Removal of Cr(VI) from Aqueous Solutions Using mino-fuctionalized Nanoporous MCM-41

An amino-functionalized nanoporous material was prepared by grafting 3-aminopropyl trimethoxysilane (APTMS) group onto MCM-41. The as-synthesized material was characterized by X-ray diffraction (XRD) analysis, nitrogen adsorption-desorption measurements (BET), thermogravimetric analysis (TGA), and Fourier transform infrared spectrometry (FTIR) to confirm the ordered mesoporous structure and the functionalization of the amino group. The NH2-MCM-41 thus obtained was employed as the sorbent to remove Cr(VI) ions from aqueous solutions. The batch adsorption process was carried out to evaluate the effects of solution pH, adsorbent dosage, metal ion concentration, and temperature. Results revealed that removal efficiency increased to a maximum of 124 mg.g‒1 and metal uptake decreased (0.1 g.l‒1) with increasing sorbent dosage from 0.1 to 3.5 g.l‒1. A reverse trend was, however, observed with increasing Cr(VI) concentration. It was also found that a pH equal to 3 was the optimum level for the removal of Cr(VI) ions from aqueous solutions. Thermodynamic examinations revealed the strong dependence of the adsorption process on temperature such that adsorption capacity increased with increasing temperature, indicating the endothermic and spontaneous nature of the adsorption process.