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Eco-friendly leather processes based on the usage of natural products have become a potentially attractive issue for leather industry during the last few decades. Synthetic protective chemicals like bactericides used in most soaking process are known as hazardous substances and cause tannery effl uents with high concentrations of Chemical Oxygen Demand (COD). In the present study, the effect of tannic acid on microorganisms, skin, wool and effl uent were investigated in order to demonstrate the applicability of tannic acid in soaking process instead of commonly used bactericides. The bacterial load (cfu/ml), COD and Nitrogen Content (N) of the soaking effl uents and Total Kjeldahl Nitrogen (TKN) content of skins and wools were investigated. Application of 0.5 and 1 wt% tannic acid concentrations was more effective than commercial bactericide, while comparable results were achieved by 0.1 and 0.3 wt% tannic acid. The application of tannic acid for soaking process resulted in lower COD and N values of effl uents. The results show that tannic acid has the potential to be an alternative, eco-friendly bactericide for leather industry by reducing the pollution of leather soaking process.

Biological degradation of many dyes is difficult. Therefore dyeing baths give high pollution load to waste water. In this work, the use of enzyme in the dyeing of leather has been studied with the aim to improve the exhaustion of dye and to reduce pollution load of dyeing waste bath. For this purpose, chromium-tanned leather were treated with different ratio enzyme after the neutralization process. Then dyeing has been carried out. The effect of bacterial protease on colour properties of leathers was investigated. Also the change of the amount of COD load in the waste dye baths and leather physical properties were investigated. The obtained test and analysis results show that when the enzyme was used in the dyeing process, the COD load of waste dye baths was reduced.