Membranes with Favorable Chemical Materials for Pervaporation Process: A Review

Pervaporation (PV) process is a process for liquid mixture separation in a liquid phase. This process is able to separate different components from mixtures such as water/organic, organic/water and organic/organic mixtures. Pervaporation process works by placing a liquid mixture to be separated (feed) in contact with one side of a membrane. Across the membrane, the chemical potential gradient works as the driving force for the mass transport of the materials. Also, using vacuum pump or an inert purge (normally air or steam) on the permeate side can help to maintain of a suitable permeate vapor pressure. Usually the kept pressure is lower than the partial pressure of the feed liquid. Finally, the permeated product (permeate) can be removed from the other side with low pressure vapor. In terms of the application or nature of the experiment, the permeate vapor may be collected after condensation or released if desired.

Basically, hydrophilic and hydrophobic membranes apply to separate the aqueous solutions and organic solvents from water mixtures, respectively. PV separation technology has superiority to other separation technologies due to the separation mechanism which is based on the difference in sorption and diffusion properties of the feed substances as well as perm-selectivity of the membrane.

Nano-Filtration and Ultra-Filtration Ceramic Membranes for Food Processing

The development of inorganic membranes started with vycor type glass membranes initially studied around the 1940’s. The first period that proceeded the current generation of inorganic membranes was related to the separation of uranium isotopes by gaseous diffusion processes. The challenge was to employmembrane materials who can sustain aggressive environment and offer reliable performances. Following such developmental work, two companies in the 1973, Ceraver and Euroceral, started to produce ceramic oxide based supports used to supply the Nuclear Fission Industry of suitable propeller. The nature of the membranes still operating in Eurodif plant (France) remains classified. 

The second period consists on the development of microfiltration (MF) and ultrafiltration (UF) inorganic membranes as a consequence of the knowledge accumulated by the companies producing gaseous diffusion plants. In the 1960’s, Carre (a subsidiary of DuPont) developed the concept of liquid filtration on dynamic zirconium hydroxide supported on stainless steel. In the 1970’s, Union Carbidedeveloped ceramic oxide layers coated on carbon supports. The first commercial cross-flow filtration system equipment with inorganic membrane was manufactured by SFEC in the 1978. The concept of multichannel support was introduced in the 1980’s from Ceraver and could be considered the starting point on the development of the new generation of ceramic membranes (CM) which began to operate at lower porosity scales: UF first and nanofiltration (NF) more recently.