Preparation,Modification And The Application Of Typical Organic Pollutants Removal Of Biochar

Phenolic compounds are common pollutants in wastewater,which are harmful to the environment and human health.Biochar is often used as an adsorbent due to its abundant microporous and active surface,but the variety of raw materials,preparation conditions and other factors limit its application in the removal of organic pollutants.This paper focuses on the problems in the biochar preparation and its removel of phenolic pollutants in water.Five pine sawdust biochar were prepared at different pyrolysis temperatures?300?⁷00??.By scanning electron microscope?SEM?,X-ray diffraction?XRD?,Fourier transform infrared spectrometer?FTIR?,elemental analyzer,specific surface area and porosity analyzer?BET?,Zeta potential analyzer and other technologies,the structure,functional groups,element composition,surface potential,specific surface area and pore properties of biochar have been characterized.The effect of adsorption environment on the adsorption characteristics of phenol and p-nitrophenol on five biochar was investigated through intermittent experiments,and the adsorption mechanism was analyzed from the adsorption kinetics,adsorption isotherm and thermodynamics.The low adsorption amount of biochar was improved.The main research contents and conclusions are as follows:?1?pyrolysis temperature influenced the physical and chemical properties of pine sawdust biochar significantly.With the increase of pyrolysis temperature,the structure of pine sawdust biochar became more complex,the specific surface area increased,and the pores size decreased.At higher pyrolysis temperature,yield and surface functional groups of biochar decreased,pH value and graphite crystal structure increased,and conductivity increased.The ratio of H/C and O/C were gradually reduced which mean the aromaticity and hydrophobicity enhanced.The biochar produced at high pyrolysis temperature was improved the stability and it has better carbon storage capacity and was difficult to biodegraded.?2?The adsorption amount of p-nitrophenol on pine sawdust biochar was observably affected by alkaline conditions.The pseudo-second-order kinetics and Temkin isothermal models can describe the adsorption of p-nitrophenol on PC300 and PC400,while the PC500,PC600 and PC700 are consistent with Elovich kinetics and Freundlich isotherm models.The adsorption capacity was PC700>PC600>PC500>PC400>PC300 when the adsorption equilibrium was reached.The maximum adsorption amount of p-nitrophenol on PC700 at35?was 117.165 mg/g The adsorption mechanism includes physical adsorption and chemical adsorption.The adsorption of p-nitrophenol on PC300 and PC400 is mainly affected by electrostatic interaction,while the adsorption on PC500,PC600 and PC700 is dominated by hydrogen bond and?-?interaction.The adsorption rate is mainly restricted by film diffusion and intra-particle diffusion.?3?There was inhibitory effect of NH₄Cl and NaNO₃ on the phenol adsorption on pine sawdust,while the promoting effect NaCl had,but the effect did not changed significantly with the increase of ion concentration.The adsorption of phenol on biochar was unaffected by the solution pH?<10?.The removal rate of phenol by PC500,PC600 and PC700 reached more than 70%of that at adsorption equilibrium at first 30 minutes The pseudo-second-order kinetics model was more suitable to describe the adsorption process of phenol on pine sawdust biochar.Langmuir isotherm model was more suitable to describe the adsorption of phenol on PC300 and PC400,while PC500,PC600 and PC700 were more consistent with Temkin isotherm model.The thermodynamic analysis result shows that the reaction between p-nitrophenol and biochar to be spontaneous and endothermic.?4?The surface structure of MC300 was more porous,the surface area increased by421.02%,the pore volume increased by 290%.The maximum adsorption amount of p-nitrophenol on MC300 was 109.294 mg/g,which was significantly higher than PC300?29.165 mg/g?,and the removal rate increased by 274.7%.The adsorption of phenol on MC300 occurred rapidly at first 60 minutes and reached 79%of the total adsorption amount.The adsorption of phenol and p-nitrophenol on PC300,DC300 and MC300 was more consistent with the pseudo-second-order kinetics model and Langmuir isotherm model.The improvement of adsorption performance of MC300 was due to its increased surface area and oxygen-containing functional groups which provided more adsorption sites.