Study On The Complexation Characteristic And Removal Mechanism Of Sodium Dodecyl Sulfate And Copper

Surfactants,due to their unique interfacial properties,exhibit various functions such as solubilization,decontamination,emulsification,wetting,foaming and defoaming,which are widely used in various areas such as industry,life,agriculture and medicine.Because of its high production and consumption in the world,some surfactants are difficult to be properly treated.The residues or degradation intermediates of surfactants can inevitably enter the ecological environment directly,causing serious environmental pollution.Therefore,in recent years,surfactants have been continuously detected in environmental samples,which has caused more attention.In addition to surfactants,there are often heavy metals coexisting in the water environment.Surfactants and heavy metals are widely present in stormwater runoff.Among them,the anionic surfactants can dissociate the negatively charged group,which may complex with heavy metals.The complexation may affect the existence of heavy metals,and then change the migration and transformation of heavy metals in environmental media.In this paper,the most common anionic surfactants Sodium Dodecyl Sulfate(SDS)and heavy metal copper(Cu)were selected as the main research objects and zeolite was used as adsorbent to explore the complexation between anionic surfactants and heavy metals and the influence on the environmental behavior of heavy metals.And the main conclusions were as follows:(1)It could be proved by characterization experiments of nuclear magnetic resonance(~1H NMR)and fourier transform infrared spectroscopy(FTIR)that SDS and Cu(II)had significant complexation,and the complexation efficiency increased with the increase of SDS concentration.At the same time,pH value,ionic strength,other divalent heavy metals,humic acid(HA)and zeolite all could affect the complexation efficiency of SDS and Cu(II).With the increased of pH value,the complexation efficiency of SDS and Cu(II)increased.As the ionic strength increased,the complexation efficiency decreased first and then stabilized.Adding other heavy metals,the complexation efficiency of SDS and Cu(II)decreased slightly,but the overall SDS still showed good complexation properties with Cu(II).Adding HA,more metal complexes would be formed.The addition of zeolite was beneficial to the increase of free Cu(II).The mechanism of complexation might be attributed to electrostatic interactions and micelle interactions between metal cations and negatively charged functional groups of SDS.(2)The surfactant-modified zeolite(SDS-NZ)was successfully prepared.The results showed that the adsorption efficiency of the adsorbent SDS-NZ on Cu(II)was higher than natural zeolite(NZ),and the load of SDS could provide more effective adsorption sites.The adsorption kinetics of adsorbent and Cu(II)accorded with Pseudo-second-order model,and the adsorption isotherm were more appropriate to Langmuir model.And the maximum adsorption amounts were 2.44 and 9.03 mg/g,respectively.The pH value and ionic strength of the solution would significantly affect the adsorption of Cu(II).The higher the pH value,the larger the adsorption amount.As the ionic strength increased,the adsorption amount decreased first and then increased.Electrostatic interactions and the contribution of oxygen-containing functional groups also affected the adsorption process.For desorption experiments,it was found that the concentration,pH value and ionic strength of the SDS solution had effects on the removal efficiency of Cu(II).As the concentration of SDS increased,the removal efficiency of Cu(II)increased.Acidified surfactant solution could facilitate the removal of Cu(II).And with the increase of ionic strength,the removal efficiency increased first and then decreased.(3)Through the study of column experiments,it was found the addition of SDS had little effect on the effluent runoff pollutants concentration.After the raw water entered the experimental column,the pH value could be increased and finally stabilized at about 6.30.The overall pH value was stable and met the standards of surface water environment quality.It had a certain removal efficiency for conventional pollutant,and adsorption was the main removal mechanism.Better removal effect on heavy metals such as Cu(II),Zn(II),Pb(II)and Cd(II)was found.However,the removal effect of Cr(VI)was relatively weak.The main removal mechanism was electrostatic adsorption.