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Media type:
E-Book
Title:
Facile Manufacture of High-Purity Znco3/Zno from Wasted Zn-Rich Paint Residues Using a Combined Processes of Indirect Bioleaching and Precipitation
Description:
Waste zinc-rich paint residue (WZPR) represents a typical hazardous waste containing both toxic organic substances and toxic heavy metals. The extraction of Zn from WZPR by traditional direct bioleaching has been attracting attentions owing to its eco-friendliness, energy conservation and low cost. However, the long bioleaching time and low Zn release cast a shadow on the reputed bioleaching. To shorten the bioleaching time, the spent medium (SM) process was first used to free Zn from WZPR in this study. The results showed that the SM process has much high performance in Zn extraction. 100% (8.6 g/L) and 44.2% (15.2 g/L) of Zn removal were achieved at pulp densities of 2.0% and 8.0%, respectively, being more than 1000 times of that by previously reported direct bioleaching. The biogenic H+ in SM attacks ZnO to free Zn(Ⅱ) through quick acid dissolution; while the biogenic Fe3+ not only strongly oxidizes Zn0 in WZPR to generate and release Zn2+ but also fiercely hydrolyzes to generate H+ which attacks ZnO to free Zn(Ⅱ). Both biogenic H+ and Fe3+ contribute to over 90% of Zn extraction as the leading indirect bioleaching mechanism. Because of high Zn2+ concentration and less impurity, the indirect bioleachate was used to successfully produce high-purity ZnCO3/ZnO by facile and simple precipitation, accomplishing the high-value recycling of Zn in WZPR