Preparation of elemental As from As-Sb fly ash using continuous reductive method with additive of lead oxide

Abstract

To recycle arsenic from an As-Sb fly ash, a newly continuous reductive method for obtaining elemental As with additive of PbO was proposed. In the first reduction stage, PbO promoted the As segregation from the As-Sb fly ash, due to which most As volatilized and Sb retained in roasted residues in phases of As-Sb-Pb-O and As-Sb-Pb alloy. With the increase of PbO and reductant amounts, the Sb fixation rate increased in the first reduction stage, and further the Sb content in the elemental As obtained from the second reduction stage decreased. After being roasted for 30 min at 550 °C with the addition of 20% activated carbon and 12% PbO in the first reduction stage, the As volatilization rate and Sb fixation rate from the As-Sb fly ash reached 92.86% and 79.38%, respectively. Then through the second reduction of the volatile matters at 650 ° C, the As and Sb contents in the obtained elemental As reached 99.07 wt% and 0.22 wt% respectively, indicating that the obtained As could be used to prepare high purity As, thereby rendering the As-Sb fly ash recycling.

摘要

为了实现砷锑烟尘中砷的循环利用,本文提出一种以PbO为添加剂,通过连续还原法从砷锑烟 尘中制备单质砷的方法。在第一段还原工艺中,以PbO为添加剂,砷大量挥发的同时将锑高效固定在 焙烧底物中,实现了砷、锑的高效分离;在第二段还原工艺中,将挥发砷物相还原为单质砷,实现了 砷的资源化利用。在PbO 作用下,第一还原阶段中锑以As-Sb-Pb-O 和As-Sb-Pb 合金形式存留在焙烧 底物中,当增加PbO 和还原剂用量时,锑固定效率增加,有效降低了第二还原阶段产物砷中的锑含 量。在第一还原阶段焙烧温度550 °C、活性炭添加量20%和PbO添加量12%,焙烧时间30 min 时,砷 锑烟尘中砷挥发效率为92.86%,锑固定效率达79.38%;挥发物经第二阶段650 °C还原后,所获得砷 产物中砷、锑含量分别为99.07 wt%和0.22 wt%。所获得的单质砷产物可作为制备高纯砷的原料,从而 实现了砷锑烟尘中砷的循环利用。