Rentention And Leaching Of N And P In Water Or Soils With The Addition Of Biochar Prepared With The Optimized Methods

Excessive intake of nutrients such as nitrogen and phosphorus will cause eutrophication of the water and seriously damage the ecological balance of the aquatic environment.Unreasonable application of chemical fertilizers and pesticides would cause a series of problems such as soil compaction and soil acidification,resulting in soil fertility.Decrease,nutrients such as nitrogen and phosphorus were more likely to enter the water through leaching.Therefore,removing excessive nitrogen and phosphorus in water and reducing the loss of nitrogen and phosphorus in the soil were great significance for the restoration of China’s agricultural ecological environment.Biochar as an environmental repair material which can adsorbed water pollutants and improve the soil quality,but due to the restrict with itself identity,there were more and more researches focus on changing and developing on biological carbon,which in order to dug out the applicational potential from the biological carbon,and that would also increase their economic profit.In this research,rice straw,bagasse,peanut shells,and garden waste were used as raw materials.Through different pyrolysis temperatures and pyrolysis times,biochar raw materials with good adsorption effect on nitrogen and phosphorus in water and their preparation conditions were selected.On this basis,Through the treatment of raw materials and biochar by 1mol·L^-1 Ca Cl₂,Fe Cl₃,KOH solution,respectively,to prepare modified biochar,and then focus on the research of modified biochar adsorption characteristics and influenced factors of nitrogen and phosphorus in water.Column leaching test to observe the effect of modified biochar on the leaching of nitrogen and phosphorus nutrients in soil.The mainly research result as below:（1）36 kinds of bio char were prepared from rice straw,bagasse,peanut shell and garden waste set by three kinds of pyrolysis temperature（400℃,500℃,600℃）and three kinds of pyrolysis time（1h,2h,3h）.The results showed that When the temperature got higher,it would reduce the yield of biochar,but would advance p H,change the time of produce it would not influence PH.Through the preliminary screening,we determined that the bagasse biochar（B-BC）and peanut shell biochar（P-BC）were modified with 1mol·L^-1 Ca Cl₂,Fe Cl₃,KOH.Each modification method was divided into the modification before the preparation of biochar,the modification at room temperature after the preparation and the activation modification at high temperature after the preparation according to the modification steps 18kinds of modified biochar were screened for the second time.They were bagasse biochar modified at room temperature（P-BC2-400K）after 400℃-2h-KOH and peanut shell biochar were modified at room temperature（B-BC2-400K）after 400℃-2h-KOH.The best modification conditions were modification after KOH.（2）The elemental composition,structure,functional group and specific surface area of B-BC2-400K and P-BC2-400K before and after modification were characterized by SEM,FTIR and BET.It was found that after modification,Bagasse biochar superficial area become much bigger,and increase electric supply regions on the surface,but reduce diameter,so it could enhance the adsorption ability of nitrogen and phosphorus;Peanut shell biochar superficial area become much smaller,but surface structure being destroy and become chaos,but increase the active site so could enhance the adsorption ability of nitrogen and phosphorus.（3）The adsorption kinetics of nitrogen and phosphorus by B-BC2-400K and P-BC2-400K followed to pseudo-second-order model,indicating that chemical adsorption is the main adsorption method of modified carbon for nitrogen and phosphorus.The experimental data of the isotherm adsorption of nitrogen and phosphorus by two kinds of modified biochar were well described by the Langmuir model,prove that the adsorption of nitrogen and phosphorus was monolayer adsorption.The maximum adsorption capacity of B-BC2-400K and P-BC2-400K to ammonium nitrogen was 2.877 mg·g^-1,2.140 mg·g^-1,B-BC2-400K and P-BC2-400K to phosphorus was 1.766 mg·g^-1,2.864 mg·g^-1.（4）After mixed the modified biochar with soil,the leaching results of soil column showed that:adding original biochar and modified biochar to the soil could slow down the leaching loss of nitrogen and phosphorus nutrients,but adding the same proportion of modified biochar could significantly and efficiently slow down the loss of nitrogen and phosphorus compared with the original biochar.With the increase of the added amount,the leaching effect was weaker.When the mixed proportion of B-BC2-400K in the soil was 9%,the leaching amount of N and P decreased by89.5%and 89.0%;when the mixed proportion of P-BC2-400K in the soil was 9%,the leaching amount of N and P decreased by 80.6%and 80.9%.