Voltammetric studies of lead (ll), cadmium(ll), copper(ll) and chromium(lll) ions in the presence of selected n-heterocyclic compound

• Main Author: Rahman, Nurul Hudah
• Format: Thesis
• Language: English; English
• Published: 2011
• Subjects: Voltammetry; Heterocyclic compounds; Cadmium
• Online Access: http://psasir.upm.edu.my/id/eprint/25739/1/FS%202011%20105R.pdf; http://psasir.upm.edu.my/id/eprint/25739/

Voltammetry behaviours of lead(II), cadmium(II), copper(II) and chromium(III) ions in the presence of ligands with nitrogen bearing group, such as picolinic acid (pyridine-2-carboxylic acid or PA), nicotinic acid (pyridine-3-carboxylic acid or NA) and pyridine-2,4-dicarboxylic (2,4-PDCA) acid were being studied using hanging dropping mercury electrode (HDME) or platinum electrode as working electrode; Ag/AgCl (3 M NaCl) as reference electrode and platinum wire as counter electrode. Enhancement of the current response using voltammetry technique due to adsorption of electroactive species was investigated. Nicotinic acid has been found to cause enhanced peak current for metal ions such as Pb(II) andCd (II) by about 4.9 folds and 1.6 folds, respectively at a mercury electrode. While, picolinic acid has been found to cause current enhancement of reoxidation Cu(II) by about 1.2 folds using mercury electrode. By using platinum electrode, in the presence of 2,4-PDCA, current enhancement was observed by about 9.6 fold in reduction of Cr(III) ions. By optimizing condition the scan rate study for Pb(II), Cd(II) Cu(II) and Cr(III) were 0.6, 0.4, 0.6 and 0.66 respectively under optimum pH. Moreover, the detection limit were 3.55μM for Pb, 1.34μM for Cd, 2.5μM for Cu and 82.4μM for Cr with the sensitivity of cyclic voltammetry is accompanied by good reproducibility. Furthermore, based on the result obtained from double potential step chronocoulometry the diffusion coefficient of Pb-NA, Cd-NA, Cu-PA and Cr(III)-2,4-PDCA complex species are 7.32 x 10-6, 7.08 x 10-7, 6.18 x 10-6 and 3.9 x 10-6 cm2/s respectively. Various studies using techniques such as Cyclic Voltammetry (CV), Square Wave Voltammetry (SWV), Chronocoulometry (CC) and Chronoamperometry (CA) demonstrated that this enhancement effect was due to the adsorption of metal-ligand complexes on the electrode surface. Thus, this procedure was successfully applied to the simultaneous determination of metal ions (Pb and Cd) in some waste water.