Synthesis of multifunctional mesoporous geopolymer under hydrothermal curing: High mechanical resistance and efficient removal of methylene blue from aqueous medium

This study created green multifunctional geopolymeric sorbent material with strong cationic dye adsorption capacity and superior mechanical strength to broaden lead sludge (LS)-based geopolymer applications. In this study, two geopolymeric sorbents (Go and G) were fabricated using slag blended with 0 and 50 wt% LS, respectively and activated with 6 wt% NaOH. The Go and G specimens were normally cured for up to 28 days, while G specimens were hydrothermally cured at different steam-pressures to modify/improve histological characteristics as well as mechanical resistance. The selected sorbents were characterized via XRD, FTIR, TGA/DTG, XPS, N2-adsorption/desorption and SEM/EDX techniques. G/5 bar′s high strength and adsorption capacity may be due to the production of CSH, CAH, CASH, and NASH, which formed a fine mesoporous zeolitic structure with the highest BET-surface area (64.55 m2/g) and lowest BJH-maximum pore diameter (9.68 nm). The maximum MB adsorption capacity of the synthesized adsorbent was 230.4 mg/g. •Hydrothermal curing affected positively on the porous structure of G/5 bar.•High mechanical resistance of G/5 bar was attributed to generation of various types of hydration products.•The interaction between G/5 bar and methylene blue is explained via the Langmuir isotherm model.•The adsorption rate is controlled by both intraparticle and diffusion mechanisms.•The adsorption mechanism was supported by XPS technique.