Effective oxidative decolourization of azo dyes over Indian Ocean manganese nodules

Abstract

The degradation of cationic dyes such as methylene blue is studied using Indian Ocean manganese nodules. Effect of various parameters, such as catalyst loading, dye concentration, initial <i style="mso-bidi-font-style:normal">p</i>H of the solution, effect of various electrolytes and effect of heat treatment of manganese nodules on the decolourization of methylene blue is investigated. The extent of decolourization decreases with increase in <i style="mso-bidi-font-style:normal">p</i>H and increases in the presence of NaCl. Anions like CO₃^2-, PO₄^3-, Cl^- inhibit decolourization, whereas SO₄^2- and NO₃^- accelerate the decolourization rate of methylene blue to a remarkable extent. The rate of dye degradation is dramatically reduced with increase in calcination temperature.