Adsorption of Pb(II) from synthetic wastewater with alkali-activated blast furnace slag and lignin composite

Lead contamination in water is a serious environmental concern due to its ecotoxic effects. Adsorption is one possible method for treating lead-contaminated water. In this study, the functionalization of alkali-activated blast furnace slag, which is a comparatively new research area, was explored using lignin, and its potential in adsorbing lead from water was investigated. The lignin integration was confirmed by total organic carbon analysis, thermogravimetry, and Fourier-transform infrared spectroscopy. The composite material exhibited 14 units higher lead removal efficiency in comparison to alkali-activated slag without lignin. The effects of contact time (0–6 h), adsorbent dose (0.25–1.5 g/L), initial concentration (50–400 mg/L), pH (3–5), and temperature (20–30°C) on lead adsorption by the composite were investigated. The optimum conditions were contact time 2 h, pH 5, adsorbent dose 1.5 g/L, initial concentration 100 mg/L, and temperature 30°C. The adsorption equilibrium was reached after 2 h. X-ray photoelectron spectroscopy analysis showed enhanced lead adsorption by the composite compared to alkali-activated blast furnace slag without lignin. The adsorption kinetics could be described by the pseudo-second order model and adsorption equilibrium by the Freundlich isotherm. The composite exhibited the highest adsorption amount of approximately 139 mg/g. Thermodynamic parameters, such as changes in enthalpy, entropy, and Gibbs energy, were also evaluated, indicating that the reaction is spontaneous and endothermic. • First study on heavy metal removal with alkali-activated blast furnace slag and lignin composite. • The composite demonstrated a maximum Pb(II) adsorption amount of 139 mg/g. • The adsorption equilibrium was achieved in 2 h. • Use of both blast furnace slag and lignin promote waste valorization.