Low temperature pickling regeneration process for remarkable enhancement in Cu(II) adsorptivity over spent activated carbon fiber

In this paper, a simple and efficient regeneration technology of low-temperature pickling regeneration process is proposed for Cu(II)-adsorbed activated carbon fiber felts (ACFFs). The regeneration process mainly uses the strong oxidation of acidic regenerant above boiling point to regenerate ACFFs in a confined space. With no demand for high temperature and high pressure, the regeneration process achieves a high efficiency regeneration and a remarkable enhancement of Cu(II) adsorptivity simultaneously for Cu(II)-adsorbed ACFFs. After parameter optimization, the pickling temperature of 383 K, pickling time of 3 h and HNO3 concentration of 150 g/L are adopted as optimum process parameters for the reutilization of ACFFs. The regeneration rates of ACFFs in five cycles are maintained at 424.08%-829.59%. Analytical results show that the enhancement of Cu(II) adsorptivity is mainly caused by the remarkable enhancement of specific surface area (increased by 106.08%), micropore volume (increased by 102.17%) and more abundant surface chemical structure (particularly carboxyl and nitro group) after treated by the regeneration process.