Extraction Of Silicon Oxide From The Partially Dealuminated Metakaolin Residue Of The Kaolin-based Aluminum Sulfate Manufacturing Process

Partially dealuminated metakaolin (PDMK) is a by-product of aluminum sulfate production. The novelty is to use PDMK as a low-cost source for extraction of silica and production of high modulus Na2Si2O3 at relatively low temperature and at normal pressure. The process of silicon oxide extraction was tested, including the thermodynamic parameters such as the heat of formation, the entropy, and the enthalpy of the reactions. The PDMK and the formed compounds were characterized using a Fourier transform infra-red spectrophotometer (FTIR), and X-ray diffractometry (XRD). The effect of the dissolved aluminate compound on the extraction procedure of the amorphous silicate was also tested. 50%, 45%, and 18%, of Al, Fe, and Ti elements were removed respectively to improve the extraction of silica. 88.7% of silica was extracted by using NaOH (5 Mol.), at 75°C for 2h. A sodium silicate of modulus (SiO2: Na2O) 1.1 was prepared as indicated in the above figure. A low silica modulus sodium silicate (1.1) was used to prepare high silica modulus sodium silicate with SiO2: Na2O = 3.11 at 80°C for 3h. At 200 °C and for 3h of alkaline digestion reaction, the ratio of SiO2 to Na2O reached 3.55.