Study On The Preparation And Modification Of Cotton Straw Biochar And Its Adsorption Of PPCPs

In this study,biochcar and modified biochar were prepared as biological adsorption materials with agricultural waste cotton straw as raw materials to remove PPCPs from aqueous solution.The surface,aperture,specific surface area and surface functional groups of biochar and modified biochar were characterized by scanning electron microscopy（SEM）,specific surface and aperture analyzer（BET）and Fourier Transform Infrared Spectroscopy（FTIR）,respectively.At the same time,on the basis of characterization,the effects of pH,the initial concentration of ofloxacin and ibuprofen,the addition of biochar and modified biochar,the adsorption time and adsorption temperature on the adsorption effect were studied.Furthermore,we have combined with adsorption kinetics,adsorption thermodynamics,adsorption isotherm to investigated cotton stalks biochar and modified biochar with adsorption mechanism of ofloxacin and ibuprofen.It provides a new way for the resource utilization of cotton straw in agricultural waste.Hence,the toxicity of cotton straw biochar,modified biochar and commercial nano-carbon was compared to explore its safety.The main results of the experiment are as follows:（1）SEM results showed that the surface of biochar and modified biochar which prepared by phosphoric acid oxidation and iron ion gasification was rough and uneven,and had abundant pore structure with different shape and irregular size.BET results showed that the surface area of cotton straw biochar was 1196.2 m²/g,the specific area of modified bichar was up to 1257.9 m²/g,both kinds of carbon had developed pore structure,and the pore size analysis showed that the pore size distribution of biochar and modified biochar was medium-microporous mixed structure.It is more favorable to have good adsorption effect on both macromolecules and small molecules.FTIR results analysis can get two kinds of carbon surface has many types of functional groups,which cotton straw biochar surface contains P=O C=C,C-H,C-O,carboxyl,-NH₂,-NH,phenol hydroxyl and other oxygen-containing functional groups.The modified biochar surface is rich in P=O,P-O-C,C=C,O-H,C=O,C-O and other functional groups,is conducive to the adsorption treatment of PPCPs drug pollutants.（2）The results of adsorption experiments showed that cotton straw biochar and modified biochar adsorbent have a good adsorption effect on the removal of PPCPs pollutants in aqueous solution.When the concentration of ofloxacin and ibuprofen was 20mg/L,the removal rate of ofloxacin from cotton stalk biochar and modified biochar was up to 99%and 100%respectively,and the removal rate of ibuprofen could reach 100%.When the biochar dosage increase to 0.2g/L,the adsorption ability of ofloxacin and ibuprofen by cotton straw biochar can reach up to 206mg/g and365.6 mg/g,while the removal rate of modified biocarbon to two pollutants can be as high as 316.2 mg/g and 375.04mg/g.Cotton Straw biochar and modified biochar have good removal effect on PPCPs pollutants in water,and the modified biochar adsorption effect is better than cotton straw biochar before modification.（3）The adsorption processes of ofloxacin and ibuprofen on cotton straw biochar and modified biochar were the highest with the simulated synthesis of pseudo-second kinetic model（R²>0.999）,the results showed that the adsorption process of ofloxacin and ibuprofen by the chemical adsorption mechanism control.The removal capacity of cotton straw biochar and modified biochar to PPCPs was proportional to the number of active sites on biosorbent.The adsorption process of ofloxacin by cotton straw biochar and modified biochar was more suitable to Freundlich model,indicating that the biochar removal process of ofloxacin belongs to multi-layer adsorption.However,the adsorption process of ibuprofen on cotton straw biochar and modified biochar had the highest fitting degree with the Langmuir isothermal model（R²>0.999）,indicating that the adsorption process of ibuprofen belongs to single-layer adsorption.In addition,cotton straw biochar and modified biochar on two pollutants is a spontaneous（ΔG<0）exothermic（ΔH<0）process,which is consistent with the results of Langmuir isothermal model simulation.（4）Cotton straw biochar,modified biochar and commercial nano-carbon,the order of inhibitory effect on the growth of protein nucleus chlorella is:commercial nano-carbon（97.8%±0.970473）>modified biochar（51.1%±0.366804）>cotton straw biochar（3%±0.397077）;The order of inhibition of three different kinds of carbon on BEAS-2B cells is:commercial nano-carbon（68.6%±0.483543）>modified biochar（25.1%±0.830565）>cotton straw biochar（2.4%±0.68306）.Commercial nano-carbon had a obvious influence on the number of late apoptosis necrosis of BEAS-2B cells,and the apoptosis of BEAS-2B cells increased,the commercial nano-carbon was significantly more toxic to BEAS-2B cells than the other two kinds of carbon.The toxicity of modified biochar extract was significantly higher than that of cotton straw biochar.