Efficient degradation of nizatidine by a Fe(II)/ persulfate system activated with zero-valent iron

Abstract

In this study, the degradation of nizatidine (NZTD) was investigated using a zero-valent iron-promoted divalent iron-activated persulfate process. Results show that complete NZTD degradation at 5 mg/L could be achieved under the optimal conditions of NZTD/zero-valent iron (ZVI)/Fe(II)/persulfate (PS) = 1:6:3:6 (molar ratio), pH = 7.0, and 25 °C. A highly alkaline environment would decrease the NZTD removal, and the NZTD degradation increased with the reaction temperature (5–35 °C). Furthermore, acidic conditions and the presence of Cl- enhanced the degradation of NZTD, but the presence of high doses of HCO3-, NO3-, and humic acid inhibited the degradation of NZTD. The fragile sites in NZTD were predicted by density functional theory (DFT) methods, and six transformation products were detected during the degradation of NZTD by PS/Fe(II)/ZVI. The toxicity of the intermediates was examined using the TEST toxicity prediction model and luminescent bacteria. The degradation process generated intermediates with higher toxicity than NZTD. However, after 60 min of reaction, the inhibition rate of luminescent bacteria decreased rapidly, and low toxicity products were generated. These results suggest that ZVI/Fe(II)/PS is promising as a new alternative process for the treatment of water containing NZTD.