草酸浸出分离中浸渣中铁锌的机理与分离条件的优化

Mechanism of Zinc and Iron Separation in Neutral Leaching Residue by Oxalic Acid Solution and Optimization of the Separation Condition

为了解决火法分离中浸渣中锌铁过程存在能耗大、碳排放量大以及湿法分离锌铁过程存在的浸出选择性差、浸出液除铁过程产出的黄钾铁钒渣和针铁矿渣需要另行处理等问题,提出采用草酸浸出分离中浸渣中铁锌的技术,并采用响应面法对铁和锌的分离条件进行优化,建立预测铁和锌浸出率的回归模型,同时对铁锌分离的机理以及伴生金属在分离过程中的行为进行了探讨。结果表明,要分解中浸渣中的ZnFe_(2)O_(4),实现铁锌的分离,则必须充分利用草酸的酸性、C_(2)O_(4)^(2-)对Fe^(3+)的络合性以及C_(2)O_(4)^(2-)与Zn^(2+)形成难溶ZnC_(2)O_(4)的性质。响应面法预测铁锌分离的优化条件为:(C_(2)O_(4)^(2-))TOT过量倍数为理论量的1.75倍,浸出时间170 min,浸出温度95℃和液固比8∶1,在该条件下,铁和锌的浸出率预测值和实测值分别为91.48%、0.63%和91.35%、0.64%。铁锌分离过程,91.35%铁以Fe(C_(2)O_(4))_(2)^(2-)和Fe(C_(2)O_(4))_(3)^(3-)的形式进入浸出液,而99.36%锌、94.24%铜及94.42%铅分别以ZnC_(2)O_(4)、CuC_(2)O_(4)和PbC_(2)O_(4)形式富集入渣,证明采用草酸能低温分解ZnFe_(2)O_(4)和分离中浸渣中的铁和锌,且分离过程不排放CO_(2),解决了现有火法和湿法方法分离铁锌过程存在的技术缺陷。

In order to solve problems of high energy consumption and high carbon emissions in the process of separation zinc and iron from the neutral leaching residue using the fire methods,as well as poor leaching selectivity in the process of separation zinc and iron using the wet methods,and potassium iron vanadium slag and needle ore produced by the process of iron removal from the leachate need to be treated,the technique of separation iron and zinc by oxalic acid was proposed,and the response surface method was used to optimize the conditions for iron-zinc separation,and regression models for predicting iron and zinc leaching rates were established.Meanwhile,the mechanisms of iron-zinc separation and the behavior of the associated metals were discussed in the process of separation.The results show that it is necessary to make full use of the acidity of oxalic acid,the complexation of C_(2)O_(4)^(2-) with Fe^(3+),the property of C_(2)O_(4)^(2-) and Zn^(2+)to form insoluble ZnC_(2)O_(4) to decompose ZnFe_(2)O_(4) for achieving the separation of iron and zinc in the neutral leaching residue.The optimization process conditions for iron-zinc separation predicted by the response surface method are as follows:(C_(2)O_(4)^(2-))TOT excess 1.75 times of the theoretical quantity,leaching time of 170 minutes,temperature of 95℃ and liquid-solid ratio of 8 mL/g,the predicted and the actual values of iron and zinc leaching rates are 91.48%,0.63% and 91.35% and 0.64%,respectively.In the process of iron-zinc separation,91.35%Fe is leached into the leachate as Fe(C_(2)O_(4))_(3)^(3-) and Fe(C_(2)O_(4))_(2)^(2-),99.36%Zn,94.24%Cu and 94.42%Pb are enriched into the leaching residue as ZnC_(2)O_(4),CuC_(2)O_(4) and PbC_(2)O_(4).It is proved that oxalic acid can decompose ZnFe_(2)O_(4) at low temperature and separate iron and zinc in the neutral leaching residue,and the separation process does not discharge CO_(2),the technical defects of the existing iron and zinc separation process by fire methods and wet methods are solved.