Development of hybrid adsorbent for effective aqueous phase sorptive removal of copper

Alginate beads (ABs) immobilized with hydrous zirconium oxide (ZO) were used as a hybrid adsorbent (ZO@AB) for the effective removal of copper ions [Cu(II)] from aqueous phase. ZO@AB was characterized using X-ray photoelectron spectroscopy to confirm the impregnation of ABs with ZO and the adsorption of Cu(II) onto ZO@AB. The maximum equilibrium sorption capacity of ZO@AB for Cu(II) was 63.1 mg·g⁻¹ at pH 5. The Cu(II) removal rate was high at the beginning of reaction, with >90% adsorption within 24 hours, and equilibrium was achieved within 48 hours. The adsorption of Cu(II) onto ZO@AB was well described by pseudo-second-order kinetic model (R² > 0.99), and the monolayer nature of sorption was supported by the Langmuir model (R² > 0.99). The sorption process was endothermic, favorable, and spontaneous in nature. Regarding the reusability of the adsorbent, its sorption capacity remained satisfactory (>90%) throughout the 5 consecutive cycles (regeneration in 0.1 mol·L⁻¹ HCl). The stoichiometric ratio of released calcium ions [Ca(II)] to adsorbed copper ions [Cu(II)] was approximately 1:1, confirming that ion exchange was the main mechanism for removal of Cu(II) from aqueous phase. The developed adsorbent (ZO@AB) shows promise as a candidate for the effective and selective removal of Cu(II) from aqueous phase.