The Pollution Research And Mechanism Analysis About Removal Of Azo Dyes By Photoactive Biochar With UV

Many kinds of azo dyes are very harmful to human.Among synthetic dyes,azo dyes are most widely used.It is very difficult to treat azo wastewater.Photochemical catalytic degradation is more efficient,but the price of the catalyst is relatively high,which limits its wide application in practical wastewater treatment.The research focus of photocatalytic degradation of dyes are to seek rational and inexpensive catalysts.Biochar(BC)has a large specific surface area and abundant pore structure.Dissolved Biochar(DBC)in some biochar can produce active oxides under ultraviolet light,which is beneficial to the sensitizing degradation of dyes.Therefore,the development of biochar as an economical and efficient photoactive material for dye degradation is very great value.However,how to select suitable raw materials for photoactive biochar and how to optimize the performance of photoactive biochar and analyze the mechanism of degradation of dyes are important scientific problems.In this paper,vermicompost biochar(VCBC)and maize straw biochar(MSBC)with 500?are selected as the tested subjects.Congo red and methylene blue are selected as the research objects.The degradation effect of two kinds of biochar and UV on two dyes is discussed preliminarily,the structure-activity relation of two kinds of biochar to the degradation of dyes is clarified,and the influencing factors of straw biochar on the degradation of dyes are explored.The reaction solution is characterized by 3D-EEMs,IR and so on.The potential mechanism of dye degradation of dissolved biochar is analyzed in detail.Finally,a new UV photoresponse material with low cost and high efficiency for removing azo dyes is proposed,which provides theoretical guidance and technical support for the practical application of photochemistry technology and opens up a new direction for the application of biochar.The results of this study are as follows:(1)The effects of VCBC and MSBC combined UV on the degradation of dyes.Biochar has a large specific surface area,rich functional groups and other physical and chemical properties.Biochar,in the environment and agriculture,has a great potential for application.But different biological carbon from different sources of biomass,the physical and chemical properties of the different determines its removal efficiency is different.The dye is degraded by VCBC and MSBC in combination with UV,and two kinds of biochar are compared the yield,ash content,pH of CEC,element,specific surface area.The results show that the yield,ash,CEC and specific surface area of VCBC are higher than that of MSBC,but H/C of MSBC,(O+N)/C and O/C are lower,the degree of carbonization is higher,and the aromaticity is stronger.There are more C=O and aromatic rings in MSBC,which promotes the interaction with the dye?-?bond and the common electron pair,and makes use of the dye degradation.The experimental results explain the impact of biodegradation of dyes from different raw materials,and provide theoretical guidance and technological support for the selection of raw materials for photoactive biochar.(2)Influence factors and Mechanism of MSBC combined with UV on degradation of Dyes.Biochar combined with UV has a good degradation effect on dyes,but the degradation effect is affected by many experimental conditions and its potential degradation mechanism is complex.Take MSBC as the experimental material combined with UV.The effects of different pH,MSBC dosage and dye concentration on the photodegradation of two dyes are studied.The potential mechanism is explored by XRD,infrared spectroscopy and elemental analysis.The results show that the removal rates of congo red and methylene blue are the highest,when pH is 11 and 7,respectively.The amount of biochar increases,which can effectively improve the degradation rate of two dyes.The removal rates of congo red and methylene blue decrease with the increase of the concentration of congo red and methylene blue.The degradation of congo red is mainly caused by photodegradation.e~-and·OH are the active aspects for methylene blue.e~-is more active than·OH.The cationic exchange is between methylene blue and biochar.There is cationic exchange between methylene blue and biochar.The carbonyl of MSBC and the arnomatic nucleus of dye use electron pair together.MSBC has a common electron pair and hydrogen bond with two dyes.The results discuss the influencing factors and potential mechanism of MSBC with UV on the degradation of dyes,and point out the optimized direction of dye degradation of light-activated biochar,which produces a foundation for the practical application of photoactive biochar.(3)Influence factors and Mechanism of DBC combined with UV on degradation of dyes.The presence of DBC in biochar will greatly affect the removal efficiency of dyes under UV conditions due to the different reaction conditions.Take DBC as the experimental material with UV.The effects of different pH,DBC concentration and dye concentration on the photodegradation of two dyes are studied.The potential mechanism is explored by 3D-EEMs,infrared spectroscopy and elemental analysis.The results show that with the increase of DBC concentration,the degradation rate of congo red decreases,the degradation rate of methylene blue first increases and then decreases.The degradation rates of congo red and methylene blue decrease with the increase of dye concentration.The removal rates of congo red and methylene blue are the highest,when pH is 11.Congo red degradation is mainly direct degradation,and the hydroxyl radical oxidation plays a major role in degradation of methylene blue.In congo red,there are the formation of alcohols;DBC produces visible-light fulvic acid and humic acid.The potential adsorption mechanism is?-?conjugation and hydrogen bond.In DBC/UV/MB,DBC leads visible light fulvic acid and humic acid.The potential adsorption mechanism of methylene blue is mainly?-?bond interaction and electron pair interaction.The results explain the intrinsic mechanism of photoactive bioactive carbon in UV degradation,and further enhance the understanding of the structure-activity relationship between photoactive biochar and photoactive biochar.They also provide theoretical basis for other similar research works.