Synthesis and characterization of graphene Th(IV) phosphate composite cation exchanger: analytical application as lead ion-selective membrane electrode

Abstract

A Pb²⁺ ion-selective membrane electrode (ISME) based on graphene Th(IV) phosphate composite cation-exchange material was fabricated using solution casting method. The effect of membrane composition on the proton conductivity was investigated using varying amounts of electroactive material. The membrane with 250 mg of electroactive material and 10 μL of plasticizer exhibited highest proton conductivity. The optimized membrane composition was used for the fabrication of ISME which exhibited a typical Nernstian response towards Pb²⁺ ions in the concentration range 1.0 × 10⁻¹ to 1.0 × 10⁻⁷ M with a sub-Nernstian slope of 27.65 mV per decade change in Pb²⁺ ion concentration. The response time of this electrode for Pb²⁺ ions was found to be 10 s and the electrode can be used for 120 d without any considerable divergence in response potential and can be used in the pH range from 3.0 to 7.0. It was found selective for Pb²⁺ ions in the presence of various monovalent and multivalent interfering ions. It was also employed as an indicator electrode in the potentiometric titration of Pb²⁺ ions using ethylenediamine tetraacetic acid, disodium salt as titrant.

Keywords:

• Composite cation exchanger
• Potentiometric determination of Pb²⁺ ions
• Graphene Th(IV) phosphate
• Membrane electrode
• Selectivity

Acknowledgements

The authors are thankful to Department of Applied Chemistry, Z.H. College of Engineering and Technology, A.M.U. (Aligarh) for providing research facilities and University Grants Commission for the financial support [vide F. No. 41-278/2012 (SR) 01/07/2012].