Intensifying gibbsite precipitation from sodium aluminate solution by adding a mixed seed

添加混合晶种强化铝酸钠溶液的晶种分解过程（英文）

Gibbsite precipitation from sodium aluminate solution was intensified by adding mixed industrial and self-prepared active seeds,and its mechanism was researched preliminarily.The interfacial properties of seed/aluminate solution were determined for separate industrial and active seed.Contact angles of seed/aluminate solution and the specific surface area of seeds were respectively measured by sessile drop and BET method,and the morphology and particle size of precipitates were recorded by SEM and laser diffraction.The results show that,compared with the industrial seed,the active seed has a better wettability,lower interfacial tension,and larger specific surface area,being conducive to enhancing gibbsite precipitation from sodium aluminate solution.SEM analysis of the precipitates indicates that the embedment and accumulation/agglomeration of extremely fine particles on the surface of coarse industrial seed can effectively control the content of fine particles in the precipitation product.With extra 3.1–4.6 g/L active seed,the gibbsite precipitation ratio was increased by 3.23%–3.92%.Moreover,the mass percentage of particles<45μm in precipitation product has even a slight decrease compared with that for the traditional precipitation product or of the industrial seed itself.The result presented is favorable to developing an intensified gibbsite precipitation process for commercial alumina manufacture.

本文报道了工业晶种和自制活性晶种组成的混合晶种强化铝酸钠溶液中三水铝石结晶析出的工艺,并初步研究了其强化机理。对比研究了活性晶种/铝酸钠溶液、工业晶种/铝酸钠溶液的界面性质。分别采用坐滴法和BET法测定了晶种/铝酸钠溶液接触角及晶种比表面积;采用激光衍射法和SEM分别测定了种分产品的粒度分布及形貌。研究结果表明,相对于工业晶种,活性晶种的润湿性能更好、比表面积更大以及晶种/铝酸钠溶液界面张力更低,这些性质均利于加速铝酸钠溶液中氢氧化铝在晶种/铝酸钠溶液界面的析出。结晶产物的SEM分析表明,细小颗粒会嵌入、堆积及附聚到粗粒度工业晶种表面,从而可有效地控制结晶产物中的细颗粒含量。额外加入3.1～4.6 g/L活性晶种,种分分解率可提高3.23%～3.92%,且种分产物中<45μm颗粒含量比工业晶种及传统种分产物的均略有减少。研究结果有利于为氧化铝工业生产开发一种新的铝酸钠溶液晶种分解过程强化工艺。