| Carbon nanotubes(Carbon nanotubes,CNTs)has a unique micro-nano structure and excellent physical and chemical properties,which is one of today’s most widely used nano-materials.With the mass production of CNTs,the research on carbon nanotubes has been involved in many fields.The research on the diffusion and aggregation of organic matter in carbon nanotubes and water environment is mainly focused on natural organic matter,while the study of synthetic organic compounds on carbon nanotubes diffusion or aggregation behavior is not much.The study on the diffusion and aggregation of CNTs in water environment and its interaction with synthetic organic matter can provide an important scientific basis for revealing and mastering the water environment behavior of CNTs and comprehensively assessing the ecological and environmental effects of CNTs,which is beneficial to the safe production and use of CNTs in the future.In this paper,the mechanism of the aggregation and adsorption of multi walled carbon nanotubes(CNTs)with the representative antibiotic-tetracycline hydrochloride in water was studied,which can make a more accurate and comprehensive evaluation of the impact of carbon nanomaterials on the environment and human health,and provide a theoretical basis for the removal of carbon nano materials in the water environment in further.In view of these problems,this paper has made the following research progress1)MWNTs can be stably dispersed in aqueous electrolyte solution,and the addition of electrolyte to promote the aggregation of MWNTs in water and change the surface properties.In the electrolyte solution,|ζ| decreases and particle size increases because of electrostatic repulsion and compression of electric double layer;The diameter of MWNTs increases with the increase of tetracycline hydrochloride concentration,which indicates that tetracycline can promote the aggregation of MWNTs in water.After adding divalent electrolytes,The particle size of MWNTs in water will increase.The growth rate of MWNTs in water environment will increase with the increase of electrolyte concentration,and it will not increase after reaching a certain concentration which is consistent with the classic Derjaguin-LandauVerwey-Overbeek(DLVO).The concentration of critical coagulation of MWNTs particles in the electrolyte CCC(Mg2+)and CCC(Ca2+)were 8.72mmol/L,7.59mmol/L,while CCC(Mg2+)and CCC(Ca2+)significantly reduced in TC·HCl system,were 5.95mmol/L and 3.43mmol/L respectively,which further illustrate TC.HCl promote the aggregation of MWNTs in water,and the α reached 1.4 in Ca2+solution.2)The adsorption of MWNTs with different concentrations of TC·HCl will increase with time.The adsorption system will reach the adsorption equilibrium at 72h.MWNTs adsorption of TC·HCl conforms with the Langmuir adsorption isotherm model,which shows that surface adsorptions are closer to chemical monolayer adsorption process.The adsorption capacity increases with the increase of ionic strength,adsorption capacity(including ion)>adsorption amount(excluding ion)and e The addition of electrolyte solution can promote the adsorption of MWNTs on TC·HCl.Ca2+is more likely to promote adsorption than Mg2+,probably due to the complexation of TC·HCl.3)The low molecular weight(<1kDa)organic matter accounts for 55.09%of the total NOM,which is the main constituent of NOM and the molecular weight is between lk-10kDa,10k-100kDa and>100KDa.With the decrease of molecular weight,The aromatic content is also weakened,the aromatic components and more hydrophobic structures exist on the macromolecule NOM.The low molecular weight NOM suppresses the agglomeration of MWNTs mainly by the steric hindrance at low concentration Ca2+/Mg2+,and the low concentration of divalent electrolytes The higher the molecular weight of NOM,the higher the inhibitory effect of agglomeration.The high molecular weight NOM enhances the agglomeration of MWNTs in CaCl2 or MgCl2 solution with high concentration. |
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