Investigation of the mechanism of chromium removal in (3-aminopropyl)trimethoxysilane functionalized mesoporous silica

Abstract

We are proposed that a possible mechanism for Cr(VI) removal by functionalized mesoporous silica. Mesoporous silica was functionalized with (3-aminopropyl)trimethoxysilane (APTMS) using the post-synthesis grafting method. The synthesized materials were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption-desorption analysis, Fourier-transform infrared (FT-IR), thermogravimetric analyses (TGA), and X-ray photoelectron spectroscopy (XPS) to confirm the pore structure and functionalization of amine groups, and were subsequently used as adsorbents for the removal of Cr(VI) from aqueous solution. As the concentration of APTMS increases from 0.01 M to 0.25 M, the surface area of mesoporous silica decreases from 857.9 m2/g to 402.6 m2/g. In contrast, Cr(VI) uptake increases from 36.95 mg/g to 83.50 mg/g. This indicates that the enhanced Cr(VI) removal was primarily due to the activity of functional groups. It is thought that the optimum concentration of APTMS for functionalization is approximately 0.05 M. According to XPS data, NH3+ and protonated NH2 from APTMS adsorbed anionic Cr(VI) by electrostatic interaction and changed the solution pH. Equilibrium data are well fitted by Temkin and Sips isotherms. This research shows promising results for the application of amino functionalized mesoporous silica as an adsorbent to removal Cr(VI) from aqueous solution.

A systematic study of hexavalent chromium adsorption and removal from aqueous environments using chemically functionalized amorphous and mesoporous silica nanoparticles

“…This explanation is reasonably consistent with the Cr(III) to Cr(VI) ratios shown in Fig. 7, although these ratios were slightly higher than previously reported values 6,39 .…”

“…Considering the fact that the characteristic Si 2p BE peaks of elementary Si and SiO 2 reported in the literature are at 99.5 and 103.5 eV 79 , respectively, our results imply that silicon in the surface layer of NH 2 -ASNs and NH 2 -MSNs may exist as intermediate sub-oxide phases (SiO x , 0 < x ≤ 1) rather than the fully oxidized SiO 2 79,80 due to a greater presence of elementary non-oxidized Si in the surface layers of NH 2 -ASNs and NH 2 -MSNs. Furthermore, these values were consistent with those reported for functionalized silica nanoparticles 39,81 , and mesoporous silica 6,46 systems.…”

“…The maximum Cr(VI) removal capacities of NH 2 -ASNs and NH 2 -MSNs were determined to be 61.9 and 76.8%, respectively. These values were comparable or marginally better than those reported for functionalized silica nanoparticles 72,73 , mesoporous silica 6,39,48,[74][75][76] , and other hybrid multifunctional nanoparticles 77,78 designed for Cr(VI) removal. Notably, the maximum Cr(VI) removal capacity of NH 2 -MSNs was 76.8%, which was 1.2 times higher than the 61.9% of www.nature.com/scientificreports www.nature.com/scientificreports/ NH 2 -ASNs.…”

“…Table 2 summarizes the adsorption and removal efficiency parameters of ASNs, MSNs, NH 2 -ASNs, and NH 2 -MSNs by the Cr(VI) adsorption batch experiments. Notably, the adsorption efficiencies (q e ) of NH 2 -ASNs and NH 2 -MSNs were ~40 to 80 times greater than those of ASNs and MSNs, which confirmed the impact of NH 2 -functionalization on the Cr(VI) adsorption efficiency 27,39 . Maximum Cr(VI) removal capacity (R) represents the ability of an adsorbent to remove Cr(VI) from aqueous environments.…”

“…Both Stöber and mesoporous silica materials have been chemically functionalized to enhance Cr(VI) adsorption 38,39 . For example, nitrogen-containing functional groups like aliphatic and aromatic amines have demonstrated to be extremely effective at enhancing Cr(VI) adsorption 27 .…”