Employment of cathodes of diffusion of oxygen in eletrotrolise of brine to produce chlorine / Emprego de catodos de difusão de oxigenio na eletrolise da salmoura para a produção de cloro

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

This work is investigating the performance of electrodes modified with gaseous diffusion of particles of Cu, for reduction of oxygen in the production of chlorine during the electrolysis of brine. Initially, the reaction was studied on the anodic oxidation of chloride ion. Using a single cell compartment, with the type DSA anode with an area of 1.5 cm2 as work of reference and the calomel electrode in KCl solution saturated cyclic voltammetries were performed using the NaClO4 solution of 0.05 mol L-1 for identifying the potential for evolution of oxygen. By adding 20g / L of NaCl in the solution of NaClO4 to see the potential for evolution of chlorine gas on the surface of the DSA. In these two tests were analyzed temperature: 25 °C and 70 °C. In preparing the cathodes of diffusion of oxygen, was used a mass precursor, composed of carbonaceous pigment Printex and suspension of the PTFE powder. The catalyst was introduced in the form of Cu metal powder. The Cu was introduced in the mass precursor using different methods, the proportion of 10% m / m. What could be reached in the great percentage of catalyst, studies were made with different percentages of Cu (5%, 10%, 15%, 20%, 25%, 30%) and the best was 10% m / m. After the bodies were prepared, the electrodes of gaseous diffusion were synthesized. For the sintering of the electrodes of gaseous diffusion (GDS) was weighed 0.2 g of mass precursor and placed on the mold. The mold was heated to a temperature of 340 ° C for the sintering of the electrode, under pressure of 146 kgf/cm2 for 2 hours. After sintering, the electrodes were being tested for permeability. In subsequent stage, the electrodes of gaseous diffusion were used in voltammetric studies and submitted to linear potential sweeps from 0 to-2V vs. ECS. To examine the reactions of reduction of oxygen in the GDS, the solution of work was 320g / L NaOH pH 13.6. Then, tests were performed using constant current electrolysis to the GDS or pyrolytic graphite as cathode and DSA as anode. In these tests, using a cell with two compartments, separated by a membrane cationic Nafion N242. Each compartment has a volume of 40mL. The electrodes were area of 3.14 cm2. The anolyte was a solution of 250g / L NaCl at pH 3 adjusted with concentrated HCl and the catholyte was a solution of 320g / L NaOH. During the electrolyses the chlorine dissolved in the form of hypochlorite and chlorine gas were quantified by iodometry titration. The electrode that had a better performance as a cathode, the GDS was modified with 10% Cu having shown a reduction of 1.95 V difference in potential in the cell when compared to pyrolytic carbon. Already with a temperature of 70 °C decreased the potential 1.2 V.

ASSUNTO(S)

chlorine oxigenio oxygen eletrodos cloro electrodes

ACESSO AO ARTIGO

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