Study On Removal And Mechanism Of Typical Organic Pollutants In Water By Biochar Based Nanocomposites

The hazards and treatment of organic pollutants in water bodies have become a hot spot of global concern.In this paper,the treatment of two kinds of typical organic pollutants?dyes and antibiotics?in water was studied.Different nanomaterials were successfully loaded onto biochar by different methods,and a series of biochar-based nanocomposites were prepared,which could effectively enhance the ability of biochar to remove dyes and antibiotics from water.In this paper,the basic properties of biochar-based nanocomposites were analyzed.The effects of biochar-based nanocomposites on the removal of dyes and antibiotics in water were investigated.The influencing factors in the removal process were studied,and the removal mechanisms of dyes and antibiotics in water by biochar-based nanocomposites were discussed.The research results of this thesis can provide a theoretical basis for the preparation of biochar based nanocomposites and the removal of typical organic pollutants in water.A novel biochar/MgAl hydrotalcite composite?CB-LDH?was synthesized by pyrolysis of magnesium aluminum hydrotalcite pretreated biomass,and the material was applied for the removal of crystal violet in water.During the preparation process,pyrolysis played two roles:conversion of biomass to biochar and calcination of MgAl hydrotalcite.Various characterization analyses indicated that the calcined hydrotalcite was successfully synthesized and coated onto the surface of the biochar.The synthesized CB-LDH had a higher pore volume and more functional groups than the original biochar.The adsorption experimental data was well fitted to the pseudo-second-order kinetic model and the Freundlich isotherm model.Thermodynamic analysis indicated that the adsorption of crystal violet was a spontaneous and endothermic process.Higher pH and temperature contributed to the improved adsorption performance of CB-LDH.CB-LDH also had the ability to remove crystal violet from actual wastewater containing high ionic strength.Hydrotalcite,electrostatic attraction,pore filling,?-?interaction and hydrogen bonding might be the main mechanism of crystal violet adsorption on CB-LDH.The results of this study indicate that CB-LDH is a highly efficient adsorbent for the treatment of crystal violet contaminated wastewater.TiO₂ was successfully loaded onto biochar substrate using a modified sol-gel process.The prepared composite material had very good adsorption and photocatalytic properties,and could effectively remove organic pollutants in the aqueous solution.SEM and XRD studies showed that the surface of the material contained crystallites and hydroxyl groups,which were beneficial to the adsorption and photocatalytic activity of the Safranine T?ST?removal process.Both adsorption and photocatalytic degradation were involved in the removal process of ST,in which the adsorption was slightly stronger.This study compared the ST removal efficiency of four TiO₂-loaded biochars.The TBC-2 sample synthesized using 2 g of biomass powder had the highest removal efficiency with an ST removal ability of 226.7 mg?g^-1.TBC-2 had good stability and activity under different pH conditions.Due to the synergistic effect of TiO₂ and biochar,TBC-2 can be used as a highly efficient material for the removal of organic pollutants in water.The modification of biochar by chitosan and BiFeO₃ effectively combined the advantages of both chitosan and biochar adsorbent materials.The composite had magnetic and high-efficiency adsorption,and was easy to collect and recycle during the adsorption process.The adsorption amount of methylene blue by BiFeO₃/biochar magnetic material increased with the increase of initial concentration of methylene blue,reaction temperature and adsorption reaction time,and the adsorption effect was better under neutral and alkaline conditions.The adsorption of methylene blue by BiFeO₃/biochar magnetic materials conformed to the pseudo-first-order kinetic model and the Langmuir adsorption isotherm model.The adsorption of methylene blue by BiFeO₃/biochar magnetic materials included both chemical adsorption and physical adsorption.The BiFeO₃/biochar magnetic material had good adsorption capacity for methylene blue,and its maximum adsorption capacity could reach 18.942 mg?g^-1 at298 K.Biochar composites loaded with calcined Mg/Al LDHs?CLDHs/BC?were synthesized by slow pyrolysis of LDHs pretreated bagasse biomass.The characterization results of the materials showed that the calcined Mg/Al LDHs?CLDHs?were successfully loaded on the biochar during the slow pyrolysis of the pretreated biomass.Synthetic CLDHs/BC was highly effective in removing tetracycline antibiotics from aqueous solutions.The loading of CLDHs significantly improved the adsorption capacity of biochar.In the tested pH range,the adsorption capacity of CLDHs/BC was more than twice that of the original biochar?BC?.At 318K,the maximum adsorption capacity of CLDHs/BC for tetracycline antibiotics was1118.12 mg?g^-1.The experimental results showed that the interaction between biochar and LDHs played a leading role in the adsorption of tetracyclines.?–?interactions and hydrogen bonding were involed in the adsorption process.This study provides a feasible and simple method for preparing high-performance material for the efficient treatment of antibiotic-contaminated wastewater.Using chaff as a raw material,manganese dioxide was successfully loaded onto biochar to obtain a biochar-supported manganese dioxide composite?BC/MnO₂?.Compared with the original biochar,MnO₂ nano-particleswas present on the surface of BC/MnO₂,the content of carbon was decreased,and the oxygen content was increased.BC/MnO₂ had a significantly larger total pore volume and specific surface area,indicating that the pore structure of the biochar was improved.The pH value had little effect on the adsorption of tetracycline hydrochloride?TC?and doxycycline?DC?by BC/MnO2.Adsorption of TC and DC by BC/MnO2 could be well described by the Freundlich adsorption model.Compared with the pseudo-first-order kinetic model,the BC/MnO₂ adsorption TC and DC data was better fitted to the pseudo-second-order kinetic model?R²=0.999?,indicating that the process of controlling TC and DC adsorption by BC/MnO₂ might be chemical adsorption.