Preparation of carbon/cobalt composite from phenolic resin and ZIF-67 for efficient tannic acid adsorption

In the present work, a carbon/cobalt composite was prepared and evaluated for adsorption of ecologically harmful tannic acid (TA). The composite was prepared by simply mixing phenolic resin with ZIF-67 and following by carbonization. TEM and SEM images showed that ZIF-67 was etched by phenolic resin and cobalt nanoparticles were formed and evenly distributed in carbon. Macroporous structure was generated between the carbonized phenolic resin and ZIF-67. N₂ adsorption-desorption isotherms results exhibited that the composite also had both micro- and meso-pores (average pore size of 5 nm)with a high surface area of 393 m² g⁻¹. Porous structure and evenly distributed cobalt nanoparticles facilitated the diffusion and adsorption of TA due to the formation of the complex between TA macromolecules and cobalt. The highest observed adsorption amount was as high as 2778 mg g⁻¹, significantly higher than that of the carbon prepared from carbonization of phenolic resin (205 mg g⁻¹)and ZIF-67 (1375 mg g⁻¹). The carbon composite material is easy to recover and reuse due to the magnetic property. The reuse experiment also showed high stability of the composite. All of the results indicated a great potential of the developed carbon composite material in wastewater treatment in the industry.