Halogen-free bleaching of shellac using electrochemically generated peroxodicarbonate

Abstract

Industrial bleaching of shellac with sodium hypochlorite causes bleaching damages, such as double bond chlorination. Peroxodicarbonate, generated from the anodic oxidation of carbonates, acts as peroxide source for a novel acetonitrile mediated bleaching protocol, applicable on shellac. Only 6 and 9 mmol g_shellac⁻¹ of peroxodicarbonate and acetonitrile, respectively, is required to bleach shellac at room temperature with a bleaching efficiency of 94% and an acid value of 109. Furthermore, this method was demonstrated on unprocessed seedlac where the ionic strength of the peroxodicarbonate buffer facilitates dewaxing. A decreased aldehyde and acetal quantity, as well as ester hydrolysis are the major bleaching damages, visualised by FT-IR and NMR spectroscopy.