Regeneration of nitrophenol loaded granular activated carbon and its effect on the surface properties of adsorbent

This study systematically investigated the adsorption properties of 2,4-dinitrophenol (DNP) on granular activated carbon (GAC), and the performance of ultraviolet (UV) light irradiation and solvent extraction in the regeneration of spent adsorbent. It also evaluated the influence of such regeneration on the change of GAC surface properties. The adsorption followed a pseudo-second-order kinetic model and was controlled by the intra-particle diffusion rate process. With an adsorption capacity of 1,476 μM (272 mg/g), the adsorption of DNP onto GAC fit the Dubinin–Astakhov mode better than it did the Freundlich and Langmuir isothermal models. These results indicate that the adsorption occurred not only on the surface, but also in the micropores and mesopores. The regeneration efficiency of spent GAC was less than 10% using either UVC or vacuum UV irradiation, which was probably because the irradiated light could not directly enter the pores to induce the degradation of the adsorbed DNP. The levels of regeneration efficiency by ethanol extraction and acetic acid extraction were 60 and 100%, respectively, in the first cycle. The surface area was slightly decreased, while the porosity and surface composition were maintained after solvent extraction.