Preparation of metallic arsenic from calcium arsenate by carbon thermal roasting reduction
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摘要: 面对石灰沉淀法除砷工艺在含砷矿物冶炼中的广泛应用,砷酸钙的无害化和资源化被日益重视。本文针对碳热焙烧还原砷酸钙制备金属砷并再生氧化钙展开研究。热重分析表明,砷酸钙与碳粉混合热解的失重分为三个阶段,阶段一和二为失水过程,阶段三为碳还原砷酸钙生成CaO和砷蒸气过程。且研究发现,可以利用相边界反应动力学模型解释阶段三反应机制。而单因素条件实验结果表明:在温度1000℃、碳配入系数1.4、恒温时长60min条件下砷挥发率高达99.94%。X射线衍射仪(XRD)、扫描电镜能谱仪(SEM-EDS)对反应体系中有关产物表征表明,产品砷主要为片状金属砷和粉末不定型砷,焙烧残渣为CaO。Abstract: In the face of the widespread use of the lime precipitation process for arsenic removal in the smelting of arsenic-containing minerals, the soundness and resourcefulness of calcium arsenate is being given increasing attention. In this paper, we investigate the preparation of metallic arsenic and regeneration of calcium oxide by the reduction of calcium arsenate by carbon thermal roasting. Thermogravimetric analysis shows that the weight loss of calcium arsenate mixed with carbon powder is divided into three stages, with stages one and two being the water loss process and stage three being the carbon reduction of calcium arsenate to produce CaO and arsenic vapour. And it was found that the phase three reaction mechanism could be explained by using the phase boundary reaction kinetic model. The results of the single-factor experiments showed that the arsenic volatilisation rate was as high as 99.94% at a temperature of 1000°C, a carbon incorporation factor of 1.4 and a constant temperature of 60 min. The characterisation of the products in the reaction system by X-ray diffraction (XRD) and scanning electron microscope energy spectrometry (SEM-EDS) showed that the arsenic products were mainly flake metallic arsenic and powder indeterminate arsenic, and the roasting residue was CaO.
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Key words:
- calcium arsenate /
- arsenic vapor /
- metallic arsenic /
- elemental arsenic
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