Effect of alkaline synthesis conditions on mineralogy, chemistry and surface properties of phillipsite, P and X zeolitic materials prepared from fine powdered perlite by-product

Abstract

Abstract The fine powdered perlite, a by-product of processing of raw perlite was used for zeolite synthesis. Perlite by-product material (PBM) is not suitable for perlite expansion, due to fine particle size, therefore it has very limited application (recently only as additive to concrete). The conversion of PBM into zeolites is proposed to recover this material (i.e. minimize its accumulation) and to obtain value-added material (i.e. zeolites). Volcanic glass was the main PBM component transformed to zeolites after reaction with NaOH solutions. As volcanic glass alteration proceeded, crystallization of zeolites having lower Si/Al ratio was favored. This was likely due to more rapid increase in the solubility of alumina than the solubility of silica with increasing concentration of reacting NaOH solution. Phillipsite, zeolite P and zeolite X were the main reaction products synthesized from PBM. The concentration of NaOH solution had significant impact on the type of synthesized zeolites whereas reaction temperature and time influenced mainly the quantity of synthesized zeolite species. The highest-grade zeolitic material synthesized from PBM contained 77 wt% of zeolites, 16 wt% of unaltered volcanic glass and 7 wt% of accessory minerals. The small amount of zeolites (11–29 wt%) was synthesized even at the lowest tested temperature of 50 °C. After shortest reaction time (24 h), from 6 to 54 wt% of zeolites was formed. Synthesized materials reached maximum total specific surface area (SBET) of 362 m2/g and cation exchange capacity (CEC) of 371 meq/100g.