Sorption Of Anionic Surfactant Linear Alkylbenzene Sulfonates On Carbon Nanotubes And Its Applications

Carbon nanotubes(CNTs) as adsorbents have been used for removal of inorganic and organic pollutants,and also used as solid phase adsorbents for preconcentration of target analytes.Recently, CNTs as SPE(solid-phase extraction) adsorbents were used for enrichment of organic compounds and metal ions at trace levels.After oxidation process,CNTs can be introduced oxygen-containing functional groups on their surface.The surface area and sorption capacities are also remarkably increased and the modified CNTs have been used for preconcentration of metal ions at trace levels due to hydrophilic and negatively charged surface.However,there is no report on the application of oxidized CNTs as adsorbent to extract LAS from environmental waters.Thus,the present study will focus on the following three aspects:1.Expoloring the possibility of using the CMMWCNTs as adsorbents combined with HPLC for LAS;,2.Expoloring the possibility of using MWCNT as the adsorbent for LAS based on the ion-pair solid phase extraction system combined with high performance liquid chromatography(HPLC);3.Expoloring the adsorption characteristics of LAS on CNTs and solution chemistry effects on LAS adsorption on CNTs.The majr conclusions were as follows:1,The effect of eluent and its volume,sample pH and flow rate,sample volume and the ultrasonic time of sample,the content of the electrolyte(NaCl) were investigated and optimized in detail.The detection limits of LAS homologues were 0.02-0.03μg L-1 with RSD(n=6) ranging from 2.04 to 10.03%.The recoveries of LAS homologues in the spiked environmental water samples ranged from 84.8 to 106.1%.Also,enrichment capability and recoveries of LAS in different water samples were also compared with commercial C8 and C18 SPE cartridge.The results indicated that CMMWCNTs cartridge showed stronger retention ability than C8 and C 18. The proposed method has been applied successfully to the analysis of LAS in aqueous environmental samples,which demonstrates that CMMWCNTs based solid-phase extraction is a precision and conveniently enrichmental method.2,A new method was developed for the determination of LAS in water samples by using MWCNT as the adsorbent of the ion-pair solid phase extraction system combined with high performance liquid chromatography(HPLC).The factors affecting enrichment efficiency such as the kind and concentration of the ion-pair reagent,the sonication time of sample,the sample pH, the kind and volume of the eluent,the flow rate of sample,and the volume of sample were investigated.And the optimal SPE conditions were shown as follows:the molar ratio of TBAH/LAS was 1000,sonication time was 3 min,sample pH value was 5,the flow rate was 6 ml/min,and eluent was 6 ml methanol.It indicated from the experimental results that relative standard deviation(RSD) for four LAS homologues were 1.55-2.54,the detection limit was 0.033-0.126μg·L^-1,respectively.The propose method was applied to determine LAS in tap water and Jialingjiang River water.3,The 25℃-adsorption isotherm displayed a five-region mode,and the 60℃-adsorption isotherm is similar to four-region adsorption isotherm.The effect of solution chemistry including different cations,anionics and humic acid,on LAS adsorption on CNTs were studied,also effect of ultrasonic treatment time was considered.The results show that effect of ions was related to their charges.Temperature plays an important role,whereas the ultrasonic treatment time shows minor effect.The effect of humic acid is determined by its concentration and its source.