Efficiency and toxicity: comparison between the Fenton and electrochemical processes Marcela Gomes Tavares, Danilo Henrique da Silva Santos, Sheyla Jaqueline Albuquerque Torres, Wagner Roberto Oliveira Pimentel, Josealdo Tonholo and Carmem Lucia de Paiva e Silva Zanta ABSTRACT This study aimed to determine the best method to treat a textile effluent containing the dye basic blue 99 (BB). Treatments by the electrochemical and the Fenton processes were compared by means of a 2 3 experimental design, and the interaction of experimental conditions for BB oxidation were determined. The electrochemical treatment gave better results in the presence of NaCl as electrolyte and high current density (30 mA cm 2 ); the Fenton reaction provided better results at H 2 O 2 and Fe 2þ concentrations of 10 mg L 1 and 0.5 mmol L 1 , respectively. Electrochemical treatment was 23 times faster than the Fenton reaction because formation of chlorinated species during electrooxidation significantly contributed to dye oxidation. Although the electrochemical process was more efficient, the resulting treated effluent was more toxic to Lactuca sativa germination and growth, which indicated some biotoxicity. Results demonstrated that both processes efficiently remediated effluents containing the dye BB, but they need to be combined with other processes to ensure complete adequacy of the effluent for disposal. Marcela Gomes Tavares Danilo Henrique da Silva Santos Wagner Roberto Oliveira Pimentel Technology Center of Federal University of Alagoas, Av. Lourival Melo Mota, s/n, Campus A.C. Simões, Tabuleiro do Martins, Maceió-AL 57072-970, Brazil Sheyla Jaqueline Albuquerque Torres Josealdo Tonholo Carmem Lucia de Paiva e Silva Zanta (corresponding author) Chemistry and Biotechnology Institute of Federal University of Alagoas, Av. Lourival Melo Mota, s/n, Campus A.C. Simões, Tabuleiro do Martins, Maceió-AL 57072-970, Brazil E-mail: zanta@hotmail.com; clp@qui.ufal.br Key words | advanced oxidative process, dye, effluent remediation, electrochemical treatment, Fenton reaction, wastewater treatment INTRODUCTION The textile industry is an industrial sector of great socioeco- nomic importance in terms of production and employability. On the other hand, the various processing stages involved in textile manufacture consume a large amount of water, dyes, and other chemical compounds, generating effluents that cause serious environmental issues when discharged with- out adequate treatment (Dasgupta et al. ). The strongest environmental impact of the textile sector is related to primary water consumption (80–100 m 3 ton 1 of finished textile) and wastewater discharge (115–175 kg of chemical oxygen demand (COD) ton 1 of finished textile). This sector releases a wide range of poorly biodegradable organic chemicals into water sources, thereby affecting water salinity and color. Among the pollutants present in textile industry efflu- ents, dyes are certainly the main source of contamination: part of these pollutants (from 2 to 50%) end up in waste- water after the dyeing process. Dyes consist of highly complex and poorly biodegradable molecules. Their discharge into water bodies gives rise to aesthetic issues and hinders light penetration. Moreover, the carcinogenic, toxic, and mutagenic effects of dyes and their corresponding sub-products cause problems in aquatic organisms (Punzi et al. ). Water resources eutrophication is the ultimate consequence of dye disposal into the environment. The high quantities of salt and fixing agents used during textile dyeing and weaving make textile industry effluents even more complex. Therefore, finding more efficient treat- ment methods to degrade these contaminants and their sub-products in effluents is an urgent matter (Gupta et al. ; Punzi et al. ). The scientific literature contains numerous papers on the development of new methods to treat effluents contami- nated with dyes (Gupta et al. ; Punzi et al. ). However, biological treatments continue to be the most promising strategy: they are economically viable, efficiently 1143 © IWA Publishing 2016 Water Science & Technology | 74.5 | 2016 doi: 10.2166/wst.2016.278 Downloaded from https://iwaponline.com/wst/article-pdf/74/5/1143/459435/wst074051143.pdf by guest on 08 November 2018