Study On The Degradation Of Drugs In Water By Iron-based Graphitized Biochar Heterogeneous Fenton Syste

Water environment pollution has become a prominent problem restricting the sustainable development of human beings,among which the new drug pollutants represented by antibiotics are frequently detected in the water environment,causing a great threat to the water ecology and human health.At present,new pharmaceutical pollutants mainly enter water bodies through pharmaceutical production wastewater,medical wastewater,domestic sewage,aquaculture wastewater,etc.Because drugs are difficult to degrade effectively in wastewater and water environment,coupled with their strong water solubility,long half-life and high biological toxicity,the pollution level of common drugs in water is always at a high level.Therefore,it is urgent to develop green and effective technologies to cope with drug pollution in water and provide theoretical basis and technical support for the efficient removal of drugs in water.Advanced oxidation process（AOP）is an effective method to remove the contamination of antibiotics and other drugs due to the formation of highly active free radicals（·OH）in situ.Heterogeneous Fenton can not only produce a variety of active species to effectively degrade organic pollutants in water,but also overcome the strong acidic p H conditions of traditional Fenton reaction,difficult recovery and utilization of catalysts,secondary pollution of metal precipitation and other problems.In heterogeneous Fenton reaction system,the preparation of highly efficient and stable catalyst is the key of system research.In this study,agricultural waste peanut shell was used as the precursor of biochar.Potassium ferrate（K₂Fe O₄）,a green water treatment agent,was used as the iron source.After mixing waste peanut shell with K₂Fe O₄,a one-step pyrolysis method was used to prepare iron-carrying graphitized biochar catalyst（PFGB）.The preparation conditions were optimized and the physicochemical properties of PFGB were characterized and analyzed by various means.The results showed that:（1）K₂Fe O₄ premodification can increase the oxygen-containing groups on the surface of biochar,and promote the graphitization and porosity of biochar.（2）The iron on PFGB mainly exists in the form of Fe⁰,which is to use the reducibility of biomass C at high temperature to reduce the iron on the load to Fe⁰ in a one-step pyrolysis process and bind it firmly and evenly on the surface of PFGB.Fe⁰ has very high catalytic oxidation performance.（3）PFGB has abundant pore structure and large specific surface area,which can provide more adsorption sites for pollutant removal.The Fe²⁺/Fe³⁺conversion rate is an important factor limiting the catalytic degradation efficiency.In order to further improve the performance,the transition metal Cu was introduced on this basis,which improved the iron valence cycle rate and the adsorption and catalytic degradation ability of the material.Bimetallic graphitized biochar catalyst（FCBC）carrying iron was prepared.The preparation conditions were optimized and the physicochemical properties of FCBC were characterized.The results show that:（1）FCBC has obvious graphitization,abundant pore structure and large specific surface area.Compared with PFGB,the mesopore volume of FCBC is relatively increased,which is conducive to the adsorption and removal of pollutants.（2）The four elements of carbon,oxygen,iron and copper are evenly distributed on the surface of FCBC,and there are abundant oxygen-containing groups.（3）Iron and copper in FCBC are mainly reduced to Fe⁰ and Cu⁰.On the one hand,Cu⁰ can be directly used as the active site to adsorb pollutants and activate H₂O₂ to degrade pollutants.On the other hand,it can accelerate the Fe²⁺/Fe³⁺cycle and promote the reaction.In order to further explore the ability of the two catalytic materials to degrade common drugs,PFGB-H₂O₂ and FCBC-H₂O₂ heterogeneous Fenton system was constructed to investigate the degradation effect and mechanism of tetracycline（TC）and acetaminophen（ACE）.The results showed that:（1）PFGB-H₂O₂ system can remove TC well,which is mainly due to the synergistic effect of Fe⁰,graphitized structure,porous structure and oxygen-containing groups in PFGB.·OH and ¹O₂ are the main active species of free radical and non-free radical pathways,respectively.（2）The PFGB-H₂O₂ system showed significant TC degradation ability in a wide range of p H（p H=2～6）.The degradation efficiency of TC increased with the increase of PFGB dosage,and reached the best when the concentration of H₂O₂ was 10 mmol/L.Under suitable conditions,the system can catalyze the degradation of 98%TC within 90min and adsorb the removal of 58.0%TC within 180min.（3）The FCBC-H₂O₂ system can efficiently degrade TC and ACE.FCBC has the highest efficiency and reaction rate（k=0.208）when the Fe-Cu doping ratio is 4:1,which is higher than that of PFGB system,which is related to the existence of bimetallic catalytic sites and synergistic effect.（4）The response surface optimization test shows that the regression polynomial can fit the removal process of TC and ACE in FCBC-H₂O₂ system well.The interaction of p H,FCBC dosage and H₂O₂ was significant,among which the effect of H₂O₂dosage was the most significant.The optimal reaction conditions were as follows:p H=3.1,FCBC dosage=0.71g/L,H₂O₂ dosage=10.2m M.The catalytic degradation of 98%TC and 97 ACE was achieved within 90min.（5）Compared with PFGB,FCBC can further expand the p H application range,and has a higher removal effect（more than 85%）at 2～6 hours,realizing the effective degradation of pollutants under neutral conditions.（6）Both systems have high reusability and stability.The PFGB five times reuse efficiency remained above 90%,and the iron leaching was stable in the range of p H=3～8.The pentatric utilization rate of FCBC was further improved.When p H was 3～6,the iron leaching was significantly lower than PFGB,and the copper leaching was stable in the range of 0.86～1.88 mg/L,which both met the requirements of Grade A of GB/T 31962-2015 standard.The FCBC system has a good degradation effect on many drugs,and the removal rate of NOR is close to 100%.The system shows good resistance to the complex components in the actual water body and has strong practical application potential.