Bismuth nanoparticles decorated on Na-montmorillonite-multiwall carbon nanotube for simultaneous determination of heavy metal ions- electrochemical methods

This study presents the preparation and application of the electrochemical sensor based on pencil graphite elec-trode (PGE) coated with a mixture of multi-wall carbon nanotube (MWCNT) and nano size-sodium montmoril-lonite (NNaM). The electrode obtained was used in the electrochemical quantification of heavy metals. The electrochemical analysis was elaborated further by collecting Bi nanoparticles (BiNP) on the electrode surface during the deposition step of the analytes. The heavy metal cations, zinc (II), cadmium (II), lead (II) and copper (II) were qualified at the potentials of about -1.0, -0.70, -0.47 and 0.00 V, respectively and they quantified within the linear concentration ranges of 2.36-40.0; 40.0-180.0 mu M, 0.32-2.0; 2.0-240.0 mu M, 0.03-5.0; 5.0-80.0 mu M and 0.52-10.0; 10.0-40.0 mu M, respectively. The characterization of the electrode surfaces was made by energy-dispersive X-ray spectroscopy (EDS), electrochemical impedance spectroscopy (EIS), and cyc-lic voltammetry (CV). The surface morphology of the electrode was investigated by scanning electron micro-scopy (SEM). The electrode developed was coded by BiNP/MWCNT-NNaM/PGE. The electrochemical quantification results indicate that the electrode developed is a low-cost tool of high conductive surface area, capable of producing a high SWAS voltammetric signal; much better for electrochemical analysis than unmod-ified PGE. Repeatability and reproducibility for BiNP/MWCNT-NNaM/PGE electrode were found to be RSD < 9.5 % and RSD < 8.0 %, respectively. The interference effects of the cations Mn2+, Al3+, Ni2+, Sb3+ Co2+, Fe3+, Cr3+, Ca2+, Mg2+ and Na3PO4 at concentrations ten-fold lower than the analytes are toler-able (< 4.5 %). Detection limits as low as 0.707 mu M, 0.097 mu M, 0.008 mu M, and 0.157 mu M, were formed for Zn (II), Cd (II), Pb (II), and Cu (II), respectively. The designed sensor was applied to a tap water sample using the standard addition method, and the results are satisfactory.

Automated summary

This study presents a electrochemical sensor based on pencil graphite electrode and its application in the quantification of heavy metals. The sensor has a high conductive surface area, capable of producing high signals, making it more suitable for electrochemical analysis compared to unmodified electrodes.