%0 Journal Article
%T Simultaneous Adsorption and Degradation of Cr(VI) and Cd(II) Ions from Aqueous Solution by Silica-Coated Fe0 Nanoparticles
%A Yongchao Li
%A Hongpu Ma
%A Bozhi Ren
%A Tielong Li
%J Journal of Analytical Methods in Chemistry
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/649503
%X Core-shell silica-coated Fe0 nanoparticles (Fe@SiO2) were prepared in one-step synthesis by aqueous reduction combined with modified St£¿ber method. The as-prepared Fe@SiO2 were then used for simultaneous removal of Cr(VI) and Cd(II) from aqueous solution. Batch tests indicated that Fe@SiO2 exhibited high removal capacity toward Cr(VI) and Cd(II). Cr(VI) was removed by Fe@SiO2 through reduction rather than adsorption, while Cd(II) removal was mainly through adsorption. The removal rate increased with increasing initial Fe NPs dose and decreased with increasing initial Cr(VI) and Cd(II) concentrations. Cd(II) adsorption was also strengthened by Cr(VI) reduction with the release of OH£¿. The removals of Cr(VI) and Cd(II) were weakened in the presence of cations or humic acid, as a result of aggregation and less active site of Fe@SiO2. Overall, the simply prepared Fe@SiO2 were potential material for the heavy metals removed from water. 1. Introduction Most heavy metals are toxic and carcinogenic even at very low concentrations and usually cause a serious threat to the environment and the public health. For example, Cr(VI) is a toxic, carcinogenic substance to human and animals [1]. Contrarily, Cr(III) is relatively nontoxic and an essential nutrient for human [2]. Cd(II) is also a potent carcinogen causing damage to the lungs, kidneys, liver, and reproductive organs [3, 4]. Therefore, US Environmental Protection Agency [5] regulates at least ten metals, including chromium and cadmium, as primary contaminants that must be removed from drinking water. There are various conventional techniques applied for removing heavy metals from water. Electroplating wastewater usually contains various heavy metals as cocontaminants; however, few studies have been reported on simultaneous removal of Cr(VI) and Cd(II) from wastewater. Among the different treatments for removing heavy metals, adsorption has been developed as a simple, efficient, and cost-effective method. Many of adsorbents such as clays, activated carbon, sewage sludge, and plant parts have been used for heavy metal removal [6¨C9]. But due to extremely small particle size and large surface area, iron nanoparticles (Fe NPs) with a high adsorption capacity are found to be one of the most effective adsorbents for removing heavy metals [10¨C12]. Moreover, Fe NPs have shown a high chemical reduction rate on several kinds of contaminants, including toxic metal ions [13¨C15]. For example, Ponder et al. [13] have found that Fe NPs acting as reductants could chemically reduce Cr(VI) to Cr(III). Besides, Fe NPs can
%U http://www.hindawi.com/journals/jamc/2013/649503/