Adsorption studies on synthetic lentil-like mordenite for column and batch removal of cadmium and lead ions: investigating isotherms and kinetics

Abstract

ABSTRACT The mordenite zeolite adsorbent, with a lentil-like structure, was synthesised using a one-step green hydrothermal method. Its textural, structural, and morphological properties were characterised through X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, and the Brunauer-Emmet-Teller (BET) method. The prepared adsorbent was employed in both continuous and batch adsorption processes to remove toxic Cd(II) and Pb(II) metal ions from aqueous solutions. Operational parameters such as flow rate, initial concentration, and bed height were varied to understand breakthrough time, mass transfer zone, adsorption capacity, and exhaustion time during continuous adsorption, which were investigated and optimised. Additionally, the study explored the influence of solid/liquid ratio, pH, assay time, and initial concentration on batch adsorption. The maximum adsorption capacities of the lentil-like mordenite zeolite in fixed-bed breakthrough experiments were determined to be 78.22 mg/g for Cd (II) ions and 80.82 mg/g for Pb (II) ions. In batch experiments, the capacities were 133.64 mg/g for Cd (II) ions and 239.57 mg/g for Pb (II) ions. Dynamic continuous adsorption isotherms exhibited an excellent fit with the Thomas and Yoon – Nelson models, while batch adsorption isotherms conformed well to the Langmuir model. This study presents a new approach for synthesising high surface area, engineered morphology, reusable, and stable zeolite for effectively adsorbing hard metal ions from wastewaters, contributing to environmental remediation.