Frequency dependence of ultrasonic wool scouring

Conventional aqueous scouring of greasy wool promotes wool felting and can be energy and water intensive. Ultrasonic wool scouring could be an alternative technology to minimize the negative impact, provided that the cleaning efficiency and fiber quality are not compromised. This study examined the influence of ultrasonic irradiation frequency and ultrasonic power variations on wool scouring performance at different liquor ratios. Scoured fiber, residual ash content, residual grease content, whiteness and yellowness were evaluated. The impact of liquor degassing on wool scouring effectiveness was studied. Fiber surface damage was also assessed in this work. It was observed that while there was no significant influence of ultrasonic frequency on the whiteness or yellowness of the scoured fibbers, wool scoured at frequencies of 28 kHz and 80 kHz had more grease and dirt removed than that scoured at 45 kHz. Low ultrasonic power and degassed bath liquor increased wool grease removal ability. Ultrasonic treatment caused scale cracking/peeling in some wool fibers. More severe cuticle damage was observed in fibers scoured at the lower frequency. This damage resulted in increased dye uptake by the fibers.