Influence of operating temperature on the reduction of high concentration p-nitrophenol (PNP) by zero valent iron (ZVI)

In this study, the effect of operating temperature on the reduction of high concentration p-nitrophenol (PNP) by zero valent iron (ZVI) system has been investigated thoroughly. The experimental results show that the elevating temperature could significantly improve the reduction efficiency of PNP by ZVI. But the lower initial PNP concentration (<1000 mg/L) would inhibit the corrosion of Fe-0, while the higher initial PNP concentration (>1000 mg/L) would accelerate this process. The high concentration PNP could cause severe corrosion of Fe; in return, the Fe corrosion facilitated the reduction of PNP. Additionally, the adding Fe2+ could accelerate the reduction efficiency of PNP when the lower concentration PNP (e.g., 500 mg/L) in aqueous solution was treated by ZVI. Furthermore, the effect of operating temperature on the other operating parameters including initial Fe-0 dosage, initial pH and stirring speed also was investigated, respectively. The results suggest that the elevating temperature could decrease the initial Fe-0 dosage and the stirring speed, and broaden the pH range of reaction solution, which would reduce the operation costs of the ZVI. According to the detected results of GC MS, it is clear that PNP in aqueous solution could be completely reduced into p-aminophenol by ZVI under the higher operating temperature (85 degrees C). Finally, the ZVI under the high operating temperature would be a cost-effective process for the toxic and refractory industrial wastewater, if the waste-heating vapor could be used to elevate the operating temperature of ZVI. (C) 2014 Elsevier B.V. All rights reserved.