Preparation Of Peony Pod-based Porous Carbon Materials For The Adsorption Of Tetracycline In Water

In recent years,the rapid expansion of biomass waste has caused serious environmental pollution.Under the background of the promotion and implementation of the national ecological civilization construction and rural revitalization strategy,the recycling and utilization of biomass waste has become the focus of contemporary scientific research,and is also one of the needs to help achieve the goal of carbon neutrality.The oil peony mainly refers to the peony plants that produce more than 22%of the oil.The peony seed oil produced from it is rich in unsaturated fatty acids and has high nutritional value.At the same time,its by-product,the peony pod,has become a type of biomass waste that is too hard to be effectively handled,which has brought hidden dangers to environmental health.However,the peony pod itself has rich carbon content,which can be used as an ideal carbon source to realize full resource utilization,and its conversion into solid carbon resources can alleviate carbon emission pollution to a certain extent,which is of great significance for alleviating energy crisis and environmental pollution.As a carbonaceous material,porous carbon typically has a large surface area and ordered nanostructures.It is widely used and has excellent performance.It is often used to build carriers of adsorption materials,while biomass waste can be used for the construction of porous carbon materials.Therefore,it is in line with the development concept of green and environmental protection to build porous carbon materials with the waste of peony pods with abundant reserves and extremely low cost as the carbon source.In this paper,peony pods will be used as carbon precursors to prepare porous carbon materials with outstanding characters,which will be used in the adsorption research of tetracycline（TC）in water.On the basis of implementing the win-win idea of"making waste from waste"and"turning waste into treasure",the relatively cheap urea and steel slag waste will be used as N and Fe sources to doped and modify the carbon materials to obtain peony pod-based porous carbon materials with excellent adsorption performance.The structure,adsorption properties and mechanism of the materials were researched by different characterization methods and adsorption experimental models.The concrete work and conclusions of this paper are as belows:（1）Peony pod-based porous carbon materials with well-developed pore structure were prepared by one-step activation with biomass waste Peony pods as carbon source and KHCO₃as activator.By adjusting the activation temperature and the mass ratio of peony pods to KHCO₃,the optimal product PC-800-3 was obtained,which was larger than the specific surface area of PC directly pyrolysis(1066.88 m²?g^-1 and 17.48 m²?g^-1,respectively).At 298 K,the maximum adsorption capacity of 100 mg·L^-1 TC solution is 394.3 mg·g^-1.The characterization results showed that the addition of activator promoted the formation of micropores and mesopores in porous carbon.In the adsorption tests,the Langmuir model and the pseudo-second order kinetic model were declared to be more consistent with the adsorption process.At the same time,The thermodynamic experiments affirmed that the adsorption was a spontaneous endothermic process,dominated by the physical adsorption of single molecular layer,and there was an electrostatic interaction.In a wide p H range and under ion interference,the adsorption performance is good.The regeneration experiment shows that PC-800-3 has good regeneration performance,and retains good removal effect after 4 cycles.（2）In order to further improve the adsorption performance of peony pod-based porous carbon on TC,on the basis of the preparation in the previous chapter,cheap urea was added as the N source,and through one-step thermal activation,the N-doped peony pod-based porous carbon material PC_N-2 was successfully prepared by adjusting the doping ratio of peony pods/cheap urea,showing excellent adsorption capacity for TC in water.The specific surface area of PC_N-2 is 2641.37 m²?g^-1,and the total pore volume is 1.297 cm³?g^-1.At 298 K,the maximum adsorption capacity of 100 mg·L^-1 TC solution is 905.1 mg·g^-1.The adsorption experiment shows that the adsorption behavior is more consistent with Langmuir isothermal and pseudo-second-order model,and the process of TC removal is mainly physical adsorption.At the same time,the thermodynamic results show that adsorption is a spontaneous endothermic process and retains excellent TC adsorption capacity under the interference of a wide range of p H solution and metal ions.After four cycles of regeneration experiments,it still has 74%of the original adsorption capacity,reflecting the improvement effect of adding cheap urea on porous carbon,and is a promising adsorbent.（3）Steel slag（SS）waste is facing the problem of large output and low utilization rate.In order to utilize it as a resource,on the basis of the previous two chapters,PC_N-2 is doped and modified with Fe by adding SS as an Fe source to endow carbon materials with magnetic recovery performance.The Fe/N doped peony pod-based porous carbon material with excellent magnetic separation and adsorption properties was successfully prepared by adjusting the mass ratio of peony pods to steel slag by one-step activation method.The best product was PC_N,Fe-0.5,with 1579.26 m²?g^-1specific surface area and average pore size 2.4 nm,which realizes the efficient removal of TC in water.At 298 K,the maximum adsorption capacity of 100 mg·L^-1TC solution was 720.5 mg·g^-1.The characterization results show that the Fe nanoparticles attached to the material surface are Fe₃O₄,and the porous carbon has a certain graphitization structure.The adsorption process accords with Langmuir and pseudo-second-order model.At the same time,thermodynamics displays that adsorption is a spontaneous endothermic process,mainly pore filling,and there are adsorption behaviors such asπ-πEDA interaction and electrostatic attraction.Under the interference of a wide range of p H and different metal ions,it shows certain stability and maintains the efficient adsorption of TC.In the four recycling experiments,82%of the adsorption capacity was retained.Therefore,the introduction of steel slag waste not only brought good magnetic recovery performance,but also implemented the idea of"turning waste into treasure",providing ideas for further application in the future.