Estudo de diferentes mecanismos para produção de persulfato utilizando ânodo de diamante dopado com boro

Abstract

In this work, electrochemical technology was used for a more detailed study of the mechanisms of the generation of persulfate, which occurs in situ and in continuous flow with boron doped diamond anode (BDD). A micro and macro electrode of BDD was developed to perform the oxidation and electrolysis experiments of the solutions with concentrated sulfuric acid (H2SO4) and with different additions of water 0,014 mmol/L, 0.022 mmol/L, 0.028 mmol/L, 0.032 mmol/L, 0.035 mmol/L, 0.037 mmol/L, 0.039 mmol/L, 0.040 mmol/L e 0.042 mmol/L), as well assodium dodecyl sulfate solution (SDS) (1.7 mmol/L) with sodium sulfate (Na2SO4) 50 mmol/L and 250 mmol/L. The results showed that hydroxyl radicals can be generated electrochemically at the anode at high concentrations of BDD favor secondary reactions such as the formation of oxygen. However from the results obtained, the favored reaction is the production of persulfates, then identified by spectrophotometry, minimizing oxygen production and enables the opening of persulfate formation. Therefore it can be concluded that the persulfate production is feasible from the reaction between the radical •OH and SO4-2 in solution. No formation of oxygen in certain concentrations was the keyto the completion of the persulfate being formed by two different mechanisms. Another important result was the SDS; Initially 50mmol/L solution of Na2SO4 was electrolyzed. It was observed than in the density of current 15 and 30 mA cm-2 the production of persulfate are very close (0.0003/0.0004 mmol/L). In the current of 60 mA cm-2, the production of this oxidant achieved its maximum 0.00015 mmol/L. However, when 500 ppm of (SDS) was added in the solution of 50 mmol/L Na2SO4, the producution of persulfate is greater than tha solution whitout SDS.