Industrial Trials for a More Ecological Chromium Tanning

In leather production the chrome tanning method is the most widely used tanning system all over the world despite the storage and disposal of solid wastes and sludge containing high amounts of chromium poses a major challenge. For this reason many researches based on higher exhausting and lower chromium used technologies have emerged in the recent past. However, these technologies are not directly accepted by the industry due to risks and some possible changes in quality issues. Accordingly, in this project one of these approaches: chromium tanning without pickling process, using less chromium salts at higher initial pH is tried in pilot scale at a leading company in Turkish leather industry. The variables used in the research were; pre-tanning agents (aldehyde, sulphonyl chloride, and synthetic tanning agent), initial pH of tanning (5.0-5.5 and 6.0-6.5) and tanning agents (standard basic chromium sulphate and commercial tanning agent with lower chromium oxide content). The wet-end processes and finishing processes of the leathers were applied according to the company's production line. Chromium content of the leathers and the Cr2O3 remaining in effluents were determined for each tanning application. Also, the physical properties of the leathers were investigated. The Cr2O3 of the leathers were found to be varying between 3.12-4.83% while the remaining chromium in the effluents was between 16.9 - 1347 mg/L. Additionally, the properties of the final leathers were evaluated comparatively with company's regular products, considering the test results and organoleptical evaluations it was concluded that many of them were comparable to conventional chromium tanned regular products.