Access to clean water remains a critical global challenge. Accordingly, there is an urgent demand for efficient, cost-effective, and environmentally sustainable sorbents for anion removal from water. In this study, biocompatible functionalized graphene oxide (GO) composites were synthesized and evaluated for their performance in removing fluoride and bromide from water. Methionine-functionalized GO (Meth@GO) and β-cyclodextrin-functionalized GO (BCD@GO) with three different loading ratios were prepared for comparison. The influence of co-anions on the removal of both target anions was investigated, with negligible competitive effects observed in water samples. The optimal composites were selected based on application performance and further used to optimize anion removal from simulated and real water samples. Linear and nonlinear models were employed to interpret the adsorption behavior. Nonlinear pseudo-second-order models suitably described the removal of fluoride and bromide by Meth@GO and BCD@GO. The maximum adsorption capacities for fluoride and bromide were 6.57 mg/g and 4.48 mg/g for BCD@GO, and 4.73 mg/g and 3.53 mg/g for Meth@GO, respectively, as determined by nonlinear models. Model results indicated differences between linear and nonlinear findings based on error functions. Both Meth@GO and BCD@GO exhibited strong reusability over four consecutive cycles, with BCD@GO demonstrating superior performance. The removal of both anions from real water samples exceeded 97.31%, highlighting the practical potential of the sustainably synthesized biocomposites.

Bromate (BrO₃⁻) 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 BrO₃⁻ 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 BrO₃⁻ concentration, pH, adsorbent dose, and contact time) on BrO₃⁻ removal efficiency were examined. A strong correlation was observed between experimental and predicted values. GO enhanced BrO₃⁻ 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 BrO₃⁻ 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 BrO₃⁻ concentration of 2 mg/L. The optimization process was further supported by desirability analysis. The BrO₃⁻ 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.