Abstract: In order to achieve harmless disposal of high-arsenic waste acid and efficient arsenic solidification, the idea of using solid iron sources for arsenic removal from waste acid was proposed, and the influence of solid iron oxide on the arsenic removal process from high-arsenic waste acid and the synthesis of scorodite was explored. The results showed that the full reaction between solid iron oxide and waste acid at room temperature could provide initial iron ions for the arsenic removal reaction and reduces the pH of the solution. This reaction was conducive to the initiation of arsenate precipitation reaction, and aided in the stable nucleation and good crystallization of scorodite. During the experiment, it was found that the presence of arsenate ions can promote the dissolution of solid iron oxides in the system, and it was revealed that the mutual promotion effect of "solid iron oxide dissolution-arsenate precipitation" existing in an acidic environment was an important way to achieve efficient arsenic removal. Fe3O4 magnetic nanoparticles (MNPs) underwent Fenton reaction during the arsenic removal process, producing abundant hydroxyl radicals. This reaction can promote the dissolution of Fe3O4 in the solution and accelerated the precipitation of arsenate, giving the Fe3O4 the best arsenic removal performance. When the reaction time was 12 h, the pH was 1.5, the Fe/As molar ratio was 2, and the reaction temperature was 90℃, Fe3O4 had the best arsenic removal efficiency in waste acid, which could reach 99.93%. Based on this, a new process was proposed for the efficient treatment of contaminated water using Fe3O4, including efficient arsenic removal of high-arsenic contaminated acid and further purification of low-arsenic contaminated acid. This process has a high arsenic removal rate while avoiding secondary pollution. By using scorodite to remove arsenic, the adsorption and magnetic characteristics of MNPs were used to achieve deep removal and efficient solidification of arsenic in waste acid.

Key words: arsenic, waste acid, scorodite, iron oxides

摘要： 为实现高砷污酸无害化处置及砷高效固化，本工作提出了固体铁源除砷的思路，探究了铁氧化物对高砷污酸除砷及合成臭葱石的影响规律。结果表明，常温下铁氧化物与污酸充分反应可以提供铁离子并降低pH，有利于砷酸根沉淀反应的启动及臭葱石的成核结晶；发现了砷酸根离子促进铁氧化物溶解的现象，揭示了酸性环境下“铁氧化物溶解-砷酸根沉淀”的互促效应是实现高效除砷的重要途径；Fe3O4磁性纳米颗粒(MNPs)在除砷过程中会发生Fenton反应，促进Fe3O4溶解、加速砷酸根沉淀，除砷性能最优；在反应时间为12 h、pH为1.5、Fe/As摩尔比为2、反应温度为90℃时，Fe3O4的污酸除砷效率达到99.93%；提出了一种MNPs高效处置污酸新工艺，在臭葱石除砷基础上利用MNPs吸附性及磁性特征，实现了砷深度脱除及高效固化。

关键词: 砷, 污酸, 臭葱石, 铁氧化物