Bilayer adsorptive ceramic membranes supported cage-like mesoporous silica for hexavalent chromium removal: Experimental and DFT studies

Abstract

In this study, an adsorptive ceramic membrane coated by new layer of cage-like mesoporous silica SBA_16 which was modified with 3-aminopropyltriethoxysilane (APTES) was employed to remove (Cr (VI)) ions from aqueous solution. The morphologies and physiochemical properties of SBA_16 and modified SBA_16 (NH2-SBA_16) adsorbents as well as adsorptive membranes were characterized through thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR), N2 adsorption-desorption isotherms, X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The adsorption isotherm data perfectly was fitted to Langmuir isotherm model and the adsorption capacity value of NH2-SBA_16 for Cr (VI) at pH of 2.5 was 61.9 mg/g. The experimental kinetic data agreed with pseudo-second-order model. The dynamic filtration test in dead-end system was utilized to evaluate the efficiency of ceramic membranes in hexavalent chromium removal. The modification of ceramic membrane (CM2) resulted in an excellent Cr (VI) removal (100 %) for permeate stream. Aminopropyl grafting on the ceramic membrane significantly enhanced the permeate flux from 56 L/m2h to 85.6 L/m2h. Density functional theory (DFT) calculations have been performed and the adsorption energy of Cr (VI) on NH2-SBA_16 was obtained 131.25 kJ/mol.