Interfacial adsorption for efficient removal of Fe3+, Mn2+, Ni2+, Cd2+, and Sr2+from wastewater using synthetic clinoptilolite via single-treatment approach

A highly effective synthetic clinoptilolite (SCP) was developed and assessed for its potential in the simultaneous removal of Cd2+, Ni2+, Mn2+, Sr2+, and Fe3+ from an aqueous solution. The present work explored the influences of SCP dosage, initial metal ion concentrations, temperature, contact time, and pH value on the adsorption performances of these metal ions. The results revealed exceptionally high adsorption capacities, reaching 2000, 1720, 1875, 1510, and 22 mg/g for Ni2+, Fe3+, Cd2+, Mn2+, and Sr2+, respectively. The specific surface area of SCP increased from 31.4 to 44.7 m2/g after five cycles. The adsorption mechanism and structure assessment were elucidated by XRD patterns and SEM images, showing that the Fe3+ adsorption conformed to the Langmuir isotherm, while that of Mn2+, Cd2+, Sr2+, and Ni2+ followed the Freundlich isotherm model with the adsorption kinetics best described by the pseudo-2nd-order kinetic model. Thermodynamic parameters showed endothermic behavior for Cd2+, Ni2+, Mn2+, and Sr2+, exothermic for Fe3+, and spontaneity for all metals except Sr2+. SCP retained over 90 % of its adsorption capacity after five regeneration cycles, maintaining structural integrity under thermal, acidic, and recycling conditions. These findings highlight SCP's robust characteristics, reusability, and potential for sustainable heavy metal removal from wastewater.