Study On The Fenton-like Catalytic Performance Of Cu/g-C₃N₄ System

In this paper,the Fenton-like catalytic performance of Cu/g-C₃N₄ system was studied based on the idea that g-C₃N₄ can promote Cu（Ⅱ）/Cu（Ⅰ）conversion.The synthesized materials were characterized by XRD,FT-IR,SEM,EDS,TEM,XPS and other means.The effects of various factors such as the amount of catalyst,the amount of H₂O₂,the pH and the initial concentration of RhB on the catalytic performance of the system were studied.Finally,the catalytic mechanism of each system was discussed.In chapter three,the Cu（Ⅰ）/g-C₃N₄ composites in different ratios were prepared by hydrothermal method with nano Cu₂（OH）PO₄@PAAS as the copper source and g-C₃N₄as the support.The structure characterization results showed that Cu formed a stable complex with g-C₃N₄ in the form of Cu（Ⅰ）.As a Fenton-like catalyst,the Cu（Ⅰ）/g-C₃N₄had excellent catalytic performance,and the decolorization rate of RhB could reach 87%after 10 min.EPR and free radical capture experiments confirmed that the main active free radical produced in the catalytic reaction was still·OH.The electron transfer on the surface of g-C₃N₄ may play an important role in the conversion of Cu（Ⅰ）/Cu（Ⅱ）.In order to verify the synthesis and catalytic performance of Cu（Ⅰ）/g-C₃N₄,in the fourth chapter of this paper,Cu₂（OH）PO₄@PAAS was replaced by Cu₂（OH）PO₄ with regular particle size,and different reducing agents were added during the hydrothermal process to prepare different Cu（Ⅰ）/g-C₃N₄ catalysts.Structural characterization confirmed that the Cu element existed in the framework of g-C₃N₄ in the form of Cu（Ⅰ）.Compared with the Cu（Ⅰ）/g-C₃N₄/N prepared by direct hydrothermal method in chapter three,the morphology of Cu（Ⅰ）/g-C₃N₄/N prepared by sodium citrate reduction became solid cylindrical,and its crystallinity was significantly improved.The catalytic performance test showed that the Fenton-like catalytic performance of the composite prepared by different reducing agents was different.The performance of Cu（Ⅰ）/g-C₃N₄/N was the best,which was better than that of Cu（Ⅰ）/g-C₃N₄ prepared by direct hydrothermal method in the third chapter.As a copper based Fenton-like catalyst,Cu（Ⅰ）/g-C₃N₄/N mainly catalyzed H₂O₂ to produce·OH to degrade pollutants.In chapter five,in order to investigate the synergistic catalytic performance of g-C₃N₄ and Cu²⁺,using the bulk g-C₃N₄ as precursor,and four g-C₃N₄ nanosheets were further prepared by ultrasonic,thermal,acid,and alkali exfoliation.The Fenton-like degradation test showed that there existed a significant synergistical Fenton catalysis between Cu²⁺and g-C₃N₄.This synergistic effect could be observed even when the concentration of Cu²⁺was as low as 1×10^-6 mol/L（0.064 mg/L）.The properties of g-C₃N₄ strongly influenced the catalytic activity of the Cu²⁺/g-C₃N₄ system.The coexistent of Cu²⁺and the alkali exfoliation g-C₃N₄（g-C₃N₄/A）showed the excellent catalytic activity.Hydroxyl radicals as oxidizing species were confirmed in the Cu²⁺/g-C₃N₄ system by ESR spectrum,the synergistic catalysis may be attributed to the easier reduction of Cu²⁺adsorbed on the g-C₃N₄.In order to improve the recyclability of g-C₃N₄/A,in chapter six,magnetic Fe₃O₄particles were prepared and loaded on g-C₃N₄/A to obtain Fe₃O₄@g-C₃N₄/A catalyst which was simple and easy to be recovered through magnetism.Structural characterization showed that Fe₃O₄ particles had been loaded on g-C₃N₄/A.Compared with the synergistic effect of g-C₃N₄/A and Cu²⁺in the previous chapter,the catalytic performance was slightly decreased,and the catalytic degradation effect was still significant.Fe₃O₄@g-C₃N₄/A could be separated directly by magnet.After five cycles,its catalytic performance did not decline and it had good stability.The investigation of its catalytic mechanism showed that Fe₃O₄ had almost no catalytic effect,and only played a role in providing magnetism.It was still the catalytic synergistic degradation of organic wastewater by g-C₃N₄/A and Cu²⁺.