Reduction of Hexavalent Chromium from Chrome Shavings
Pages : 24-27
The chrome tanned leather shavings which are produced by chrome tanning process and disposed as a waste, has to be treated and recycled. In this study the chrome shavings were incinerated at 1000oC to transform chromium III to chromium VI. In our previous work on extraction of chromium six from chrome shavings, the dichromate was leached and all the factors affecting leaching were determined, the optimum values of these factor: were solid/liquid ratio of 1:10, time of 1 hour and temperature of 37oC with mixing at 200rpm. The hexavalent chromium was reduced to basic chromium sulphate using 250% water, 92% Sulphuric acid and 25% sugar based on the dichromate weight. The basic chromium sulphate obtained was of 33% basicity and 21% chromic oxide with conversion of 96.80%. Experiments on the reaction kinetics were performed to determine the reaction order, the reaction rate and conversion. These were found to be first-order reaction and 100% conversion after ageing for two weeks. Complete reduction was achieved in three hours with pH of 2.5. A chrome tanning trials were performed using pickled sheep skin. The tannage was completed and the pelts passed the boiling test, then pelt were neutralized and fat-liquored and left overnight. The dried pelts were conditioned and the crusts produced were subjected to chemical and physical analysis, with chromic oxide 4.4, moisture content 14%, ash content 4.6%, shrinkage temperature 100oC, fat content 3.4% , tensile strength 171kg/cm2, elongation at break 49% , tear strength 100kg/cm, and load at grain burst 40 kg.
Keywords: Chrome shavings, Hexavalent chrome, Reduction, Solid waste, Leather
Article published in International Journal of Advance Industrial Engineering, Vol.1,No.1 (March- 2013)