Preparation Of Biochar-Based Bismuth-Based Photocatalysts And Research On Its Efficient Degradation Of 17α-Ethinyl Estradiol (EE2) And 17β-Estradiol (E2)

As one of exogenous nutrients,environmental endocrine disruptors（EDCs）cause severe damage to human reproductive and developmental problems.Among various EDCs,17α-ethinyl estradiol（EE2）and 17β-estradiol（E2）present the features of the most typical and the strongest estrogenic effect in synthetic and natural product respectively,which are widely exist in water bodies.With the increasing attention to environmental protection,it is an urgent hope for human that is seeking efficient and green way and solving the pollution problem of EDCs.Due to its high efficiency,environmental protection,low toxicity,multi-functionality and low cost,visible light catalytic degradation of organic pollutants has become a conspicuous water treatment method in recent years.In this paper,EE2 and E2 were taken as the target pollutants,highly active and multifunctional photocatalysts which based on the eco-friendly and clean biochar（BC）were prepared to achieve the two pollutants effective and efficient degradation.Further,the improvement effect of BC on photocatalyst performance was investigated in detail by studying the effect of BC on the reaction rate of single-component semiconductor photocatalyst Bi₂WO₆ and compound semiconductor photocatalyst Bi VO₄/Ag I.Meantime,in the hope of further exploration more suitable synthesis process for large-scale industrial production,Bi PO₄/Ag I/BC composite photocatalysts were synthesized by precipitation method at room temperature to enhance its practical applications.In addition,the properties of prepared photocatalysts were characterized,including physical phase,morphology,specific surface area and functional groups,which were used for the process of efficient degradation of EE2 and E2,and thereby identified the degradation products,pathways and mechanisms.Last,focused on the phytotoxicity and antibacterial experiments,the detoxification and antibacterial functions were investigated.The main contents were as follows:1.Microwave-assisted hydrothermal method was used to prepared Bi₂WO₆/BC composite photocatalyst,and its effect and mechanism of different biochars on the performance of single semiconductor photocatalyst were studied.Compared with other samples,the leaf part of woody plants represented by poplar showed the most significant improvement for the properties of photocatalytic system.Then,it obtained optimal Bi₂WO₆-BC_2%by optimizing the synthesis conditions of the photocatalyst.Meanwhile,cooperating with the advanced oxidizer（PS）,the optimal product achieved EE2 and E2 removal rate up to 99.41%（12 min）and 97.84%（15 min）under the initial concentration of 3 mg/L.Besides,according to the result of plant toxicity experiment,the addition of BC and PS significantly not only enhanced the activity of single-component photocatalysts,and also notably reduced the toxic effects of pollutants on plants.Moreover,BC was mainly through the following four paths to further enhance the catalytic activity of single component semiconductor photocatalyst,include increasing the specific surface area of photocatalytic system,enriching the types of functional groups,enhancing the separation ability of photogenerated electrons and holes,and promoting the concentration of active free radicals.Thus,the reactive radicals were h⁺and·O₂^-during the photocatalytic process.Both BC and PS increased the concentration of h⁺and·O₂^-in the system substantially.2.The high-efficiency and multifunctional Bi VO₄/Ag I/BC composite photocatalyst was synthesized by microwave-assisted hydrothermal method,at the same time the paper investigated the effect and mechanism of BC on the catalytic activity of the composite photocatalyst.After 40 min of visible light,99.68%and 99.44%of EE2 and E2 was degraded by the optimal photocatalyst(BV-Ag I_0.8-BC_5%)at the initial concentration of 3 mg/L,respectively.During the above progress that the main active substance was·O₂^-,while BC had a significant improvement on the concentration of active radicals.Besides,the results of phytotoxicity and antimicrobial test demonstrated that BV-Ag I_0.8-BC_5%have exceptional performance in pollutants degradation and lower toxicity of degradation pathway.Also,it showed excellent antimicrobial performance due to over 99.99%removal of E.coli under dark and light.Sum,the addition of BC can significantly enhance the photocatalytic activity of the composite photocatalyst,its mechanism is similar to that in single-component catalyst.3.Through green,simple and low-cost precipitation method at room temperature,the highly active and multifunctional Bi PO₄/Ag I/BC composite photocatalyst was synthesized in this research.Similarly,the optimal BP-Ag I_0.6-BC_5%achieved 99.16%and 99.7%removal rate of EE2 and E2 at the initial concentration of 3 mg/L after 40min of visible light exposure.In the whole system,the main active substance was O₂^-and BC played an important role in enhancing the·O₂^-concentration.Additionality,based on the results of phytotoxicity and antimicrobial test,they described BP-Ag I_0.6-BC_5%efficiently degraded pollutants and significantly reduced the toxicity of degradation products.More importantly,the result further presented excellent antimicrobial performance because the removal rate of E.coli exceeded 99.99%in both dark and light conditions.The research constructed bismuth-based photocatalyst by introducing BC and silver materials,while the contributions involve efficient degradation of EE2 and E2 under visible light and outstanding sterilization function.The method used in this study,preparation method at room-temperature,is conducive to industrial scale production and attractive prospects for practical applications.