Plasma synthesis of β-cyclodextrin/Al(OH)3 composites as adsorbents for removal of UO22 + from aqueous solutions

The β-cyclodextrin/Al(OH)3 composites (β-CD/Al(OH)3) were synthesized using the plasma-induced grafting technique and were employed to remove UO22 + from aqueous solutions under ambient conditions. Based on the characteristic results of SEM, FT-IR, XRD, and TGA techniques, β-CD was satisfactorily grafted onto the Al(OH)3 surface. The maximum adsorption capacity of β-CD/Al(OH)3 composites calculated from Langmuir model at pH 6.0 and 303 K was 63.29 mg/g, which was significantly higher than Al(OH)3 (23.31 mg/g). The high adsorption capacity of β-CD@Al(OH)3 composites was due to the inner cores of the hydrophobic cavity of CD incorporated with UO22 + ions. The calculated thermodynamic parameters showed that the adsorption of UO22 + on Al(OH)3 and β-CD@Al(OH)3 composites was an endothermic and spontaneous process. The batch desorption indicated that the adsorption of UO22 + on β-CD@Al(OH)3 composites was an irreversible process. Based on the surface complexation modeling, the adsorption mechanism of UO22 + on Al(OH)3 and β-CD@Al(OH)3 composites was outer-sphere surface complexation at pH < 5.0, whereas inner-sphere surface complexation dominated the UO22 + adsorption on Al(OH)3 and β-CD@Al(OH)3 composites at pH > 6.0. These observation showed that β-CD/Al(OH)3 composite can be used as a promising adsorbent for the preconcentration and immobilization of UO22 + ions in environmental pollution cleanup.