Rapid in situ regeneration of phenol-saturated activated carbon fiber by an electro-permonosulfate-ozone process: Performance, operators and mechanism

In this study, a new method that encompasses electricity, permonosulfate (PMS), and ozone (E-PMS-O3) was proposed and applied in the regeneration of phenol-saturated activated carbon fiber (ACF). Compared with traditional regeneration technology, the E-PMS-O3 process simultaneously regenerated exhausted ACF in situ and mineralized the desorbed pollutants effectively (78.67%) with relatively low energy consumption (4.338 kWh m−3). Furthermore, the E-PMS-O3 regeneration process only required 2 h, which was shorter than other well-documented electro-advanced oxidation processes (EAOPs), such as the E-O3 process lasting for 3 h, the E-persulfate process for 6 h, and the E-Fenton process for 6 h. Possible pathways in the regeneration process include direct electron transfer, ozone oxidation, PMS oxidation, non-radical reactions, and reactive oxygen species (ROS) oxidations. Two main ROS — hydroxyl radical (O•H) and sulfate radical (SO4•−) were probed and their contribution ratio was approximately 1:1. An external electric field visibly enhanced the recovery adsorption capacity of ACF and accelerated the decomposition of PMS. Interestingly, additional experiments revealed that adding two different oxidants (PMS/O3) provided a better protection effect on the properties of ACF against oxidation of oxidants and ROS. It's important to mention that the maximum concentration of byproducts remained below 5 mg g−1, which effectively minimized the potential for subsequent pollution. In the end, multiple regeneration cycles demonstrated that the regeneration efficiency was nearly 60% even after 6 cycles. Hence, the E-PMS-O3 process was promising for further exploration and discussion when applied in regeneration of exhausted AC materials.