The effect of valonea and henna treatment and post-mordanting on Cr (VI) and free formaldehyde formation in leather

Present study aims the use of natural vegetable tannins as antioxidant phenolic materials in the processing of chromium tanned leathers and to investigate their effect on Cr(VI) and free formaldehyde formation. For this purpose valonea and henna were selected as tannins and their antioxidant capacities were determined by FRAP and TEAC/ABTS methods. These vegetable tannins were used in retanning process of chromium leathers in combination with copper, aluminium and iron based mordants to evaluate their potential on reduction of Cr(VI) and formaldehyde content of the leathers as well as their effect on colour tones.