Adsorption of chlorophenols from aqueous solution over amino-modified ordered nanoporous silica materials

Arezoo Ghaffari,Mansoor Anbia,Syed Waqif Husain,Mohammad Saber Tehrani,Parviz Aberoomand Azar

doi:10.1007/s40097-014-0114-1

Abstract

The capability of the adsorption of 2-chlorophenol (2-CPh) and 2,4-dichlorophenol (2,4-DCPh) from aqueous solutions with mesoporous silica material MCM-48 after functionalizing with amine groups, such as 3-(trimethoxysilyl)propyl amine and tetraethylenepentamine, was investigated in this study. It was found that amino-modified ordered mesoporous silica materials show significant adsorption for 2-CPh and 2,4-DCPh. This is possible due to the alkaline and acid interactions among the amine functional groups and chlorophenols. The adsorbents were characterized by X-ray diffraction, nitrogen adsorption–desorption isotherms and Fourier transform infrared. Batch adsorption studies were done to study the effect of various parameters like chemical modification, pH, contact time, adsorbent dose and initial concentration. It was found that adsorption of 2-CPh and 2,4-DCPh depends upon the solution pH. Adsorption data were modeled with the Langmuir and Freundlich adsorption isotherms. The data fitted the Freundlich isotherm model better than Langmuir. The kinetics analysis revealed that the overall adsorption process was successfully fitted with the pseudo-first-order kinetic model. .

Highlights

The rapid increase of organic wastes from various industries and other sources over the past several decades has led organic pollutants to be widely distributed in the hydrosphere
The reactants used in this study were tetraethyl orthosilicate (TEOS) as a silica source, cetyltrimethylammonium bromide (CTAB) as a surfactant, sodium hydroxide (NaOH) and sodium fluoride (NaF) for synthesis of mesoporous silica (MCM-48), tetraethylenepentamine and ethanol for functionalization of mesoporous silica (MCM48/TEPA); 3-(trimethoxysilyl)propyl amine and dry Toluene were used to prepare modified mesoporous silica (MCM-48/TMSPA). 2-Chlorophenol (2-CPh) and 2,4dichlorophenol (2,4-DCPh) were used as adsorbate
For the adsorption kinetics measurement of chlorophenols onto adsorbent, 25 mL of the chlorophenol solution with an initial concentration of 500 mg L-1 was transferred into a flask and mixed with 0.01 g of amino-modified ordered mesoporous silica materials

Summary

Introduction

The rapid increase of organic wastes from various industries and other sources over the past several decades has led organic pollutants to be widely distributed in the hydrosphere. The nanoporous silica material offers a number of potential advantages as adsorbents including regular channel type structures, high surface area and larger pore diameter and volume. Their modification by functionalized molecules can lead to adsorbents with specific properties [35, 36]. MCM-48 was prepared and functionalized with 3-(trimethoxysilyl)propyl amine (TMSPA) and tetraethylenepentamine (TEPA) by post-synthesis treatment. The reactants used in this study were tetraethyl orthosilicate (TEOS) as a silica source, cetyltrimethylammonium bromide (CTAB) as a surfactant, sodium hydroxide (NaOH) and sodium fluoride (NaF) for synthesis of mesoporous silica (MCM-48), tetraethylenepentamine and ethanol for functionalization of mesoporous silica (MCM48/TEPA); 3-(trimethoxysilyl)propyl amine and dry Toluene were used to prepare modified mesoporous silica (MCM-48/TMSPA). The Fourier transform infrared spectra (FT-IR) for the materials were measured on a DIGILAB FTS 7000 instrument under attenuated total reflection mode

Adsorption procedure

Results and discussion

Conclusion