Studies On The Determination Of 4-Chlorophenol And Phenol Using Cetyltrimethyammonium Bromide-functionalized Montmorillonite Modified Electrode

In this paper, a cationic surfactant: cetyltrimethylammonium (CTAB) was used to functionalize montmorillonite by inserting into the layers of montmorillonite. The resulting CTAB-functionalized montmorillonite (denoted as CTAB-MMT) exhibits higher accumulation ability to organic species. After that, the CTAB-MMT was used to modify carbon paste electrode, and its application in the determination of organic pollutants was studied. The major work is as follows:Montmorillonite calcium was mixed with different amounts of CTAB in water, and then subjected to mechanical stirring for 5 h at room temperature. After that, the mixture was collected by filtration and washed by distilled water. Finally, the solid was dried and grinded into powder, resulting in the CTAB-functionalized montmorillonite. The CTAB-MMT was used to modify carbon paste electrode by homogeneously mixing with graphite powder and paraffin oil. The electrochemical behavior of 4-chlorophenol at the unmodified carbon paste electrode, the montmorillonite modified carbon paste electrode and CTAB-MMT modified carbon paste electrode was investigated. It is found that the CTAB-MMT modified carbon paste electrode exhibits higher accumulation efficiency to 4-chlorophenol. It remarkably improves the oxidation current of 4-chlorophenol, and shifts the oxidation peak potential to more negative potential (from 0.76 V to 0.65 V). The effects of supporting electrolytes, pH value, CTAB/MMT mass ratio, content of CTAB/MMT and accumulation time were examined on the electrochemical signal of 4-chlorophenol. A novel electrochemical method was developed for the determination of 4-chlorophenol after optimizing the parameters. The linear range of this method is over the range from 5.0×10-8 to 1.0×10-5 mol/L. After 2-min accumulation, the detection limit is evaluated to be 2.0×10-8 mol/L. The relative standard deviation (RSD) is 3.3% for 10 parallel determinations. Finally, this new method was used to determine 4-chlorophenol in water samples, and the recovery is in the range from 92.6% to 103.6%.The application of CTAB-MMT in the electrochemical determination of phenol was also studied. Due to the higher adsorption ability to phenol, the CTAB-MMT modified electrode significantly increases the determining sensitivity of phenol. The experimental parameters such as kind of supporting electrolyte, pH value, amount of CTAB, accumulation time and the content of CTAB-MMT were optimized for the determination of phenol. Therefore, a simple and sensitive electrochemical method was established for the determination of phenol. The oxidation peak current of phenol is proportional to its concentration over the range from 1.0×10-7 to 3.0×10-5 mol/L (R = 0.996). The lowest detectable concentration is estimated to be 6.0×10-8 mol/L after 3-min accumulation. This newly-developed method was applied to determine phenol in waste water samples. The recovery is between 83.1% and 102.0%, revealing that this method is reliable and effective.