Removal of Uranium from Aqueous Solution and Simulated Seawater Using a Mixed Matrix Membrane Fabricated by Cyclophosphazene and Triazine-Based Inorganic–Organic Hybrid Material

Abstract

The efficient removal of uranium ions from aqueous and simulated seawater is reported by using a mixed matrix membrane (MMM-2) fabricated by cyclophosphazene and triazine-based inorganic–organic hybrid material (CTHM-2) as the adsorbent. CTHM-2 with a specific surface area of 76 m2 g–1 was synthesized within 60 min by microwave-assisted polycondensation reaction. In batch mode adsorption, the concentration of uranium has been decreased from 5 ppm to <15 ppb (permissible limit of uranium by the World Health Organization) within 120 min at pH of 6 and 298 K. However, a maximum adsorption capacity of 580 mg g–1 is estimated with 500 ppm of the initial concentration. The isotherm and kinetic studies indicate that it could fit well with the Freundlich isotherm and pseudo-second order kinetics. The negative ΔG and ΔH values indicate the spontaneous and exothermic adsorption processes, respectively. When the MMM-2 was used to treat 5 L of 5 ppm U(VI) solution, with a water flux of 8.1 L m–2 h–1 and 2 bar transmembrane pressure, it provides safe drinkable water (<15 ppb) for 300 min. Additionally, the CTHM-2 and MMM-2 could be further used to remove uranium ions from the simulated seawater with adsorption capacities of 53 and 167 mg g–1, respectively.