Degradation reaction of Diazo reactive black 5 dye with copper (II) sulfate catalyst in thermolysis treatment

Abstract

The theme of present research demonstrates performance of copper (II) sulfate (CuSO₄) as catalyst in thermolysis process to treat reactive black 5 (RB 5) dye. During thermolysis without presence of catalyst, heat was converted to thermal energy to break the enthalpy of chemical structure bonding and only 31.62% of color removal. With CuSO₄ support as auxiliary agent, the thermally cleaved molecular structure was further destabilized and reacted with CuSO₄. Copper ions functioned to delocalize the coordination of π of the lone paired electron in azo bond, C=C bond of the sp² carbon to form C-C of the sp³ amorphous carbon in benzene and naphthalene. Further, the radicals of unpaired electrons were stabilized and RB 5 was thermally decomposed to methyl group. Zeta potential measurement was carried out to analyze the mechanism of RB 5 degradation and measurement at 0 mV verified the critical chemical concentration (CCC) (0.7 g/L copper (II) sulfate), as the maximum 92.30% color removal. The presence of copper (II) sulfate catalyst has remarkably increase the RB 5 dye degradation as the degradation rate constant without catalyst, k₁ is 6.5224 whereas the degradation rate constant with catalyst, k₂ is 25.6810. This revealed the correlation of conversion of thermal energy from heat to break the chemical bond strength, subsequent fragmentation of RB 5 dye molecular mediated by copper (II) sulfate catalyst. The novel framework on thermolysis degradation of molecular structure of RB 5 with respect to the bond enthalpy and interfacial intermediates decomposition with catalyst reaction were determined.