Removal of dyes and pigments from industrial effluents

Abstract

Dyes are widely used in food, cosmetic, pharmaceutical, printing, textile, and leather industries during manufacturing process. As a result, a considerable amount of undesired coloured effluents is generated. The presence of dyes and pigments in water resources not only renders them aesthetically unacceptable, but also poses serious health-risk factors on living organisms and the environment. Therefore, it is essential to remove such dyes before discharging them into natural water streams. A technically effective and cost-effective treatment method is needed. Removal of parameters such as colour, chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total organic carbon (TOC) from dye containing industrial effluent have become the present topics of research. A wide range of treatment techniques have been explored, including (1) physical treatment (ion exchange, adsorption, etc.), (2) chemical treatment (oxidative processes, coagulation and precipitation, etc.), (3) biological treatment (aerobic, anaerobic, etc.), (4) thermal treatment (thermolysis, wet oxidation, etc.), and (5) combined treatment (adsorption/coagulation, coagulation-flocculation/nanofiltration, etc.), some of which have been applied in some industries' wastewater treatment process. Current trends and efficient treatment technologies for dyes and pigments wastes are discussed and their strengths and weaknesses are to be compared.