Effects of a bolaform electrolyte on the sorption of acid dyes by a silk fibre

The sorption behaviour of sodium 1-phenylazo-2-hydroxy-6-naphthalenesulphonate and sodium 1-(3-methylphenylazo)-2-hydroxy-6-naphthalenesulphonate by a silk fibre was investigated in the presence and absence of a bolaform electrolyte. The addition of the bolaform electrolyte influenced the dye sorption to an extent that was dependent on the pH of the dyebath. At pH 3 the amount of dye sorbed by the silk fibre decreased slightly with increasing bolaform electrolyte concentration, while at pH 4 and in pure water it increased. The sorption parameters determined from the sorption isotherms considering the dual sorption mechanism were affected by the addition of the bolaform electrolyte: most importantly, the partition coefficients were significantly enhanced. Furthermore, the effects of the bolaform electrolyte on the dye sorption by the silk fibre were quite different to those seen with a nylon 6 film.