Experimental and computational insights: green synthesis, characterisation and application of MgO-NPs for adsorption-desorption of toxic metals and Sardol Black G dye from Tannery wastewater

This investigation delineates the synthesis and comprehensive characterisation of magnesium oxide nanoparticles (MgO-NPs) employing Azadirachta indica leaf extract as a sustainable reducing agent, to develop an efficacious adsorbent for the concomitant removal of toxic heavy metals (Cd 2+ , Cr 6+ , and Pb 2+ ) and Sardol Black G (SBG) dye from ternary effluent systems, utilising Response Surface Methodology (RSM). The synthesised MgO-NPs were rigorously characterised using an array of spectroscopic and analytical techniques, including SEM-EDX, XRD, FT-IR, UV–Vis, BET, TGA, pHzpc, and N 2 adsorption–desorption isotherms. The systematic investigations were conducted to elucidate the effects of critical adsorption parameters, namely MgO-NPs dosage, adsorbate concentration, pH, and agitation time, on the percentage removal of target pollutants. The optimal conditions for maximal pollutant removal were determined to be: MgO-NPs dosage = 55 mg, agitation time = 70 min, adsorbate concentration = 100 mg/L, and pH = 4. The adsorption kinetics were modelled using pseudo-first-order (PFO), pseudo-second-order (PSO), and Elovich kinetics (EK) models, with the PFO model providing the best fit to the experimental data, indicating a physisorption-dominated process. The maximum adsorption capacities of MgO-NPs for Cd 2+ , Cr 6+ , Pb 2+ , and SBG dye molecules were determined to be 5.9156, 0.4936, 1.2750, and 3.3877 mg/g, respectively. These findings underscore the potential of MgO-NPs as an effective adsorbent for the remediation of pollutants from real wastewater systems.