Investigation of phosphate adsorption from aqueous media using synthetic mordenite and modified natural clinoptilolite zeolite adsorbents: characteristics, kinetics, and isotherms

This study investigates phosphate removal from aqueous solution by synthetic mordenite and modified clinoptilolite zeolite. The mordenite zeolite was synthesized using the solvothermal method, and natural clinoptilolite zeolite was modified by ultrasound energy and manganese dioxide. The adsorbents were characterized by utilizing X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Scanning electron microscope (SEM) images, energy dispersive X-ray analysis (EDXA), and the Brunauer-Emmet-Teller (BET) method. This study investigated the adsorption behavior of the two adsorbents, including the influence of solid/liquid ratio, contact time, initial concertation, and modification of the adsorption process, adsorption kinetics, and isotherms. The maximum phosphate adsorption capacity of the modified synthetic mordenite and the modified clinoptilolite are 23.06 and 17.9 mg.g-1, respectively, which is higher than the values reported in other studies. The present study shows that the amount of adsorption of modified synthetic mordenite for phosphate removal is higher than the modified clinoptilolite zeolite. The kinetics study shows that the pseudo-second-order kinetic equation better describes the adsorbents' adsorption behavior. The isotherms study suggests that the adsorption process of synthetic mordenite and modified clinoptilolite zeolite follow the Langmuir and Freundlich models, respectively.