In situ synthesis of zeolites by geopolymerization with NaOH/KOH mixed solution and their potential application for Cd(II) immobilization in paddy soil
- 1 June 2021
- journal article
- research article
- Published by Mineralogical Society in Clay Minerals
- Vol. 56 (2), 156-167
- https://doi.org/10.1180/clm.2021.29
Abstract
Geopolymers can be transformed into zeolites under certain synthesis conditions. However, zeolite formation is not frequently reported in KOH-activated geopolymers. This study attempted to explore zeolite synthesis through geopolymerization for a curing time of 24 h using mixed NaOH/KOH alkaline solution as an activator, and then applying the geopolymer-supported zeolites to immobilize Cd(II) in paddy soil. The K2O/M2O-H2O/SiO2 and K2O/M2O-OH-/SiO2 binary zeolite crystallization phase diagrams were obtained. Zeolite A, faujasite and sodalite formed at lower K2O/M2O molar ratios (0-0.2), ferrierite formation was favoured at a K2O/M2O molar ratio of 0.2-0.4 and zeolite K-I and zeolite F-K (both K-zeolites) were observed at a K2O/M2O molar ratio of 0.6. The geopolymer-supported zeolites had micropores and mesopores and specific surface area values of 44.2-74.8 m(2) g(-1). The material displayed a considerable Cd(II) immobilization efficiency (55.6-58.7% at 4-6 wt.% addition of zeolite).Keywords
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