Novel porous geopolymeric formulation as green material applied to the recovery of contaminated effluent aiming environmental protection

Abstract

Geopolymeric materials have been widely applied in a wide variety of industrial processes due to their structural versatility, which depends primarily on the raw material, its composition and the techniques used in the synthesis. This work focused on the synthesis of highly porous geopolymers (PGPs) to be applied as adsorbents in the treatment of effluents. Different compositions, which involved the addition of rice husk silica, were tested to optimize the porosity of the materials synthesized. In the synthesis of PGPs, the best mass proportions of raw materials and reagents were 5.0:0.4:0.6:1.9:0.55:3.3 for K/MK/RHS/KOH/Na2SiO3/H2O, respectively, and the molar ratio for SiO2/Na2O was 3.3. The formation of geopolymer nanoparticles was favored by the mixture of different materials in predefined proportions, and in the presence of activated amorphous silica microparticles. The BET (Brunauer-Emmett-Teller) surface area of the porous geopolymers was 76.93 m2/g and the BJH (Barrett-Joyner-Halenda) value was in the range of 69.84 m2/g. Methylene blue was used as a model compound for the evaluation of the performance of the material when applied to adsorptive processes, both experimentally and theoretically. Batch experiments were conducted to determine the kinetics of MB adsorption in the prepared PGP. The material demonstrated excellent characteristics for the application in the removal of contaminants from effluents by adsorption.