Brazilian Journal of Chemical Engineering Print version ISSN 0104‐6632 Braz. J. Chem. Eng. vol.26 no.4 São Paulo Oct./Dec. 2009 http://dx.doi.org/10.1590/S0104‐66322009000400004 ENVIRONMENTAL ENGINEERING Electroflocculation for textile wastewater treatment A. Cerqueira; C. Russo; M. R. C. Marques* Programa de Pós‐graduação em Química, Mestrado em Química Ambiental, Instituto de Química, Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, CEP: 20550‐900, Rio de Janeiro ‐ RJ, Brasil. E‐mail:monicamarques@uerj.br ABSTRACT This work reports on the viability of the electroflocculation (EF) process for chemical oxygen demand (COD), turbidity and color removal from a raw effluent originated from a particular textile industry related to hemp manufacture. Firstly, the following operational parameters were optimized: current density; initial pH; electrolysis time; material of the electrode (iron, aluminum or iron‐aluminum); and interelectrode distance. Additionally, the effects of these parameters on specific electrical energy consumption (SEEC) were studied under the optimum conditions. The best removal efficiencies obtained were 93% for color, 99% for turbidity and up to 87% for COD using an aluminum electrode, the initial pH was 5, the cell time operation was 30 min and current density was 15 A/m2. These results indicate that, under the studied operational conditions, electroflocculation of these efluents may constitute a viable alternative for COD, turbidity and color removal. INTRODUCTION The textile industry is one of many industries that utilizes large volumes of water in the manufacturing process. This water, used in the dying and finishing processes, ends up as wastewater, which needs to be treated before its final discharge. Frequent changes of the dyestuff employed in the process cause considerable variation in the wastewater characteristics, such as intense color, high chemical oxygen demand (COD), dissolved solids values and highly fluctuating pH, the last being especially troublesome because pH tolerance of conventional biological and chemical treatment systems is very limited. Hence, without continuous pH adjustment, normal operation of the treatment process is impossible (Gürses et al, 2002). Color is one of the most important water quality parameters. During the dying process, about 5 ‐ 20% of the dye are lost due to its partial adsorption on the fibers (Paschoal and Tremiliosi‐Filho, 2005). Dyes are manufactured to have high chemical resistance because they are normally chemical species that are very difficult to degrade (aromatic dyes). Moreover, dye solutions usually contain antibacteria and antifungi agents, which are used to give the fibers more resistance to biological degradation (O'Neil et al, 1999). Even at relatively low concentrations, the intense color associated with the dye affects not only the aesthetics, but also the transparency of waters, thus interfering in photosynthesis, and the solubilization of gases in lakes, rivers and other surface water bodies. It damages both the aquatic flora and fauna. Furthermore, colored effluents may contain considerable amounts of toxic compounds, especially azo dyes, that are known to be highly carcinogenic (Daneshvar et al, 2007; Kunz et al, 2002). Color removal from these effluents before being discharged constitutes a great challenge for the textile industry due to strict water quality parameters imposed by environmental agencies. Hence, conventional treatment processes have been applied, namely: adsorption, precipitation, chemical degradation, photochemical degradation, biodegradation, flocculation, and so on (Paschoal and Tremiliosi‐Filho, 2005). Over the ...
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