锑冶炼砷碱渣短流程制备金属砷基础研究

Basic research on the preparation of metallic arsenic via a short process from arsenic-alkali slag in antimony smelting

  • 摘要: 金属砷是半导体材料的核心原料. 锑冶炼砷碱渣中砷含量高、成分复杂,利用其制备金属砷的关键在于砷与各种杂质的高效分离. 本文基于砷地球化学成矿原理,创新性提出了砷酸复盐高精度矿化沉淀理论,开发了砷酸复盐一步还原焙烧制备金属砷的关键技术,突破了高碱/盐溶液中砷与碱、相似杂质的高效分离难题,实现了含砷固废短流程高效制备金属砷. 研究表明:采用双氧水进行氧化浸出实现了砷碱渣中砷的高效选择性脱除,最佳反应条件下浸出液中碱、砷与硫组分含量较高;通过碳化处理浸出液回收碱,产品中碱含量达98.79%;砷酸复盐矿化沉淀实现了砷酸盐和碳酸氢盐的选择性分离,含砷渣品位达29.75%;通过对高砷渣中加入碳粉进行还原焙烧处理,得到了纯度达99.81%的金属砷单质,单质砷中锑、硫杂质的含量仅为3%和0.16%,分析还原焙烧过程和冷凝过程中温度与吉布斯自由能的关系可知,为避免影响单质金属砷的品质,硫酸盐还原过程温度应设为620℃,增加还原物质碳粉用量或者升高还原焙烧温度,均有利于提高还原挥发效率以及降低单质砷中硫杂质的含量. 本研究不仅可以为含砷固废的资源化处置提供理论依据,还有望为金属砷的高效制备提供技术支撑.

     

    Abstract: Metallic arsenic is a critical raw material in the semiconductor industry. Arsenic-alkali slag from antimony smelting contains a high concentration of arsenic and has a complex composition. The key to preparing metallic arsenic lies in the efficient separation of arsenic from various impurities. In this study, based on the geochemical mineralization principles of arsenic, we propose an innovative theory of high-precision mineralization and precipitation of arsenate complex salts. We developed a key technology involving one-step reduction roasting of arsenate complex salt precursors for metallic arsenic production. This approach overcomes the challenges of efficiently separating arsenic and alkali in high alkali/salt solutions and similar issues with impurity separation, enabling a shortened process for converting arsenic-containing solid waste into high-purity metallic arsenic. Our findings show that oxidative leaching using hydrogen peroxide enables effective and selective removal of arsenic from arsenic-alkali residue. The liquid-solid ratio, temperature, and hydrogen peroxide dosage significantly influence the leaching rate. Under optimal reaction conditions, the leachate contains high concentration of alkali, arsenic, and sulfur. Carbonation of the leachate allows for alkali recovery, yielding a product with an alkali content of up to 98.79% and a uniform particle size distribution. Arsenate salt mineralization and precipitation achieve selective separation of arsenate from bicarbonate and alkali. With increased dosage of ammonium salts and magnesium sources, the arsenic removal rate improves. The arsenic content in slag increases with magnesium salt dosage and then decreases. Reaction time positively influences arsenic removal, while higher temperatures reduce both the arsenic removal rate and the arsenic grade in slag, the latter reaching 29.75%. Through reduction roasting of high-arsenic slag using carbon powder, metallic arsenic with 99.81% purity was obtained. The monomeric arsenic contained only 0.03% antimony and 0.16% sulfur impurities. Analysis of the reduction roasting and condensation processes, considering the temperature and Gibbs free energy, indicates that to maintain the quality of the metallic arsenic monomers, sulfate reduction should occur at 620 °C. Increasing the carbon powder dosage or elevating the roasting temperature promotes reduction volatilization and lowers sulfur impurity content in the final product. This study provides both a theoretical basis for the resource-efficient disposal of arsenic-containing solid waste and technical support for the efficient preparation of metallic arsenic.

     

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