Coagulation and flocculation of reactive Black 5 azo dye using different types of coagulants: a comparison study

Abstract

Coagulation and flocculation is a method to remove dye from water and wastewater because dye is well-known as the major contributor of water pollution due to the aesthetical, health and environmental effects. In this research, three types of inorganic chemicals are used as coagulants in treating the water sample from Reactive Black 5 (RB5) azo dye which are alum, MgCl2 and CaCl2. A few characterization tests of RB5 have been done which are the infrared spectrophotometry, pH test, chemical oxygen demand analysis and UV-Vis spectrophotometry. The purpose of these analyses is to know the mechanism of RB5 removal by comparing the initial and final conditions which is only evaluated by the UV-Vis photometry. The optimum pH of alum, MgCl2, CaCl2 dosages are 4, 11 and 5 respectively. Meanwhile, their optimum dosages are 300 mg/L, 2000 mg/L and 500 mg/L respectively. Last but not least, MgCl2 is found to be the most excellent coagulant for dye removal with up to 97% efficiency.