Eco-friendly synthesis of magnetic zeolite A from red mud and coal gasification slag for the removal of Pb2+ and Cu2+

Abstract

The issue of heavy metal pollutants has gained global attention, while the disposal of industrial wastes remains a critical environmental concern that requires urgent treatment. In this study, the successful synthesis of magnetic zeolite A (MZA) aimed at the Pb2+ and Cu2+ removal was accomplished by capitalizing on the synergetic interplay between the red mud (RM) and coal gasification slag (CGS) compositions. A reduction roasting reaction involving iron and carbon was innovatively integrated into the conventional alkali fusion-activation process of silicon-aluminum components. The physicochemical properties and preparation mechanism of MZA were characterized using various analytical techniques. Adsorption isotherms and kinetics were analyzed employing various well-known models, and the reusability of MZA was investigated. The result showed that hematite in RM was converted into magnetite and metallic iron during the alkali fusion-synchronous reduction roasting process, and the aluminosilicates from RM and CGS were transformed into zeolite A through a hydrothermal method. The Langmuir and pseudo-second order models well described the Pb2+ adsorption behavior, while the adsorption process of Cu2+ followed the Freundlich and Elovich models best. These results confirmed the successful synthesis of MZA with excellent adsorption performance and magnetic properties, thereby demonstrating the potential of RM and CGS in heavy metal removal through resource utilization.