Ultrafast degradation of contaminants in a trace cobalt(II) activated peroxymonosulfate process triggered through borate: Indispensable role of intermediate complex

Among all homogeneous catalysts, cobalt ions show the highest catalytic performance for the activation of peroxymonosulfate (PMS). Herein, we report a Co2+/PMS/H3BO3 system that can effectively generate reactive oxygen species (ROS) with ultra-low Co2+ dosage (5 mu g/L). Co2+/PMS/H3BO3 system showed ultrafast reactivity and wide applicability for various pollutants. Sulfamethoxazole (SMX, 2 mg/L) could be completely removed within 5 min, and the corresponding k o b s reached up to 1.1239 min(-1). The introduction of H3BO3 significantly promoted the generation of ROS. The turnover frequency (TOF) calculated through dividing k(obs) by the cobalt ions concentration is as high as 224.78 min(-1), which is much higher than most of the current research. Through a series of theoretical and experimental analyses, the complex of H2BO3--MS (HSO5B(OH)(3)(-)) was inferred to be the key substance that led to the excellent performance of the system. This work provides new insights into the Co2+/PMS system in the presence of borate buffer.

Automated summary

This study presents a Co2+/PMS/H3BO3 system that can effectively generate ROS with ultra-low Co2+ dosage, showing fast reactivity towards various pollutants. The introduction of borate buffer significantly promotes the generation of ROS, with the key substance inferred as H2BO3--MS. Through theoretical and experimental analyses, the system's high performance is attributed to a turnover frequency much higher than current research.