Cathodic stripping square-wave voltammetry for assessing As(III) removal with synthetic mixed oxides

Mechanistic analysis of the cathodic stripping square-wave voltammetric response of the copper‑arsenic system at a mercury electrode

“…In presence of great excess of Cu 2+ ions, the reduction of As(OH) 3(sol) on Hg can be described according to the following expression for the accumulation step, where = -0.4 V [21,22]:…”

“…It is not easy to study the reaction of a compound that accumulates in low concentration levels on the surface of a drop of mercury while anodic potentials are applied. With the aim of increasing the surface concentration of Cu x As (ads) , several researchers have varied diverse chemical characteristics of the experimental system [10,11,14,20,21]. However, irrespectively of the electrochemical technique used for the J o u r n a l P r e -p r o o f Journal Pre-proof stripping scan, the dependence of cathodic peak current on the arsenic acid bulk concentration (…”

“…Instead of this, calibration curves with 2 different slopes, the formation of peak-shoulders, and variations of peak-shapes are typical problems found during the electrochemical quantitation of arsenic species [10,21]. Because of this, diverse research groups have found that addition of extremely low amounts of small organic molecules presenting one or more thiol groups enhances the voltammetric response of arsenic [9,10,19].…”

“…Because of this, diverse research groups have found that addition of extremely low amounts of small organic molecules presenting one or more thiol groups enhances the voltammetric response of arsenic [9,10,19]. Those ligands would stabilize the base line, allowing the determination of lower concentrations of arsenic [10,20,21]. However, the addition of low amounts of Na-pyrrolidine dithiocarbamate (< 0.2 μM) does not affect the average value of the half-peak width (∆E p1/2 ) nor the shape of SW voltammograms corresponding to solutions with > 5 μg L −1 and concentrations of Cu 2+ ions between 0.1 and 1 mM [21].…”

“…Those ligands would stabilize the base line, allowing the determination of lower concentrations of arsenic [10,20,21]. However, the addition of low amounts of Na-pyrrolidine dithiocarbamate (< 0.2 μM) does not affect the average value of the half-peak width (∆E p1/2 ) nor the shape of SW voltammograms corresponding to solutions with > 5 μg L −1 and concentrations of Cu 2+ ions between 0.1 and 1 mM [21].…”