用煅烧-沥滤工艺从粉煤灰中提取高纯超细氧化铝

介绍了1种采用煅烧-沥滤工艺从粉煤灰中提取氧化铝(Al2O3)的新方法.以碳酸钠(NaCO3)为活化剂,在900 ℃下煅烧,使粉煤灰中惰性的Al2O3转变成活性的可以溶出的铝盐.选用硫酸(H2SO4)为活性铝盐的溶出剂,在一定温度下溶出铝盐,使活化后粉煤灰中的Al2O3以液相形式溶出.用乙二胺四乙酸为络合剂有效除去铝盐Al2(SO4)3]中的杂质铁(Fe3 )等,用蒸馏水洗涤除去钠(Na )和其它可溶性杂质,有效提高Al2O3粉体的纯度.通过添加合适的分散剂、控制氢氧化铝Al(OH)3]的结晶、干燥及煅烧的工艺条件,大大提高了Al2O3粉体的细度.通过X射线衍射、透射电子显微镜和N2吸附等技术分析获得的Al2O3粉体的组成与微观结构.通过以上工艺,获得Al2O3的提取率超过98%.将干燥后的Al(OH)3粉体在800 ℃下煅烧得到分散性好的纤维状γ-Al2O3,其纯度(质量分数)达99.6%.

HIGH PURITY ALUMINA POWDERS EXTRACTED FROM FLY ASH BY THE CALCINING-LEACHING PROCESS

A new calcining-leaching process was used to extract high purity alumina (Al2O3) powders from fly ash in this study. The fly ash was mixed with soda (Na2CO3) and calcined at 900 ℃ to yield soluble aluminates. Subsequently the calcined ash was leached with sulfuric acid (H2SO4) to produce a solution containing aluminum. The unwanted metal ions including Fe3+ and Na+ were removed by ethylene diamine tetraacetic acid (EDTA) and water washing. Then added the proper dispersant, controlling the crystallization of aluminum trihydroxide precipitation, and the drying and calcining process was carried out, resulting in ultra fine Al2O3 powders with high purity. The characteristics of the Al2O3 powders were examined by means of X-ray diffraction, transmission electron microscope and the Brunauer, Emmet and Teller (BET) surface analysis method. The extraction efficiency of Al2O3 can surpass 98%by optimization of the calcination and lixiviation processes. Well-dispersed fibriform γ-Al2O3 powders were obtained by calcining at 800 ℃ and the purity of the ultra fine Al2O3 powders was more than 99.6%.