MER Division, National Metallurgical Laboratory, Jamshedpur, India; Academy of Scientific and Innovative Research, New Delhi, India.
MER Division, National Metallurgical Laboratory, Jamshedpur, India; Indian Institute of Technology-Baranas Hindu University, Varanasi, India.
J Environ Manage. 2020 Feb 15;256:109985. doi: 10.1016/j.jenvman.2019.109985. Epub 2019 Dec 13.
Galvanizing dross-a waste product from steel industries but it can be a potential secondary resource for zinc through urban mining and recycling. In this concern, a novel and scalable recycling route with zero effluent strategy is developed for the recovery of zinc from galvanizing dross as high grade zinc salts along with value-added products through hydrometallurgical processing. In particular, as-such dross block was leached in 9% (v/v) sulphuric acid medium, wherein strong hydrogen gas effervescence results in alleviating the pulverization and stirring requirements; which are material and energy intensive. Leached zinc is purified and recovered as high purity ZnSO.(HO/7HO) and Zn(PO).4HO through controlled crystallization and phosphate precipitation respectively; which find application in fertilizers and anti-corrosive paints. Temperature difference method was opted for the crystallization of zinc sulfate salts, wherein 70 °C and 30 °C were found to be stability range of crystallization of ZnSO.HO and ZnSO.7HO respectively. ZnSO-HO phase diagram is developed using Factsage calculations to corroborate crystallization study. Moreover, exhaustive thermodynamic analysis of Zn-PO-HO system at 303 K on precipitation of zinc phosphate using di-ammonium hydrogen phosphate (80-240 g/L) is conducted and the results reveal that with increasing pH (3-6), intermediate hydrogen phosphate species (HPO, HPO and HPO) decompose to produce stable PO ions leading to zinc phosphate precipitation. Impurity like Iron and supernatant solution left after crystallization are recovered as hydrated iron-calcium sulfate mixture and ammonium sulfate salt respectively. This explored route is economical and easily adaptable with zero effluents, therefore, transcends serious challenges in terms of energy requirement, scale-up and effluent generation.
热镀锌浮渣——钢铁行业的一种废物，但通过城市采矿和回收，它可以成为锌的潜在二次资源。在这方面，开发了一种新颖的、可扩展的回收路线，采用零废水策略，通过湿法冶金处理从热镀锌浮渣中回收高品位的锌盐以及附加值产品。特别是，原样的浮渣块在 9%（体积/体积）的硫酸介质中浸出，其中强烈的氢气沸腾有助于减轻粉碎和搅拌的要求；这些要求耗费大量的材料和能源。浸出的锌通过控制结晶和磷酸盐沉淀分别纯化和回收为高纯度的 ZnSO.(HO/7HO) 和 Zn(PO).4HO；这些产品可应用于肥料和防腐涂料。选择温差法进行硫酸锌盐的结晶，分别在 70°C 和 30°C 下得到 ZnSO.HO 和 ZnSO.7HO 的结晶稳定范围。使用 Factsage 计算开发了 ZnSO-HO 相图，以验证结晶研究。此外，在 303 K 下对使用二铵氢磷酸盐（80-240 g/L）沉淀锌磷酸盐的 Zn-PO-HO 体系进行了详尽的热力学分析，结果表明，随着 pH 值（3-6）的增加，中间的磷酸氢盐物种（HPO、HPO 和 HPO）分解产生稳定的 PO 离子，导致锌磷酸盐沉淀。杂质如铁和结晶后留下的上清液分别回收为水合铁钙硫酸盐混合物和硫酸铵盐。这条探索出的路线经济且易于适应，零废水，因此克服了能源需求、规模化和废水产生方面的严重挑战。
