An insight of enhanced natural material (calcined diatomite) efficiency in nickel and silver retention: Application to natural effluents

Natural diatomite is widely used worldwide as an alternative to synthetic adsorbents and its adsorbing capacity towards nickel and silver ions is assessed in this work. Diatomite was heated up to 550, 750 or 950 degrees C to modify its physico-chemical and binding properties. A thorough characterization of the resulting material was done by X-ray diffraction, Fourier Transform Infrared Spectroscopy (FTIR), ThermoGravimetric Analysis (TGA), Scanning Electron Microscopy (SEM) and porosity measurements. The adsorption of nickel and silver ions onto these materials was studied as a function of the adsorbent concentration, organic matter as well as the presence of competitor ions. Diatomites demonstrated a better retention capacity when compared to materials of close composition. Best removal capability was obtained by calcination at 550 degrees C. This material was successfully tested for nickel and silver removal from both natural river waters as well as industrial wastewater. Due to high regeneration and reusability, this low cost, easily prepared, natural material may be an attractive alternative for adsorbent in wastewaters treatment. (C) 2020 Elsevier B.V. All rights reserved.