Lightweight geopolymer-expanded glass composites for removal of methylene blue from aqueous solutions

Abstract In this work, monolithic geopolymer-expanded glass composites were prepared for the purpose of methylene blue removal from wastewaters. Zeolite A was found to form during geopolymerization process, e.g. sodium hydroxide solution alkali-activation of metakaolin and metakaolin with expanded glass aggregates blends, and curing at 80 °C for 24 h. The effect of expanded glass content on density and compressive strength of the obtained samples was examined and showed the decrease from 1.1 g/cm3 and 20.4 MPa (sample without expanded glass) to 0.5 g/cm3 and 1.6 MPa (sample with a 50%-replacement of metakaolin with expanded glass). The addition of expanded glass positively affected sorption capacity and removal efficiency. The sample without expanded glass reached 3.4 mg/g and 70%, while sample with a 50%-replacement of metakaolin with expanded glass reached 4.9 mg/g and 99%, respectively. The influence of methylene blue initial concentration and sorption time on the dye uptake and removal efficiency was also analyzed.