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

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 C2O42- with Fe3+, the property of C2O42- and Zn2+ to form insoluble ZnC2O4 to decompose ZnFe2O4 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: (C2O42-)TOT excess 1. 75 times of the theoretical quantity, leaching time of 170 minutes, temperature of 95 °C 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(C2O4)33- and Fe(C2O4)22-, 99. 36%Zn,94. 24%Cu and 94. 42%Pb are enriched into the leaching residue as ZnC2O4, CuC2O4 and PbC2O4. It is proved that oxalic acid can decompose ZnFe2O4 at low temperature and separate iron and zinc in the neutral leaching residue, and the separation process does not discharge CO2, the technical defects of the existing iron and zinc separation process by fire methods and wet methods are solved. [ABSTRACT FROM AUTHOR]