Composite zeolite/carbonized polyaniline electrodes for p-nitrophenol sensing

Electrodes based on composites of zeolites with carbonized polyaniline prepared in the presence of 5-sulfosalicylic acid are evaluated for both qualitative and quantitative determination of phenols in aqueous solutions. Zeolites used included NaX and NaY, as well as their transition metal (Mn and Cu) cation-exchanged forms, and they were all characterized using XRPD, FTIR and SEM. Cyclic voltammetry was used to study composites' electrochemical response in the presence of p-nitrophenol, phenol and 5-aminophenol in acidic, neutral and alkaline media. Linear dependence of current on p-nitrophenol concentration in acidic media was obtained in 0.1-1 mM concentration range. The comparative evaluation of the electrochemical response of NaX/carbonized polyaniline composite and its individual components revealed significantly lower limit of detection obtained using composite electrode (1.27 μM) compared to that obtained using pure zeolite (135 μM) or pure carbonized polyaniline (94.5 μM) electrode. Composite electrode gave response to p-nitrophenol presence in neutral media as well, but it quickly disappeared with continuous scanning, while no clear response could be seen in highly alkaline media. Thus, this work demonstrates benefits of using novel composite based on zeolites and carbonized polyaniline for sensing of phenols in acidic aqueous solutions.