Mechanism of Acceleration Effects by N,N,N',N'-Tetramethyl-p-phenylenediamine in Persulphate Bleaching Solutions

Abstract

Acceleration effects by N,N,N',N'-tetramethyl-p-phenylenediamine(TM PPD) in persulphate bleaching solutions were studied by voltammetry, spectrometry, and bleaching tests of films. Immediately after the preparation of the bleaching solution, the oxidation products of TMPPD underwent deamination to become p-benzoquinone(Q). Even in the absence of persulphate Q showed the almost equal bleaching power with that in the presence of persulphate. Q diminished by bleaching was restored in the presence of persulphate with a rate constant of 5.8 × 10^-4 M^-1 S^-1 The results suggest that the effect by TM PPD is not to accelerate the bleaching by persulphate, but persulphate acts as a restoring agent of Q.