Enhanced Cr (VI) Removal from Landfill Leachates using Nanoscale Zero-valent Iron

摘要

Nanoscale zero-valent iron modified by citric acid (m-NZVI) was used to remove hexavalent chromium (Cr (VI)) from landfill leachates. Citric acid was useful to enhance the dispersion of NZVI. The results demonstrated that the m-NZVI particles were uniform with a mean diameter of 45.6 nm and the specific surface area was about 22.8 m~2/g. The Cr (VI) removal rates increased as an increase of the dosage of m-NZVI and the temperature but decreased as an increase of pH and the initial concentration of HA. Cr (VI) adsorption kinetics followed a pseudo-first-order rate expression and the reaction rate constants ranged from 0.05 to 0.32 min~(-1). X-ray photoelectron spectroscope (XPS) analysis confirmed that the Fe(III)-critic acid and/or Cr(III)-HA compounds were formed on the m-NZVI surface, which could hinder the formation of Fe(III)-Cr(III) compounds. It was also shown that removing Cr (VI) by m-NZVI was a chemical controlled and irreversible process.