Influence Of Different Raw Material Derived And Iron-based Biochar On Inorganic Nitrogen And Phosphorus Leaching Loss

In recent years,the concentration of NO₃^--N in groundwater has increased extremely rapidly.One of the important reasons is the excessive use of nitrogen fertilizer in agriculture.At the same time,after the excessive application of phosphate fertilizer,the more difficult mobile phosphorus also has the risk of leaching loss,which pollutes the groundwater and causes the eutrophication of the water body.Therefore,it is urgent to seek an effective method to prevent the loss of nitrogen and phosphorus nutrients.This experiment selects corn stalk,wheat stalk,the production rate,elemental composition,IR spectrum and electron microscope of biochar were prepared from peanut shell as raw material at pyrolysis temperature of 400?,500?,600?and 700?,and the optimum carbonization temperature of biochar was determined by adsorption experiment,which was 500?.The use of 500?carbonized biochar Preparation of the best modified carbon,because the biological carbon surface contains a large number of negative charges,easy and anion generation electrostatic mutual exclusion,modified biocarbon contains more cationic can and negatively charged anion combination,thereby enhancing the adsorption capacity.Adsorption kinetics,isothermal adsorption experiments and soil column leaching experiments were carried out to study the adsorption effects of biochar and modified carbon on nitrate and phosphorus,as well as the effects of biochar and modified carbon on soil inorganic nitrogen and phosphorus leaching.The main findings of the experiment are as follows:1.With the increase of carbonization temperature from 400?to 700?,the yield of three kinds of biological carbon decreased gradually,the yield of C-BC decreased from 34.34%to24.88%,the yield of W-BC decreased from 32.43%to 22.76%,and the yield of P-BC decreased from 36.83%to 25.76%,and the content of C in biological carbon gradually increased,and the content of N,H and O decreased gradually.2.The structure and functional groups of biochar and modified carbons were characterized by SEM,FTIR and other instruments.SEM photos show that the surface of modified carbon is coarser and contains a lot of attachments.The functional groups of biochar before and after modification were basically the same,and the characteristic absorption peaks of Fe appeared,mainly Fe-OH and Fe-O.3.When the carbonization temperature is 500?,the adsorption capacity of three kinds of biological charcoal is the strongest,and iron carbon ratio of 0.7 is the best modification condition of corn straw and wheat straw biochar,and iron carbon ratio of 0.56 is the best modification condition of peanut shell biochar.4.The adsorption of nitrate nitrogen and phosphorus by biochar and modified charcoal is more consistent with the pseudo-second-order kinetics,the results showed that the adsorption of nitrogen and phosphorus by biochar and modified carbon was mainly chemical adsorption and physical adsorption was secondary.The adsorption characteristics of nitrate and phosphorus by biochar and modified carbon accord with the Langmuir adsorption equation,the theoretical maximum adsorption capacity of phosphorus for C-BC,W-BC and P-BC is 1.723 mg/g,1.660 mg/g,1.265 mg/g,the theoretical maximum adsorption amount of phosphorus for MC-BC,MW-BC and MP-BC is 16.062 mg/g,15.550 mg/g,12.133 mg/g.The maximum adsorption capacity of biochar after modification from adsorption of nitrate nitrogen to modified MC-BC,MW-BC,and MP-BC was 2.561 mg/g,2.414 mg/g,1.287 mg/g,respectively.5.In the leaching experiment,there was no significant difference in the content of nitrogen and phosphorus in the drenched solution treated by the blank group and the original powder separation layer of three materials,indicating that the adsorption capacity of the nitrogen and phosphorus nutrients in the powder isolation layer was weak.The content of ammonia nitrogen,nitrate nitrogen and phosphorus in the drenched solution treated with biological carbon and modified carbon were significantly reduced,and the biological carbon and modification of corn straw were changed.It is best to reduce the leaching effect of soil inorganic nitrogen and phosphorus.The leaching loss of C-BC and MC-BC nitrate nitrogen is reduced by 39.49%and 67.36%respectively,the leaching loss of phosphorus is significantly reduced by 66.05%and 83.40%,and the leaching loss of ammonia nitrogen is significantly reduced by 43.60%and 68.63%,respectively.