Study On The Adsorption And Removal Of Polychlorinated Biphenyls In Municipal Wastewater By Carbon Nanotubes

Polychlorinated bipHenyls(PCBs)is a typical persistent organic pollutant(POPs).High toxicity,persistence,bioaccumulation and semi-volatility can cause great harm to human body.As an important carrier of various pollutants in people's life and production,urban sewage is an important environmental medium for the existence of PCBs.Adsorption method is an efficient means to remove organic pollutants in water.Carbon nanotubes(CNTS)are a new and efficient adsorbent with unique functional structure.The adsorption and removal of organic pollutants in carbon nanotubes are promising.The polychlorinated bipHenyls used in this study are PCB28,PCB52,PCB101,PCB118,PCB138,PCB153 and PCB180 respectively.The effect of carbon nanotubes after ultrasonic treatment on the adsorption of PCBS in water was investigated.The effects of environmental factors such as humic acid,temperature and pH on adsorption efficiency were investigated.The main results as follows:After ultrasonic processing,specific surface area of CNTs has increased and SWCNT,MWCNT-50,MWCNT-30,a larger specific surface area increased,but for MWCNT-8 less in terms of its specific surface area increased.Analysis its reason may be the carbon nanotubes in ultrasonic shock after processing,processing of carbon nanotubes to dry processing,in the process of drying process,by ultrasonic dispersing aperture will be closed again.In the case of MWCNT-8,it may be that some aperture reclosure causes less than the surface increase.After ultrasonic treatment,the adsorption capacity of CNTs was significantly improved,indicating that after ultrasonic treatment,the adsorption capacity of carbon nanotubes to PCBs was improved.Single-walled carbon nanotubes have the highest adsorption capacity for PCBS,but SWCNT is the most expensive.From a practical point of view,MWCNT-8 is a good choice for adsorption of PCBs.The adsorption process of multi-walled carbon nanotubes and single-walled carbon nanotubes to PCBS is adsorbed by pHysical adsorption,and the reaction process is spontaneous.The adsorption reaction process of single wall carbon nanotubes and multi-walled carbon nanotubes is endothermic,and the increase of temperature is favorable to the adsorption reaction.Single-walled carbon nanotubes and multi-walled carbon nanotubes on the characters in the process of polychlorinated bipHenyls(PCBs),polychlorinated bipHenyls(PCBs)adsorption onto the surface of the carbon nanotubes,polychlorinated bipHenyls(PCBs)degrees of freedom to reduce,the process is a process of entropy.The higher the HA concentration,the lower the adsorption rate of the carbon nanotubes to PCBs,the longer the reaction time is,and the equilibrium adsorption decreases,but the equilibrium adsorption decreases less.The closer the solution is to neutral,the smaller the electrostatic interaction between carbon nanotubes and PCBS is,and the equilibrium adsorption capacity is higher than that in acidic solution.Carbon nanotubes on the adsorption of polychlorinated bipHenyls(PCBs)reaction has the characteristics of endothermic reaction,with the increase of temperature,the more conducive to the adsorption reaction,the higher the temperature within a certain range,the greater the equilibrium adsorption quantity.