Fabrication of Activated Carbon-HKUST-1 MOF Nanocomposites for Enhanced Adsorption and Decontamination of Acidic and Basic Dyes in Wastewater

The discharge of effluent containing synthetic dyes into aquatic systems presents significant environmental and health challenges, requiring modern treatment techniques. This study presents the production of an activated carbon–HKUST-1 (AC@HKUST-1) nanocomposite by an in situ ultrasonically assisted growth technique and its application for the simultaneous removal of cationic and anionic dyes. Structural characterisation (FTIR, XRD) demonstrated excellent crystallinity and retention of functional groups. Dynamic light scattering analysis revealed a Z-average hydrodynamic diameter of 26.11 nm and a polydispersity index of 1, indicating a relatively uniform size distribution. Batch adsorption experiments revealed fast absorption, with approximately 92% elimination of Rhodamine B (RhB) in 120 minutes and around 78% elimination of Methyl Orange (MO) in 180 minutes. The saturation sorption capacity attained was 276 mg g-1 for RhB and 160 mg g-1 for MO. Kinetic modelling demonstrated a superior fit to the pseudo-second order model (RhB: R2 = 0.996; MO: R2 = 0.992) in contrast to the pseudo-first order model (RhB: R2 = 0.945; MO: R2 = 0.932), thereby affirming chemisorption as the rate-limiting mechanism. Isotherm study revealed Langmuir monolayer adsorption for RhB (R2 = 0.991; qmax ~300 mg g-1) and Freundlich heterogeneity for MO (R2 = 0.968; KF = 22, n = 1.9). The thermodynamic characteristics (ΔH° > 0; ΔG° −15 to −17 kJ mol-1) indicate that the process is endothermic, spontaneous, and driven by entropy. These results underscore AC@HKUST-1 as a high-capacity, pH-adjustable, and sustainable adsorbent, demonstrating significant potential for scalable dye wastewater remediation.