Synthesis of natural zeolite agglomerates: clinoptilolite-based geopolymers through aluminate activation

Abstract

Natural zeolite (clinoptilolite)-based geopolymers were synthesized using alkali aluminate solution, including aluminate anodizing waste solution. The effect of calcination of the clinoptilolite sample at 900°C was investigated. The samples were studied by powder X-ray diffraction, thermal analysis, scanning electron microscopy and N2-specific surface area. The alkali aluminate-activated clinoptilolite geopolymers are characterized by satisfactory compressive strength (up to 37 MPa), low density and acceptable shrinkage. The clinoptilolite geopolymer obtained contains an X-ray amorphous phase and newly formed phillipsite and zeolite NaP. The presence of zeolite phases in the geopolymer agglomerate could be beneficial in products with specific qualities and properties, such as ion exchange, passive cooling, antimicrobial activity, etc.