Dithizone-functionalized oxidized chitosan blend for Pb(II) and surfactant adsorption: Adsorption performance and RSM Optimization

The present study reports the development of a dithizone immobilized oxidized chitosan blend (DOCs) as an efficient adsorbent for the removal of Pb 2 + ions and sodium dodecyl sulphate (SDS) from aqueous media. The synthesized DOCs was characterized using FT-IR, XRD, BET surface area analysis, and thermal analysis to confirm its structural and physicochemical characteristics. The adsorption performance was evaluated as a function of solution pH, adsorbent dose, initial pollutant concentration, and contact time. The batch adsorption was systematically optimized and statistically confirmed using Response Surface Methodology. Under the optimized conditions, effective adsorption was achieved at pH 6.0 for Pb 2+ and pH 3.0 for SDS, using 50 mg of DOCs and a contact time of 60 min for both pollutants at room temperature. The equilibrium adsorption data were best obeyed by the Freundlich isotherm (R 2 =0.9819 (Pb 2+ ), R 2 = 0.9948 (SDS)), indicating multilayer adsorption behaviour on the DOCs. Kinetic studies discovered that the adsorption method followed the PFO model (R 2 =0.990), for Pb 2+ and Elovich model (R 2 =0.928) for SDS. Thermodynamic parameters indicated that the adsorption of Pb 2+ on DOCs is enthalpy-entropy driven and SDS is enthalpy driven in nature. The maximum adsorption capacities of DOCs were found to be 86.34 mg g −1 for Pb 2+ and 950.98 mg g −1 for SDS, demonstrating the strong affinity of the developed material toward both heavy metal ions and surfactant molecules. Regeneration and reusability studies demonstrated that DOCs retained considerable adsorption efficiency even after five consecutive adsorption-desorption cycles, highlighting its stability. The findings suggest that DOCs is a promising, recyclable, sustainable, and multifunctional adsorbent for the efficient removal of heavy metals and surfactants from contaminated water systems.