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Among all homogeneous catalysts, cobalt ions show the highest catalytic performance for the activation of peroxymonosulfate (PMS). Herein, we report a Co2+/PMS/H 3 BO 3 system that can effectively generate reactive oxygen species (ROS) with ultra–low Co2+ dosage (5 μg/L). Co2+/PMS/H 3 BO 3 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 obs reached up to 1.1239 min−1. The introduction of H 3 BO 3 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 H 2 BO 3 −–MS (HSO 5 B(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. [Display omitted] • Trace cobalt(II) (5 μg/L) can efficiently activate PMS in the presence of boric acid. • The corresponding k obs value reached up to 1.1239 min−1 in Co2+/PMS/H 3 BO 3 system. • H 2 BO 3 −-PMS was the key substance that caused the excellent performance of the system. • Co2+/PMS/H 3 BO 3 system showed wide applicability for various pollutants. • This study provides novel insights into the Co2+/PMS system in borate buffer. [ABSTRACT FROM AUTHOR]

• The performance of ZVI/peroxymonosulfate could be enhanced with the Cu2+. • Radicals and non-radical species both contributed to the degradation. • The generation of singlet oxygen was investigated in the bimetallic AOPs systems. • Nine main byproducts and degradation pathways were identified. • Accurate toxicity of the byproducts was calculated. Advanced oxidation processes (AOPs) based on the bimetallic system has been demonstrated as a promising way to enhance the degradation of pollutants in the water. In this study, the degradation of Rhodamine B (RhB) in a zero-valent iron (ZVI)/ peroxymonosulfate system with Cu2+ was thoroughly investigated. RhB could be efficiently removed (99.3 %) in the optimal ZVI/PMS/Cu2+ system, while only 58.2 % of RhB could be degraded in the ZVI/PMS system. The influence of reaction parameters on the degradation of RhB was further investigated. Quenching experiments and electron paramagnetic resonance (EPR) tests revealed that various reactive oxygen species could be generated in the ternary system, of which, 1O 2 and O 2 − were identified for the first time. The effect of various anions, NOM and different water matrix were also considered at different concentrations. A variety of byproducts and degradation pathways were identified using HPLC/MS/MS. Finally, the Quantitative Structure Activity Relationship (QSAR) method of Toxicity Estimation Software Tool (TEST) was applied to estimate the toxicity of the byproducts and the results indicated that the overall toxicity of the target was relatively reduced. This study demonstrated the potential for the removal of environmental reluctant pollutants in water via the combined radical and non-radical pathways. [ABSTRACT FROM AUTHOR]