The invention relates to a method for the removal of metals from starting materials comprising proteinaceous substances by labilizing and solubilizing the metal with a treatment with chemical agent which includes leaching out, extraction, removal by means of redox and/or acid-base reactions, wherein this chemical treatment is combined with a treatment causing cross-linking of the proteins in the proteinaceous material. The invention allows for the treatment of e.g. leather wastes for the removal of chromium therein. After the appropriate treatment collagen is obtained. This collagen is structurally undamaged, free of chromium and suitable for uses in cosmetics, drugs, high quality gelatin, food, etc.
