Experimental and mechanistic study on the removal of lead from solution by sulfuric acid modified steel slag adsorbent

Abstract

In this study, sulfuric acid modified steel slag (SS-HS) was prepared using a one-step hydrothermal synthesis method, utilizing converter steel slag as the raw material, to remove heavy metal Pb2+ from water. Single-factor experiments were conducted to determine the influence of different factors on the adsorption capacity. The obtained material was characterized using EDS and FT-IR to analyze its composition. Response surface methodology was employed to optimize the preparation conditions of SS-HS, and the optimal conditions were determined as follows: sulfuric acid dosage of 8.07 mL, reaction time of 9.98 h, and reaction temperature of 99.44 ℃. SS-HS was prepared under the optimized conditions obtained from the response surface methodology. The physicochemical properties of the prepared SS-HS were analyzed using SEM, EDS, and BET. It was observed that the specific surface area of SS-HS increased from 8.0041 m2/g to 131.8312 m2/g. The average pore volume was 0.2101 cm3/g and the average pore size was 6.3737 nm for mesoporous material. Additionally, the influence of different adsorption conditions on the adsorption capacity of Pb2+ was investigated. The optimum adsorption conditions reached the maximum adsorption amount of 193.05 mg/g at Pb2+ solution concentration of 700 mg/L, adsorbent mass of 0.03 g, temperature of 55 °C, pH= 5. To further understand the adsorption process, kinetic and isotherm models were established. The results indicated that the adsorption process followed a pseudo-second-order kinetic model and Freundlich isotherm model, suggesting a monolayer chemical adsorption. XPS analysis was employed to determine the composition and valence state of the materials, confirming that the adsorption mechanism of SS-HS primarily involved electrostatic adsorption, ion and ligand exchange, and surface precipitation. This study not only introduces a novel approach for the resource utilization of steel slag but also presents an innovative adsorbent for efficient removal of Pb2+ from aqueous solutions.