Energy-efficient polymeric gas separation membranes for a sustainable future: A review

In the face of water shortages, the world seeks to explore all available options in reducing the over exploitation of limited freshwater resources. One of the surest available water resources is wastewater. As the population grows, industrial, agricultural, and domestic activities increase accordingly in order to cater for the voluminous needs of man. These activities produce large volumes of wastewater from which water can be reclaimed to serve many purposes. Over the years, conventional wastewater treatment processes have succeeded to some extent in treating effluents for discharge purposes. However, improvements in wastewater treatment processes are necessary in order to make treated wastewater re-usable for industrial, agricultural, and domestic purposes. Membrane technology has emerged as a favorite choice for reclaiming water from different wastewater streams for re-use. This review looks at the trending membrane technologies in wastewater treatment, their advantages and disadvantages. It also discusses membrane fouling, membrane cleaning, and membrane modules. Finally, recommendations for future research pertaining to the application of membrane technology in wastewater treatment are made.

Membrane Technologies in Wastewater Treatment: A Review.

Before the injection--modern methods of sample preparation for separation techniques.

High purity hydrogen has many applications one of which is in the hydrogen fuel cell industry. Hydrogen can be easily produced from water electrolysis; however, the most economical method is steam reforming of methane. This delivers a mixture of gaseous compounds from which hydrogen can be extracted. Besides various techniques such as pressure swing adsorption and cryogenic distillation, dense metal membranes offer an energy efficient and highly selective method for separating hydrogen from a hot gas mixture achieving high purity levels. This review article covers the fundamentals of hydrogen selective membranes for both the porous and dense kind. An in-depth look at dense and porous membranes is taken to establish their current development and a comparison is drawn between both types showing that dense metal membranes have the best hydrogen flux and selectivity. A variety of commercial dense metal membranes are compared revealing the Group V elements such as vanadium (V), niobium (Nb) and tantalum (Ta) to have the highest hydrogen permeability. A major limitation with these metals is their tendency to form a stable oxide layer under ambient conditions. Palladium (Pd) does not suffer this problem at typical membrane operating conditions and with relatively high hydrogen permeability is a suitable alternative as a dense metal membrane. Over the years it has been discovered that alloying Pd with elements such as silver (Ag), yttrium (Y) and copper (Cu) results in marked improvements in hydrogen permeability, mechanical durability and in some cases resistance to contamination by sulphur containing compounds. Nevertheless, there are still opportunities to improve the performance of the existing commercial Pd-based membranes by investigating the endless scope of unexplored Pd binary and ternary alloys.

Hydrogen selective membranes: A review of palladium-based dense metal membranes

In the past several decades, membrane separation has gone from a laboratory curiosity to commercial reality These membranes often have a separating layer thickness

Polymer membranes for gas separation

1 Microfiltration and ultrafiltration (W Eykamp) 2 Polarization phenomena and membrane fouling (MHV Mulder) 3 Vapor permeation (Y Cen, RN Lichtenthaler) 4 Reverse osmosis (CJD Fell) 5 Pervaporation (J Neel) 6 Electrodialysis and related processes (H Strathmann) 7 Liquid membranes (liquid pertraction) (L Boyadzhiev, Z Lazarova) 8 Membrane bioseparations (SL Matson) 9 Food and beverage industry applications (M Cheryan, JR Alvarez) 10 Membrane contactors (BW Reed, MJ Semmens, EL Cussler) 11 Analysis and design of membrane permeators for gas separation (A Sengupta, KK Sirkar) 12 Gas separation using inorganic membranes (K Keizer, RJR Uhlhorn, AJ Burggraaf) 13 Economics of gas separation membrane processes (R Spillman) 14 Catalytic membrane reactors (JL Falconer, RD Noble, D Sperry) Subject index

S. Alexander Stern

Papers

Membrane separations technology : principles and applications