关键词: 霓辉正长岩, 预脱硅, 脱硅剂, 水化石榴石

Abstract:

The principal phase of potassium-distilled filter residue of aegirine-augite syenite is sodium aluminum silicate hydrate rich in Al2O3  and SiO2. The high caustic ratio sodium aluminate solution was obtained from filter residue treated by high pressure hydrochemical process. The desilication reaction was experimentally studied by adding different types of desilication agents. The orthogonal experimental results show that in the process of the desilication from sodium aluminate solution, the descending order of affecting factors is as follows：desilication agent type, desilication time, desilication temperature. The optimal conditions of desilication are that the desilication agent is tricalcium hydroaluminate, and desilication temperature is 160 ℃ and the desilication time is 3.5 h. The silicon index of the refined aluminate solutions was obtained to be above 1,800 by one-step desilication procedure. According to X-ray diffraction analysis, the major phase of derived products is hydrogarnet. The diffraction intensity of hydrogarnet  increases sharply with the desilication time increasing. The results of scanning electron microscopy and EDS analysis show that hydrogarnets reveal high crystallinity and perfect fine-grains, and SiO2 impurities easily attached with the small crystals, so a better effect of silicon removal is achieved.

Key words: aegirine-augite syenite, pre-desilication, desilication agent, hydrogarnet