Role of a surfactant in caustic alkali cleaning of polyethylene terephthalate surfaces fouled with organic substances

Abstract

The role of polyoxyethylene lauryl ether (POELE), a nonionic surfactant, in removing bovine serum albumin (BSA) and catechin from polyethylene terephthalate (PET) particles was quantitatively studied. Relatively large fractions of adsorbed BSA and catechin were removed from PET particles under weak alkaline conditions below pH 9, whereas cleaning with high concentrations of NaOH was not so effective, especially on the removal of BSA. This was attributed to the lower susceptibility of PET particles to water-based alkali (OH-) cleaning because of the lower degree of the polarity of PET surfaces. The combined use of NaOH solutions of moderate pHs and POELE could successfully improve the efficiency of cleaning of PET particles without a significant dissolution of PET materials. There was a good correlation between the lowered surface tension (γ) of the NaOH solution with POELE and the removal efficiency of BSA or catechin. No effect of POELE was observed on the NaOH cleaning of hydrophilic alumina (Al2O3) particles fouled with BSA. It could be concluded that the role of POELE in NaOH cleaning of PET particles was to lower the γ of the NaOH solution and hence to facilitate penetration of OH ions into the PET-BSA and PET-catechin interfaces.