Kinetic Study of the Discoloration of Rhodamine B with Persulfate, Iron Activation

The discoloration of the fluorescent dye, Rhodamine B (Rhd B) by persulphate (KSP), was investigated by spectrophotometric methods. The discoloration reaction of Rhd B by KSP is slow. It’s first order with respect to Rhd B and KSP. It’s effective at any pH and was found to increase linearly for pH< 4, temperature, and after addition of Fe(II) and Ag(I). The rate of discoloration remained the same after addition of Co(II), Ni(II), Cu(II) and carbonate salts, but decreased after addition of ethanol and chloride salts. The TLC experiment showed the formation of colored intermediates. The activation parameters (Ea, ΔG #, ΔH# and ΔS#) of the discoloration reaction of Rhd B by KSP in absence and in presence of Fe(II) were calculated.