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

Jinhyeong Lee,Jun Hee Lee,Jeong-Ann Park,Jung-Hyun Lee,Seok Won Hong,Jae-Woo Choi,So-Hye Cho,Hee-Gon Kim,Keunsu Choi,Jae-Hyun Kim,Seung Yong Lee,Soonjae Lee

doi:10.1038/s41598-018-29679-x

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.

Highlights

Chromium (Cr) is extensively used in various industries, including leather tanning, electroplating, paint processing, and wood preservation
An effective method to improve the performance of the Cr(VI) adsorbent is to use mesoporous silica, the surface of which is functionalized by amine groups. 3-aminopropyl trimethoxysilane (APTMS) can be grafted to silanol in mesoporous silica
The results clearly demonstrate that functionalization of APTMS occurred over the entire mesoporous silica (MPS) surface

Summary

Introduction

Chromium (Cr) is extensively used in various industries, including leather tanning, electroplating, paint processing, and wood preservation. Several methods have conventionally been applied to treat chromium-contaminated wastewater, including coagulation, chemical precipitation, ion-exchange, membrane separation, electrolysis, and electrodialysis Of these methods, adsorption is considered one of the most promising processes because of its operational simplicity and economic efficiency[5]. Combining the use of silica with nitrogen-containing organic groups, such as aliphatic amines and aromatic amines, has been widely studied[18] Mesoporous silicas, such as SBA-1, MCM-4119, MCM-4820, and SBA-1521, have been modified with functional groups. An effective method to improve the performance of the Cr(VI) adsorbent is to use mesoporous silica, the surface of which is functionalized by amine groups. The aim of this study was to prepare amino-functionalized mesoporous silicas, and apply them to Cr(VI) removal from aqueous solution in batch systems. Fourier-transform infrared (FT-IR) spectrometry and X-ray photoelectron spectroscopy (XPS) were used to investigate the Cr(VI) sorption characteristics of the adsorbents

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