Design and synthesis of covalent organic framework based on 2,4,6-triaminopyrimidine for efficient capture of Au(III) ion

Gold is a widely used non-renewable resource, and its recycling is the key to solve the problem of dwindling gold resources. In this study, a novel covalent organic framework adsorbent (COF-pPDI@TAP) is developed for efficient Au(III) capture. The synthesis of the adsorbent was confirmed by FTIR and XRD characterization. The adsorption performance of COF-pPDI@TAP was studied by batch adsorption experiments. The maximum adsorption of Au(III) by COF-pPDI@TAP reached 779.02 mg/g in the adsorption experiments. Kinetic and isotherm results show that the adsorption is a monolayer chemisorption process controlled by particle diffusion. The positive value of ΔH indicates that COF-pPDI@TAP needs to absorb energy to maintain the reaction during the adsorption of Au(III), and the reaction is endothermic. In addition, COF-pPDI@TAP maintained a very high adsorption efficiency after five cycles of experiments, and could selectively capture Au(III) from different concentrations of polymetallic solutions. COF-pPDI@TAP has excellent anti-interference ability and good reusability. It is demonstrated by zeta potential, XRD, XPS and FT-IR that electrostatic interaction, chelation and reduction occurred during the adsorption process. These studies demonstrate the value of COF-pPDI@TAP for gold recovery applications.