Arsenic Adsorption On The Modified Carbon Nanotubes And Its Application

The present stduy investigated the possibility of using cation surfactant modified carbon nanotubes(CNTs) as adsorbent for solid phase extraction(SPE) of arsenic.The adsorption characteristics and SPE conditions were studied detail.The end functionalization of CNTs can introduce oxygen-containing negatively functional groups such as -COOH,-OH,or -C=O on their surface site.If cationic surfactant such as cetyltrimethylammonium chloride(CTAC) was added to the functionalized CNTs,then interactions such as hydrophobic and ionic may lead to formation of hemimicelle/admicelle aggregates on the CNTs,a new kind of adsorbents,namely, the hemimicelle capped carboxyl modified multi-walled carbon nanotubes(CMMWCNTs),is obtained.The application of the hemimicelle capped carbon nanotubes-based nanosized solid-phase extraction adsorbents in environmental analysis is reported for the first time using arsenic as model target.The effect of adsorption and desorption conditions for arsenic including the amount of surfactant,initial pH of sample solution,the ultrasonic time of sample solution,the amount of electrolyte,flow rate,eluent and its amount were investigated and optimized prior to its determination by atomic fluorescence spectrophotometry(AFS).Arsenic can be quantitatively retained on the hemimicelle capped CMMWCNTs at pH 5-6 from sample volume up to 500 mL and then eluted completely with 2 mol/L HNO3 in the presence of 10 mg/L CTAC.The method detection limit for arsenic determination with AFS detection was 2 ng/L,and the relative standard deviation(RSD,n = 11) was 5.3%at the 0.5μg/L level.The recoveries of arsenic in the spiked environmental water samples ranged from 94%to 104.29%with 500mL of water sample.The proposed method has been applied successfully to the analysis of arsenic in aqueous environmental samples,which demonstrates the hemimicelle capped CMMWCNTs can be an excellent SPE adsorbents for arsenic pretreatment and enrichment from real water samples.The effect of various factors such as concentration and diameter of CMMWCNTs,cationic surfactant concentration,initial concentration of arsenic,solution pH,humic acid concentration and concentrations of anion and cation.Experiment results indicated that the optimized conditions of 100 ng/mL of arsenic adsorption as follows:10 g/L of CMMWCNTs concentration,22.5 mg/L of cationic surfactant concentration,solution pH 5 to 6.The humic acid has no significant effect on arsenic adsorption.However,anion and cation show some effects on arsenic adsorption.