Leather Industry, Unhairing-Liming
The aim of the unhairing-liming step is to remove from the raw skin all the components which are not transformed into leather, such as the superficial epidermis including the hair and the subcutaneous adipose layer. The liming step introduces chemicals such as lime (Ca(OH)2) and sodium sulfide (Na2S) or sodium hydrosulfide (NaHS) which open the fibrous structure of the skin. Consequently, exhausted effluents are highly polluted for the presence of sulfide, amines, organic matter coming from degradation of hairs and epidermis, and high concentration of alkalis. The COD of exhausted effluents ranges between 20,000 and 40,000 mg/L of consumed oxygen.
- Cassano A, Drioli E, Molinari R (1998) Integration of ultrafiltration into unhairing and degreasing operations. J Soc Leath Technol Chem 82:130–135Google Scholar