Preparation of ZIF-8-derived Porous Carbon and Its Adsorption Properties Towards Phenanthrene from Liquid Paraffin Oil

Abstract

To address the limitations of the existing catalytic hydrogenation and sulfuric acid sulfonation intended to remove aromatic hydrocarbons from liquid paraffin oils, the adsorption method was chosen for the adsorptive separation of phenanthrene, a typical aromatic hydrocarbon, from liquid paraffin oils. A zeolite imidazolate framework-8 (ZIF-8) precursor was firstly prepared, and then ZIF-8-derived porous carbon (ZDPC) adsorbents were obtained using different temperatures of carbonization of the precursor under nitrogen atmosphere; these adsorbents were then used for the adsorption and separation of phenanthrene from liquid paraffin oils. The experiment showed that the maximum specific surface area of a ZDPC adsorbent could reach 1458 m²/g at 900°C. However, the total pore volume and adsorption capacity of ZDPC porous carbon were maximal at the carbonization temperature of 800°C (1.59 cm³/g and 931 mg/g, respectively). The obtained results showed that an increase in the specific surface area of the adsorbent did not necessarily enhance the adsorption performance. However, compared with the specific surface area of the adsorbent, its adsorption performance is improved in the case of larger pore structures. Therefore, the pore structure of the adsorbent has a very important influence on the adsorption performance. The results of kinetic and thermodynamic studies showed that the pseudo-second-order model could better explain the adsorption process of ZDPC on phenanthrene, while the intra-particle diffusion model revealed that the adsorption mechanism represented a continuous three-stage process.