Reduction of hexavalent chromium by carboxymethyl cellulose-stabilized zero-valent iron nanoparticles

Abstract

The reduction of hexavalent chromium or Cr(VI) by zero-valent iron (Fe(0)) nanoparticles has received increasing attention in recent years. However, Fe(0) nanoparticles prepared using conventional methods suffered several drawbacks due to their high reactivity towards surrounding media, which led to the formation of much larger flocs and significant loss in reactivity. To overcome these problems, we synthesized Fe(0) nanoparticles by applying water-soluble carboxymethyl cellulose (CMC) as a stabilizer. CMC-stabilized Fe(0) nanoparticles displayed much less agglomeration but greater Cr(VI) reduced power than those prepared without a stabilizer. At a dose of 0.15 g L(-)(1), CMC-stabilized Fe(0) nanoparticles were able to reduce 100% of 10 mg L(-)(1) Cr(VI) in minutes. Several factors that may affect the efficiency of Cr(VI) removal were investigated. These included the concentration of CMC, the concentration of Fe(0) nanoparticles, the initial Cr(VI) concentration, the pH value, the reaction temperature and the concentration of the calcium cation in the reaction mixture. Our study suggested that the introduction of an innocuous stabilizer such as CMC could significantly improve the performance of Fe(0) nanoparticles for environmental remediation applications.