Overhaul slag is a hazardous waste which is from the process of aluminum electrolysis industry. In this work, a technology of calcium sulfate roasting and water leaching was developed to dispose of overhaul slag. The effects of roasting and leaching parameters were investigated in detail. Under the optimal roasting conditions, the fluorine could be stably solidified into CaF2, and lithium could be converted into soluble NaLi(SO4). The roasted clinker was then subjected to water leaching for the selective extraction of lithium. About 99.74 % of lithium was extracted and 99.82 % of fluoride was solidified by the leaching process under the optimal leaching conditions. After water leaching, the concentration of lithium can reach 2.3 g/L. XRD analysis shows that the main phases of the aqueous solution after evaporation and crystallization are NaLi(SO4) and Na2SO4, and a small amount of impurities can be further removed and concentrated to prepare Li2CO3. The main components of leaching slag are C, Al2O3 and CaF2, which can be used as fast setting cement. The process proposed in this paper is not limited to the recovery of high-value lithium from overhaul slag, and can be applied to the extraction of other valuable waste substances in aluminum industry.

中文翻译：

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硫酸钙焙烧水浸选择性提取大修渣中锂和固化氟化物


大修渣是铝电解工业生产过程中产生的危险废物。本研究开发了硫酸钙焙烧水浸技术来处理检修渣。详细研究了焙烧和浸出参数的影响。在最佳焙烧条件下，氟可以稳定固化为CaF2，锂可以转化为可溶性NaLi(SO4)。然后对焙烧熟料进行水浸以选择性提取锂。在最佳浸出条件下，浸出过程中锂的提取率约为99.74%，氟化物的固化率约为99.82%。水浸后锂浓度可达2.3g/L。 XRD分析表明，蒸发结晶后的水溶液主相为NaLi(SO4)和Na2SO4，少量杂质可进一步脱除、浓缩制备Li2CO3。浸出渣的主要成分是C、Al2O3和CaF2，可用作快凝水泥。本文提出的工艺不仅限于从大修渣中回收高价值锂，还可以应用于铝工业中其他有价值废物质的提取。