铬酸钠溶液中和除铝浆液沉降性能的改善

Improvement in settlement property of alumina tri-hydrate slurry by neutralization in sodium chromate solution

研究铬酸钠碱性液中和除铝方式、温度和碱性液种类对除铝浆液沉降性能的影响规律。结果表明:晶种中和法获得的铝泥前2 min平均沉降速率达107.1 mm/min,含水率小于38%,铬带损小于0.26%;而采用传统的直接中和法获得的铝泥前2 min平均沉降速率小于7.25 mm/min,含水率大于67%。氢氧化铝粒度分布、扫描电镜和接触角测定结果表明:提高中和除铝的温度、降低碱性液SiO2等杂质含量有利于改善除铝浆液的沉降性能。铝泥颗粒粗、结晶好,且其表面疏水性强、表面能低、溶剂化趋势小,能提高铝泥的沉降性能。

The influence of neutralization method,temperature and types of chromate solution on the settlement property of alumina tri-hydrate was studied in the removal of alumina from chromate solution.The results show that the average settlement rate of alumina tri-hydrate is up to 107.1 mm/min in initial 2 min,and water content and loss of chromate in alumina tri-hydrate is less than 38% and 0.26%,respectively by seeded neutralization.In contrast,the average settlement rate of alumina tri-hydrate is less than 7.25 mm/min in initial 2 min period,and water content is more than 67% by traditional direct neutralization process.In addition,increasing temperature or removing SiO2 in solution benefits the improvement of the settlement property for alumina tri-hydrate in the seeded neutralization process.Based on the measurement of the contact angle,particle size distribution and SEM,the results also indicate that the better settlement property of alumina tri-hydrate can be attributed to coarse particle,good crystallization,hydrophobic,low surface free energy and little solvent tendency of alumina tri-hydrate in the removal of alumina in chromate solution.