Synthesis Of Alkali(Earth) Metal Doped Boron Nitride Nanosheets And Their Application In Adsorptive Separation Of Antibiotics From Water

With the development of pharmaceutical and chemical industry,the discharge and treatment of pharmaceutical wastewater has gradually become the focus of social attention.Traditional wastewater treatment technology is difficult to effectively removal antibiotics from pharmaceutical wastewater,which leads to a large number of antibiotic residues detected in lakes,rivers and other water bodies around the world,even in daily drinking water.Residual antibiotics continue to accumulate in the natural ecosystem,and the phenomenon of microbial drug resistance is becoming more and more serious,which seriously threatens the balance of ecosystem and human health.For the effective treatment of antibiotics in pharmaceutical wastewater,adsorption is considered as one of the most promising technologies due to its advantages of environmental protection,low price,no secondary pollution and simple operation.In recent years,the research and development of high-efficiency adsorbents has become a research hot-spot.In this paper,a series of metal-doped boron nitride（BN）-based nano-adsorbents were synthesized by pyrolytic method by introducing different alkali（earth）metals,and they were used to study the adsorption and separation of antibiotics in pharmaceutical wastewater.SEM,FT-IR,XPS,TEM,N₂ adsorption-desorption curves were used to analyze the material structure and the physical and chemical properties.The mechanism of adsorption process was discussed through optimizing conditions of adsorption,kinetics,thermodynamics and isotherm properties.Finally,through the recycling experiment to investigate the stability of the boron nitride nanotubes adsorbent.1.A new method for the synthesis of alkali sodium doped boron nitride（Na-BN）nanosheets by one-step pyrolysis was established by introducing alkali metal sodium sources with different molar ratios in situ.The synthesis of thin layer BN nanosheets and doping of Na metal active sites were realized simultaneously by high temperature pyrolysis.Through the screening of sodium source and dosage,the removal rate of tetracycline TC in water by in-situ synthesis of Na-BN with the introduction of 0.075mol Na₂CO₃ was increased by 29.78%compared with that by BN.The equilibrium adsorption capacity of ciprofloxacin CIP was as high as 211 mg/g.The adsorption process follows the pseudo-second-order kinetic model and Freundlich isotherm model.The main adsorption forces areπ-πhydrophobic interaction and electrostatic interaction.The experimental results of 6 adsorption-desorption-adsorption cycles show that Na-BN has good cyclic stability.2.A new method for the synthesis of alkaline earth metal calcium doped boron nitride nanosheets（Ca-BN）by one-step pyrolysis was established by introducing alkaline earth metal calcium sources with different molar ratios in situ.The preparation of thin BN nanosheets and the doping of Ca active sites were completed simultaneously during the pyrolysis process.The removal rate of TC in water by Ca-BN was 34.47%higher than that by BN.The equilibrium adsorption capacity of Ca-BN for TC was 346mg/g,and the adsorption kinetics followed the pseudo-second-order model.The fitting degree of adsorption isotherm model was Freundlich>Tempkin>Langmuir>D-R.The adsorption process is spontaneous heat absorption.In addition toπ-πhydrophobic interaction and electrostatic interaction,the cationic bridge between alkaline earth metal calcium and TC plays a key role in the significant improvement of adsorption performance.The experimental results of 6 cycles show that the Ca-BN cycle has good stability.3.Using sodium methylcellulose as carbon source,a new method of one-step pyrolysis synthesis of alkali（earth）bimetallic sodium/magnesium doped thin layer boron carbon nitrogen nano-adsorbent（Na/Mg-BCN）was established by introducing alkaline earth metal magnesium source with different molar ratio in situ.Through the selection of carbon and magnesium content,the removal rate of TC in water by Na/Mg-BCN synthesized by 0.5 g CMC-Na and 0.15 mol Mg CO₃ in situ is 41.13%higher than that by BN.The equilibrium adsorption capacity of CIP was 964.38 mg/g,and the adsorption kinetics followed the quasi second order model.The order of fitting degree of adsorption isotherm model was Freundlich>Tempkin≈Langmuir>D-R.The adsorption was mainly multi-layer adsorption on heterogeneous solid surface,and the adsorption process was self exothermic.The main adsorption forces areπ-πinteraction,metal-πcomplexation,hydrophobic interaction and electrostatic interaction.The stability of Na/Mg-BCN is good,and the removal rate of CIP remains at 97.4%after six cycles of regeneration.