Removal of Zinc from Aqueous Solutions by Magnetite Silica Core-Shell Nanoparticles

Masoomeh Emadi,Mohammad Kazem Amini,Esmaeil Shams

doi:10.1155/2013/787682

Abstract

Magnetite silica core-shell nanoparticles (Fe3O4-SiO2) were synthesized and evaluated as a nanoadsorbent for removing Zn(II) from aqueous solutions. The core-shell nanoparticles were prepared by combining coprecipitation and sol-gel methods. Nanoparticles were characterized by X-ray diffraction, transmission electron microscopy (TEM), and FT-IR. The magnetization values of nanoparticles were measured with vibrating sample magnetometer (VSM). The adsorption of Zn(II) ions was examined by batch equilibrium technique. The effects of pH, initial Zn(II) concentration, and contact time on the efficiency of Zn(II) removal were studied. The equilibrium data, analyzed by using Langmuir and Freundlich isotherm models, showed better agreement with the former model. Using the Langmuir isotherm model, maximum capacity of the nanoadsorbent for Zn(II) was found to be 119 mg g−1at room temperature. Kinetic studies were conducted and the resulting data were analyzed using first- and second-order equations; pseudo-second-order kinetic equation was found to provide the best correlation. The adsorption and sedimentation times were very low. The nanoadsorbent can be easily separated from aqueous solution by a magnet. Repeated adsorption acid regeneration cycles were performed to examine the stability and reusability of the nanoadsorbent. The result of this study proved high stability and reusability of Fe3O4-SiO2as an adsorbent for Zn(II) ions.

Highlights

Water pollution due to toxic heavy metals remains a serious environmental and public problem [1]
Low concentration of zinc is necessary for the growth of living systems, but it can form large aggregates, which may become harmful to health once beyond the permissible limits [3]. us, the removal of zinc like other heavy metals from aqueous solutions is a critical challenge for environmental researchers
Adsorption is one of the most effective and economic techniques for removing heavy metal ions from aqueous solutions. e efficiency of adsorption relies on the capability of the adsorbent to concentrate or adsorb metal ions from solution onto its surfaces and the rate of removing ions from the solution

Summary

Introduction

Water pollution due to toxic heavy metals remains a serious environmental and public problem [1]. Various processes and methods such as precipitation, electrochemical treatment, chemical oxidation reduction, membrane separation, solvent extraction, and ion exchange have been employed to remove metal pollutants from aqueous solutions [4]. Attachment of chitosan [26], humic acid [27], αα-ketoglutaric acid-modi ed chitosan [14], and dimercaptosuccinic acid [19] on Fe3O4 nanoparticles resulted in magnetic sorbent materials effective for the removal of heavy metal ions from water. Silica can be gra ed with a variety of functional groups, leading to considerable enhancement of their surface properties In spite of their good characteristics, the use of silica-coated core-shell MNPs in heavy metal removal is quite rare [32, 33]. Magnetite nanoparticles were synthesized by coprecipitation method and their surface covered with silica shell using sol-gel technique in alkaline solution. e nanoparticles were characterized and tested as adsorbent for Zn(II) removal from aqueous solutions. e important factors affecting the adsorption efficiency such as solution pH, contact time, and initial Zn(II) concentration were investigated. e best kinetic and isotherm models were found from experimental data

Materials and Methods

Results and Discussion

Metal Removal Experiments

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Conclusions