Carbon materials have been used to activate peroxydisulfate (PDS) for the degradation of organic pollutants. The mechanism involved, especially whether radicals are formed in these processes, is still under debate. In this research, multi-walled carbon nanotube (MWCNT) was employed to activate PDS for the removal of 2,4-dichlorophenol (2,4-DCP). The effects of solution pH, PDS concentration, 2,4-DCP concentration, and MWCNT loading on the degradation of 2,4-DCP were investigated. The mechanism was explored via radical scavenging experiments, electron paramagnetic resonance (EPR) and MWCNT surface characterization. The results showed that the rate of 2,4-DCP degradation increased with the increasing solution pH, PDS concentration and MWCNT loading. The presence of OH and SO₄⁻ signals in EPR studies, no inhibitory effect in radical scavenging experiments, and the chlorination of MWCNT observed by X-ray photoelectron spectroscopy (XPS) suggested that surface reactions involving both surface-bound radicals and direct electron transfer were responsible for 2,4-DCP degradation. Reusability tests showed that the surface sites responsible for surface-bound radical formation were poisoned after PDS activation, while those responsible for direct electron transfer remained active after five cycles. This research provided the first in-depth insights for the dual roles of MWCNT in the PDS activation process.

碳材料已被用于活化过二硫酸盐 (PDS) 以降解有机污染物。所涉及的机制，尤其是在这些过程中是否形成自由基，仍在争论中。在这项研究中，采用多壁碳纳米管 (MWCNT) 激活 PDS 以去除 2,4-二氯苯酚 (2,4-DCP)。研究了溶液 pH、PDS 浓度、2,4-DCP 浓度和 MWCNT 负载对 2,4-DCP 降解的影响。通过自由基清除实验、电子顺磁共振 (EPR) 和 MWCNT 表面表征探索了该机制。结果表明，2,4-DCP 的降解速率随着溶液 pH、PDS 浓度和 MWCNT 负载量的增加而增加。OH和 SO ₄的存在^-EPR 研究中的信号、自由基清除实验中没有抑制作用以及 X 射线光电子能谱 (XPS) 观察到的 MWCNT 的氯化表明，涉及表面结合自由基和直接电子转移的表面反应是 2,4-DCP 的原因降解。可重用性测试表明，在 PDS 活化后，负责表面结合自由基形成的表面位点被毒化，而负责直接电子转移的表面位点在五个循环后仍保持活性。这项研究首次深入了解了 MWCNT 在 PDS 激活过程中的双重作用。