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

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 (Cu 2+ ), zinc (Zn 2+ ), and tetracycline (TC) in water. The results showed that maximum capacities of the adsorption of Cu 2+ , Zn 2+ , 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 Cu 2+ or Zn 2+ in a binary system. When the concentration of Cu 2+ or Zn 2+ is low, i.e., <30 mg·L −1 , it will promote GHC’s ability to adsorb TC. When the concentration of Cu 2+ or Zn 2+ 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 Cu 2+ and Zn 2+ 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 C O, C O, and C C are involved in the adsorption of Cu 2+ , Zn 2+ , and TC, and C O and C O have stronger capacities than C C for Cu 2+ , Zn 2+ , and TC. GHC has stable adsorption properties for Cu 2+ , Zn 2+ , and TC in different water samples, and has good regeneration performance. Thus, GHC is an economical and efficient adsorbent with good application potential.