Preparation Of Co₃O₄/Hydrogen Titanate Composite Catalyst And Its Catalytic Degradation Of Phenolic Pollutants By PM

Advanced oxidation technologies based on sulfate radical（SR-AOPs）are a new technology for degrading phenolic pollutants with long-term risks and toxicity in environmental water.Developing efficient catalysts to effectively activate peroxymonosulfate（PMS）to produce sulfate radicals is a key challenge.The transition metal Co oxide with high catalytic ability is loaded into the titanate carrier with advantages such as adjustable,high specific surface area,porous structure,and rich alkaline centers.The obtained composite catalyst has higher catalytic activation efficiency for PMS than the homogeneous Co based catalyst.At the same time,titanate has high adsorption,which can effectively inhibit the dissolution of cobalt ions and reduce the risk of secondary pollution.This article uses electrospinning technology to obtain Ti O₂/Si O₂/Co₃O₄composite fibers as precursors.Through alkali heat treatment,Co₃O₄ nanoparticles are successfully loaded onto hydrogen titanate nanosheets to prepare Co₃O₄/hydrogen titanate composite catalysts（Co₃O₄/HTO）.Furthermore,the effect of Co₃O₄/HTO catalytic activation of PMS on the degradation of phenolic pollutant 2,4-dichlorophenol was studied.The main results obtained are as follows:（1）The catalytic activity of Co₃O₄/HTO prepared under the conditions of Co/Ti ratio of 1:1 and alkali heat treatment time of 12 h is the highest.Through characterization by SEM,TEM,BET,XRD,XPS and so on,it was found that the catalyst exhibits a nanosheet assembly structure as a whole,with a specific surface area of 87.5 m²/g,which is 5.24 times that of Co₃O₄.The surface has abundant mesopores of about 10 nm and a large number of interconnected pore structures.The large specific surface area and rich pore structure are conducive to the contact of PMS and phenolic pollutants with the composite catalyst to enhance mass transfer and significantly improve catalytic efficiency.In Co₃O₄/HTO,Co₃O₄ is dispersed in the nano sheet,and ultrafine（about 5 nm）Co₃O₄ nanocrystals are obtained,so that more active site in Co₃O₄are exposed to the surface of the composite catalyst,thus improving the catalytic activity.In addition,the surface of Co₃O₄/HTO also contains abundant hydroxyl groups,which can act as alkaline centers,promote Co cycling in the catalyst,and further improve the catalytic activity of the catalyst.Compared with Co₃O₄,the catalytic efficiency of Co₃O₄/HTO has increased by 4.37 times.Co²⁺was the main active site in the catalyst,and the active oxygen produced by PMS was mainly SO₄^·-,O₂^·-,and ¹O₂,while a small amount of·OH was also produced.（2）In the catalytic activation of PMS by Co₃O₄/HTO for the degradation of phenolic pollutants,factors such as Co₃O₄/HTO concentration,PMS concentration,substrate concentration,p H,and different anions can all affect the degradation effect.Under the conditions of Co₃O₄/HTO concentration of 100 mg/L and PMS concentration of 200 mg/L,the best degradation effect can be achieved.This system has a good degradation effect on 10-50 mg/L of 2,4-dichlorophenol and for 30 mg/L of 2,4-dichlorophenol,the degradation rate can reach over 97%within 30 minutes.The system has the best degradation effect at p H 11 and can maintain good degradation ability in complex water environments.In addition,the intermediate products of the degradation of 2,4-dichlorophenol in this system were analyzed by GC-MS,and a total of 13possible intermediate products were identified.Based on the occurrence time of different intermediate products,possible degradation pathways were speculated.The final degradation products of 2,4-dichlorophenol in this system are mainly H₂O and CO₂,which will not cause secondary pollution to the environment.