A novel composite adsorbent for the separation and recovery of indium from aqueous solutions

Abstract

In this study, a novel approach for preparing SiO2@GO-PO3H2 composite using a simple method has been reported, which can be used as an efficient adsorbent for separating In(III) ions from aqueous solutions. The adsorbent was characterized on the basis of Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) technique. The adsorption behavior of In(III) ions on the adsorbent was investigated based upon batch experiments. The adsorption equilibrium was achieved within 50 min and the adsorption kinetics of In(III) ions followed the pseudo-second-order model. The adsorption equilibrium study exhibited good agreement with the Langmuir isotherm model and the maximum adsorption capacity was as high as 149.93 mg·g−1. Furthermore, competitive adsorption demonstrated that the adsorbent maintained good affinity for In(III) ions even in mixed solutions containing K(I), Ca(II), Na(I), Mg(II), Al(III), Zn(II), Fe(II), Pb(II) and Cu(II). The mechanism of the adsorption of In(III) ions SiO2@GO-PO3H2 surface was mainly attributed to the fact that P element in the adsorbent coordinated with In(III) ions to generate InP bond, which confirmed that the adsorption of In(III) ions on SiO2@GO-PO3H2 belonged to a chemical adsorption process. The SiO2@GO-PO3H2 can be repeatedly used and regenerated ten times without obvious decrease in adsorption capacity, demonstrating that the adsorbent is of high stability and reusability. The results indicated that SiO2@GO-PO3H2 could serve as a promising adsorbent for efficient recovery and elimination of In(III) ions from aquatic environment.