Fabrication of magnetic bentonite/carboxymethyl chitosan/sodium alginate hydrogel beads for Cu (II) adsorption.

In this work, composite hydrogel beads based on magnetic bentonite/carboxymethyl chitosan/sodium alginate (Mag-Ben/CCS/Alg) were fabricated and their ability to adsorb copper ions in water was studied. The structure and properties of the composite were characterized via SEM, FTIR, XPS, TGA, VSM, and Zeta potential tests. The effects of the adsorbent dosage, adsorption time, pH, temperature, and initial concentration of Cu(II) on the adsorption results were studied. The results showed that Mag-Ben/CCS/Alg reached equilibrium after 90 min of adsorption, the removal rate of Cu(II) was 92.62 ± 0.39%, and the maximum adsorption capacity was 56.79 mg/g (30 °C). The removal rate of Cu(II) by Mag-Ben/CCS/Alg still remained above 80% after recycling four times. The adsorption process of Cu(II) by Mag-Ben/CCS/Alg occurred in accordance with the quasi-second-order kinetic model and Langmuir adsorption isotherm. The adsorption process was spontaneous and endothermic.