Preparation And Catalytic Performance Of Activated Carbon Supported Cobalt-Based Metal Catalysts

Printing and dyeing wastewater has always been a hot topic and difficult point due to their high chromaticity,stubborn toxicity and complex composition in textile industry and environmental field.In recent years,advanced oxidation processes（AOPs）has been considered the most promising technology in environmental remediation,owing to the rapid reaction rate and strong oxidation ability.Among these AOPs,peroxymonosulfate（PMS,2KHSO₅·KHSO₄·K₂SO₄）has a series of advantages in comparison with H₂O₂,such as the convenient transportation and storage,high redox potential（E⁰=2.5-3.1 V）and wide range of pH adaptation（3-10）.Therefore,the methods based on PMS activation have raised worldwide interest in the field of environmental protection.Nowadays,the transition metal cobalt has been considered the best activator of PMS.However,the practical applications are limited due to its stubborn toxicity,secondary contamination and high cost.Therefore,the development of cobalt-based catalysts with low cost,high efficiency and well stability for PMS activation was urgently desired.On the other hand,the activated carbon（AC）was chosen as the support due to its low cost and excellent adsorption performance to design the cobalt-based bimetallic catalyst for PMS activation to remove the target pollutant in our work.The paper focuses on the properties,repeatability,as well as mechanism of the catalytic behaviors.The main research contents are as follows:Activated carbon was selected as the support,followed by hydrothermal and calcination to prepare the catalyst（AC-CuCo₂O₄）.It was characterized by X-ray diffraction（XRD）,scanning electron microscope（SEM）and X-ray photoelectron spectroscopy（XPS）.3BF was chosen as the probe to estimate the catalytic oxidation performance of AC-CuCo₂O₄/PMS.The main influencing factors,such as the catalytic performance,reusability and the effect of anions(such as Cl^-,H₂PO₄^-,HPO₄^2-and PO₄^3-)were also investigated in the AC-CuCo₂O₄/PMS system.The experimental results demonstrated that the AC-CuCo₂O₄/PMS system could exhibit excellent catalytic oxidation performance for removing 3BF within 10 min and over 98%removal rate was reached.Moreover,the removal rate of the M-3BE（3BF）could still reach about 85%after five reuses of AC-CuCo₂O₄,indicating that AC-CuCo₂O₄ had good repeatability.Additionly,the AC-CuCo₂O₄/PMS system has a good catalytic performance on other dyes（such as active red X-3B,acidic red AR1,active yellow M-3RE,active blue KN-R,etc.）.The Cl^-,PO₄^3-,HPO₄^2-and CO₃^2-had inhibitory effects on the AC-CuCo₂O₄/PMS system,and a small amount of H₂PO₄^-would promote the reaction rate to remove 3BF in the AC-CuCo₂O₄/PMS system.Electron paramagnetic resonance（EPR）technology with various spin-trapping agents and the radical quenching such as methanol（MA）,tert-butanol（TBA）,ascorbic acid（AA）and L-histidine were employed to study the reaction mechanism.The results indicated that the various reactive oxygen species(¹O₂,·OH,SO₄^·-and O₂^·-)involved in the AC-CuCo₂O₄/PMS system.In order to further improve the activity of the cobalt-based catalyst,phosphorus was chosen as the dopant based on the AC-CuCo₂O₄ catalyst.The catalyst AC-P-CuCo₂O₄was prepared by phosphorous doping AC-CuCo₂O₄ by means of hypophosphoric phosphorization.ComparedwiththeAC-CuCo₂O₄/PMSsystem,the AC-P-CuCo₂O₄/PMS system had a faster removal rate(1.025 min^-1)of 3BF,which was 2.23 times than that of the AC-CuCo₂O₄/PMS system(0.46 min^-1).Combining electron paramagnetic resonance（EPR）with the radical quenching experiments,the reaction mechanism of the AC-P-CuCo₂O₄/PMS system was investigated.The results suggested that the reactive oxygen species generated in the AC-P-CuCo₂O₄/PMS system were similar to the AC-CuCo₂O₄/PMS system.Various reactive oxygen species(¹O₂,·OH,SO₄^·-and O₂^·-)were generated in the AC-P-CuCo₂O₄/PMS system.