碱式氧化焙烧-水浸-还原法从电镀污泥中制备三氧化二铬

Preparation of Cr_(2)O_(3) from electroplating sludge using combined process of alkaline-oxidizing roasting followed by water leaching and Na_(2)S reduction

电镀污泥中铬主要以氧化物或氢氧化物形式存在,氧气气氛中以Na_(2)CO_(3)为添加剂对电镀污泥进行焙烧,并对焙烧渣进行水浸处置,最后加入Na_(2)S还原,可实现铬资源的高效回收。结果显示:O_(2)流量40 mL/min条件下,焙烧过程中控制Na_(2)CO_(3)添加量100%、焙烧温度700℃和焙烧时间90 min,焙烧渣水浸工艺中铬浸出率可达97.8%,一定范围内,增加Na_(2)CO_(3)添加量、提高焙烧温度和延长焙烧时间,可促进Cr由尖晶石相(FeCr_(2)O_(4)和AlCr_(2)O_(4))转变为Na_(2)CrO_(4),使铬浸出率提高;Na_(2)CrO_(4)浸出液Na_(2)S还原工艺中,在60℃条件下,控制还原反应物料比n(CrO_(4)^(2-))/n(S^(2-))为8∶9,反应80 min,还原工艺中铬回收率可达92.3%,增加Na_(2)S添加量、提高反应温度和延长反应时间,可以促进Na_(2)CrO_(4)转变为Cr_(2)O_(3),提高铬收率,但过多的Na_(2)S会使体系pH值升高,导致Cr_(2)O_(3)反溶,造成铬回收率下降。研究实现了电镀污泥中铬的高效回收。

The chromium in the electroplating sludge occurred mainly in forms of oxides and/or hydroxides, which could be recovered through a combined process of Na_(2)CO_(3) assisted oxidizing roasting and water leaching in this research. The results show under the condition of Na_(2)CO_(3) amount of 100%, roasting temperature of 700 ℃, and roasting time of 90 min, the Cr recovery rate reached 97.8% in the subsequent water leaching process;in a certain range, the Cr recovery rate increased with the increase of Na_(2)CO_(3) amount, roasting temperature and time;in the Na_(2)S reduction of Na_(2)CrO_(4) leaching solution, the chromium yield increased with the increase of the amount of Na_(2)S addition, reaction temperature and reaction time;however, excessive Na_(2)S amount would increase the pH of the leaching solution, resulting in the reverse dissolution of Cr_(2)O_(3) and the decrease of chromium recovery;under the optimized condition of reaction temperature of 60 ℃, n(CrO_(4)^(2-))/n(S^(2-)) of 8∶9, and reaction time of 80 min, the chromium recovery reached 92.3%. The study achieved an efficient recovery of chromium from electroplated sludge.