Treatment of azo dye using hybrid process of thermolysis and coagulation/flocculation

Abstract

Currently, plenty of azo dye has been used in several industries such as food, textiles, cosmetics and other industries due to excessive demand of the society. With its hardly degradable characteristics, azo dye is responsible for the impairing light penetration, and present of colour in wastewater, and compromising ecosystems in the receiving water media. The colour removal of azo dyeing wastewater was conducted by using combination of two single processes which are thermolysis and coagulation/flocculation in a reactor. Reactive Black 5 was used as the azo dye for the hybrid process of thermolysis and coagulation/flocculation. Copper (II) sulphate catalyst that used in thermolysis was found to be the most effective in comparison to zinc oxide. The removal of colour of azo dyeing wastewater for the thermolysis process was 92.34 % with 0.7g/L copper (II) sulphate catalyst concentration at pH 9.5. Besides that, magnesium chloride was used as a coagulant in coagulation-flocculation process. It was found that 99.14% of colour removal at pH 12 with coagulant dose of 2400 ppm. Supernatant obtained after hybrid process treatment by the optimum condition of thermolysis resulted of 99.25 % at pH 12 and a coagulant dose of 1200 ppm. The optimum condition of hybrid process consisted 0mV zeta potential. The application of hybrid process of thermolysis and coagulation-flocculation is the most effective treatment method in removing 99.25% colour at lower dose of coagulant (1200 ppm). Thus, the sludge produced would contain lower inorganic mass coagulant and therefore less amount of inorganic sludge.