ZIF-8 catalyzed transformation and removal of disinfection byproduct halobenzoquinones in water

Halobenzoquinones (HBQs) are emerging toxic disinfection byproducts in water. Development of effective methods to decompose or remove HBQs from water is imperative. Herein, we report the exploration of a metalorganic framework ZIF-8 as an effective catalysis of the transformation and removal of HBQs in darkness. Three HBQs (2,6-dichlom-1,4-benzoquinone (DCBQ), 2,6-dibromo-1,4-benzoquinone (DBBQ) and tetrachloro-1,4-benzoquinone (TCBQ)) were taken as examples and main degradation product of HBQs was studied. In the presence of ZIF-8, 90 % of the HBQs transformed in <10 min and the transformation followed pseudo-first-order kinetics with large reaction rate constants of 0.163-0.181 min(-1). ZIF-8 further made the major transformation product OH-HBQs disappear completely within the following 24 h. In addition, >80 % of ZIF-8 initial activity was maintained after 4 cycles. Radical and holes inhibition experiments verified that the holes in ZIF-8 dominated HBQs hydroxylation. Except for OH-HBQ, several other possible products were found and all of them were predicted as less toxic than their parent compound. This study offers a potential approach for HBQs removal from disinfected waters.

Automated summary

In this study, a metal-organic framework ZIF-8 was explored as an effective catalyst for the transformation and removal of HBQs in darkness. The results showed that HBQs could be transformed within a short period of time and the transformation product could completely disappear within 24 hours in the presence of ZIF-8. In addition, the method demonstrated sustainable removal of HBQs. This study offers a potential approach for the removal of HBQs from disinfected waters.