Effect of fly ash content on zeolite synthesis from coal fly ash prepared by hydrothermal treatment

摘要

We investigated the effect of fly ash content on the synthesis of zeolites from coal fly ash prepared by hydrothermal treatment.Both phillipsite and hydroxysodalie are synthesized from fly ash of relativelylow silica content.It is found that only phillipsite and hydroxy sodalite are synthesized from fly ash of relatively low silica content.It is found that only phillipsite is synthesized selectivley by hydrothermal treatment when concentration of silicate ion is higher than that of aluminate ion in NaOH solution. We proposed and formulated the formation mechanism of phillipsite.Silicate and aluminae ions dissolve in NaOH solution from fly ash and formal uminosilicate,from which phillipsite crystal are generated.Teh changes in ion concentrations and phillipsiite mass calculated by the newly proposed model agrees with the experimental results.It is suggested that the critical concentration of crystal lization and the rate constants of gelation and crystallization are constant,Iindependent of fly ash morphology.