Preparation Of Biochar-based Nano-composites And Their Applied Research

In this paper,iron salt modified biochar and carbon nanotube modified biochar were prepared by simple and novel one-step pyrolysis method,and used for the treatment of nitrobenzene wastewater.These two composite materials combine the advantages of both biochar and nanomaterials.The structural properties of the two composites were analyzed by elemental analysis,nitrogen adsorption desorption,thermogravimetry,Raman spectroscopy,FTIR,XRD and SEM.The paper focuses on the effects of pyrolysis temperature for the structural properties of biochar and iron salt modified biochar materials and the removal mechanism of nitrobenzene.The removal process of nitrobenzene was investigated by various kinetic models and isothermal adsorption models.The paper first studied the effect of pyrolysis temperature on the structural properties of biochar materials and iron salt modified biochar materials.Research results show: The increase of pyrolysis temperature can increase the specific surface area of biochar and iron salt modified biochar.When the temperature rises to 600°C,the specific surface area reaches the maximum value,and the temperature rise continues to decrease the specific surface area;However,the specific surface area of iron salt modified biochar(Fe/BC-800)prepared at 800°C is much larger than that of unmodified biochar,and the nano-zero-valent iron particles can be successfully generated in situ on biochar,the diameter is about 100 nm,these two reasons can make the removal capacity of Fe/BC-800 up to 134.8 mg/g.The mechanism of removal of nitrobenzene by Fe/BC-800 was studied by UV spectroscopy,liquid chromatography,mass spectrometry,mass balance and XPS.Research shows: Nitrobenzene is first adsorbed on the surface of Fe/BC-800 material and then reduced to aniline by nano-zero-valent iron.It is a synergistic process of adsorption and reduction,and the adsorption rate is higher than the reduction rate.Subsequently,the paper investigated the effects of iron salt doping amount,material dosage and solution pH on the removal of nitrobenzene by Fe/BC-800.The results show that the doping amount of iron salt is not as large as possible,and there is a suitable ratio;increasing the dosage of the material and lowering the pH of the solution can improve the efficiency of Fe/BC-800 for removing nitrobenzene.Finally,in order to further enhance the adsorption capacity of biochar,carbon nanotube doping modification was also studied for biochar.Research shows: The increase of the doping amount of carbon nanotubes can increase the carbon content,specific surface area and thermal stability of the composite,reduce the Zate potential,and increase the adsorption capacity of nitrobenzene;the adsorption kinetics process has the highest fitting degree of pseudo second order kinetics.The adsorption isotherm experiments show that the adsorption of nitrobenzene on carbon nanotube modified biochar composites is consistent with the Langmuir model,and the adsorption process belongs to single layer adsorption.