Efficient removal of copper ions, zinc ions, and tetracycline in water by functionalized Canadian horseweed hydrothermal carbon: The combination of experiment and DFT calculation

Abstract

A silicate-hydrothermal carbon composite material (GHC) was prepared by a one-step hydrothermal method using Canadian horseweed as raw material and cheap sodium silicate and magnesium sulfate as modification reagents for the adsorption of copper (Cu2+), zinc (Zn2+), and tetracycline (TC) in water. The results showed that maximum capacities of the adsorption of Cu2+, Zn2+, and TC by GHC are 211.92 mg·g−1, 224.96 mg·g−1, and 358.58 mg·g−1. TC can provide certain active sites for GHC to adsorb Cu2+ or Zn2+ in a binary system. When the concentration of Cu2+ or Zn2+ is low, i.e., <30 mg·L−1, it will promote GHC’s ability to adsorb TC. When the concentration of Cu2+ or Zn2+ is greater than 30 mg·L−1, the adsorption capacity of GHC to TC began to decrease. This may be related to the presence of too many complexes on the surface of GHC. Too many complexes will block the pores on the surface of GHC and reduce the effective adsorption sites of GHC. The different mechanisms for the adsorption of Cu2+ and Zn2+ are different from the adsorption of TC. In this study, 2D-COS and DFT calculations are used to explore these mechanisms. The results show that CO, CO, and CC are involved in the adsorption of Cu2+, Zn2+, and TC, and CO and CO have stronger capacities than CC for Cu2+, Zn2+, and TC. GHC has stable adsorption properties for Cu2+, Zn2+, and TC in different water samples, and has good regeneration performance. Thus, GHC is an economical and efficient adsorbent with good application potential.