Alkali-Activated Zeolite 4A Granules—Characterization and Suitability Assessment for the Application of Adsorption

Pauls P. Argalis,Laura Vitola,Kristine Vegere,Diana Bajare

doi:10.3390/cryst11040360

Abstract

A major problem in the field of adsorbents is that binders (kaolin clay, bentonite) introduced to bind zeolites and ensure the needed mechanical strength, are not able to sorb gases like CO2 and N2, and decrease the overall adsorption capacity. To solve this problem, one of the pathways is to introduce a binder able to sorb such gases. Thus, in this study, the physical and mechanical properties of a novel binder based on metakaolin and its composite with zeolite 4A in the granular form were studied. Metakaolin was used as a precursor for alkali-activated binder, which was synthesized using an 8M NaOH activation solution. Raw materials were characterized using granulometry, X-ray diffraction (XRD), and differential thermal analysis (DTA); and final products were characterized using density measurements, a compressive strength test, XRD, Brunauer–Emmett–Teller (BET) analysis, and scanning electron microscopy (SEM). Alkali-activated metakaolin was found to be efficient as a binding material when data for morphological properties were analyzed. A relationship was observed—by increasing the liquid-to-solid ratio (L/S), compressive strength decreased. Zeolite granule attrition was higher than expected: 2.42% and 4.55% for ZG-0.8, 3.64% and 5.76% for ZG-1.0, and 2.73% and 4.85% for ZG-1.2, measured at 4 and 5 atmospheres, respectively.

Highlights

During this last decade, a shift has been seen toward more research dedicated to alkaliactivated materials [1,2,3,4,5,6,7,8], because of their applications and properties
As alkaliactivated binders (AABs) are categorized as zeolite-like materials [13], one of their potential uses is to combine them with zeolites to increase the overall adsorption capacity, as well as to ensure the needed mechanical strength
The samples of series AAB-1.0 exhibited material densities of 1.127–1.178 g/cm3 depending on time

Summary

Introduction

A shift has been seen toward more research dedicated to alkaliactivated materials [1,2,3,4,5,6,7,8], because of their applications and properties. Many researchers like Awoyera and Rivera studied how alkali-activated binders could be incorporated with Portland cement [1]. The sustainability advantage is coupled with its potentially enhanced properties, and due to the limitations of the use of alkaliactivated binders (AABs) in terms of their hardened-material properties for commercial and large-scale production, as mentioned in Adesina’s study [12], those issues must be overcome for AAB to be universally accepted and compete with other binders. As AABs are categorized as zeolite-like materials [13], one of their potential uses is to combine them with zeolites to increase the overall adsorption capacity, as well as to ensure the needed mechanical strength

Methods

Results

Conclusion