Desiliconization reaction in sodium aluminate solution by adding tricalcium hydroaluminate

The desiliconization reaction in sodium aluminate solution was studied by adding tricalcium hydroaluminate (C3AH6). C3AH6 prepared at 323 K has a relatively high desiliconization capacity. Kinetic results show that the desiliconization reaction is first-order in SiO2 concentration, and the apparent activation energy is estimated to be 96 kJ/mol between 363 and 393 K, which is lower than that from adding Ca(OH)2. During the desiliconization process, SiO2(OH)2− ions enter the interior of C3AH6 particles and react with them further. As a result, the distribution of SiO2 in the desiliconization product (DSP) is more uniform than that from adding CaO. Also, the SiO2 content in DSP is higher.