فهرست نشریات علمی دسترسی آزاد ایران

In this work, chitosan was obtained from shrimp shell waste by acid-alkali extraction. It was then cross-linked with glutaraldehyde to form chitosan hydrogels. The obtained solid particles with average sizes of about 50 μm (high molecular weight) and 39 μm (low molecular weight) were prepared and used as adsorbents for Pb (II) and Cd (II) ions from aqueous solutions. The effects of contact time, solution pH, temperature, adsorbent amount, and initial metal ion concentration were investigated. The prepared adsorbents were characterized using SEM, FTIR, and XRD analyses. 200 mg of low molecular weight modified chitosan was able to adsorb 20 mg/L of lead and 2 mg/L of cadmium to the extent of 87.2% and 91.2%, respectively, in 24 h at 30 °C and pH=7. The adsorption isotherm of this reaction follows the Langmuir model, and the adsorption process follows a pseudo-second-order kinetic model. The effect of other ions on the adsorption rate was investigated, and it was found that the presence of other metal cations can reduce the adsorption of Pb and Cd by about 15%. The validity and reliability of the method were confirmed through recovery experiments on real contaminated samples, yielding recoveries of 85.8% for Cd and 89.6% for Pb. The reusability of the adsorbent was investigated, and after 6 consecutive adsorption-desorption cycles, the removal efficiency decreased by 10–14%. This study shows that chitosan hydrogels derived from marine biowaste have significant potential as economical, sustainable, and environmentally friendly adsorbents for the treatment of heavy metal-contaminated wastewater.