Cleaner tanning process for the manufacture of upper leathers

There is a growing need for eco-benign tanning systems owing to stringent environmental regulations. In this study, a combination tanning process based on henna and tetrakis hydroxymethyl phosphonium sulphate (THPS) for the production of upper leathers as a cleaner alternative is presented. Extract from the leaves of Lawsonia inermis (henna) has been evaluated for its tanning characteristics in a combination tanning system based on henna and THPS. Both tanning methodologies, henna followed by THPS (henna–THPS) and THPS followed by henna (THPS–henna), have been attempted. It has been observed that THPS–henna combination tanning, employing 20% henna and 1.5% THPS, provides a shrinkage temperature of 96°C. The characteristics of the leathers indicate that the THPS–henna combination system provides leathers with good organoleptic properties and comparable strength properties. The combination system provides significant reduction in the discharge of total dissolved solids in the wastewater. These leathers showed opened up, split compact fiber structure, indicating that the tanning process did not bring about any major change or destruction on the fiber structure of the leathers. The leathers have been further characterized for chemical analysis and scanning electron microscopy. The leathers obtained from the combination system are lighter in color compared to control leathers. Possibility of making upper leathers from THPS–henna combination system as an effective alternative cleaner tanning methodology is established in this work.