Amino-functionalized mesoporous MCM-41 silica as an efficient adsorbent for water treatment: batch and fixed-bed column adsorption of the nitrate anion

Mehdi Ebrahimi-Gatkash,Afsaneh Shahbazi,Habibollah Younesi,Ava Heidari

doi:10.1007/s13201-015-0364-1

Mehdi Ebrahimi-Gatkash, Afsaneh Shahbazi + Show 2 more

Open Access

https://doi.org/10.1007/s13201-015-0364-1

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Abstract

In the present study, amino-functionalized Mobil Composite Material No. 41 (MCM-41) was used as an adsorbent to remove nitrate anions from aqueous solutions. Mono-, di- and tri-amino functioned silicas (N-MCM-41, NN-MCM-41 and NNN-MCM-41) were prepared by post-synthesis grafting method. The samples were characterized by means of X-ray powder diffraction, FTIR spectroscopy, thermogravimetric analysis, scanning electron microscopy and nitrogen adsorption–desorption. The effects of pH, initial concentration of anions, and adsorbent loading were examined in batch adsorption system. Results of adsorption experiments showed that the adsorption capacity increased with increasing adsorbent loading and initial anion concentration. It was found that the Langmuir mathematical model indicated better fit to the experimental data than the Freundlich. According to the constants of the Langmuir equation, the maximum adsorption capacity for nitrate anion by N-MCM-41, NN-MCM-41 and NNN-MCM-41 was found to be 31.68, 38.58 and 36.81 mg/g, respectively. The adsorption kinetics were investigated with pseudo-first-order and pseudo-second-order model. Adsorption followed the pseudo-second-order rate kinetics. The coefficients of determination for pseudo-second-order kinetic model are >0.99. For continuous adsorption experiments, NNN-MCM-41 adsorbent was used for the removal of nitrate anion from solutions. Breakthrough curves were investigated at different bed heights, flow rates and initial nitrate anion concentrations. The Thomas and Yan models were utilized to calculate the kinetic parameters and to predict the breakthrough curves of different bed height. Results from this study illustrated the potential utility of these adsorbents for nitrate removal from water solution.

Highlights

Water has a vital role in life on earth
NNN-Mobil Composite Material No 41 (MCM-41) adsorbent was used for the removal of nitrate anion from aqueous solutions due to high adsorption performance which obtained from batch experiments
It can be observed that the slope of breakthrough curves decreased by increasing the bed height. Both breakthrough and exhaust times were found to be increased with increasing the bed height from 2 to 6 cm, which resulted in a higher removal percentage of nitrate anion in the column because of the more prominent number of binding sites for adsorption process and because the transfer zone requires more time to reach the column end for the nitrate anion to have more time to be in contact with NNN-MCM-41

Summary

Introduction

Water has a vital role in life on earth. High level of nitrate anion in aquatic environments is a serious environmental worldwide problem, because this anion is implicated in the eutrophication of receiving surface waters and the presence of nitrate anions in drinking water causes many public health problems (Kapoor and Viraraghavan 1997). The investigation was performed to remove nitrate anion from aqueous solution by amine functionalized mesoporous silica MCM-41 in a fixed-bed column and to investigate the impacts of operating conditions, for example, bed height, flow rate and initial concentration on the column dynamics.

Results

Conclusion