Analysis of metal ions in water using SAM-modified EQCM electrodes

• Main Author: Hewas, Agab Mohamed
• Other Authors: Ryder, Karl; Hillman, Arthur
• Published: University of Leicester 2014
• Subjects: 541
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.617632

The toxic nature of some metal ions makes it necessary to monitor their concentrations in the environment. In this thesis there are two fundamental objectives. The first is to develop a portable electrochemical sensor, which is capable for detecting and monitoring Pb[superscript 2+], Ni[superscript 2+] and Co[superscript 2+] rapidly, selectively and accurately. The second is to develop an extraction procedure for these metal ions by using some ionic liquids (ILs), with the QCM and colorimetric indicators being used to investigate this process. Mercaptosuccinic acid (MSA), 2, 2'-Thiodisuccinic acid (2.2'-TDS), 4-Mercaptobenzoic acid (4-MBA) and 4-Mercaptophenylacetic acid (4-MPAA) thiols were used to prepare self-assembled monolayers on the gold electrodes of 10MHz AT-cut piezoelectric quartz crystal resonators. The extent of immobilisation of each ligand was determined by measuring the resonant frequency change of the crystal and the quality of the SAM was investigated voltammetrically, with [Fe(CN)[subscript 6]][superscript 3-/4-] as a probe redox couple. The focus was on Au-MSA as the most effective ligand for Pb[superscript 2+], Ni[superscript 2+] and Co[superscript 2+]. Adsorption of these metal ions, individually and competitively, by Au-MSA from aqueous solution was measured as a function of solution concentration and the data fitted to a range of isotherms. Structural and compositional information on the SAMs was acquired using Raman spectroscopy and XPS.