Highly efficient and selective recovery of Cu(II) from wastewater via ion flotation with amidoxime functionalized graphene oxide as nano collector

In this work, amidoxime functionalized graphene oxide (AMID@GO) was prepared with 1,3-diamino-1,2,3-trioximido-propane as chelation group and used as nano collector for enhancing and selectively recovering Cu(II) from wastewater via ion flotation. AMID@GO was characterized by scanning electron microscope/energy dispersive X-ray detector (SEM/EDX), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Effects of pH, contact time, AMID@GO and hexadecyl trimethyl ammonium bromide (HTAB) concentration, and aeration rate on Cu(II) recovery and the turbidity of the residual solution were examined systematically. The experimental results showed that as compared with GO, the adsorption capacity and selectivity of AMID@GO for Cu(II) was greatly improved. Almost 99.26% of Cu(II) could be recovered with selectivity coefficient of 54.161, 73.430, 50.365 and 21.630 for Cu(II)/M(II) (M = Co, Ni, Zn and Cd, respectively). Moreover, the relative Cu(II) recovery maintained over 90.45% after five flotation- desorption cycles, indicating AMID@GO could be reused as nano collector in ion flotation. In addition, density functional theory (DFT) calculation suggested that AMID@GO had a stronger affinity to Cu(II) originated from both O and N from oximido contributed to the stable configuration of AMID@GO@Cu(II) complexes, endowing it possessed a higher selectivity coefficient for Cu(II).