Nano-porous hydrosodalite fabrication via hydrothermal modification of processed kaolin by boehmite: Aluminum source effect on physico-chemical characteristics of product

Abstract

The nano-porous hydrosodalite was produced from a poor kaolin containing quartz, as major impurity, via the hydrothermal modification with boehmite and sodium aluminate. The physico-chemical characteristics of products were evaluated by XRD, SEM and BET techniques. The obtained results indicated that the direct reaction between poor metakaolin and sodium hydroxide leads to the zeolite compound formation in which the partially crystallized hydrosodalite and remained quartz were embedded in amorphous phase. Different trends were observed in crystallinity of produced materials with aluminum source content revealed the predominantly crystalline structure for hydrosodalite fabricated via use of sodium aluminate. There is an inverse relationship between the boehmite content and crystallinity whilst the increase in the sodium aluminate content led to production of a well-crystalline hydrosodalite. Although, the dense cabbage-like particle structure was successfully created by hydrothermal reaction between metakaolin and sodium aluminate, NaAlO2/MK: 0.36, and the nano-porous hydrosodalite can be fabricated at limited content of boehmite, AlOOH/MK: 0.20. Moreover, the hydrothermal reaction in the presence of boehmite causes the generation of nano-porous structure with average pore size of 8.0 nm, accompanied with negligible co-crystallization of cancrinite. This change in porous structure could be useful in engineering applications like water and wastewater treatments.