Removal of Cu (II) from aqueous solutions using ZIF-8@GO composites

ZIF-8@GO-X (X ​= ​0, 2.48%, 4.07%, 7.83%, and 20.03%) composites were prepared using GO and ZIF-8. The composites were used to absorb Cu(Ⅱ) from aqueous solutions. With increasing GO content, the adsorption of the ZIF-8@GO-X composites first increased and then decreased. The Cu(Ⅱ) adsorption of ZIF-8@GO-7.83% reaches a maximum among ZIF-8@GO-X composites (X ​= ​0, 2.48%, 4.07%, 7.83%, and 20.03%). The adsorption kinetics , adsorption isotherm , adsorption thermodynamics, and adsorption mechanism of Cu (II) by ZIF-8@GO-7.83% were studied in this paper. The results showed that the adsorption reached equilibrium at 120 ​min, and ZIF-8@GO-7.83% approached equilibrium relatively quickly. When the temperature was 45 ​°C and the Cu(Ⅱ) concentration was 40 ​mg/L, the maximum adsorption capacity of ZIF-8@GO-7.83% for Cu(Ⅱ) reached 482.29 ​mg/g. The equilibrium data and kinetics were well described by Langmuir and pseudo-first-order models, respectively. Final experiments with real factory wastewater (initial Cu(Ⅱ) concentration of 670 ​mg/L) revealed that 0.37 ​g/L ZIF-8@GO-7.83% can efficiently reduce the Cu(Ⅱ) concentration to below 2 ​mg/L.