Study on why FeOCl has high Fenton activity in wide range of initial pH and its corresponding stability

Abstract

FeOCl was successfully synthesized by partial pyrolysis method and used as catalyst in Fenton-like reaction. The catalytic activity and stability of FeOCl at different initial pH were evaluated in degradation of isoniazid (INH). The experimental results showed that the pH of the solution had an important effect on the catalytic activity and stability of FeOCl. The point of zero charge (pHPZC) of FeOCl was measured to be 1.75. Adding FeOCl could change pH (before addition of FeOCl) of the solution from 3.0, 6.0, 9.0–3.0, 3.9 and 4.4, respectively, being conducive to Fenton-like reaction. The removal rates of INH by FeOCl/H2O2 system at initial pH 3.0, 6.0, 9.0 were 94.48%, 92.45%, 42.32%, respectively. However, degradation efficiency was rapidly degenerative at initial pH 3.0 and 9.0 in stability test. By means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM), it was found that the rapid inactivation of FeOCl at initial pH 3.0 was caused by crystal structure transformation of FeOCl into FeOOH and the dissolved Fe, but at initial pH 9.0 was owing to the weakened pH regulation ability of the used FeOCl (only from 9.0 to 6.6).