Treatment of simulated chromium-contaminated wastewater using polyethylenimine-modified zero-valent iron nanoparticles

Abstract

Abstract The treatment of hexavalent chromium (Cr(VI)) contaminated water is considered the highest priority in the environmental field. Cr(VI) is a known carcinogen and is toxic even at parts per billion levels. In recent years, zero-valent iron nanoparticles (nZVI) have been regarded the best candidate for the decontamination of heavy metals such as chromium (Cr) in contaminated groundwater. Surface modification of nZVI has proven to enhance its stability and mobility in groundwater. In this work, the decontamination of a Cr-contaminant (Cr(VI)) through reductive reaction with polyethylenimine (PEI) coated nZVI (PEI–nZVI) was studied. Characterization was conducted using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and X-ray absorption near edge structure (XANES). The XRD patterns indicated that the nZVI product after Cr-contaminated water treatment corresponds to Fe3O4. Interestingly, the XANES and XPS analyses revealed the reduction of toxic Cr(VI) to less toxic Cr(III) with concurrent oxidization of nZVI to form Fe2O3, Fe3O4, or FeO. A Cr(VI) degradation efficiency of over 99.9% was observed within 10 min for the Cr concentration range 150–300 ppm. Cr(VI) was significantly adsorbed onto the surface of the nZVI nanoparticles; this could represent a cost-effective process for the in-situ remediation of Cr-contaminated groundwater. Owing to its excellent performance for the removal of Cr(VI), the environmentally friendly PEI–nZVI core-shell nanoparticle signifies an effective method for Cr(VI) decontamination.