Application of iron/aluminum bimetallic nanoparticle system for chromium-contaminated groundwater remediation. (October 2020)

• Record Type: Journal Article
• Authors: Ou, Jiun-Hau; Sheu, Yih-Terng; Tsang, Daniel C.W.; Sun, Yong-Jun; Kao, Chih-Ming
• Is Part Of: Chemosphere. Volume 256(2020)
• Publication Date: 2020-10
• Subjects: Bimetallic nanoparticle (BNP) -- Groundwater contamination -- Hexavalent chromium (Cr6+) -- Nanoscale zero valent iron (nZVI) -- Site remediations; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2020.127158
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: When the nanoscale zero valent iron (nZVI) is used for the reduction of hexavalent chromium (Cr 6+ ) to trivalent chromium (Cr 3+ ) in groundwater, the reduction efficiency is decreased due to the passivation of reactive sites by precipitation. The bimetallic nanoparticle (BNP) can be created with the addition of the second metal to achieve a higher activity and reduce the occurrence of the ferrous/ferric hydroxide precipitation. In this study, the iron-coated aluminum (Fe/Al) BNP and aluminum-coated iron (Al/Fe) BNP systems were designed for remediating Cr 6+ -contaminated groundwater. The chemical liquid-phase deposition and co-reduction method was applied to produce BNPs. Cr 6+ removal rate by Fe/Al BNPs was directly proportional to the saturation concentration and reactive sites, which caused a higher Cr 6+ removal rate. The pseudo-first-order kinetic model could be used to describe the Cr 6+ adsorption mechanism by Fe/Al BNPs. Results show that Fe/Al BNPs and Al/Fe BNPs could reduce Cr 6+ to Cr 3+, and the removal efficiencies for Cr 6+ were 1.47 g/g BNP and 0.07 g/g BNP, respectively. Detection of Cr 3+ in the aqueous phase was observed during the Cr 6+ removal process. Results from X-ray diffraction (XRD) analysis confirmed that Cr(OH)3 was present on the surface of BNPs. Main mechanisms caused Cr 6+ removal included reduction, precipitation, and adsorption. The reduction of Cr 6+ produced OH −, which created alkaline environment and facilitated the formation of chromium hydroxide precipitates [Cr(OH)3 ]. Thus, the migration of Cr 3+ was prevented and the environmental risk was reduced. BNP had a higher activity and stability, and it was applicable for Cr 6+ -contaminated site remediation. Highlights: Fe/Al and Al/Fe bimetallic nanoparticle (BNP) can reduce Cr 6+ to Cr 3+ effectively. Removal efficiency for Cr 6+ by Fe/Al BNPs was 1.47 g/g BNP. Cr 6+ reduction by BNP produced OH − resulting formation of Cr(OH)3 precipitates. Cr 6+ removal mechanisms by BNP include reduction, precipitation, and adsorption. Chemical liquid-phase deposition and co-reduction can produce two BNPs effectively.