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Xiao-Lin Wang

Xiao-Lin Wang

Tsinghua University, China

Title: Understanding nanofiltration: A molecular separation with nanometer effects

Biography

Xiao-Lin Wang has published more than 300 papers and taken out more than 20 patents. He is a standing committee of the society of seawater desalination and water re-use in China from 2006, a vice dean of the Membrane Engineering and Application Committee subjected to China Membrane Industry Association from 2006, the secretary-general of Beijing Membrane Society from 2005, and the council member of Aseanian Membrane Society from 2004. He was the chairman of the organization committee of the 3rd conferences of Aseanian Membrane Society in 2005 in Beijing China and the 8th conferences of Aseanian Membrane Society in 2014 in Xi’an China. He was one of congress chairmen of the 10th international congress on membranes and membrane processes (ICOM) in 2014 in Suzhou China.

Abstract

Nanofiltration (NF) membrane, firstly named as “loose” reverse osmosis (RO) or “dense” ultrafiltration (UF) membrane has two remarkable features: one is that the molecular weight cut-off (MWCO) ranges from 200 to 2000 Da, and the other is that the salt rejection depends on the ion valence and concentration. Several models for NF processes have been proposed, such as the pore model based on the sieving effect, the charge model based on the electrostatic effect, the electrostatic sterichindrance (ES) model, and the Donnan–steric pore model (DSPM), which play an important role in understanding the separation mechanism and promoting the application of NF. However, the performances of these NF membranes with features of “loose” RO membranes cannot be predicted by commercial RO simulation software. It leads to a long period of previous experiments and scale-up processes, which severely restricts the large scale standardization applications of NF. In regard to these problems, we proposed a simple simulation model for the separation performance of mixed salts solution across NF membranes to promote the application of NF during the water treatment in the light of the competitive effect among co-ions and regulation effect among counter-ions. Both the effects can be determined by some specific experiments and then based on the in-depth experimental studies on rejection performance and the attendant electrokinetic properties, some researchers have found that the performance of NF membranes cannot be predicted completely by merely considering the sieving and electrostatic effect; However, some drawbacks still exist in the analysis of electrokinetic properties. The further studies have contributed to a deeper understanding on the particular effect caused by the nano-scale pore size and charge features caused by the complicated interaction in solution. Moreover, the dielectric effect in the transport process of ions through NF membranes has been addressed and quantitatively analyzed. Recent studies have been paid much attention on the new generation of NF membranes improved by various nanostructured materials. We are also trying to develop some novel thin-film nanocomposite NF membranes derived from the dual layer (PES/PVDF) hollow fiber UF membranes.