Title: A new view of membrane fouling with 3D ultrasonic imaging techniques: Taking the canola oil with phospholipids for example

Journal: Journal of membrane science

Authors: Li-Hua Chenga, b, Yun-Chen Yangb, Junghui Chenb, Yi-Hsun Linc and Shyh-Hau Wangc
a Department of Environmental Engineering, Zhejiang University, Hangzhou 310027, PR China
b R&D Center for Membrane Technology and Department of Chemical Engineering, Chung-Yuan Christian University, Chung-Li 32023, Taiwan, ROC
c Department of Computer Science and Information Engineering, and Institute of Medical Informatics, National Cheng Kung University, Tainan City 701, Taiwan, ROC

The original and creativity of paper: The paper examined membrane fouling using the ultrasonic imaging technique. This method is the signal capturing during ultrafiltration of phospholipids from the crude oil. 

Summary:

Generally, membrane fouling has been studied by the experimental evaluation (i.e., flux decline behavior). However, in this paper, ultrasonic imaging technique was developed for fouling evaluation. The technique provided more vivid and clear visualization by 3D construction than other techniques.

The ultrasonic system 

 
Fig.1 Schematic representation of the ultrasonic measurement system.

How ultrasonic measurement system work?
1.    Ultrasonic transducer is used to convert electrical energy into ultrasonic or acoustic energy and vice versa
2.    Transducer is immersed in the commercial aqueous gel directly emitting on sample which can adjust the range of the distance between transducer and membrane using a three dimensional motor stage
3.    Pulser is used to eliminate low amplitude noise and also drive the transducer to produce ultrasonic waves
4.    Amplifier is used to amplify received echo signals backscattered from membrane, and then a bandpass filter is used to remove the noise out of the main bandwidth
5.    The received signals are passed through a commercial limiter  to provide protection for the sensitive receiving circuit
6.    The radio frequency signals are digitized by an analog-to-digital converter at 500 MHz sampling frequency with 8-bit resolution
7.    The experimental data is stored using a personal computer 
8.    Signal processes are performed on a personal computer using MATLAB
Results and discussion (Fig. 2)

1.    Results showed that ultrasonic imaging method (UIM) provided the better image than SEM
2.    The biggest image size of UIM (up to 2mm x 2mm) is bigger than SEM
3.    UIM cannot characterize the interface of the bottom support layer and the sampling platform because the attenuation of air existed in the much more porous nonwoven support
4.    UIM can be considered as a rapid, non-invasive method which has effectively characterized the control membrane structure with much wider measurement range

 
Fig. 2. Comparison of ultrasonic image with SEM for the control PES membrane (a) cross section, (b) layers upon the non-woven support, and (c) thin film layer.



Application & further study: The new method for fouling evaluation is very meaningful for the others who interested about fouling evaluation. 


By Monruedee Moonkhum
Email: moon@gist.ac.kr