Preparation And Adsorption Of Pb(Ⅱ) From Different Modified Banana Peel Hydrothermal Carbon

Lead(Pb)is a widely used but not easily degradable heavy metal,and its unreasonable emissions have caused serious environmental damage.Hydrothermal method is a common wet waste treatment technology,and its products are also applied in the field of heavy metal adsorption,but the adsorption effect is not good.In order to enhance its adsorption capacity,modification treatment is needed.In order to increase its adsorption capacity,modification treatment is required.Banana peel is directly discarded as biomass waste,which not only pollutes the environment,but also causes resource waste.Due to the large amount of cellulose,hemicellulose,lignin,and other substances in banana peel,it has a rich pore structure and is suitable as a raw material for adsorbent.In this paper,different concentrations of phosphoric acid and potassium hydroxide solutions and different mixing ratios of cow dung were used to modify hydrothermal carbon.Firstly,scanning electron microscopy,Fourier transform infrared spectroscopy,and X-ray diffraction spectroscopy were used to characterize its morphological characteristics,functional groups,and material structure changes,and explore its physical and chemical properties.Then,Pb(II)adsorption experiment was conducted on the modified hydrothermal carbon.The effects of various single factors on Pb(II)adsorption were studied by controlling p H value,dosage,temperature,initial concentration,and adsorption time.The adsorption mechanism of Pb(Ⅱ)on hydrothermal carbon was studied using two isotherm models and three kinetic models.The adsorption capacity and removal rate of adsorbed Pb(Ⅱ)were predicted using a mathematical model based on artificial neural networks.The main conclusions are as follows:(1)Using phosphoric acid(1～3 mol/L)to modify hydrothermal carbon has improved the adsorption capacity and removal rate of Pb(II),and its surface oxygen-containing functional groups are greatly affected by the concentration of phosphoric acid.In the single factor experiment of p H value,the adsorption amount showed a trend of first increasing and then decreasing.At 45℃,p H=7,the maximum adsorption capacity of Pb(Ⅱ)is 101.19 mg/g.The adsorption process is irreversible single molecular layer adsorption,dominated by chemical adsorption.The neural network model can effectively predict the adsorption of Pb(Ⅱ)on phosphoric acid modified hydrothermal carbon(R=0.99).(2)The adsorption capacity and removal rate of Pb(Ⅱ)on modified hydrothermal carbon impregnated with potassium hydroxide(0.05～1 mol/L)showed a trend of first increasing and then decreasing,and its surface morphology,structure,and active functional groups were greatly affected by the concentration of potassium hydroxide.In the single factor experiment of p H value and dosage,the adsorption amount showed a trend of first increasing and then decreasing.At 45℃and p H=7,the maximum adsorption capacity of Pb(Ⅱ)is 133.87mg/g.The adsorption process is multi molecular layer adsorption,and the process is chemical physical adsorption.The neural network model can effectively predict the adsorption of Pb(Ⅱ)by potassium hydroxide(R=0.99).(3)Co-hydrothermal carbonization of cow dung and banana peel(mixing ratio:2:5,3:5,4:5,5:5)can improve the adsorption capacity and removal rate of Pb(Ⅱ),and mixing cow dung can also increase the co hydrothermal carbon yield.Its surface has Si O~-and Si-O-Si active sites.The adsorption process is irreversible single molecular layer adsorption,dominated by chemical adsorption.Analysis shows that there are physical adsorption,ion exchange,electrostatic attraction,surface complexation,and chelation in the process of co hydrothermal carbon adsorption.