Cu or Fe-Exchanged Natural Clinoptilolite as Sustainable Light-Assisted Catalyst for Water Disinfection at Near Neutral pH.

Abstract

Natural zeolites can be used to obtain effective catalysts for heterogeneous photocatalytic reactions due to their low cost and favorable physicochemical properties for water treatment. In this work, a natural clinoptilolite is modified by incorporating iron (NZ-Fe) and copper (NZ-Cu) as compensation cations through ion exchange processes. Metals incorporation and structural stability are demonstrated through X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. DR-UV-Vis measurements are used to estimate the bandgap and predict the photocatalytic performance of both materials. Their effectiviness in heterogeneous photocatalytic systems is confirmed by evaluating the inactivation of E. coli as a model pathogen in water. The bacterial detection limit (initial ≈10⁶ CFU/mL) is reached using 1 gL^-1 of both catalysts, 100 ppm of H₂O₂ under visible light (410-710 nm) and near neutral pH in 2 h, with no post-treatment regrowth observed. Experimental data are analyzed according to the Chick-Watson, Weibull, and Hom disinfection kinetic models. Although more hydroxyl radicals are generated (trapping tests) and less iron leachate is observed for NZ-Fe, good reusability is attained for three disinfection cycles when NZ-Cu is used. This makes copper-exchanged clinoptilolite a suitable and low-cost photocatalyst for water disinfection through heterogeneous photo-Fenton-type processes.