The comparing on the adsorption/desorption of Pd(II) and Pt(IV) ions by using 4-chlorophenyl sulfoxide modified the reduced graphene oxide composite

The reduced graphene oxide aerogel modified by 4-chlorophenyl sulfoxide was obtained by a simple self-assemble process under the basic reduction-oxide condition, then freeze-dried for future using. The prepared aerogel was shortly named 4CS-rGO, which was characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscope, et al. 1 mg of 4CS-rGO composite was used as an adsorbent to adsorb Pd(II) and Pt(IV) in 1.0 mL 40 mM Britton-Robinson buffer solution with various pH. The adsorption efficiency of Pd(II) increased with the increase in pH, whereas the hydrolysis of Pd(II) happened at pH 13, and the maximum adsorption efficiency of Pd(II) was 91.82% at pH 12, which was mainly driven by electrostatic attraction. Besides, the adsorption behavior of the 4CS-rGO composite for Pt(IV) was explored to evaluate the possibility to isolate Pd(II) and Pt(IV) ions by using aerogel. We found that, quite interestingly, hydrogen bond, hydrophobic interaction and van der Waals force can strongly conquer electrostatic repulsion driven Pt(IV) ions adsorption behavior at pH 5, and Pt(IV) ions displaced by cationic surfactant. Moreover, a tighter Pt(IV) ions adsorption behavior than Pd(II) ions was observed while we adsorb them respectively with/without 4-chlorophenyl sulfoxide modified the graphene, while branched TBAB was easier and more effectively replaced the adsorbed Pt(IV) ions than strained CTAB.