A new ultrasonic cleaning model for predicting the flux recovery of the UF membrane fouled with humic acid

Ultrasonic cleaning is an alternative promising method to control the membrane fouling. At present, the urgent task of further promoting its application is to establish a model to predict the instantaneous membrane flux. In this study, a new model was proposed by considering the power intensity and temperature, and the ultrasonic cleaning mechanism was revealed with ultrasonic cavitation theory and extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory. Results showed that the predictions of the model were in good agreement with the experimental data (σ < 1.23%) for the polyethersulfone (PES) ultrafiltration (UF) membrane fouled with humic acid (HA) and its accuracy was higher for the polyvinylidene fluoride (PVDF) UF membrane (σ < 0.72%) or actual sewage (σ < 1.18%). Meanwhile, the HA cake resistance was removed 79.10~88.91% and the corresponding available membrane area increased 0.42–0.57 times within 1 min, and the membrane flux recovery (FR) could be reached to 91.07% within 5 min (100 W and 30 °C). In addition, the main mechanism of ultrasonic cleaning was that the kinetic energy of the ultrasonic cavitation microjet (6.28 ×10−10 J) was much bigger than the interaction energy between the HA foulants and the membrane surface (7.92 ×10−13 J).