Study On Photocatalysis And Activation Of Sodium Persulfate With Metal-rich Biochar Modified TiO₂

Human chemical production and the use of pesticides have lead to a large number of chlorophenol organic pollutants remaining in the environment,causing serious threat to the ecological environment and people’s health.Advanced oxidation technology（AOPs）is currently recognized as a safe and effective treatment technology.In this paper,two advanced oxidation technology systems are studied for the degradation of organic pollutants:（1）Advanced oxidation system based on sulfate radicals,uses metal-rich biochar as an activator to activate sodium persulfate to degrade 2,4-dichlorophenol;（2）In the photocatalytic oxidation system,metal-rich biochar modified TiO2 semiconductor is used as a photocatalyst for 2,4dichlorophenol to undergo photocatalytic degradation.The characteristics of the two system catalysts and the degradation efficiency and degradation mechanism of 2,4-dichlorophenol were studied.Finally,the two advanced oxidation technologies are combined to further improve the degradation efficiency of 2,4-dichlorophenol.The best-performing lead-rich biochar and lead-rich biochar/TiO2 materials were characterized by a variety of characterization methods.Characterization found that the lead element in the lead-rich biochar mainly exists in the form of zero-valent lead and divalent lead,which can promote the generation of free radicals through oxidation-reduction.Biochar can fix,adsorb pollutants and transfer electrons in the material.In lead-rich biochar/TiO2,TiO2 mainly exists in anatase phase with good stability.The loading of lead-rich biochar reduces the band gap of TiO2,accelerates the movement of electrons,enhances the absorption performance of visible light,and greatly improves the photocatalytic performance.The experimental results showed that the lead-rich biochar activated sodium persulfate degraded 76.7%of 50 mg/L 2,4-dichlorophenol in 10.5 h.The photocatalytic degradation of 100 mg/L2,4-dichlorophenol by lead-rich biochar/TiO2 at 4 h was 95.4%.The degradation efficiency was improved by combining the two advanced oxidation systems.It can completely degrade 100 mg/L of 2,4-dichlorophenol in 3 h under UV light,which saves energy and time.This article has explored the degradation mechanism of 2,4-dichlorophenol by two advanced oxidation systems,but the mechanism of the combination of the two advanced oxidation technologies is more complicated,and only certain inferences have been made at present.