The widespread discharge of carcinogenic dyes from industrial effluents poses serious health and environmental hazards, necessitating efficient remediation strategies. In this study, hybrids (3a-h) of modified sodium bentonite, guar gum and chitosan were synthesized and employed for organic dyes adsorption. The confirmation of prepared hybrids was accomplished by FTIR, XRD, SEM and EDX analysis. The thermochemical treatment of bentonites resulted in improved crystalline structure that was more pronounced in hybrids. The surface roughness and porosity was increased in prepared hybrids and more visible in 3g hybrid. These results were further supported by chemical composition where high carbon and oxygen contents were observed. Among the synthesized hybrids, sample 3g exhibited high adsorption capacity for both Congo red (CR) (95.5%) and methylene green (MG) dye (76%). Adsorption behaviour was systemically evaluated by varying the pH, temperature, contact time and adsorbent dosage. The best results were achieved at ambient temperature in 120 minutes, at an adsorbent dosage of 0.05 mg.g-1 and pH 8 for Methyl green. The same hybrid demonstrated maximum adsorption under identical conditions, except at an acidic pH of 2 with contact time at 150 min for Congo Red. The data fit both Langmuir and Freundlich isotherm models, indicating monolayer and heterogeneous multilayer adsorption. Kinetic studies supported pseudo second order reaction mechanism, suggesting chemisorption dominance. Thermodynamic analysis revealed that MG adsorption was spontaneous and exothermic, whereas CR showed a non-spontaneous behavior due to electrostatic repulsion. Molecular logic gates were constructed to demonstrate the intelligent sensing capability of the synthesized hybrids by varying pH and temperature. The synthesized hybrid composites demonstrated promising potential for sustainable wastewater treatment applications with high adsorption capacity, selectivity and cost-effectiveness.
Anam Ilyas, Amna Ashfaq, Nayab Siddique, Ambreen Ghani, Manahal Furqan and Erum Akbar Hussain
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