Adsorption of Ni 2+ on aminofunctionalized mesoporous silica templated by an anionic surfactant route
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In the present study, aminofunctionalized mesoporous silica (AFMS) was synthesized using the anionic surfactant N-lauroylsarcosine sodium as template and 3-aminopropyltrimethoxysilane as costructure directing agent. The synthesized mesoporous silica was characterized by the Fourier transform infrared spectra, x-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, and transmission electron microscopy techniques. The application for the removal of Ni21 from aqueous solution using the synthesized mesoporous silica as adsorbent was investigated. It was found that the solution pH affected adsorption of Ni21 greatly. The kinetic data of adsorption showed that the removal rate of Ni21 was substantially high. The adsorption isotherms were fitted using the Sips, Langmuir, and Freundlich models, respectively, and the results showed that the Sips model was the best one to describe the experimental data. From the data of Sips, the maximum adsorption capacity of Ni21 in respect of the extracted sample is 2.48 mmol/g, much higher than those reported in other literature. The possible adsorption mechanism of Ni21 on the AFMS was proposed. I. INTRODUCTION
Industrial activity generates large quantities of aqueous effluents that contain high levels of toxic heavy metals, resulting in the discharge of industrial wastewater. It is well known that the heavy metals have accumulating characteristics in nature and cannot be biodegraded, leading to be hazardous for living organisms. Therefore, treatment of water contaminated by heavy metals is a critical environmental issue. Many researches have indicated that Ni21 was frequently detected in industrial wastewater (e.g., effluents discharged from mines drainage, plating plants, paint and ink formulation units, and porcelain enameling). It is obvious that the occurrence of nickel in industrial effluents beyond permissible limits will bring serious environmental pollution, threatening human health and ecosystem.1 As we know, lung damage, nose and bone cancer, and headache can be caused by the presence of excessive nickel in the aqueous solution.2 Consequently, industrial effluents containing high levels of nickel must be purified before being released into the environment. The conventional methods used for removing heavy metals from wastewater are precipitation, ion exchange, adsorption, coagulation, electrocoagulation, reduction, membrane processes, etc.3–5 Among these methods, adsorption is effective and simple. Recently, many kinds of adsorbents such as activated carbon, natural sepiolite, and activated alumina have been used for nickel ions removal.6–8 a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2013.33 J. Mater. Res., Vol. 28, No. 17, Sep 14, 2013
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However, these adsorbents always suffer from low adsorption capacities and/or removal efficiencies. For example, the adsorption capacity of Ni21 on modified activated carbon (MAC)-II is 4.89 mmg/g.6 The removal efficiency of Ni21 on activ
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