Dyeing and UV-protection properties of water extracts from orange peel

We report a novel application of using orange peel as a new natural dyestuff with strong ultraviolet absorbance. Orange peel (OP) is an abundant, cheap and readily available agricultural byproduct. Water extracts from OP were used to dye wool fabrics. Effects of extraction temperature and time on UV-Vis absorbance of the extracted liquor, and effects of dyeing methods and conditions, including pH value, temperature, time and concentration of OP extracts on the colors of the dyed wool fabrics, were studied. OP extracts can be readily sorbed by wool directly, with aluminum or iron mordants, both of which are benign to the environment and human health. The optimum dyeing conditions included dyeing temperature of 100 °C, dyeing time of 120 min, pH 3 for direct dyeing and pH 7-9 for one-bath mordant dyeing. All the dyed wool fabrics demonstrated good colorfastness to washing with soap, good colorfastness to rubbing and acceptable colorfastness to light. Furthermore, OP extracts had strong and durable UV-protection properties. The value of UV-protection Factor (UPF) of the wool fabric dyed with OP extracts using direct dyeing method was about 6 times higher than that of the wool fabric dyed with normal synthetic dyes with similar shade and depth of shade. After 30 home laundering cycles, the UPF value of the former was still about 4 times higher than that of the latter. In general, the abundantly available agricultural byproduct OP has great potential to be utilized as a natural textile dyestuff that could impart textiles with remarkable UV-protection properties.