利用还原焙烧-碱性浸出工艺处理高铁锌焙砂以解决现有炼锌工艺锌铁分离的难题,通过还原焙烧将高铁锌焙砂中铁酸锌分解为氧化锌和铁氧化物,氧化锌在碱性体系被选择性浸出,铁氧化物赋存于浸出渣中实现锌铁分离.以锌、铁浸出率为评价指标,考察还原焙烧及碱性浸出条件对锌铁分离效果的影响,并对焙烧产物及浸出渣进行XRD、SEM-EDS分析.结果表明:最佳还原焙烧条件如下,焙烧时间45 min,焙烧温度800℃,CO浓度4%(体积分数);最佳浸出条件如下,NaOH浓度240 g/L,液固比12:1,浸出温度80℃,浸出时间60 min.在最佳条件下总锌浸出率约为90%,总铁浸出率约为0.25%,SEM分析显示:浸出渣中锌铁氧化物镶嵌现象严重,这是锌浸出率不能进一步提高的原因.
To resolve the problem of zinc-iron separation of zinc ferrite in conventional zinc smelting process, a reduction roasting-alkaline leaching process was proposed. Zinc ferrite in high iron-bearing zinc calcine was decomposed to zinc oxide and iron oxide by reduction roasting, then, zinc oxide was selectively leached in alkaline system, the iron oxide remained in the leaching residues. The effects of roasting conditions and leaching conditions on the separation of zinc-iron were evaluated by the leaching rate of zinc and iron. The roasted products and leaching residues were analyzed by XRD and SEM-EDS. The results show that the optimal roasting condition as follows: roasting temperature of 800℃, CO concentration of 4% (volume fraction), roasting time of 45 min; the optimal leaching condition is leaching temperature of 80℃, NaOH concentration of 6 mol/L, liquid-solid ratio of 12:1 and leaching time of 60 min. Under this optimal condition, the leaching rates of zinc and iron are 90.4% and 0.25%, respectively. But the analysis result of SEM-EDS shows that the mosaic phenomenon of zinc oxide and iron oxide in leaching residue is serious, this is the reason why the leaching rate of zinc is hard to be further improved.
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