Hetero-aggregation And Sedimentation On Typical Carbon Nanomaterials In Water

Graphene Oxide?Graphene Oxide,GO?and Carbon Nanotubes?Carbon Nanotubes,CNTs?are the two most popular new nanomaterials in the field of nanotechnology at present,they have been widely used in many fields of production and scientific research.But its life cycle process may be released into the water body in many forms,causing ecological environmental risks,so it is considered as a potential new pollutant in the water environment.Environmental behaviors such as aggregation and sedimentation of GO and CNTs in water can cause changes in their morphology and properties in water,and then affect their bioavailability and environmental toxicity.This study focuses on GO and MWNTs?Multi-Walled Carbon Nanotubes,MWNTs?,using DLVO theory and Dynamic Light scattering techniques to describe the behavior of hetero-aggregation and sedimentation between them and with natural colloids.At the same time,the effects of electrolyte,natural organic matter and other conditions on the aggregation and sedimentation of go particles are investigated,which provides a theoretical basis for in-depth understanding of the migration and transformation laws of carbon nanomaterials in water.The main research contents and results are as follows:?1?The electronegativity of the GO and MWNTs surfaces is strong and can be stably dispersed in the water body.The addition of electrolyte can promote GO and MWNTs homo-aggregation and hetero-aggregation.Due to the chemical bond,the hetero-aggregation rates of GO and MWNTs are larger than both homo-aggregation rates.The hetero-aggregation process is divided into two stages:reaction condensation and diffusion condensation.The CCC of GO and MWNTs were 103.44 mmol/L?Na⁺?,4 mmol/L(Mg²⁺)and 1.8 mmol/L(Ca²⁺),respectively.The addition of HA?FA and Alginate can inhibit the hetero-aggregation of GO and MWNTs due to steric hindrance,the intensity of inhibition:HA>FA>Alginate.HA promote the hetero-aggregation through bridging in the system.?2?The first-order settlement kinetic model can better describe the sedimentation process after aggregation of GO and MWNTs.Under the same attachment efficiencies,the higher the?,the higher the concentration of electrolyte,the higher the sedimentation rate of GO?MWNTs alone and the co-sedimentation rate,and the GO and MWNTs co-sedimentation rate is larger than that of individual sedimentation rate.The effect of natural organic matter on co-sedimentation of GO and MWNTs is the same as that of hetero-aggregation,and the two behavior changes are similar.aggregation is the main factor that affects sedimentation,the two are inseparable..?3?GO?MWNTs nanoparticles can heteroaggregrate and cosediment with Hem NPs nanoparticles because of electrostatic attraction,and the rate of aggregation and sedimentation is faster than that of individual nanoparticles.The variation law of GO?MWNTs and Hem NPs hetero-aggregation rate increases first and then decreases with the increase of GO?MWNTs concentration;When the GO/Hem NPs?MWNTs/Hem NPs concentration ratio is 0.1 and 0.18,respectively,that is,the optimal concentration ratio,the hetero-aggregation rate is the largest and the Hem NPs surface charge is close to zero.Under the optimum concentration ratio,the effect of electrolyte on GO?MWNTs and Hem NPs hetero-aggregation and sedimentation is that with the increase of electrolyte concentration,the rate of hetero-aggregation and sedimentation and the first rapid increase tend to be flat;The critical condensed concentration CCC in the condensation process were 17.69 mmol/L?GO+Hem NPs?and 42.54 mmol/L?MWNTs+Hem NPs?,respectively.When HA and BSA were added to the optimum concentration ratio,the GO?MWNTs and Hem NPs hetero-aggregation and sedimentation were inhibited due to steric hindrance and electrostatic repulsion,and the higher the concentration was,the stronger the inhibition was.BSA inhibition was weaker than that of HA due to the neutral surface.