Efficient extraction of heavy metals from aqueous solution by novel hybrid material based on silica particles bearing new Schiff base receptor

Abstract

During the last years, contamination of water by heavy metals has become a serious health hazard and environmental problem. In particular, mercury, lead, cadmium and zinc are considered as the most dangerous elements and are included on the US Environmental Protection Agency's (EPA) list of priority pollutants. To this end, the search for an effective material based adsorbent is a well-established technology. In this work, a novel and efficient host for the above toxic metals was synthesized by covalent immobilization of a new (E)-3-((2-nitrobenzylidene)amino) propan-1-ol Schiff's base receptor onto silica in a heterogeneous way to yield the material Si-CSB. The functionalized porous surface has been analyzed through elemental analysis, FT-IR spectroscopy, solid state 13C NMR, nitrogen adsorption–desorption isotherms, BET surface area, Barrett–Joyner–Halenda (BJH) pore diameters methods and thermogravimetric analysis (TGA). The new material showed great thermal and chemical stabilities examined in various acidic and buffer solutions. The adsorbent was applied in solid-phase extraction (SPE) and showed quantitative retention of Hg2+, Pb2+, Cd2+ and Zn2+ compared to previous described materials. The adsorption capability towards toxic metals was studied using kinetics, pH and temperature effects prior to their determination by ICP-AES. Adsorption was rapid as evidenced by equilibrium achieved within 25min. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) revealed that the adsorption was spontaneous and endothermic. Alkali coexisting ions did not interfere with separation and determination. The material can be used continuously without reducing its extraction percentage. The newly synthesized material appears to be a low cost, effective and alternative adsorbent for efficient removal of heavy metals from aqueous solution.