Sustainable nanocellulose-supported ZIF-8/ZnO/activated carbon heterostructures enhance charge separation for efficient photocatalytic dye remediation

Abstract The presence of synthetic dyes such as Methylene Blue (MB) and Methyl Orange (MO) in water sources presents a significant environmental issue, attributed to their stability and toxic properties. This study presents the fabrication and evaluation of a multifunctional ZIF-8/ZnO/Activated Carbon/Nanocellulose composite for its photocatalytic efficiency under optimized conditions. The characterization results confirmed the development of a hierarchical porous structure characterized by an increased surface area, enhanced light absorption, and improved charge separation. Photocatalytic degradation tests demonstrated that the composite attained maximum efficiencies of 91.8% for MB and 87.4% for MO under optimal conditions of pH 7, a catalyst dose of 0.3 g/L, a temperature of 30 °C, and 60 min of UV irradiation. The adsorption behavior conformed to the Langmuir model, exhibiting high monolayer capacities of qmax (53.0 mg/g for MB and 50.1 mg/g for MO), which indicates a strong affinity between the composite and the dye molecules. Kinetic analyses indicated a pseudo-second-order mechanism, and thermodynamic findings validated the spontaneous and exothermic characteristics of the process. The composite exhibited strong stability across five cycles, demonstrating negligible efficiency loss. The interaction between ZIF-8, ZnO, activated carbon, and nanocellulose markedly improved adsorption, charge transfer, and radical generation, rendering this composite an efficient material for sustainable wastewater treatment .