Mild Solvent–thermal Treatment of Chitosan for Enhanced Cu(II) removal

Heavy-metal removal is vital for water quality and human health. A coupled DMF solvation–mild thermal treatment enhanced chitosan Cu(II) binding without grafting or crosslinking. Treatment at 40 °C increased Cu(II) uptake by 83%, giving an equilibrium capacity of 85.6 mg g−1 at 20 °C and pH 3 after 6 h. XRD, FTIR, and TGA revealed local ordering, hydrogen-bond reorganization, and improved thermal stability. Adsorption followed a pseudo-second-order model (R2 > 0.99), demonstrating a simple route to improved biopolymer adsorbents.