Fotoeletrodegradação e determinação voltamétrica de Propranolol

Abstract

In this work, efforts were made to study the electrochemistry and application of semiconductor materials for the degradation of the drug propranolol. Semiconductors play a significant and indispensable role in advancing approaches to wastewater treatment. Within this context, this work developed photoanodes made from the semiconductor bismuth vanadate (BiVO4) deposited on the surface of conductive glass with fluorine-doped tin oxide (FTO). The photoanode was modified with copper oxide (CuO) to form a heterostructure and the system was photosensitized with electrodeposited silver phosphate (Ag3PO4). Four photoanode configurations were developed for comparison, namely: FTO/BiVO4; FTO/BiVO4/CuO; FTO/BiVO4/Ag3PO4 and BiVO4/CuO/Ag3PO4. The materials were morphologically characterized using the techniques of scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The electronic characterization of the materials was carried out using the diffuse reflectance technique. The electrochemical characterizations of the photoanodes studied were carried out using linear sweep voltammetry and chronoamperometry measurements. Firstly, the voltammetric profiles of the photoanodes developed were evaluated and the photoanode with the highest current density, FTO/BiVO4/CuO/Ag3PO4. Subsequently, optimization studies of the photoanode were carried out, such as silver phosphate electrodeposition time and potential, LED power, support electrolyte, pH, among others, in order to verify the best experimental condition, since these studies can influence the intensity of the photocurrent. The processes of photodegradation, electrodegradation and photoelectrodegradation were evaluated to verify the influence of UVc radiation and the application of + 1.4 V during 4 hours of drug degradation. The degradation of the propranolol molecule was monitored using UV-vis spectroscopy. The percentage degradation of propranolol using each process and the FTO/BiVO4/CuO/Ag3PO4 photoanode was calculated, giving degradation percentages of 35.0, 25.0 and 68.5% for photocatalysis, electrocatalysis and photoelectrocatalysis, respectively. Propranolol concentration decay curves using the photoelectrodegradation system and the FTO/BiVO4/CuO/Ag3PO4 photoanode were obtained and used to calculate the kinetic constant, where k = 5.52 × 10˗3 min˗1 was obtained. For comparison purposes, propranolol degradation experiments were carried out using the photoanodes FTO/BiVO4; FTO/BiVO4/Ag3PO4; FTO/BiVO4/CuO and FTO/BiVO4/CuO/Ag3PO4, where the degradation rate was 25,5%; 13,7%, 33,5% and 68.5%, respectively. Finally, the Total Organic Carbon (TOC) analysis was carried out using the different photoanodes FTO/BiVO4; FTO/BiVO4/CuO; FTO/BiVO4/Ag3PO4; and FTO/BiVO4/CuO/Ag3PO4, where values of 15.6%, 20.0%, 23.2% and 25.7% were obtained, respectively. Based on these results, the energy involved in the degradation system was estimated at 10,1 kWh kg˗1. As the second part of the work, a sensor was developed using carbon black (CB) and tungsten trioxide (WO3) materials, where the voltammetric profile of the analyte was first evaluated against the different electrodes (GCE; CB/GCE and WO3-CB/GCE). The compositions and pH values for the support electrolyte were studied in order to obtain the best analytical signal (voltammetric response) for the determination of the antihypertensive. The parameters that influence the differential pulse voltammetry technique, such as amplitude, modulation time and speed, were evaluated and optimized. The values were selected (a = 30 mV, t = 15 mV and v = 20 mV s-1) considering the repeatability, stability and magnitude of the analytical signal for WO3-CB/GCE in the determination of PROP. The analytical response was linear over the concentration range 1.00 × 10˗7 to 2.53 × 10˗6 mol L˗1, and followed the following linear regression equation: Ip (μA) = 1.88 × 10˗2 + 0.122 [PROP] (μmol L˗1); r2 = 0.998 with a detection limit of 4.04 × 10˗8 mol L˗1 calculated as three times the standard deviation of the blank (n = 10), divided by the slope of the analytical curve (analytical sensitivity). The accuracy of the voltammetric procedure was verified through intra-day (n = 10) and inter-day (n = 3) repeatability studies for two different concentrations of propranolol. As a result, intra-day repeatability values of 4.52 and 1.59 were obtained for the two concentrations of 6.95 × 10˗7 and 2.15 × 10˗6, respectively. For inter-day repeatability, values of 5.39 and 1.84 were obtained for 6.95 × 10˗7 and 2.15 × 10˗6, respectively.