Abstract
Hexavalent chromium Cr(vi), one of the most toxic contaminants, is released in the environment due to various anthropogenic activities. This study presents a novel sandwiched nanocomposite synthesized using graphene oxide (GO), manganese dioxide (MnO2) nanowires, iron oxide (Fe3O4) nanoparticles and polypyrrole (PPy) to remove hexavalent chromium ion Cr(vi) from water by an adsorption–reduction mechanism. In the sandwiched nanocomposites, GO provided enough surface area, functional groups, and hydrophilic surface for efficient absorption. Fe3O4 nanoparticles with excellent magnetic properties make it easy to separate and recover from water. Under acidic conditions, MnO2 nanowires act as both template and oxidant to initiate the polymerization of pyrrole monomers on its freshly activated surface to obtain GO/MnO2/Fe3O4/PPy (designated as GMFP) nanocomposite. GMFP could effectively adsorb Cr(vi) through electrostatic attraction, and the adsorbed Cr(vi) ions were partly reduced to trivalent chromium Cr(iii) (62%), resulting in the efficient adsorption and high removal of Cr(vi) from water. Hexavalent chromium adsorption by GMFP is strongly pH dependent and the adsorption kinetics followed the pseudo-second-order model. The Langmuir isothermal model described the adsorption isotherm data well and the maximum adsorption capacity was up to 374.53 mg g−1 at pH 2.0. These experimental results suggested that GMFP had great potential as an economic and efficient adsorbent of hexavalent chromium from wastewater, which has huge application potential.
Highlights
The existence of heavy metal ions, such as Pb(II), Fe(III), Hg(II), Cu(II) and Cr(VI) in groundwater is one of the most serious environmental problems today.[1,2] These toxic contaminants are a serious danger to human health
This study presents a novel sandwiched nanocomposite synthesized using graphene oxide (GO), manganese dioxide (MnO2) nanowires, iron oxide (Fe3O4) nanoparticles and polypyrrole (PPy) to remove hexavalent chromium ion Cr(VI) from water by an adsorption–reduction mechanism
Aim to design materials with high adsorption capacity for the chromium removal, a sandwiched nanocomposite has been developed with utilizing graphene oxide (GO), manganese dioxide (MnO2) nanowires, iron oxide (Fe3O4) nanoparticles and polypyrrole (PPy), as illustrated in Scheme 1
Summary
Different types of adsorbent materials have been widely used for the removal of Cr(VI) from wastewater. Conventional adsorbents o en show a limited adsorption capacity or not separated even cause potential secondary pollution because they do not have enough surface area, functional groups, and hydrophilic surface.[12] it is important to fabricate a nanomaterials with excellent performances of adsorption, reduction, and collectability simultaneously for the removal of Cr(VI) from wastewater. Paper efficient adsorbent to remove heavy metal ions because of having an ultralarge speci c surface area and abundant oxygencontaining groups –OH and –COOH).[13,14,15,16] And the idea of GO coated with MnO2 may be utilized in synthesizing new nanocomposite materials which would have better performances in metal ions adsorption applications. This work provides a facile, efficient, and environmentally-friendly approach for the remediation of Cr(VI)contaminated wastewater
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