation of p-ASA/ROX, but PO and humic acid compromised sorptive removal of the released arsenate due to their competitive sorption on the Fe(III) oxide-hydroxide precipitate. Ferrate oxidation is green and fast, and the operation is simple, thus it could serve as a promising and environment-friendly option for mitigating the risk of phenylarsenic feed additives in animal waste.
对氨基苯胂酸（p-ASA）和洛克沙胂（ROX）是两种主要的苯胂饲料添加剂，仍在许多国家广泛使用，而这些化合物的动物废物的土地应用可能会将大量的砷引入环境中。在本研究中，我们提出了一种动物废物处理方案，该方案首先通过水浸出粪便中的 p-ASA/ROX，然后用高铁酸盐（Fe(VI)）氧化，并通过原位形成的 Fe(III)氧化物-氢氧化物去除释放的砷酸盐。系统评估了溶液 pH 值、Fe(VI)用量、溶液离子强度和基质种类对处理性能的影响。选择初始溶液 pH 值分别为 4.1 和 2.0 来氧化 p-ASA 和 ROX，而通过适当调整最终溶液 pH 值（至 4.0）即可实现有效的砷酸盐去除。在 2.0-12.0 的 pH 范围内，高铁酸盐与 p-ASA 和 ROX 之间的 pH 依赖的二级反应速率常数估计分别为 7.13×10-2.01×10 和 8.91×10-1.65×10 M s。根据鉴定出的无机和有机中间体，提出了高铁酸盐氧化过程中 p-ASA/ROX 的降解途径。根据 p-ASA/ROX 的含量，通过灵活调整 Fe(VI)用量可以实现有效的处理。在 5 分钟内，可有效处理猪粪浸出液中的 10 mg-As/L 的 p-ASA/ROX，整体砷去除效率高于 99.2%。常见离子（K、Ca、Na、Mg、SO、NO 和 Cl）的存在对处理性能几乎没有影响，而腐殖酸、Mn、Ni、Fe 和 Co 抑制了 p-ASA/ROX 的氧化。PO 和 NH 的存在可以加速 p-ASA/ROX 的氧化，但 PO 和腐殖酸由于竞争吸附在 Fe(III)氧化物-氢氧化物沉淀物上，会影响释放的砷酸盐的吸附去除。高铁酸盐氧化是绿色快速的，操作简单，因此是一种有前途的环保选择，可以降低动物废物中苯胂饲料添加剂的风险。
