Bezafibrate (BZF), an extensively used lipid-regulating agent, has been frequently detected in aqueous environments. In this work, we systematically investigated the Fe(II)/sulfite process for degrading BZF and its impact on disinfection byproducts (DBPs) during postchlorination. Degradation conditions were optimized by adjusting the pH, sulfite concentration, Fe(II), and BZF concentration. Under the conditions of pH = 4, [BZF] 0 = 5 μM, [Fe(II)] 0 = 25 μM, and [sulfite] 0 = 250 μM, the BZF removal efficiency reaches 97.9% in 15 min. Sulfate radicals (SO 4 ●– ) and singlet oxygen ( 1 O 2 ) are recognized as the main reactive agents, with Fe(IV) also contributing to the removal of BZF. Common anions (Cl − and HCO 3 − ) and humic acid generally impede the degradation process, except that trace amounts of Cl − can slightly accelerate BZF degradation. A total of ten products are recognized by ultra high performance liquid chromatography and quadrupole time-of-flight mass spectrometry, and four major degradation pathways are proposed: hydroxylation, cleavage of amino bonds, removal of fibrate chains, and dechlorination. Meanwhile, the toxicity assessment shows that the majority of products exhibit lower biological toxicity and less bioaccumulation potential than BZF itself. The Fe(II)/sulfite pretreatment alters the DBP formation potential, especially when Br − is present. The formation of trichloromethane (TCM) is diminished following pretreatment with the Fe(II)/sulfite process, whereas a noticeable increase in the formation of dichloroacetonitrile (DCAN) is found. Moreover, Fe(II)/sulfite pretreatment enhances the formation of brominated DBPs. Therefore, special consideration should be given to DBP formation when a Fe(II)/sulfite system is employed as a pretreatment for the removal of BZF in water. Graphical abstract
The thermal decomposition kinetics of bezafibrate in a nitrogen atmosphere has been investigated by analyzer DTG-60. The thermal behavior of bezafibrate at the different heating rates 4, 8, 12, 16 and 20 °C min −1 displays two-stage decomposition processes among 500–650 K. The activation energy ( E ) and pre-exponential factor ( A ) were calculated to be 128.72 kJ mol −1 and 3.56 × 10 10 min −1 by Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, Doyle, Kissinger and Šatava–Šesták methods for the second-stage decomposition process. The results show that the non-isothermal thermal decomposition mechanism of bezafibrate is classified as three-dimensional diffusion model, and the integral and differential equations are \(g(\alpha ) = [1 - (1 - \alpha )^{1/3} ]^{2}\) and \(f(\alpha ) = \frac{3}{2}\left( {1 - \alpha } \right)^{{{\raise0.7ex\hbox{$2$} \!\mathord{\left/ {\vphantom {2 3}}\right.\kern-0pt} \!\lower0.7ex\hbox{$3$}}}} \left[ {1 - \left( {1 - \alpha } \right)^{{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 3}}\right.\kern-0pt} \!\lower0.7ex\hbox{$3$}}}} } \right]^{ - 1}{.}\) The enthalpy (Δ H
≠ ), entropy (Δ S
≠ ) and Gibbs free energy (Δ G
≠ ) were calculated to be 123.74 kJ mol −1 , −91.07 J mol −1 K −1 and 178.29 kJ mol −1 , respectively.
Shi Xue-Ting,Liu Yong-Ze,Tang Yu-Qing,Feng Li,Zhang Li-Qiu
UV/chlorine, as a novel disinfection method, has attracted great interest due to its effective removal for pathogenic microorganism and degradation of trace organic contaminants existed in water environment. This paper investigated the degradation kinetics and pathways of Bezafibrate (BZF), a typical antilipemic drug, during UV/chlorine process. The results showed that 92.3% of BZF was degraded after 20 min in UV/chlorine process. This indicated HO• and reactive chlorine species (RCSs) formed in UV/chlorine played the dominant role in degrading BZF. Observed rate constants of BZF degradation ( k
obs,BZF ) in UV/chlorine process increased linearly in a wide chlorine dosage from 0.1 to 1.0 mM, which implied that ClO• generated from the reactions of chlorine with HO• and Cl• could react with BZF rapidly. The steady-state kinetic modeling result proved this deduction and the rate constant of ClO• with BZF was fitted to be 5.0 × 10 8 M −1 s −1 . k
obs,BZF was affected by Cl − and HA. The total contribution of RCSs (including Cl•, Cl 2 • − , and ClO•) to the degradation of BZF was determined to be ~ 80%, which is much higher than that of HO•. Thirteen degradation products of BZF were identified by LC-MS/MS. Initial degradation products were arisen from hydroxylation, chlorine substitution and cyclization by HO• and RCSs, and then further oxidized to generate acylamino cleavage and demethylation products.
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