Estudo da interação de íons cobre e cromo com eletrodos de pasta de carbono modificada e polianilina em meio aquoso por técnica de voltametria de pulso diferencial

Abstract

The electrochemical sensors to measure metallic ions in water and waste water are among the most important areas of research nowadays. The environmental control and monitoring chalenges that stimulated the aim of this work are tanification for industrial leather finishing and cuprous and cupric organic and inorganic fungicides. The features for characterization of metallic ions in water, specially for Cu2+ e Cr6+ and the properties of Humic Acid extracted from Turfe, or Turf Humic Acid (AHT) and Lignossufonic Acid, or Sulfonated Lignin (LigS), were exposed, as well as the properties and synthesis methods for Polyaniline (PAni). The following electrodes were prepaired and used on this work: The carbon paste modified electrodes, prepared with AHT extracted at Mogi river estuarine region near Luis Antonio city São Paulo State, Brazil. Another carbon paste was prepared for comparison with LigS obtained from pinus pulp processing and treatment by Melbar Company (Parana State, Brazil). The working electrode that used PAni films were prepared by electrochemical synthesis onto graphite rods. The cyclic voltammetry technique was used to synthesize PAni in acid media of 0.5 to 1.0 mol L-1 H2SO4 (PAni-H2SO4) and scanning speed of v=20mVs-1, v=50mVs-1. The same procedure was used to synthesize the PAni films, in the same acid media, and the solution has 0.05 mg L-1 of dispersed LigS (PAni-H2SO4+LigS). These electrodes had their Differential Pulse Voltammetry (DPV) current peak response studied with Factorial Planning. The most important results were compared by linear response, sensibility, limit of detection (LD) and repetability. The best electrodes for Cr6+ ions was PAni-H2SO4+LigS with a sensibility of 10.3A/10-7molL-1, 2.87% of repeatability, 5.6% of reproducibility and LD = 1.96 10-8 mol L-1. For copper ions the Carbon Paste modified with LigS was the best electrode wich has a sensibility of 9.5 A/10-7mol L-1, 1.5% of repeatability, reproducibility of 3.5% and LD = 4.9 10-8 mol L-1. Both electrodes have, each other, a linear calibration curve for Ip response that includes the limits of concentration for brazilian s environmental laws (CONAMA 397/april 2008), by DPV method, obtained on acetate buffer, pH=4,5, pulse height zE=75 mV, Ed = -0.35 V and scanning speed v= 20mVs-1.