A stiff ZnO/carbon foam composite with second-level macroporous structure filled ZnO particles for heavy metal ions removal

A stiff zinc oxide/carbon foam (ZnO/CF) composite as a desirable adsorbent for heavy metal ions was innovatively designed and fabricated by loading ZnO particles into a carbon foam with capsule-like second-level macropores. The features of the resulting composite were characterized by FESEM, XRD, BET, FTIR, and XPS. The effects of adsorption parameters on the Pb(II), Cr(III), and Cu(II) ions removal were studied through batch experiments. Results show that the ZnO/CF composite possesses a second-level macroporous structure filled ZnO particles, which has both mesoporous structure and Zn-O-C bond with the strongly synergistic effect. And meanwhile, it has a relatively high compression strength of 2.18 MPa at a density of 0.18 g cm^-3. The experimental maximum adsorption capacities for Pb(II), Cr(III), and Cu(II) ions reach 170.85 mg g^-1, 168.74 mg g^-1, and 104.61 mg g^-1 with relatively high partition coefficients of 5.803 mg g^-1 μM^-1, 1.169 mg g^-1 μM^-1, and 0.648 mg g^-1 μM^-1, respectively. The experimental data are in accordance with Langmuir isotherm and pseudo-second-order kinetic model. Moreover, the composite still exhibits a good adsorption performance even after five cycles.