Arsenic (As) is considered one of the most serious inorganic pollutants, and the wastewater produced in some smelters contains a high concentration of arsenic. In this paper, we purified the high-concentration arsenic solution with red mud and Fe³⁺ synergistically. In this system, arsenite anions reacted with Fe(III) ions to form ferric arsenite, which attached on the surface of red mud particles. The generated red mud/Fe_1−x(As)_x(OH)₃ showed a better sedimentation performance than the pure ferric arsenite, which is beneficial to the separation of arsenic from the solution. The red mud not only served as the carrier, but also as the alkaline agent and adsorbent for arsenic treatment. The effects of red mud dosage, dosing order, pH, and molar ratio of Fe/As on arsenic removal were investigated. The efficiency of arsenic removal increased from a pH of 2 to 6 and reached equilibrium at a pH of 7. At the Fe/As molar ratio of 3, the removal efficiency of arsenic ions with an initial concentration of 500 mg/L reached 98%. In addition, the crystal structure, chemical composition, and morphological properties of red mud and arsenic removal residues (red mud/Fe_1−x(As)_x(OH)₃) were characterized by XRD, XPS, X-ray fluorescence (XRF), SEM-EDS, and Raman spectroscopy to study the mechanism of arsenic removal. The results indicated that most of the arsenic was removed from the solution by forming Fe_1−x(As)_x(OH)₃ precipitates on the red mud surface, while the remaining arsenic was adsorbed by the red mud and ferric hydroxide.

中文翻译：

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通过在红色泥浆表面形成三价铁从高浓度砷（III）溶液中去除砷（III）

砷（As）被认为是最严重的无机污染物之一，某些冶炼厂产生的废水中砷含量很高。在本文中，我们用赤泥和Fe ³⁺协同纯化了高浓度砷溶液。在该系统中，亚砷酸根阴离子与Fe（III）离子反应形成亚铁酸亚铁，并附着在赤泥颗粒的表面。产生的赤泥/ Fe _1-x（As）_x（OH）₃具有比纯亚铁砷更好的沉降性能，这有利于从溶液中分离砷。赤泥不仅用作载体，而且还用作砷处理的碱性试剂和吸附剂。考察了赤泥用量，投加顺序，pH和Fe / As摩尔比对除砷的影响。砷的去除效率从pH值2提高到6，并在pH值为7时达到平衡。在Fe / As摩尔比为3时，初始浓度为500 mg / L的砷离子去除率达到98％。 。此外，赤泥和除砷残留物（赤泥/ Fe _1-x（As）_x（OH）₃的晶体结构，化学组成和形态学特性用XRD，XPS，X射线荧光（XRF），SEM-EDS和拉曼光谱进行表征，以研究除砷的机理。结果表明，通过在赤泥表面形成Fe _1-x（As）_x（OH）₃沉淀物，从溶液中除去了大部分砷，而其余​​的砷则被赤泥和氢氧化铁吸附。