Treatment of chromium-containing wastewater from an electroplating plant using nanoscale zero-valent iron (nZVI)

• Main Authors: Sheu, Yih-Terng, 許藝騰
• Other Authors: Chen, Ku-Fan
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/31956828840958678194

碩士 === 國立暨南國際大學 === 土木工程學系 === 99 === In this study, nanoscale zero-valent iron (nZVI) was applied to treat chromium-containing wastewater collected from an electroplating plant. Batch experiments were conducted to evaluate the efficiency of chromium removal under closed and semi-closed conditions. The wastewater used in this study contained approximately 1,400 mg/L of total chromium (total Cr), including 1,000 mg/L of hexavalent chromium (Cr6+). Results of the closed system experiments show that the removal efficiencies of total Cr by 0.1, 0.5, 1, 2 and 5 g/L of nZVI were 7.8, 30.3, 57.1, 100, and 100%, respectively, during 24 hours of reaction. The removal efficiency of total Cr reached 100% rapidly with the addition of 5 g/L nZVI during a 5-minute reaction. Trivalent chromium (Cr3+) was detected in the aqueous phase during the removal of Cr6+. X-ray photoelectron spectroscopy (XPS) analysis confirmed that Cr3+ was present on the surface of nZVI. This indicates that nZVI can reduce Cr6+ effectively, and then adsorbs Cr3+ onto its surface. The total Cr removal capacity of nZVI was approximately 0.7-0.8 g total Cr/g nZVI. In addition, nZVI was capable of removing anions including NO3-、NO2-、PO43- and SO42-. Results also show that the removal rate of total Cr by nZVI increased with increased temperature. The adsorption of Cr by nZVI fits the pseudo-second-order kinetic model and the Freundlich isotherm. The results of the semi-closed system experiments show that the removal efficiency of total Cr was decreased due to oxygen penetration. The adsorbed Cr3+ can be recovered from the produced iron-chromium sludge by hydrochloric acid pickling, and then the residual spent iron particles can be collected to reproduce nZVI for further applications. Experimental results reveal that the removal efficiency of total Cr by the reproduced nZVI was similar to that of directly synthesized nZVI. The results of this study show that the application of nZVI can treat chromium-containing wastewater rapidly and effectively. In addition, the reproduced nZVI also has the potential to be reused in the treatment process.