工业氢氧化铝重溶重结晶制备高纯氧化铝试验研究

Preparation of High-purity Alumina Using Industrial Aluminum Hydroxide by Reconstitution and Recrystallization

研究了用高浓度氢氧化钠溶液溶解工业氢氧化铝并重结晶制备高纯度氧化铝,考察了水质、分级过筛及洗涤、初始氢氧化铝浓度、种分时间和温度对产物中杂质含量的影响。结果表明:用高纯水配制Na2O和Al2O3初始质量浓度分别为170、184 g/L的铝酸钠溶液,并在30℃下种分60 h,所得氢氧化铝中SiO2、Fe2O3杂质质量分数分别低于3.0×10-3%和5.0×10-3%,纯度相对较高,但仍需深度除钠;种分氢氧化铝产物用稀盐酸水热处理后进行焙烧,在超声波作用下,热稀酸中氧化铝晶体和晶间残留的Na2O被脱除,最终所得Al2O3产物中Na2O质量分数低至3.8×10-2%,纯度在99.9%以上。

High-purity alumina was prepared by using high concentration sodium hydroxide solution to dissolve industrial aluminum hydroxide and recrystallizing.The effects of water quality,sieving and washing,initial aluminum hydroxide concentration,seed precipitation time and temperature on impurity content in product were examined.The results show that under the conditions of initial Na2O and Al2O3 mass concentrations of 170 and 184 g/L,respectively in sodium aluminate solution prepared using high purity water,seed precipitation time 60 h at 30℃,the silica and iron oxide impurities content in aluminum hydroxide is less than 3.0×10-3%and 5.0×10-3%,and requires further removal of sodium.After hydrothermal treatment with dilute hydrochloric acid,the alumina crystal and residual Na2O in the hot dilute acid are removed by ultrasonic wave.At last,the Na2O content in Al2O3 decreases to about 0.038%,and the final alumina purity is over 99.9%.