羟胺聚合物诱导的泡沫分离脱除铝酸钠溶液中有机物的基础研究

Organics in sodium aluminate solution significantly raises soda loss, reduces precipitation rate, degrades alumina quality and increases product cost. Economically removing organics is extremely difficult in alumina production. A novel method of foam separation was given to remove organics on basis of existence of substantial stable foam in Bayer liquor with addition of polymer containing hydroxyl and amino. The polymer with different ratio between hydroxyl and amino was synthesized to improve polymer’s solubility. Afterwards, molecular interaction among organics was studied. Interfacial behavior, micellar and micellar’ solubilization were also discussed. Moreover, hydrogen bond, Van der Waals force and electrostatic interaction were coupled to affect the organic aggregation, foam property and interface property. Accordingly, organics was remarkably richened by reducing repulsive force together with regulation of other molecular interaction. Removal rate of organics was significantly improved and negative effect of organics on alumina production was eliminated. Therefore, complex process, large consumption and high production cost in traditional processes, such as causticisation of sodium oxalate with lime, Bayer liquor sintering and treatment with seawater, will be overcome. In addition,these results will remarkably benefit the economical utilization of bauxite with high organic content or high silica content in China or abundant gibbsite in foreign.

铝酸钠溶液中有机物会增加碱耗、降低分解率、降低产品质量和增加生产成本，经济脱除有机物一直是研究的难点。本项目充分利用拜耳法铝酸钠溶液中泡沫丰富、稳定等特性，通过羟胺聚合物诱导，采用泡沫分离方法脱除中高分子量有机物。首先，设计羟基和胺基比例，合成溶解性较好的羟胺聚合物。然后，通过阐明有机物分子间相互作用规律，阐述铝酸钠溶液中有机物的表面行为、胶束状态和胶束增溶作用，提出有机物分子间氢键、范得华力和静电作用等多种分子间相互作用协同调控机理，揭示铝酸钠溶液中有机物的聚集行为、泡沫性质和界面性质的调控原理，突破铝有机物在界面上同性排斥和有机物聚集难的技术瓶颈，促进泡沫对有机物的富集，显著提高泡沫分离有机物的效率，经济消除有机物对氧化铝生产的负面影响，解决传统的石灰苛化脱除草酸钠、溶液燃烧法和海水法等工艺复杂、消耗大和成本高等问题，为丰富我国铝土矿资源和充分利用国外优质铝土矿提供技术支撑。

经济脱除铝酸钠溶液中的有机物一直是研究的难点。本项目充分利用拜耳法铝酸钠溶液中泡沫丰富、稳定等特性，通过添加剂诱导，采用泡沫分离方法脱除中高分子量有机物。首先，发现了铝酸钠溶液中中高分子量阴离子有机物都具有强表面活性，表面吸附量随有机物浓度增多而升高，胶束的生成可导致铝酸钠溶液粘度升高。然后，混和有机物的临界胶束浓度符合非理想混和表面活性剂临界胶束浓度模型，分子间相互作用强，胶束尺寸大；同时有机物浓度升高至cmc以上，泡沫中有机物富集比和有机物脱除率仍在升高，在气液界面不符全Lamgmuir吸附模型，在LB膜研究中证明气液界面上存在胶束，这些发现表明了铝酸钠溶液中界面上存在多层界面结构。还发现了含有机物铝酸钠溶液中的泡沫尺寸小、泡沫更丰富，稳定性更高，温度升高降低泡沫的稳定性。基于多层界面结构，提出了泡沫富集分离有机物的技术原型，有机物的富集比达3.4，有机物脱除率达42%。此外，基于铝酸钠溶液中有机物的多层界面结构，提出了水合铝酸钙高效吸附脱除拜耳法有机物的技术，进行了工业化试验。这些研究结果为经济高效脱除我国拜耳法溶液中有机物提供了新的思路，也为深入理解碱体系中表面活性剂分子间相互作用提供了理论依据。