Zeolite based Geopolymer from Biomass: a Sustainable Adsorbent for Water Softener

Abstract

Water quality in several areas in Semarang, especially in Tugu sub-district, is still very low and unsuitable for drinking. Ground water contaminated with Ca2+ and Mg2+ ions which is commonly known as hard water. This study aims to examine the potential of zeolite-based geopolymer adsorbents, materials which have a zeolite-like structure but are basically geopolymers. Synthesis of zeolite based geopolymers from rice husk ash, kaolin and NaOH activators has been successfully carried out by the sol gel method. Three-dimensional networks have been formed from Silica (SiO2) and Alumina (Al2O3). Activator solution, NaOH, with variations in concentrations of 4 M (Geopolymer 4), 8 M (Geopolymer 8) and 12M (Geopolymer 12) gives significant differences. As the higher the concentration of activator solution, the more silica and alumina dissolved so that the geopolymer becomes amorphous. These results are consistent with XRD and FTIR data. Geopolymer 12 has an adsorption capacity of 97.4% is the best adsorbent in adsorbing Ca2+ and Mg2+ metal ions with operating conditions at 40°C for 60 minutes. This shows that there is a close relationship between synthesis methods, structural characterization and geopolymer adsorption activities. The higher concentration of NaOH gives amorphous geopolymers. NaOH will activate the silica and alumina surfaces on the geopolymer, making it easier for adsorbents to absorb and interact with the adsorbate molecules, namely Ca2+ ions and Mg2+ ions.