Adsorption characteristics of Pb ²⁺ onto porous steel slag based geopolymer block

A porous geopolymer block (SPG), featuring three distinct pore characteristics, was employed for the removal of Pb 2+ ions. Comprehensive batch adsorption experiments were conducted to investigate the adsorption behavior of SPG towards Pb 2+ under varying conditions such as contact duration, solution pH, initial solute concentration, and temperature. Advanced analytical techniques, including scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), were employed to assess both the chemical and physical properties of SPG pre-and post-adsorption, thereby facilitating a detailed elucidation of the underlying adsorption mechanisms. Moreover, the adsorption process was further scrutinized through kinetic studies and isotherm analyses. The findings revealed that the efficiency of Pb 2+ adsorption onto SPG was profoundly influenced by its pore structure and morphology, with specific surface area and pore volume playing crucial roles. The primary mechanisms identified encompassed ion exchange, electrostatic interactions, precipitation phenomena, coordination complex formation, and ion replacement reactions. The experimental data best conformed to the pseudo-first-order kinetic model and the Sips isotherm model, providing robust descriptions of the adsorption process. At a temperature of 298 K and pH of 5, the maximum adsorption capacity attained for Pb(II) in a single-solute system was 45.95 mg·g -1 .