Selective recovery of Pb(II) from a waste electrolyte via ion flotation with iminodiacetic acid-functionalized graphene oxide as a nanocollector

In this work, iminodiacetic acid-functionalized graphene oxide (IDA@GO) is prepared and used as a nanocollector for enhancing and selectively recovering Pb(II) from a strongly acidic waste electrolyte via ion flotation. IDA@GO is characterized by Fourier transform infrared spectroscopy, zeta potential measurements and atomic force microscopy. The effects of pH, reaction time, cetyl trimethyl ammonium bromide (CTAB) dosage and aeration rate on the Pb(II) concentration and turbidity of the residual solution are examined systematically. The experimental results show that the adsorption capacity of Pb(II) on IDA@GO can reach 91.21 mg/g at pH 2. After froth flotation, the turbidity of the treated solution decreased to 0.55 NTU under the optimal CTAB dosage and aeration rate. In addition, as compared with GO, the relative selectivity coefficients of IDA@GO are up to 1.304, 1.471, 1.807 and 1.509 for Co(II), Ni(II), Zn(II) and Cd(II), respectively, thereby exhibiting better selectivity performance. Moreover, IDA@GO can be reused as a nanocollector in ion flotation and exhibits ideal regeneration performance. In addition, the recovery mechanism is found to proceed through Pb(II) adsorbing on IDA@GO by electrostatic attraction, ion exchange and surface complexation, with the addition of CTAB improving the hydrophobicity of Pb(II)-loaded IDA@GO flocs, thus achieving the recovery of Pb(II) via froth flotation.