Effects Of Pineapple Residue-derived Biochar On Environmental Behavior Of Chlorpyrifos In Soil And Numerical Simulation

In this study,pineapple residue was chosen as the raw material to pyrolysis the three biochars(BL350,BL500 and BL650)at 350,500 and 650?,respectively.The chlorpyrifos removal efficiency in planting soil and biochar was studied by batch equilibrium adsorption experiments,and obtained relevant adsorption parameters.Moreover,the degradation process of chlorpyrifos in soil and biochar-added soil was studied by a culture experiment to obtain degradation parameters.Finally,the leaching experiment of chlorpyrifos in a one-dimensional soil column was investigated.The necessary parameters were obtained form these work for Hydrus-1D software to simulating and predicting the migration process of chlorpyrifos in nature soil.This study aimed to understand the removal effect of biochar adsorption chlorpyrifos in planting soil,and provide reference data and guidance for the pollution control.Main achievements were shown as follows:(1)With the increase of the pyrolysis temperatures,the yield was decreased and the ash content,surface area,specific surface area,total pore volume,pore volume and microporosity of the micropore of biochar was increased.The biochar had more adsorption sites and better removal efficiency to chlorpyrifos.(2)The adsorption kinetics of chlorpyrifos on biochar was firstly increases rapidly,and then increases slowly,finally reached the equilibrium.The kinetic data were best fitted to the pseudo second-order model.The isotherm data were well described by the Freundlich model and the Langmuir model.Increased external temperature was significantly increasing the adsorption of chlorpyrifos by biochar.It was a spontaneous and exothermic adsorption reaction.The main adsorption mechanisms of chlorpyrifos to biochar might be pore filling,hydrophobic interaction,?-? electron interaction,and ion exchange.(3)The adsorption kinetics of chlorpyrifos on biochar-added soil had three steps:firstly increases rapidly,and then increases slowly,finally reached the equilibrium.Biochars added into soils could improve adsorption ability for chlorpyrifos.With the increase of biochar preparation temperature and the content of biochar,the biochar-added soils had the higher adsorption capacity,showing in an order of 3%>1%>0.3>0%,and adsorption isotherms curves were more nonlinear than soil sample(CK).The isotherm data were well described by the Freundlich model,the Langmuir model and the Temkin model.The increase in external temperature could significantly increase the amount of biochar adsorbed.A thermodynamic study indicated that the adsorption of chlorpyrifos in biochar-added soils was spontaneous,exothermic and entropy increase reaction.It is beneficial to the adsorption reaction.(4)The half-life of chlorpyrifos in planting soil was 50.59 days.The application of biochar could affect the degradation of chlorpyrifos in soil,and the greater the input of biochars,the more significant the effect.Biochar that prepared at high temperature has a stronger adsorption capacity for chlorpyrifos,which inhibits the degradation process of chlorpyrifos in soil.(5)The result of leaching experiment was indicated that there was some asymmetry and tailing characteristics of the breakthrough curve of chlorpyrifos in the soil column.Adding bicohars could significant reduce the migration of chlorpyrifos in soil column.Application of Hydrus-1D software to the fitting of the breakthrough curves of Cl ions,chlorpyrifos in planting soil and biochar-added soil.The results show that the local equilibrium model(LEA)was well fitted the breakthrough curves.Adsorption effects were the main influence on outflow dynamics under the experimental conditions.