Controllable Preparation Of Magnetic Carbon Microspheres And Studies On Its Adsorption Properties

In China,the overuse of antibiotics has led to serious antibiotic contamination,especially water pollution.In terms of adsorption method,carbon material is commonly used with its good chemical stability and good biocompatibility.Especially,the spherical carbon microspheres exhibit many advantages such as high hardness and good stackability,thus having high application potential.At present,the popular carbon microsphere carbon source materials mainly include new types of carbohydrates and resins.However,in terms of applications,carbon microspheres face difficulties in separation afterwards.And the use of filtration or centrifugation methods would result in low efficiency and complicated operation.Therefore,a method of combining magnetic particles with carbon microspheres has been obtained.Because magnetic carbon composite particles are easy to achieve non-contact separation using a magnetic field.However,unmodified carbon microspheres themselves have a small specific surface area and a small pore volume,which limits the application of carbon microspheres in practical processes.Therefore,the step of modifying the carbon layer outside is indispensable.This study aims to synthesize magnetic carbon composite particles,which can be widely used in the field of adsorption.The research ideas are to select carbon source materials and better process conditions,optimize the synthesis process of magnetic carbon composite particles,and modify carbon layers outside.Firstly,a process for synthesizing carbon microspheres using glucose or resorcinol-formaldehyde resin(RF)as carbon sources was studied.For the preparation process of glucose hydrothermal carbonization,it is proved that the additives trisodium citrate or Fe3O4 both catalyzed the hydrothermal carbonization process of glucose,which marked by the particle size increase of the carbon sphere from 80 nm to 270 nm or 950 nm and the yield increase by 4.2 and 4.9 times,respectively.It turns out to improve carbon utilization effectively.Meanwhile,for the synthesis of resorcinol-formaldehyde resin-based carbon spheres,the synthesis temperature has little effect on the particle diameter of the resin sphere.However,the resin microspheres obtained at 40? are more uniform than that obtained at 20? and have less surface adhesion.Secondly,the synthesis of magnetic carbon microspheres was studied.In order to obtain core-shell structured magnetic carbon microspheres with complete coating and uniform particle size,the key is to obtain Fe3O4 magnetic core with good dispersion performance and uniform particle size.This study chose to add a dispersant during the solvothermal process of synthesizing magnetic particles.The best dispersant,poly(4-styrenesulfonic acid-co-maleic acid)sodium salt(PSSMA),was screened out among three dispersants and its amount was optimized.The formula for the solvothermal synthesis of magnetic particles was finally determined to be 0.68 g of ferric chloride hexahydrate,20 g of ethylene glycol,1.2 g of sodium acetate,0.3 g of PSSMA,and kept at 200 ? for 10 h.Then,the obtained magnetic particles were used as a core material coated with a later carbon layer.The thickness of the carbon precursor RF shell,which ranges from 30 to 120 nm,can be easily controlled by the amount of resorcinol and formaldehyde solution.After coating RF,the magnetic composite microspheres still maintain good monodispersity.After the carbonization treatment,the final magnetic carbon microspheres were obtained.Finally,in order to improve the pore structure of the carbon layer of magnetic carbon microspheres to expand its application,the modification towards pore structure was studied.The mesoporous carbon layer is obtained by using a silicon precursor,tetraethyl orthosilicate TEOS or propyl orthosilicate TPOS,which can hydrolyze to form nanoscale SiO2,as pore expanding agent,in the environment in which the resin microspheres are formed.When TPOS was used as the silicon precursor and in a manner of batch feeding within first 4 hours of the reaction,the obtained product's specific surface area was the largest,which was 3.2 times higher than that before the modification,and its pore volume was increased by 8.9 times.The adsorption capacity of the obtained mesoporous carbon microspheres for erythromycin was up to 112.4 mg/g,which was 4.5 times higher than that before modification.The pseudo second-order kinetic model and the Langmuir isotherm adsorption model have a good fitting effect on the kinetics and thermodynamics of the adsorption process,respectively.The process is a favorable adsorption of erythromycin onto magnetic carbon microspheres,and is a monomolecular chemical adsorption with a fast adsorption speed.The research results in this paper provide theoretical support and basic data for the synthesis and application of magnetic carbon composite particle,whose processing methods feature simple operation and easy shell or pore size control.