Graphene oxide nanocomposite decorated zeolitic imidazolate framework-8 as an effective sorbent for acid orange 10 dye removal

Abstract

Global industrialization is associated with the release of high amounts of toxic pollutants, such as synthetic dyes, into the environment. Zeolitic imidazolate frameworks (ZIFs), a subclass of metal-organic frameworks (MOFs), are renowned for their exceptional chemical and thermal stability, making them promising candidates for pollutant's adsorption. In this study, a ZIF-8/graphene oxide (GO) composite was synthesized via a hydrothermal method at three ZIF-8 to GO ratios (5 , 10 , and 15 ) to enhance the sorption of acid orange 10 dye (AO10). The ZIF-8/GO (10 ) composite exhibited high crystallinity, a specific surface area of 418 m2/g, and functional groups (e.g., hydroxyl and carboxylate (O-H and COO-)), which facilitated superior dye sorption. Under optimal conditions (pH = 3, sorbent dose = 4.8 mg/L, AO10 concentration = 5 mg/L, reaction time = 90 min), the composite achieved complete (100 ) removal of AO10. The sorption process followed the Freundlich isotherm model, indicating multilayer sorption on heterogeneous surfaces, with a maximum sorption capacity (qe) of 6780-7250 mg/g. Kinetic studies revealed pseudo-first-order behavior (kf = 0.15-0.18 min-1), suggesting physisorption as the dominant mechanism, supplemented by pi-pi interactions and electrostatic forces between the sulfonate groups of AO10 and the positively charged ZIF-8/GO surface. These results highlight thecomposite's novelty as a high-capacity, fast-acting sorbent for wastewater treatment, addressing critical chal- lenges in dye pollution remediation.