Development of GO@ZIF‐9 Nanocomposite for the Simultaneous Removal of Congo Red and Hexavalent Chromium from Aqueous Solutions

Industrial wastewater frequently contains mixtures of dyes and toxic heavy metals, creating treatment challenges that are not adequately represented by single‐contaminant adsorption studies. In this study, a graphene oxide–zeolitic imidazolate framework‐9 nanocomposite (GO@ZIF‐9) was synthesized through a modified solvothermal method and evaluated for the simultaneous removal of Congo red (CR) and hexavalent chromium [Cr(VI)] from aqueous solutions. The synthesized nanomaterial was characterized using scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), which confirmed the successful formation and stability of the nanocomposite. Adsorption performance under competitive conditions was optimized using response surface methodology (RSM). Compared with pristine GO and ZIF‐9, GO@ZIF‐9 exhibited markedly enhanced adsorption performance because of the synergistic combination of both components. Kinetic and equilibrium analyses showed that the pseudo‐second‐order (PSO) and Redlich–Peterson models best described the adsorption process, while the Langmuir model predicted maximum adsorption capacities of 2166.6 mg/g for CR and 2137.5 mg/g for Cr(VI). Thermodynamic results confirmed that adsorption was spontaneous and endothermic. Machine learning models successfully predicted adsorption performance, with the support vector machine (SVM) providing the highest predictive accuracy. These findings demonstrate the potential of GO@ZIF‐9 for simultaneous dye and heavy‐metal removal from aqueous systems.