Optimal Intermittent Ultrasound-Assisted Latex Particle Fouling Remediation in Ultrafiltration

Abstract

The ultrafiltration process is a promising technology and considered the most effective method for diversified water and wastewater treatment. However, commercialization for this process has been limited due to the decline of the permeation flux. This decline is the result of membrane fouling that is an accumulation of suspended particles on the surface of the membrane. These particles will hinder the permeate solution that passes through the porous membrane. The objective of this study was to evaluate the effect of ultrasound (US) on the ultrafiltration process. Ultrasound has a cavitation effect that facilitates continuous membrane cleaning; collapse of cavitation bubbles produced can give the energy to remove particles from the membrane. The size and velocity of bubbles are determined by the US frequency and power, respectively. This research focused on using different frequencies (20 kHz, 28 kHz, and 40 kHz) and different power intensities (50 W, 60W, and 100 W). It was found that the flux enhancement at 20 kHz and 28 kHz were significant, while the flux enhancement at 100 kHz was not noticeable. Intermittent ultrasound was tested as to lower the cost of production and increase the lifetime of the membrane. Intermittent ultrasound was controlled by a timer with different time intervals (30 seconds on and 60 seconds off, 60 seconds on and 60 seconds off, and lastly, 90 seconds on and 90 seconds off,).The feed solid concentration used in the experiments was at 0.5wt% of latex paint. Ultrasound irradiation affected the cake layer resistance and concentration polarization which led to the reduction in the total resistance and increase in the permeate flux. Simultaneously, the flux at 20kHzand 28 kHz was higher than that at 40 kHz. Experimental results demonstrate the frequency at 28 kHz can produce better results in terms of enhancing the permeate flux. Overall, utilizing low frequency and low pressure can produce better results for enhancing the permeate flux and lowering the concentration of polarization and cake layer resistance.