Combined Influence of Low-Grade Metakaolins and Natural Zeolite on Compressive Strength and Heavy Metal Adsorption of Geopolymers

Metakaolins (MKs) prepared from low-grade kaolins located in the Alvarães (A) and Barqueiros (B) regions of Portugal were used as aluminosilicate source to compare their effect on compressive strength heavy metal adsorption geopolymers. Natural zeolite, an inexpensive, efficient adsorbent, was additive formulations enhance geopolymers’ capacities reduce MK utilization’s environmental footprint. Geopolymers synthesized with replacement by zeolite up 75 wt.% (A25, B25—25% 75% zeolite; A50, B50—50% 50% A75, B75—75% 25% A100, B100—100% MK). The molar ratios SiO2/Al2O3 Na2O/Al2O3 kept at 1 sodium silicate hydroxide impact. Geopolymers’ crystallography identified using X-ray diffraction analysis. surface morphology observed scanning electron microscopy understand incorporation. Chemical analysis fluorescence spectroscopy energy dispersive yielded information about Si/Al ratio. Compressive values geopolymers obtained after 1, 14, 28 days curing indicate high strengths 100% (A100—15.4 MPa; B100—32.46 MPa). Therefore, did not aid improvement both MK-based (Cd2+, Cr3+, Cu2+, Pb2+, Zn2+) tests exhibit relatively higher for all metals except Cd2+. Moreover, positively influenced divalent cations’ produced B75 exhibits highest capacities, but such influence is general trend Pb2+ > Cd2+ Cu2+ Zn2+ Cr3+ when fitted Langmuir isotherm model. characteristics structure, strength, capacities.