Effective bromate removal from water utilizing ZIF-67 and ZIF-67/GO nanocomposites: Optimization and mechanism analysis

Bromate (${\text{BrO}}_3^{-}$) is a toxic disinfection byproduct frequently formed during ozonation in water treatment processes and is classified as a potential human carcinogen. Its effective removal from drinking water is therefore a pressing concern for public health and environmental safety. This study investigated the removal of ${\text{BrO}}_3^{-}$ from water using the synthesized zeolite imidazolate framework (ZIF)-67 and ZIF-67/graphene oxide (GO) nanocomposites through a comparative approach. The morphology, composition, and crystallinity of both ZIFs were characterized. The effects of four independent parameters (initial ${\text{BrO}}_3^{-}$ concentration, pH, adsorbent dose, and contact time) on ${\text{BrO}}_3^{-}$ removal efficiency were examined. A strong correlation was observed between experimental and predicted values. GO enhanced ${\text{BrO}}_3^{-}$ removal not only through synergistic interactions with ZIF-67 but also by improving dispersion and providing additional functional groups that facilitate electrostatic interactions and adsorption. The Box–Behnken design was employed to evaluate both individual and interactive effects of the parameters on ${\text{BrO}}_3^{-}$ removal, achieving an optimum removal efficiency of approximately 99.6% using 1.5 g/L of ZIF-67/GO at a pH value of 4 with an initial ${\text{BrO}}_3^{-}$ concentration of 2 mg/L. The optimization process was further supported by desirability analysis. The ${\text{BrO}}_3^{-}$ removal mechanisms are primarily attributed to porosity, electrostatic interactions, and adsorption onto active sites. Compared to ZIF-67 alone, ZIF-67/GO demonstrated superior anion removal efficiency, highlighting its potential for water treatment applications.