Organotemplate-free synthesis of MOR zeolite from coal fly ash through simultaneously effective extraction of Si and Al

Abstract In this study, high-purity mordenite (MOR) zeolite was successfully synthesized from coal fly ash (CFA) using a simple and green method without organotemplate. The Al and Si used for MOR synthesis were simultaneously extracted from CFA, which were transformed to aluminosilicate gel by co-precipitation and then coupled with MOR seed for MOR synthesis instead of using organotemplate in common method. The results showed that the Al and Si extraction efficiencies were high, reaching up to 82.18% and 93.15%, respectively. The synthesized CFA-based MOR zeolite had a low Si/Al ratio of 3.92, and micropores is the dominating pore structure in the synthesized zeolite, accounts for up to 63.16% of its total pore volume. The possible mechanisms of MOR zeolite from CFA by gel coupling seed assisted synthesis were discussed. Furthermore, the CFA-based MOR was applied in CO2 adsorption, heavy metal ions adsorption in aqueous solution and catalyst carrier for NH3-SCR reaction. The results presented that the CO2 adsorption capacity of the CFA-based MOR was 1.92 mmol/g with high cycle stability. The removal rate of Pb2+ was above 99.99% with Pb2+ initial concentration of 51.30 mg/L. Mn-MOR catalyst was obtained through loading 3.36 wt% Mn by ion-exchange, which had a NO conversion rate of 93.58% at 200 °C. This study demonstrates that the gel coupling seed assisted method without organotemplate is a potential way to synthesize zeolite materials using the Si and Al simultaneously extracted from CFA.