Reaserch On Modification Of Biochar And Adsorption Properties Of Tetracycline In Water

Since tetracycline is not easily metabolized and decomposed in organisms,it remains in the environment and poses a threat to the ecosystem and human health.Therefore,how to effectively remove tetracycline in the environment is very important.Adsorption is one of the effective ways to treat tetracycline wastewater.Biochar is a cheap and effective adsorbent.Many studies have shown that biochar has a good removal rate of tetracycline.In this experiment,traditional Chinese medical sludge and cow dung were used as raw materials,and the original biochar was prepared by Muffo furnace for 2 h at 700°C with limited oxygen.Vitamin C was used to modify the biochar to improve its adsorption capacity on tetracycline.The optimal immersion ratio was screened for batch adsorption experiments to explore the influence of different environmental conditions on the adsorption of tetracycline.In order to predict the adsorption effect of biochar on tetracycline,combined with this experiment and related literature,the physical and chemical properties of biochar and adsorption environmental conditions were set as input variables,and six machine learning models including decision tree model,random forest model,gradient boosting decision tree model,artificial neural network model,support vector machine model and Xgboost model were fitted.The main results of this experiment are as follows:(1)In this paper,tetracycline was a pollutant.Biochar was prepared from traditional Chinese medicine sludge and cow dung,and modified with vitamin C.The adsorption properties of biochar prepared with three different impregnation ratios on tetracycline were compared.The optimum impregnation ratio was 1:2,and the influence of adsorption conditions on the adsorption effect was further discussed.(2)Scanning electron microscope,organic element analysis,fourier transform infrared spectrometer and other characterization results showed that vitamin C modification increased the surface roughness of biochar,reduced the aromaticity and surface polar functional groups of biochar,improved the hydrophobicity,and observed the hydroxyl and benzene rings on the biochar.(3)In the batch adsorption experiment,the amount of biochar was all 0.4 g/L;The adsorption equilibrium time was set as 90 min(MSBC and MSBC)and 720 min(CDBC and CDBC-VC),respectively.The initial concentration of solution was set to 10 mg/L;Chinese medicine sludge base biochar and cow dung biochar at p H 5.0 and 6.0 respectively achieved the highest removal rate,as the MSBC(91.91%),MSBC-VC(98.02%)and CDBC(82.36%),CDBC-VC(97.14%).Salt ions can promote MSBC and inhibit CDBC to adsorb tetracycline.The removal rate of MSBC and its modified biochar can reach more than 80%after three times of regeneration.Biochar treated industrial wastewater the best,aquaculture wastewater the second,and domestic sewage the last,which may be due to complex reaction,microbial synergism and ion competition.(4)The pseudo-second-order kinetic fitting results were better,and the R~2of MSBC,MSBC-VC,CDBC and CDBC-VC were 0.9954,0.9986,0.9788 and 0.9994,respectively,indicating that the adsorption process was dominated by chemical adsorption.Traditional Chinese medicine sludge-based biochar fitted Langmuir model better,while cow dung based biochar fitted Freundlich model better.The maximum adsorption capacities were 82.10 mg/g,115.56 mg/g,40.06mg/g and 54.39 mg/g,respectively.(5)The main mechanisms of tetracycline adsorption on biochar were hydrogen bonding,π-πelectron donor acceptor interaction,hydrophobic interaction and electrostatic interaction.(6)The prediction results of machine learning model showed that R~2,RMSE and MSE of Xgboost model were 0.9992,0.5844 and 0.3012,which showed the best fitting effect and good stability.Ratio of initial tetracycline concentration to biochar dose,specific surface area of biochar,Isoelectric point and ash content have great influence on the predicted results of adsorption efficiency.In summary,the raw materials used in this experiment were traditional Chinese medicine sludge and cow dung,which were cheap and easy to obtain.Vitamin C modification improved the adsorption capacity and adsorption rate of biochar for tetracycline,which provided a new idea for recycling waste and treating tetracycline in water.The machine learning model can predict the adsorption of tetracycline by biochar,which can avoid the waste of time and materials.Relative importance can be analyzed to guide the important conditions of biochar in the treatment of tetracycline wastewater.