As the environment preservation gradually becomes a matter of major social concern and more strict legislation is being imposed on effluent discharge, more effective processes are required to deal with non-readily biodegradable and toxic pollutants. Synthetic organic dyes in industrial effluents cannot be destroyed in conventional wastewater treatment and consequently, an urgent challenge is the development of new environmentally benign technologies able to mineralize completely these non-biodegradable compounds. This review aims to increase the knowledge on the electrochemical methods used at lab and pilot plant scale to decontaminate synthetic and real effluents containing dyes, considering the period from 2009 to 2013, as an update of our previous review up to 2008. Fundamentals and main applications of electrochemical advanced oxidation processes and the other electrochemical approaches are described. Typical methods such as electrocoagulation, electrochemical reduction, electrochemical oxidation and indirect electro-oxidation with active chlorine species are discussed. Recent advances on electrocatalysis related to the nature of anode material to generate strong heterogeneous OH as mediated oxidant of dyes in electrochemical oxidation are extensively examined. The fast destruction of dyestuffs mediated with electrogenerated active chlorine is analyzed. Electro-Fenton and photo-assisted electrochemical methods like photoelectrocatalysis and photoelectro-Fenton, which destroy dyes by heterogeneous OH and/or homogeneous OH produced in the solution bulk, are described. Current advantages of the exposition of effluents to sunlight in the emerging photo-assisted procedures of solar photoelectrocatalysis and solar photoelectro-Fenton are detailed. The characteristics of novel combined methods involving photocatalysis, adsorption, nanofiltration, microwaves and ultrasounds among others and the use of microbial fuel cells are finally discussed.

Decontamination of wastewaters containing synthetic organic dyes by electrochemical methods. An updated review

Treatment of dairy wastewaters by electrocoagulation using mild steel electrodes.

The decolorization of C.I. Reactive Black 5 in aqueous solution by electrocoagulation using sacrificial iron electrodes

Techno-economical evaluation of electrocoagulation for the textile wastewater using different electrode connections

Treatment of tannery liming drum wastewater by electrocoagulation.

The removal of color from synthetic wastewater containing a reactive dye, C.I. reactive red 124, was experimentally investigated using direct current (D.C.) electrocoagulation (EC) . In the EC of the reactive dye the effects of initial pH, electrolysis time, initial concentration of dye, conductivity and current density, were examined. The dye in the aqueous phase were effectively removed when iron was used as sacrificial anode. The optimum operating range for each operating variable was experimentally determined. The batch experimental results were assessed in terms of color. They revealed that the color of the reactive dye in aqueous phase was effectively removed (100 %). The optimum current density, pH and electrolysis time for 100 mg L –1 initial dye mass concentration were 1.351 mA cm –2 , 8 and 5 min, respectively.

http://pierre.fkit.hr/hdki/cabeq/pdf/18_4_2004/CABEQ_2004_04_9.pdf

I. A. Sengil

Papers

Decolorization of C.I. reactive red 124 using the electrocoagulation method