Surface Charge and Isoelectric Point of Leather: A Novel Determination Method and its Application in Leather Making

Surface charge and isoelectric point (pI) of leather play animportant role in leather making processes. However, a propermethod for the determination of surface charge and pI of leatheris unavailable nowadays due to the complexity of leatherstructure and property, especially for the burgeoning chromefreetanned leathers. Therefore, it is necessary to develop aquantitative determination method. In this study, a novelmethod for determining zeta potential (to characterize thesurface charge of leather) of solid-state leather was establishedusing a zeta potential analyzer based on the principle ofstreaming potential. Test conditions including suspensionconcentration, sample grain size, temperature and conductivitywere optimized. Then the pI (the pH value at the zero point ofzeta potential) of a variety of chrome-free tanned leathers, suchas mineral, vegetable, organic and combination tanned leather,were obtained by this zeta potential method. Moreover, wemanaged to monitor the pI and surface charge state of zirconiumtanned leather during post-tanning processes using this method.As a result, application of this precise and rapid determinationmethod enables us to reasonably regulate the pI and surfacecharge of chrome-free leather so as to effectively improvetanning and post-tanning performances.