Adsorptive removal of heavy metal ions from wastewater using shrimp chitosan-cysteine-glutaraldehyde hydrogel as a sustainable biosorbent.

A new biosorbent, crosslinked chitosan-cysteine-glutaraldehyde hydrogel (CSCys-HG), was successfully synthesized and characterized using microanalytical and spectroscopic methods. CSCys-HG exhibited a high gel fraction and swelling capacity, indicating the highest degree of crosslinking and porosity. To optimize the performance of CSCys-HG as a scavenger for heavy metal ions (HMIs), its adsorptive removal of Cu(II) and Pb(II) ions from wastewater was studied through batch adsorption experiments under various conditions. The optimal parameters were determined to be an adsorbent dose of 5 mg/mL, contact times of 90 and 5 min, pH levels of 5 and 4, initial concentration of 25 ppm, and temperatures of 303 K and 308 K for Cu(II) and Pb(II), respectively. The CSCys-HG efficiently removed Cu(II) and Pb(II) ions, achieving adsorption capacities of 171.10 and 132.56 mg/g, respectively. CSCys-HG exhibited M(II) ion sorption performance that aligned with the nonlinear Langmuir isotherm model. For Cu(II), the parameters were b = 0.01411 L/mg and R = 0.99151, whereas for Pb(II), they were b = 0.02571 L/mg and R = 0.98908. The kinetics followed a pseudo-second-order model, with Cu(II) showing k = 4.34 × 10 g/mg min and R = 0.99924, and Pb(II) displaying k = 6.54 × 10 g/mg min and R = 0.99918.