Study On The Adsorption Mechanism Of Biochar-based Composites On PAEs

Biochar is produced by pyrolysis of agricultural waste under anaerobic conditions,and has certain adsorption and removal ability to pollutants.In order to improve the adsorption performance of PAEs by biochar,in this paper,iron and manganese oxides were used to modify the biochar to study the adsorption effect and mechanism of DEHP,and investigate the adsorption effect of biochar prepared by different proportions of lignin and cellulose.The main results are as follows:1. Adsorption of DEHP by Fe-Mn oxide modified biochar compositesThe quasi-second-order kinetic equation can better fit the kinetic adsorption,indicating that the adsorption of DEHP by Fe-Mn oxide modified biochar composites is a combination of physical and chemical adsorption.Freundlich fits better.R²are all above 0.96,indicating that the modified biochar composite carbon materials for DEHP are multilayer adsorption sites and heterogeneous adsorption.Among them,the adsorption effect of Fe₁Mn₄C₂₅was the best,and the maximum adsorption capacity of DEHP was 34.04 mg/g.Compared with the original carbon,the maximum adsorption capacity of Fe₁Mn₄C₂₅was 3.98 times that of the original carbon.With the decrease of p H,the adsorption capacity of iron-manganese oxide modified biochar composites for DEHP increased.At p H=3,Fe₁Mn₄C₂₅has the largest adsorption capacity.Nitrate ionic strength has little effect on the adsorption of DEHP by Fe-Mn oxide modified biochar composites.Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis showed that Fe-Mn supported on corn straw biochar and the functional groups on the surface of biochar will be changed during the DEHP adsorption process.Mn?III?plays a major role in the DEHP adsorption.2. Adsorption of DBP on lignin and cellulose biochar-based materialsThe adsorption process of DBP by biochar-based materials with different lignin and cellulose ratios can be better fitted by quasi-second-order kinetic equation,and Freundlich model can describe isothermal adsorption process better than Langmuir model.At the same temperature,the biochar-based materials?L4:C6?with lignin and cellulose ratio of 4:6 have the best adsorption effect on DBP;the biochar-based materials made at 300°C have the best adsorption performance at the same proportion.L4:C6?300??has the best adsorption effect on DBP with a maximum adsorption capacity of 24.3 mg/g,which is 1-3 times of the adsorption capacity of the prepared biochar under different conditions.With the decrease of p H,the adsorption of DBP by biochar-based materials increased significantly;with the increase of nitrate ion intensity,the adsorption of DBP by biochar-based materials increased slightly.