Adsorption Behavior Of Colloidal Carbon Nanotubes And Plant-Based Biochar On PPCPs

Over the past two decades,the widespread presence of pharmaceutical and personal care products?PPCPs?in water environments and their potential hazards to aquatic organisms have attracted widespread attention,and PPCPs have been recognized as new environmental pollutants.Studies have shown that PPCPs induce acute effects only in the range of?g·L^-1or even ng·L^-1.Therefore,it is especially important to conduct in-depth processing of PPCPs.In recent years,carbon-based materials have been increasingly used as adsorbents for pollutants due to their special porous structure and large specific surface area.As a typical carbon-based material,artificial carbon nanomaterial carbon nanotubes and natural plant-based carbon material biochar have been proposed as adsorbents for PPCPs advanced treatment due to their large specific surface area and excellent adsorption properties.Although carbon nanotubes have a large specific surface area,due to the relatively strong van der Waals force between the carbon nanotubes,it is easy to entangle or aggregate into bundles,which seriously restricts the application of carbon nanotubes;Economic costs also affect the use of carbon nanotubes to some extent.Biochar raw materials usually come from animal shells,plant roots,peels,etc.,which are relatively cheap and easy to obtain,and have large specific surface area and no agglomeration.They have been widely used in the adsorption of heavy metals and polycyclic aromatic hydrocarbons.However,its adsorption effect and mechanism for PPCPs remains to be investigated.Therefore,this paper selects artificial carbon nanomaterials carbon nanotubes and natural plant-based carbon materials biochar as adsorbents to investigate their adsorption mechanism and effects on typical PPCPs.In this paper,the adsorption characteristics of colloidal carbon nanotubes on different PPCPs were studied in depth,and a multi-parameter linear free energy model?pp-LFERs model?was established.The adsorption of typical PPCPs by plant-based biochar at different carbonization temperatures and the effect of water chemical conditions on adsorption were investigated.Details are as follows:?1?The adsorption characteristics of colloidal carbon nanotubes and triclosan?TCS?dispersed by anionic surfactant sodium dodecyl benzene sulfonate?SDBS?and sodium dodecyl sulfate?SDS?,cationic surfactant cetyltrimethylammonium bromide?CTAB?and nonionic surfactant octylphenol ethoxylate?TX-100?were studied.The results showed that the presence of anionic surfactants SDBS and SDS significantly inhibited the adsorption of triclosan on carbon nanotubes;the presence of cationic surfactants promoted the adsorption of carbon nanotubes;for nonionic surfactants,when the concentration of surfactants was low,the adsorption of CNTs is inhibited,and when the concentration is high,adsorption is promoted.The adsorption coefficient K_d is linearly related to absorbance?UV?,zeta potential and surfactant concentration.In systems where anionic surfactants?SDBS/SDS?are present,the effect of surface charge on the adsorption of carbon nanotubes is critical.For the cationic surfactant CTAB,the concentration of the surfactant is a major factor affecting the adsorption.For the nonionic surfactant TX-100,the dispersion state is the most important factor.The adsorption isotherms of triclosan on carbon nanotubes dispersed on different surfactants agree well with the Toth model.The cationic surfactant CTAB dispersed carbon nanotubes have the largest adsorption capacity.?2?The adsorption characteristics of 9 kinds of different PPCPs by carbon nanotubes dispersed by anionic surfactant?SDS?were studied.The correlation analysis of the data was carried out to establish the pp-LFERs model under different dispersion conditions.Studies have shown that the ultrasonic treatment of carbon nanotubes inhibits the adsorption of atrazine and carbamazepine,and the inhibitory effect on carbamazepine is more obvious.The sonicated carbon nanotubes slightly promoted the adsorption of bisphenol A,estradiol,estrone,oxybenzone and triclosan,but the effect was not obvious.For chlorpromazine and trifluoropropazine,the ultrasonic treatment of carbon nanotubes hardly changes the adsorption effect of carbon nanotubes.After adding the anionic surfactant SDS and sonicating the carbon nanotubes,the adsorption amount changed significantly.For the six contaminants of atrazine,carbamazepine,bisphenol A,estradiol,estrone and oxybenzone,the amount of adsorption decreased significantly after the addition of the anionic surfactant SDS.For triclosan,when the concentration of triclosan is low,the addition of the anionic surfactant SDS inhibits adsorption;when the concentration of triclosan increases,it promotes adsorption.For chlorpromazine and trifluoropropazine,the amount of adsorption is significantly increased after the addition of the anionic surfactant SDS.In addition,through the correlation analysis,the pp-LFERs model of carbon nanotubes adsorbing PPCPs under three different dispersive characteristics is obtained.The higher r² value shows that the model has good fitting degree,indicating that the model has statistical significance and prediction.?3?The adsorption characteristics of biochar of corn stalk and grapefruit skin at different temperatures for bisphenol A and carbamazepine were studied.The results showed that the adsorption of bisphenol A and carbamazepine on corn stalk biochar was better than that of citron peel biochar at the same carbonization temperature,and the adsorption was consistent with the second-order kinetics and Freundlich model.With the increase of pH,the adsorption capacity of bisphenol A decreased with the two biochars,while the adsorption capacity of carbamazepine decreased first and then increased,and the adsorption amount was the lowest at pH=10.The carbonization temperature of different biochars has different effects on adsorption.The adsorption capacity of bisphenol A on corn stover biochar changes with temperature:300°C corn stalk>600°C corn stalk>450°C corn stalk.The adsorption amount of carbamazepine on corn stalk biochar increased with temperature:600°C corn stalk>450°C corn stalk>300°C corn stalk.The adsorption amount of bisphenol A and carbamazepine on grapefruit skin biochar was changed with temperature:300°C grapefruit skin>450°C grapefruit skin>600°C grapefruit skin.This may be related to the structural properties of the contaminant itself,the adsorption site,the specific surface area and the pore size.The research results of this subject can help to improve the adsorption characteristics of artificial carbon nanomaterials carbon nanotubes and natural carbon materials biochar to PPCPs,and clarify the adsorption mechanism and influencing factors,and improve the interaction mechanism theory between carbon-based materials and PPCPs.Research and provide a scientific basis for the application of carbon-based materials in the advanced treatment of PPCPs.