Recycling of Soaking water and Unhairing ــ Liming Solution

Abstract

The aim of this research was to recycle the spent soaking water and lime-sulphide liquors several times to reduce the effect of pollution to the environment and to minimize the cost of soaking and liming operations by saving water and chemicals compared to the conventional method without the influence in the quality of the produced leather by this method of recycling. It has been found on the basis of this work, that average savings were 75% water, 33.3% sodium sulphide and 28.5% lime in addition to the reduction of the cost of handling the tannery effluent. For the purpose of this research, raw sheep, goat skin and cattle hides in the stage of wet- salted were processed with the normal recipe and the once used lime sulphide solution was analysed for lime and sulphide content to make-up the same concentration of the fresh liquor at the initial level of composition adding lime and sodium sulphide to make-up a new liquor for recycling. This process was repeated 13times. After the end of each operation the pelts were checked visually ,the pHs were taken and the results were satisfactory. Then the pelts were processed to pickled, wet in blue, crust and finished stages with the recipes applied patches in the EL NASR TANNERY. The skins were analysed physically and the results were satisfactory. The leather produced is normal, soft, full with good break and good tensile strength. The resultant leather has similar properties as the one produced with conventional method. This process of recycling is recommended to be applied in the tanneries gradually until it is well established because until now it is not recognized as standard process. Extensive researches are on going in ITALY, Australia, and other countries on recycling of tannery effluents. This is because there is a save in chemicals used and hence there is a reduction in the cost of handling the effluent and reduction in pollution hazards. Its application is simple and requires a collection pit, filter, pump and a pipe line to and from a drum or even paddles.