How can ultrasonic scouring of sheep’s wool chemically modify its surface?

Ultrasonic wool scouring has the potential to replace the traditional method using detergents and other additives. This study aims to investigate the effect of important parameters of an ultrasonic bath operating at 38 kHz frequency on the possible chemical modification of wool scoured in tap water without any additives on a laboratory scale. The parameters tested were bath temperature (20-40-60) °C, scouring time (10-20-30) min and ultrasound intensity (30-60-90) % power of 350 VA. The measured characteristics were the content of basic groups (obtained in the range of 7.9-8.5 mmol/g) and acidic groups (obtained in the range of 9.9-8.9 mmol/g) formed on the wool as well as the ability to remove zinc salt from the solution by adsorption (97-86 %). ANOVA analysis of basic and acidic group dispersion showed the dominant effect of temperature in contrast to scouring time and intensity (F = 88.495; p < 0.001 for basic group and F = 73.101; p < 0.001 for acidic groups). The Zn(II) removal was statistically significantly affected by temperature (F = 17.652; p < 0.001) and scouring time (F = 4.913; p = 0.011), while the effect of ultrasound intensity was at the threshold limit of significance. The smallest chemical changes in the fiber occur at the bath temperature of 20 °C, scouring time of 10 min and intensity of 90 %.