Ultra-fast and highly efficient hybrid material removes Cu(II) from wastewater: kinetic study and mechanism

Abstract Water pollution by toxic elements represents a significant risk to the environment and human ecosystem, and a number of efforts are developed to find a suitable solution. In this work, a new adsorbent based on silica gel as an inert material modified on surface by a pincer ligand was prepared. The hybrid material has been synthesized via a simple Schiff base reaction and characterized by several relevant physical methods. The adsorbent shows an extremely rapid efficiency in removal of copper (less than 8 min) with maximum sorption capacity of 1.90 mmol g-1 and a rapid efficiency for zinc, cadmium and lead (less than 20 min) with adsorption capacities 0.52, 0.49 and 0.43 mmol g-1, respectively. A kinetic study shows that the sorption can be described by a pseudo second-order model, and that the process is thermodynamically spontaneous and endothermic. The adsorbent shows a high selectivity to Cu(II) and a great reusability after five adsorption-desorption cycles. Theoretical, energy dispersive X-ray fluorescence (EDX) and Fourier transform-infrared spectroscopy studies demonstrate that the uptake occurs by a coordination reaction between metal ions and the pincer ligand on the surface of the adsorbent. The efficiency of this new hybrid material was confirmed in removal of Cu(II) from real water samples originating from Abidjan Atlantic sea bay, one of the most polluted region in West Africa, as well as from rivers located near Oujda, Morocco.