To our surprise, supplying energy to the mixture by means of an ultrasound bath dissolved remarkably more of the PA 6 filaments than the energy supply with microwaves during an equal dissolution time of t ≤ 16 h, as shown in Figure . For example the PA 6 recovery was increased more than 21% points when energy was introduced into the system with ultrasound instead of microwaves during 5 h of dissolution. Alternatively, this can be stated as ultrasound dissolving the same amount in a clearly shorter time period when compared to microwave-assisted dissolution. To the best of our knowledge, we are the first to report these findings for PA in CEW. Therefore, ultrasound was chosen as energy supply mode for further investigations. For dissolution times above 16 hours the differences between the energy supply modes were less pronounced. Further discussion on the comparison between the two modes of energy supply is given in section 3.4.