Abstract
Nanometer zero-valent iron (nZVI) has been widely used in the treatment of heavy metals such as hexavalent chromium (Cr(VI)). A novel composite of bead string-structured nZVI on modified activated carbon (nZVI–MAC) is prepared here, using polyethylene glycol as the stable dispersant rather than traditional ethanol during the loading process. The microstructure characterization shows that nZVI particles are loaded on MAC with a bead string structure in large quantity and stably due to the addition of hydroxyl functional groups on the surface by polyethylene glycol. Experiments on the treatment of Cr(VI) in wastewater show that the reaction process requires only 20 min to achieve equilibrium. The removal rate of Cr(VI) with a low concentration (80–100 mg/L) is over 99% and the maximum saturation removal capacity is up to 66 mg/g. The system converts Cr(VI) to trivalent chromium (Cr(III)) through an oxidation-reduction effect and forms an insoluble material with iron ions by coprecipitation, which is then adsorbed on the surface of the nZVI–MAC. The process conforms to the quasi-second order adsorption kinetics equation (mainly chemical adsorption process).
Highlights
Chromium is widely used in lots of industrial productions such as paper making, electroplating, dye manufacturing, leather tanning and paint manufacturing [1,2,3]
The following steps were involved in the synthesis of Nanometer zero-valent iron (nZVI)–MAC
Liu et al [35] believed that microcrystalline cellulose played a role in providing nucleophile group functions here, which enabled the formation of carbon microspheres and the appendage of carbon particles with activated carbon
Summary
Chromium is widely used in lots of industrial productions such as paper making, electroplating, dye manufacturing, leather tanning and paint manufacturing [1,2,3]. Due to loopholes in mining, smelting, use and disposal processes, chromium has caused many incidences of water contamination in industrialized areas, especially in China’s Bohai Rim region with developed industry [3,4]. Chromium primarily exists as Cr(III) and Cr(VI) in the natural environment, and Cr(VI) is more soluble and toxic than Cr(III) [5,6]. The US Environmental Protection Agency (EPA) issues the national primary drinking water regulations, which stipulate a maximum concentration of 0.1 mg/L total chromium in drinking water [8]. The treatment of Cr(VI) wastewater, has become an exigent environmental issue
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