Characterization of Zeolite in Zeolite-Geopolymer Hybrid Bulk Materials Derived from Kaolinitic Clays

Abstract

Zeolite-geopolymer hybrid materials have been formed when kaolin was used as a starting material. Their characteristics are of interest because they can have a wide pore size distribution with micro- and meso-pores due to the zeolite and geopolymer, respectively. In this study, Zeolite-geopolymer hybrid bulk materials were fabricated using four kinds of kaolinitic clays (a halloysite and three kinds of kaolinite). The kaolinitic clays were first calcined at 700 °C for 3 h to transform into the amorphous aluminosilicate phases. Alkali-activation treatment of the metakaolin yielded bulk materials with different amounts and types of zeolite and different compressive strength. This study investigated the effects of the initial kaolinitic clays on the amount and types of zeolite in the resultant geopolymers as well as the strength of the bulk materials. The kaolinitic clays and their metakaolin were characterized by XRD analysis, chemical composition, crystallite size, 29Si and 27Al MAS NMR analysis, and specific surface area measurements. The correlation between the amount of zeolite formed and the compressive strength of the resultant hybrid bulk materials, previously reported by other researchers was not positively observed. In the studied systems, the effects of Si/Al and crystalline size were observed. When the atomic ratio of Si/Al in the starting kaolinitic clays increased, the compressive strength of the hybrid bulk materials increased. The crystallite size of the zeolite in the hybrid bulk materials increased with decreasing compressive strength of the hybrid bulk materials.

Alkaline Activation of Kaolin Group Minerals

“…Zeolite-geopolymer hybrid bulk materials are composites that combine the advantages of zeolites as a dispersed phase and geopolymer as a matrix. Their structure contains the meso-porosity of the geopolymer and the micro-porosity of the zeolite [3]. The range of porosity in those materials is very wide, and reaches from 5 Å up to 2 µm [4].…”

“…The range of porosity in those materials is very wide, and reaches from 5 Å up to 2 µm [4]. It was proven [3] that there is a relationship between the properties of initial kaolinite, its meta phase and the final product: zeolite-geopolymer hybrid bulk material, which gives opportunity to adjust the contents of desirable phases, and in consequence, the range of porosity.…”

“…or natural clays, for instance, kaolinite and halloysite. Using those natural minerals for the synthesis of zeolite and zeolite-geopolymer hybrid bulk materials is a topical issue [3,5,6]. Despite the fact that both kaolinite (Al 2 Si 2 O 5 (OH) 4 ) and halloysite (Al 2 Si 2 O 5 (OH) 4 •2H 2 O) have similar compositions [7], their reactivity is different.…”

Geopolymer/Zeolite composite materials with adsorptive and photocatalytic properties for dye removal

“…To precipitate the zeolite, a temperature of 100°C or more must be maintained in the aluminosilicate mixture for a certain period [ 19 ]. Zeolites are also found in geopolymers, particularly at the curing temperature of > 85°C; the zeolite amount increased with curing time [ 20 , 21 ]. The chemical compositions of geopolymers are relatively similar to zeolites; however, a geopolymer possesses an amorphous microstructure that leads to several different properties.…”

Effect of Grinding Treatment of Fly Ash on Compressive Strength of Hardened Geopolymers using Warm Press Method

“…Generally, geopolymer hardened bodies are fabricated by curing a mold of starting slurry consisting of amorphous aluminosilicate, such as fly ash exhausted from a power plant or metakaolin obtained by heating kaolinite clay at approximately 700 °C, and alkali solution [1][2][3]. Alkali silicate solution is most often added to the starting slurry as a reaction accelerator, but the use of alkali silicate solution is not necessary when geopolymers are fabricated from volcanic ash [4].…”