Low energy electrochemical oxidation efficiently oxidizes a common textile dye used in Thailand

Abstract

Organic dyes are extensively used worldwide in the textile industry. Thailand's textile industry, which is mostly composed of small- and mid-sized factories that produce wastewater streams, would benefit from efficient, small-sized, and easy to operate treatment technologies. Electrochemical oxidation (ECO) is an alternative to historic solutions (e.g., biological treatment, coagulation, membranes, ozone) to treat dyebath effluents and reuse the water for secondary, non-potable purposes. ECO is an advanced oxidation process capable of in-situ electrogeneration of hydroxyl radical to completely mineralize organic pollutants. This work demonstrates the capability of electrochemically-driven systems to efficiently decolorize and mineralize dyebath effluents containing anthraquinone dye Acid Green 25. Achieving color and chemical oxygen demand abatement to below effluent discharge limits was attained using only 100 mA cm−2. Breaking the aromatic rings successfully produced readily biodegradable, low molecular weight carboxylic acids and inorganic (ammonium, nitrate) total nitrogen below 7 mg-N L−1, which can be readily discharged to sewers or even urban surface waters. The competitiveness of the electrochemical system is analyzed using engineering figures of merit, and the impacts of operational variables are discussed in terms of removal percentage, efficiency, and electrical energy per order. Results suggest wide applicability as an alternative for treating textile manufacturing waste streams.