Heterogeneous activation of peroxymonosulfate by Co3O4 loaded biochar for efficient degradation of 2,4-dichlorophenoxyacetic acid

Recent advances in catalyst design, performance, and challenges of metal-heteroatom-co-doped biochar as peroxymonosulfate activator for environmental remediation

The escalation of global water pollution due to emerging pollutants has gained significant attention. To address this issue, catalytic peroxymonosulfate (PMS) activation technology has emerged as a promising treatment approach for effectively decontaminating a wide range of pollutants. Recently, modified biochar has become an increasingly attractive as PMS activator. Metal-heteroatom-co-doped biochar (MH-BC) has emerged as a promising catalyst that can provide enhanced performance over heteroatom-doped and metal-doped biochar due to the synergism between metal and heteroatom in promoting PMS activation. Therefore, this review aims to discuss the fabrication pathways (i.e., internal vs external doping and pre-vs post-modification) and key parameters (i.e., source of precursors, synthesis methods, and synthesis conditions) affecting the performance of MH-BC as PMS activator. Subsequently, an overview of all the possible PMS activation pathways by MH-BC is provided. Subsequently, Also, the detection, identification, and quantification of several reactive species (such as, •OH, SO4•-, O2•-, 1O2, and high valent oxo species) generated in the catalytic PMS system by MH-BC are also evaluated. Lastly, the underlying challenges associated with poor stability, the lack of understanding regarding the interaction between metal and heteroatom during PMS activation and quantification of radicals in multi-ROS system are also deliberated.

Insights into Enhanced Peroxydisulfate Activation with B and Fe Co-Doped Biochar from Bark for the Rapid Degradation of Guaiacol

A boron and iron co-doped biochar (B-Fe/biochar) from Masson pine bark was fabricated and used to activate peroxydisulfate (PDS) for the degradation of guaiacol (GL). The roles of the dopants and the contribution of the radical and non-radical oxidations were investigated. The results showed that the doping of boron and iron significantly improved the catalytic activity of the biochar catalyst with a GL removal efficiency of 98.30% within 30 min. The degradation of the GL mainly occurred through the generation of hydroxyl radicals (·OHs) and electron transfer on the biochar surface, and a non-radical degradation pathway dominated by direct electron transfer was proposed. Recycling the B-Fe/biochar showed low metal leaching from the catalyst and satisfactory long-term stability and reusability, providing potential insights into the use of metal and non-metal co-doped biochar catalysts for PDS activation.

Highly efficient activation of peroxymonosulfate by cobalt ferrite anchored in P-doped activated carbon for degradation of 2,4-D: adsorption and electron transfer mechanism

The dispersing effect of carbon materials on nanoparticles can enhance the full exposure of their active sites. Herein, phosphorus (P)-doped activated carbon-supported trace cobalt ferrite composites (P-CoFe@BC_X) were achieved by two-step pyrolysis for efficient peroxymonosulfate (PMS) activation and water pollution remediation. The removal efficiency of 2,4-dichlorophenoxyacetic acid (2,4-D) was optimized by adjusting the coupling ratio of carbon substrate and cobalt ferrite. P-CoFe@BC₅/PMS oxidation system (0.10 g L^-1, 0.50 mM) eliminated 98.3% of 2,4-D (20.0 mg L^-1) within 60 min at unadjusted pH. The constructed adsorption enrichment and oxidative degradation pathways are highly efficient in utilizing reactive oxygen species (ROS), and the dual tracks of free and non-free radicals achieve the rapid degradation of 2,4-D. P-doped activated carbon acts as an electron shuttle to accelerate electron transfer between active sites and enhances the adsorption efficiency of 2,4-D and PMS onto the composites. In addition, the P-CoFe@BC₅/PMS oxidation system still exhibited strong 2,4-D removal performance at a wide pH range of 2.0-10.0. The inhibitory effect of environmental components was related to their concentration, such as chloride, bicarbonate, sulfate and humic acid. Density functional theory calculations show that ROS tends to attack the CO bond on the 2,4-D branch chain, and the degradation products show lower biological toxicity. Hence, the constructed cobalt ferrite anchored P-doped activated carbon activated PMS system has great potential in treating organic wastewater.

Reutilization of waste self-heating pad by loading cobalt: A magnetic and green peroxymonosulfate activator for naphthalene degradation

The disposal and recovery of solid wastes and the remediation of polycyclic aromatic hydrocarbons (PAHs) are the key issues of environmental pollution control. In this study, micro cobalt loaded on iron-carbon-vermiculite composite (Co-ICV) was prepared for the first time by the reutilization of waste self-heating pad as a carrier of cobalt catalyst, which exhibited better performance than bulk cobalt catalyst in peroxymonosulfate (PMS) activation for the degradation of naphthalene (NAP) in water. Above 98% of NAP (2.0 mg/L) was effectively eliminated within 15 min by the Co-ICV (0.2 g/L) activated PMS (0.5 mmol/L) in a pH range of 5.0-9.0. High magnetism and very limited cobalt leaching realized the convenient separation and stable reusability of Co-ICV. Mechanism investigation indicated that Co(II) species were the main active sites to activate PMS decomposition for the generation of SO₄^•- and ^•OH, contributing to the rapid degradation of NAP. Meanwhile, the NAP degradation pathways were deduced via combining the identification of intermediates and the calculation of frontier electron densities (FEDs). Furthermore, the ability of the Co-ICV/PMS system for the NAP degradation in actual lake water and the removal of other refractory pollutants demonstrated that the combination of Co-ICV and PMS was a prospective method for the removal of PAHs. Overall, Co-ICV is a green and promising activator of PMS, and the future development will provide more insights into the comprehensive utilization of solid wastes for the remediation of wastewater containing PAHs.