Polymer Filtration Membranes

Abstract

Polymer filtration membranes have been a focus of research since the late eighteenth century and became a thriving industry in the twentieth century. Today, membranes are used in commercial applications spanning from drinking water purification to gas separations, with a market that is expected to grow to more than $10 billion by 2010. This article describes the materials and morphologies commonly found in today's commercial membranes, along with their methods of manufacture. Membranes classified according to retentate size as microfiltration, ultrafiltration, nanofiltration, or reverse osmosis are introduced, along with ion exchange and gas separation membranes. The primary mechanisms by which these different membranes achieve separation during filtration are described, as well as example applications. Permeability, molecular weight cutoff, and rejection/retention are introduced as metrics for membrane performance comparisons. Membrane fouling is discussed as a chief obstacle to the more widespread use of membranes in wastewater treatment and other applications involving high concentrations of organics in the feed stream. Mechanisms of membrane fouling are described along with approaches commonly employed to limit fouling, including membrane surface modification, process optimization, and pretreatment of the feed. The future outlook of the polymer filtration membrane industry is touched upon in the context of increasing demand for fresh water and continuing improvements in membrane performance anticipated by research advances.

Electro-Conductive Membranes for Permeation Enhancement and Fouling Mitigation: A Short Review

“…According such a rationale several biosensors, electronic devices, and biomimetic devices have been prepared from electrically conductive polymer membranes [ 20 , 21 , 22 , 23 ]. The specific reactivity/polarity/conformation of used conducting polymers, virgin or properly functionalized for a better integration in the pore structure, enables an electro-responsiveness in filtration membranes usually adopted for water treatment [ 24 , 25 ].…”

Responsive filtration membranes by polymer self-assembly

“…Membranes on the market today are typically classifi ed according to their pore size 2,3 . Microfiltration (MF) membranes have pore sizes between 0.1 and 10 μm and are typically used for removing bacteria and particulates.…”

“…Th e polymer precipitates on the substrate, forming a polymer-rich and polymer-poor phase. Th ese two phases form the solid membrane matrix and the membrane pores, respectively 2,3 .…”

“…Membrane technology is crucial for many separation processes including water treatment, bioseparations, and food and beverage processing [1][2][3] . Membranes are widely used in seawater and brackish water desalination, generating drinking water by removing microorganisms, and treating wastewater to remove a wide range of contaminants.…”

“…Th is leads to downtime, chemical costs, and more complicated module designs. Fouling can be a severe impediment to energy-effi cient and reliable operation of membrane systems, and extensive academic and industrial research focuses on preventing and remedying fouling [1][2][3] .…”