Zeolite-Clinoptilolite conditioning for improved heavy metals ions removal: a preliminary assessment

The emerging problem of nickel allergy is increasingly widespread due to the increase in nickel content in everyday foods. The physicochemical structure of the zeolites makes it possible to adsorb nickel ions in solution. The properties of molecular sieves, together with those of a size and a chemical composition compatible with the human gastrointestinal tract, are present in a particular zeolite called clinoptilolite. In this work, a type of natural clinoptilolite was characterized before and after being subjected to two different conditioning processes with NaCl to increase its adsorption efficiency and specificity against nickel. The three forms of clinoptilolite, natural, conditioned, and biconditioned, were compared based on analysis of absolute density, X-ray diffraction pattern, granulometry, porosity, chemical composition, and grain morphology. Finally, nickel ion removal tests were performed in an aqueous solution that simulates the conditions of the gastrointestinal tract. The Ni2+ removal efficiency of natural clinoptilolite is 73.2%, while after conditioning it reaches 96.6%. Double conditioning with Na does not generate a considerable increase in removal efficiency which remains at 96.8%