Aqueous Congo Red degradation induced by plasma with glow discharge electrolysis / Degradação do corante Vermelho Congo em solução aquosa através de plasma obtido por eletrólise de alta tensão




Due to the concern with environmental impact and the need for the use of dyes for the textile industries, during the last years several studies has been undertaken to develop new technologies for energetic treatments that allow the degradation of compounds present in industrial waste. In this present work, the construction of a system for degradation of organic substance by high voltage and low current is proposal, using Congo Red (CR) as tested compound. This technique is part of the called Advanced Oxidation Process (AOP) that is based on the generation of highly oxidative species, mainly the hydroxyl radical (OH.). The used system is constituted of a continuous current high voltage source, a thermostatic cell and two electrodes where the plasma is established. The cathode is formed by a spectroscopic graphite electrode and the anode is formed by a platinum electrode sealed in a glass tube, with a microelectrode in contact to the solution. In all samples, a potential difference of approximately 580 volts was applied for a total reaction time of 60 minutes for the degradation of the CR. The monitoring of the degradation of the CR was done by spectroscopic scanning in the region of 600 to 400 nm, in aliquots removed from the reaction solution each 10 minutes of contact with the plasma. Studies of pH, kinetic characteristics, variation of initial concentration and pH value of the solutions were done. The characteristics of the voltage and current in the solution were investigated. The proposed degradation system for CR under plasma obtained by high voltage electrolysis caused the degradation of 80% of the compound, in pH 6. A pH interference in the rate of degradation of the compound was observed, and adjusting the sample to pH 8, a degradation of 90% of the compound was obtained. The constant K of the process was calculated, showing a first order law of reaction dynamics. The activation energy (Ea) was also calculated and its value was 834.31 J mol-1. The electrolysis by electric discharge is a technique with great potential for the degradation of organic compounds.


eletrólise electrolysis quimica analitica degradation degradação corante vermelho congo congo red dyes

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