Potentiometric Determination of Mercury Ions by Sol-gel Synthesized Multi-walled Carbon Nanotubes Zr (IV) Phosphate Composite Fabricated Membrane Electrode

Background: The nanocomposites are formed by introducing inorganic nano-clusters, fullerenes, clays, metals, oxides with numerous organic polymers. The assembly of these materials exhibits better properties such as catalytic, thermal stability and adsorption properties, than the individual materials. Objective: The nanocomposite synthesized here by the sol-gel method was primarily evaluated for cation exchange properties viz, elution concentration, elution behavior, and the effect of temperature on ion-exchange capacity. The synthesized composite was used as an electroactive component for the fabrication of the Hg²⁺ ion-selective membrane electrode. Methods: The sol-gel technique was used to synthesize multi-walled carbon nanotubes Zr(IV) phosphate composite cation exchanger. By the technique of solution casting, the material as an electroactive part was used for the fabrication of mercury ion-selective membrane electrode. The potential response of the electrode was also investigated as a function of membrane composition and plasticizer. Results: The composite cation exchanger exhibited 1.8 meq g^-1 ion-exchange capacity (IEC). It retained almost 65% of its initial IEC up to a temperature of 400°C. Distribution studies showed the selective nature of the composite for Hg(II) ions. The ion-selective membrane electrode exhibited a typical Nernstian response towards Hg²⁺ ions in the concentration range 1×10^-1-1×10^-1 M. Conclusion: The results discussed reveal that the new cation composite exchanger-multi-walled carbon nanotubes Zr (IV) phosphate exhibited excellent cation exchange properties and was found to be preferentially selective towards the Hg²⁺ ions. It was also used as an indicator electrode in the titration of Hg²⁺ ions using ethylenediaminetetraacetic acid as a titrant.