Removal Of Bisphenol A By Chlorella Pyrenoidosa And Its Modified Biochar

In recent decades,drugs,personal care products,and endocrine disruptors have attracted extensive attention due to their potential negative impact on human health and ecosystems.These pollutants are discharged into the aquatic environment through different ways,including domestic sewage,hospital sewage,pharmaceutical industry sewage,garbage infiltration liquid,aquaculture sewage discharge in urban or agricultural areas and so on.Bisphenol A（BPA）,as a typical environmental pollutant,has been reported in many pieces of literature.In this study,Chlorella pyrenoidosa was selected as biomass to study the effects of Polystyrene（PS）microplastic,Sodium Acetate（Na Ac）and BPA on the physiological and biochemical changes of Chlorella pyrenoidosa,and to study the removal of BPA by Chlorella pyrenoidosa in the presence of PS or Na Ac.In addition,BPA was selected as the target pollutant,and Chlorella pyrenoidosa powder was used as the raw material.After calcination into biochar,it was modified with iron salt to activate Persulfate（PDS）to degrade BPA,and the related activation mechanisms involved in the degradation process were explained.This study provides important data support and theoretical significance for water pollution treatment.The main research contents are as follows:1.The influence of polystyrene microplastics on the toxic effects and biodegradation of bisphenol A in the microalgae Chlorella pyrenoidosaBPA and PS microplastics have received great attention due to their widespread distribution in the environment,but their combined toxicity to aquatic organisms has been rarely studied.Therefore,this study investigated the toxic effects and biodegradation effects of PS and BPA on Chlorella pyrenoidosa.The results showed that during the 16days cultivation process,PS（5 mg/L）increased the growth inhibition of BPA（1 mg/L and 10 mg/L）on Chlorella pyrenoidosa compared to the absence of PS.Similarly,PS（5mg/L and 100 mg/L）also improved the removal efficiency of Chlorella pyrenoidosa on BPA（1 mg/L and 10 mg/L）.The trend of changes in chlorophyll content and the maximum light energy conversion rate（F_v/F_m）value was the opposite.In addition,this study also found that due to the presence of oxidoreductases and glycosyltransferases,five intermediate products were formed during the degradation of BPA.The research results provide important information for the joint toxicity of PS and BPA to microalgae and the biodegradation of PS and BPA by microalgae.2.Addition of exogenous organic carbon assist Chlorella pyrenoidosa to remove BPAIn recent years,microalgae-mediated antibiotic biodegradation has attracted wide attention from the international scientific community.However,information on microalgae-mediated BPA biodegradation in co-metabolism systems are limited.In this study,BPA was selected as the target pollutant,Na Ac as the co-metabolic substrate,and Chlorella pyrenoidosa as biomass.The growth of microalgae,photosynthetic pigments and efficiency,BPA removal,and changes in enzyme activity during removal were studied.The results showed that the microalgae added with Na Ac showed better growth ability at the initial stage,but the growth was inhibited at the later,and the degree of inhibition increased with the increase of Na Ac concentration,and the F_v/F_m value also showed the same performance.After 10 days of incubation,1 mg/L BPA combined with0.5 g/L Na Ac increased the chlorophyll content of algae,while combined with 1 g/L and2 g/L Na Ac inhibited the production of chlorophyll.After 10 days of culture,the addition of 2 g/L Na Ac significantly increased the degradation efficiency of BPA（1 mg/L）from14.68%to 76.65%.The degradation of BPA conformed to the first-order kinetic model.The apparent rate constant（k）was 0.0157～0.1389 day^-1,and the half-life(T_1/2)was 4.49～44.48 days.The activities of Malondialdehyde（MDA）,Superoxide Dismutase（SOD）and Catalase（CAT）increased with the increase of Na Ac concentration,which may be due to the changes of photosynthesis-related genes and electron transport chains induced by BPA and Na Ac,resulting in ROS damage to microalgae.Compared with the previous section,the removal efficiency of BPA in this study was significantly improved,so it provided important information for improving the removal strategy of pollutants by microalgae.3.The degradation of BPA by microalgae modified biochar activated PDSIn this work,Iron-based biochar（ZVI-BC）was used as an activator to degrade BPA by PDS,and it was found that the degradation efficiency was great.PMSO was used as a probe compound to analyze tetravalent iron（Fe（Ⅳ））in the process of ZVI-BC activating PDS.We confirmed that in addition to Fe（Ⅳ）,free radicals（sulfate radicals（SO₄·^-）,hydroxyl radicals（·OH）,superoxide radicals（O₂·^-））and non-free radicals（singlet oxygen（¹O₂））were also involved in the degradation process of the activation system,and Fe（Ⅳ）was the main active oxygen（ROS）.In general,organic substrates with electron-donating groups are more likely to react with Fe（Ⅳ）,and the relative contribution of Fe（Ⅳ）decreases with increasing p H.This study provides a new idea for the quantitative analysis of Fe（Ⅳ）in the ZVI-BC/PDS system,and provides important theoretical support for broadening the application range of iron/persulfate system in wastewater.