含氟、砷氧化锌烟灰制备活性氧化锌

Preparation of Active Zinc Oxide from Fluorine and Arsenic Containing Zinc Oxide Fume Dusts

摘要: 以氧化锌烟灰为原料，采用NH₃-NH₄Cl溶液浸出，浸出液采用FeCl₃作为除砷剂进行除砷，采用CaCl₂作为除氟剂进行除氟，再经锌粉置换除杂和活性炭吸附处理后，采用浓盐酸调节pH进行沉锌、进而进行二次加水水解转化和煅烧以制备活性氧化锌。研究结果表明，在NH₄Cl浓度4mol/L、NH₃•H₂O浓度2mol/L、浸出温度50℃、浸出时间1h的浸出条件下，锌的浸出率达到98%以上。当n_Fe/n_As= 5时，FeCl₃作为除砷剂除砷率达到99.7%；当n_Ca/n_F= 1时，CaCl₂作为除氟剂除氟率达到98.5%。采用浓盐酸调节pH至6.70时，Zn(NH₃)₂Cl₂沉淀的析出率达到最大，为82.85%。Zn(NH₃)₂Cl₂沉淀物经一次水解转化得到Zn(OH)_1.6Cl_0.4，经二次水解转化得到Zn(OH)₂，再经500℃煅烧2h后可得活性氧化锌，产品质量均达到HG/T2572-2012标准指标，锌的直收率达80%以上。

Abstract: Zinc oxide fume dusts as raw material were leached with NH₃-NH₄Cl solution. The arsenic and flu-orine in leaching solution were removed with FeCl₃ and CaCl₂ respectively. After the zinc powder displacement process and activated carbon adsorption treatment, precipitation of Zn(NH₃)₂Cl₂ was carried out by adjusting the pH value of leaching solution with concentrated hydrochloric acid. Then active zinc oxide was prepared from two-step hydrolytic conversion of Zn(NH₃)2Cl₂ followed by calcination. The results show that the zinc leaching rate is more than 98% at the condition of 4 mol/L NH₄Cl, 2 mol/L NH₃•H₂O, leaching temperature and leaching time of 50˚C and 1 h. The re-moval rates of arsenic and fluorine are 99.7% and 98.5% respectively when the molar ratio of Fe to As is 5 and Ca to F is 1. The precipitation rate of Zn(NH₃)₂Cl₂ reaches its maximum, which is 82.85% at pH = 6.7. The products of two-step hydrolytic conversion are Zn(OH)_1.6Cl_0.4 and Zn(OH)₂ in sequence. Active zinc oxide is finally obtained by calcination at 500˚C for 2 hours. The quality of product is up to the standards of HG/T2572-2012 and the direct recovery rate of zinc is above 80%.