利用铬渣制备重铬酸钠

研究了采用焙烧—硫酸酸化法利用铬渣制备重铬酸钠的工艺.通过L16(44)正交实验得出铬渣焙烧—浸出的最佳工艺条件为:焙烧温度1 000℃,m(碳酸钠)∶m(铬渣)=0.18,液固比4,焙烧时间8h.在此条件下Cr(Ⅵ)回收率为99.3％.硫酸酸化制备重铬酸钠的最佳工艺条件为:浸出液pH为6.6,酸化液pH为3.5,浓缩液中重铬酸钠质量分数为83.1％.此条件下制备的产品重铬酸钠结晶率为44.5％,纯度为99.5％,符合GB1611-92《工业重铬酸钠》的一等品质量标准.处理1t铬渣可制备重铬酸钠约120 kg,增加收入660元.

Preparation of Sodium Dichromate from Chromium Slag

The process for preparation of sodium dichromate from chromium slag by calcination-sulfuric acid acidification was studied.The optimum calcination-leaching conditions obtained through the orthogonal experiments L16(45) are as follows:calcination temperature 1 000 ℃,calcination time 8 h,m(Na2CO3)∶ m(chromium slag)= 0.18,ratio of liquid to solid 4.Under these conditions,the recovery rate of Cr(VI) is 99.3%.The optimum conditions for sulfuric acid acidification are as follows:leaching solution pH 6.6,acidification solution pH 3.5,sodium dichromate mass fraction in concentrated solution 83.1%.Under these conditions,the crystallization rate of sodium dichromate is 44.5%,and the product purity is 99.5%,which can meet the first grade standards of GB 1611-92.About 120 kg of sodium dichromate can be produced from 1 t of chromium slag gaining 660 yuan of profit.