Metal Coupled Nanocarbon Catalysts Activating Peroxymonosulfate For Degrading Refractory Organics In Refinery Wastewater

Refractory organic wastewater from petrochemical process obtains a huge discharge volume.Moreover,its complex composition and high biological toxicity hinder the effective treatment by the conventional processes such as adsorption and filtration.In addition,conventional treatment processes usually require high energy and material consumption and long treatment cycle.The proposal of"double carbon policy"puts forward higher requirements for the efficient treatment technology of refractory organics in petrochemical wastewater.Achieving the"efficiency-emission reduction"is the key to upgrading the treatment techniques.Heterogeneous catalytic peroxymonosulfate（PMS）oxidation,as an advanced oxidation technology,has emerged as a promising treatment technique in the field of environmental remediation.The activated PMS can produce highly reactive oxidizing species（ROS）,which can efficiently and thoroughly mineralize organic pollutants into CO₂ and H₂O.In terms of heterogeneous catalysts,although metal-based catalysts obtain high activity,metal cations are easy to leach from the bulk catalysts and result in secondary pollution.Carbon-based materials can not only directly act as the active catalysts for PMS,but also as carriers for loading metal oxides.With these merits,carbon-based materials have been intensively employed as the catalysts for PMS activation.In addition,the metal-free doping sites on carbon-based catalysts can anchor the active metal components through strong coordination,which effectively reduces the dissolution of metals,and promotes the electron transfer ability and improves the catalytic activity by regulating the local charge distribution.Therefore,utilizing metal-carbon composites as the catalysts is an effective way to activate PMS for ROS production and to achieve the goal of"efficiency and emission reduction"treatment.In this study,Co doped graphene（Co NG）was synthesized via a facile microwave-assisted method with graphene oxide,ammonium bicarbonate,and cobalt salt as precursors.Results revealed that 25 mg/L of phenol can be completed degraded within 25 min with 0.025 g/L Co NG and 0.25 g/L PMS dosage.It is suggested that the synergistic effect between Co and N doped graphite layer accelerated the transfer of interface electrons and promoted the process of catalytic PMS oxidation.Characterization results indicated that surface adsorbed PMS（*PMS）and singlet oxygen（¹O₂）were the dominant active species for phenol degradation.This type of nonradical oxidation is not easy to be affected by inorganic anions in wastewater,which greatly improves the applicability of the oxidation system.Based on the above research results,the microbial carbon-based catalyst（MnNBC）loaded with manganese was prepared by using biomineralization,and its catalytic activity and structural characteristics were preliminarily studied.It is found that the porous structure of MnNBC made it had strong adsorption capacity for refractory organic pollutants and facilitated the activation of PMS to produce*PMS and other nonradical ROS to effectively remove refractory organic pollutants.This study not only provides a new idea for the design of efficient and stable catalysts,but also builds a bridge between the utilization of microbial waste and the preparation of carbon-based catalysts,and the nonradical oxidation in the system can greatly improve the treatment efficiency of real wastewater.