Zeolite prepared from high-calcium ladle furnace slag and fly ash for Pb2+ removal

Abstract

The stockpiling of industrial solid waste and lead (Pb) pollution have become a worldwide problem, which can be potentially solved by using solid waste such as ladle furnace slag (LFS) and fly ash (FA) to prepare Pb adsorbents. In this paper, zeolites prepared from untreated high-calcium LFS and FA were used to remove Pb2+ by adsorption. The optimal adsorption conditions were an adsorbent dose of 1 g/L, pH 5, a contact time of 180 min, and an initial Pb2+ concentration of 300 mg/L. The zeolites prepared from high-calcium solid waste had a Pb2+ adsorption capacity of 292.8 mg/g and an adsorption efficiency of 97.6 %. Adsorption mainly occurred via the ion exchange of Pb2+ with Ca2+ and Na+, as well as the complexation of Pb2+. The pseudo-second-order kinetic model and the Langmuir model were used to analyze adsorption kinetics and isotherm data, supporting the occurrence of chemisorption and monolayer adsorption. Regeneration experiments demonstrated that the zeolite synthesized in this study exhibited good repeatability and cost-effectiveness. The zeolites derived from LFS and FA-based geopolymers removed Pb2+ from wastewater, offering new perspectives on utilizing high-calcium industrial waste and advancing geopolymer-based adsorbents for sustainable industrial solid waste management and water pollution treatment strategies.