Preparation Of Poplar Leaf-based Biochar And Its Adsorption Performance

The high consumption of organic dyes in the production of leather,food,paints and fabrics causes excessive dye emissions that seriously degrade the environment and ecosystems.One of the more representative organic dyes is methylene blue(MB),which can cause serious harm to humans as well as aquatic plants and animals through long-term exposure.Antibiotics are widely used to treat human and animal diseases,and norfloxacin(NOR)is widely used because of its amphoteric structure.The presence of NOR in water bodies enhances bacterial resistance and threatens human and animal health.Therefore,efficient removal of MB as well as NOR wastewater is urgent.Biochar,a widely available raw material with low cost and good adsorption properties,is used for the removal of harmful toxic substances from water bodies.Most of the current research has been on the treatment of wastewater by de-oxidation of sodium hypochlorite(NaClO)itself.Combining biomass carbon with NaClO improves both the utilisation of the active ingredients of NaClO and the adsorption properties of biochar for pollutants.Magnetic nanoparticles have both the advantages of nanoparticles and superb magnetic properties.Combining biomass char with magnetic nanoparticles can achieve both efficient adsorption performance and better magnetic properties for later recycling.In this thesis,poplar leaf biomass carbon(PLBC)was used and modified with NaClO and Fe Co nanoparticles to prepare two biochar with good performance.The main studies and conclusions are as follows:(1)Poplar leaf-based biochar modified by the sodium hypochlorite solution(NaClO-PLBC)was prepared and utilized to improve the removal efficiency of MB.The structure and morphology of the material are systematically characterized by XPS,XRD,SEM,FT-IR,TEM,and et al.In addition,the effects of adsorption time,temperature,adsorbent dosage,initial MB concentration,cation species,and intensity on the adsorption of MB by NaClO-PLBC were also studied.In order to explore the mechanism of MB adsorption,the isotherms,kinetics,and thermodynamics of its adsorption were explored.The results show that when the modification temperature of sodium hypochlorite is 85°C,the modification time is 4 h,and the mass fraction of NaClO is 60%,the adsorption capacity of MB reaches the maximum.Moreover,the number of oxygencontaining functional groups after modification increases,and the adsorption performance is also improved.At a temperature of 40 °C,a time of 60 min,an adsorbent dose of 60 mg,and an initial concentration of MB of 200 mg/L,the adsorption amount of MB can reach 229.12 mg/g.Langmuir and Pseudo-second-order kinetic model models are more suitable for fitting the adsorption process,indicating that the adsorption is mainly based on a single-molecule layer and chemical adsorption,and the maximum adsorption amount of MB obtained by Langmuir is 244.34 mg/g,and Freundlich obtains adsorption as favorable adsorption.Thermodynamic results show that the adsorption process is spontaneous,endothermic,and random.The results show that NaClO-PLBC exhibits good adsorption efficiency and high practical applicability.(2)Magnetic poplar leaf-based biochar(Fe Co-BC)was prepared and utilized for the first time to improve the removal efficiency of NOR.The structure and morphology of the material are systematically characterized by XPS,SEM,EDS,TEM,XRD and et al.In addition,the effects of adsorption time,temperature,adsorbent dosage,initial NOR concentration,p H value,and ionic strength on Fe Co-BC adsorption NOR were also investigated.To understand the adsorption mechanism,the adsorption isotherm,kinetic and thermodynamic parameters were explored.The results show that when the carbonization temperature reaches 600°C,Fe CoBC has the most efficient adsorption capacity.The adsorption performance of NOR is optimal at a temperature of 40°C,a time of 240 min,an adsorbent dose of 80 mg,and an initial concentration of NOR of 70 mg/L.In addition,nor adsorption has the best fit with Langmuir and Temkin isotherms models,which indicates that NOR’s adsorption on Fe Co-BC is monolayer,and physical adsorption plays a certain role in adsorption.The Freundlich model shows that adsorption is a favorable process.The adsorption process and Pseudo-second-order kinetic model fitting results are good,indicating that the adsorption process involves chemical adsorption.Thermodynamic results show that the adsorption process of Fe Co-BC for NOR is spontaneous,endothermic,and random.The results show that Fe Co-BC exhibits good adsorption efficiency and can be used to treat wastewater containing NOR.