Fabrication of feldspar-based geopolymers from perlite toward decontamination of heavy metals from aqueous solution: Hydrolysis process, characterizations, kinetic and isotherm studies

Nowadays, alkali-activated materials have widely attracted great attention in the adsorption process. The present study describes a novel approach for fabricating feldspar-based geopolymers and investigates their applications for the adsorption of heavy metals. The processes involved for this purpose are i)-using perlite as the precursor, ii) extraction of silicate (water glass) by NaOH solution, iii) fabrication of feldspar-based geopolymers and iv) employing heavy metals pollution to find out the possible potential in the adsorption process. The structure of the raw perlite and synthesized compounds were identified through XRD, XRF, FT-IR, SEM, and BET analyses. The XRD characterization clarified the formation of albite (a plagioclase feldspar mineral) as the only common mineral in the fabricated adsorbents. BET results indicated an increase in the surface area of samples after hydrolysis. The experiment results demonstrated the adsorption ability of TTA (hydrolyzed by tartaric acid) and TSU (hydrolyzed by sulfuric acid) samples for the removal of Cd(II), Co(II), and Zn(II) from an aqueous solution. The maximum adsorption capacity of Cd(II), Co(II), and Zn(II) ions onto the TTA sample was 50.251, 36.764, and 39.525 mg/g, respectively; while this amount for TSU adsorbent was 52.63, 24.449, and 20.161 mg/g, respectively. In addition, isotherm and kinetic studies confirmed that the adsorption process was done chemically and desirably. Considering this paper's results, the newly fabricated geopolymeric feldspars from low-cost perlites can be used for heavy metals adsorption.