Polyvinyl alcohol modified chitosan composite as a novel and efficient adsorbent for multi-metal removal

[Display omitted] •PVA modified chitosan composite developed for efficient metal removal.•Qm obtained as 303.29 mg/g, 209.08 mg/g, 173.39 mg/g for Cu+2, Ni+2, and Zn+2.•Langmuir and Pseudo second order models best fit the experimental data.•Thermodynamic values of ΔSo, ΔGo, and ΔHo heats estimated.•Stability achieved upto 10 cycles with effective regeneration protocol.•Proposed possible adsorption mechanisms. This study focussed on the development of a novel and efficient adsorbent derived from polyvinyl alcohol-modified chitosan composite for the removal of Cu+2, Ni+2, and Zn+2 from wastewater. The characterization of composite exhibits mesoporous, thermal stability, and rich with functional groups. The Box-Behnken method of Response Surface Methodology framework was employed, and attained optimum conditions for Cu+2 (1000 mg/l, 20 min, 1 g/l), Ni+2 (1000 mg/l, 20 min,1 g/l), and Zn+2 (972.28 mg/, 20 min, 1 g/l) respectively. Langmuir isotherm and Pseudo-Second order kinetic model best fit, indicating chemisorption-driven monolayer adsorption and achieved maximum adsorption capacity 303.29 mg/g, 209.08 mg/g, and 173.39 mg/g for Cu+2, Ni+2, and Zn+2 respectively. In competitive adsorption of binary and ternary systems, Cu+2 displayed superior removal efficiency compared to Ni+2 and Zn+2. Furthermore, the adsorbent's efficacy was evaluated using industrial effluent, demonstrating higher removal efficiency for Cu+2 (79.09 %) compared to Ni+2 (50.73 %) and Zn+2 (46.97 %). Thermodynamic study (Enthalpy: 19.08 to 26.29 kJ mol−1, Gibb’s free energy: −0.32 to − 3.10 kJmol−1, Entropy: 65.10 to 90.95 J mol−1 K−1) underlined the spontaneity and endothermic nature of adsorption. The desorption efficiency ranging from 88.94 % to 48.90 %, 88.19 % to 41.31 %, and 84.09 % to 48.19 % up to 10th cycles for Cu+2, Ni+2, and Zn+2 using 0.4 mol/l H2SO4, 0.6 mol/l HNO3, and 0.6 mol/l HCl respectively. The adsorption mechanisms, primarily surface complexation, ion exchange, and electrostatic attraction, prevail over physisorption. The PVA-CS, recognized as highly efficient and environment friendly adsorbent provides a practical solution for water decontamination.