Application Of Biochar Prepared From Rape Straw For Pesticide Loading-release

Straw is a common biomass resource in nature and often burned as waste directly or discarded,which will cause waste of resources and environmental pollution.Now,slow release pesticide often present drug dispersion unevenness,low drug loading,burst release,high cost.In this thesis,biochar?PRS-BC?prepared from rape straw and activated with H₃PO₄,the price was low and the performance was excellent,then the above problems could be solved well.The PRS-BC was used as drug carrier,carbendazim fungicide and herbicide pyrazosulfuron were used as sustained release drug,We studied the load-release propertiesof pesticides on PRS-BC and field release effect of biochar.The main contents and results are as follows:?1?N₂ adsorption and desorption isotherm,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,Fourier transform infrared spectroscopy?FTIR?,elements analysis,and thermogravimetric analysis?TG?were used to characterize the PRS-BC.With the temperature increase,the moisture content of PRS-BC was gradually reduced,but the ash content,aromaticity,specific surface area and total pores volume were gradually increased.The average pore size was greater than 2 nm,which indicated that the biochars were mesoporous materials.?2?When the concentration of phosphoric acid was 10% and the pyrolysis temperature was 600?,the biochar was marked as 10PRS-BC600.The amount of carbendazim adsorption on 10PRS-BC600 was the highest one,and the amount was249 times of that on rape straw.The adsorption behavior could be well described as the pseudo-second-order kinetics model and the Langmuir isotherm model.Thermodynamics parameters indicated that the adsorption process was spontaneous,exothermic and mainly physical adsorption process,and the adsorption equilibrium was achieved within 6 h for 10PRS-BC600.The rotational speed and surface functional groups played a certain role in the adsorption process,the effect of ionic strength and pH on the adsorption were not significant.When mentioned the carbendazim sustained release on biochar,we found that organic species,content and the ratio of ethanol/PBS had an obvious effect on the carbendazim release,themaximum release rate was 73%.When ethanol:PBS ratio was 6:4,the cumulative release of carbendazim was 62%.The higuchi model was more suitable for the release process and its R2=0.9570,so the release mechanism belonged to Fick diffusion.The release mechanism of 10PRS-BC600 as carrier to carbendazim was mainly diffusion process.?3?When the concentration of phosphoric acid was 20% and the pyrolysis temperature was 400?,the adsorption amount of pyrazosulfuron was the highest and was more than 105 times than that of rape straw.The adsorption behavior could be well represented as the pseudo-second-order kinetics model and the Langmuir isotherm model,the thermodynamics parameters indicated that the adsorption process was spontaneous,exothermic and mainly physical adsorption process,the adsorption equilibrium was achieved within 6 h for 20PRS-BC400,and the shaker speed,pH and surface functional groups played a role in the adsorption process,the effect of ionic strength is weak.In the study of pyrazosulfuron sustained release,we found that the ratio of ethanol/PBS had an effect on the release of pyrazosulfuron,the maximum release rate was 54%.When ethanol:PBS ratio was 3:7,the cumulative release of pyrazosulfuron was 42%.The higuchi model was more suitable for the release process and its R2=0.9798,so the release mechanism belongs to Fick diffusion.The release mechanism of 20PRS-BC400 as carrier to pyrazosulfuron was mainly diffusion process.?4?Compared to the control sample,the biochar-loaded pesticides could release carbendazim,avoid interference from bacteria and promote rape growth in the field slow release experiment.The results showed that carbendazim/PRS-BC had sustained-release effect,and 10PRS-BC600 had the most obvious effect on the promotion of rape.The experimental results were consistent with the adsorption experiment.