Professor Glenn Lipscomb presents a state-of-the-art and the future challenges for the use of membranes for separation processes in industrial application; this is a technology which could lead to substantial energy savings (it requires less energy than thermal methods such as distillation) and make industry more sustainable.
The world energy consumption has been increasing steadily in recent years. Such an increase is partly due to the larger world population, but also to the higher technological development of our society.
According to some data published by the US Energy Information Administration (EIA), the amount of consumed energy increased by about 8% between 2008 and 2012. Moreover, some researchers estimate over the next two decades the increase will be even larger.
Such levels of energy consumption are not sustainable, due to the limited availability of many energy sources, and for the possible impact on the environment.
It is therefore essential to develop new technologies which could lead to substantial energy savings. Indeed, one of the 12 principles of the green chemistry is about the design for energy efficiency.
Separation Processes – Distillation
Many industrial processes, for the production of different products and goods, employ separation processes. To produce a compound with a high level of purity, for instance, it is necessary to separate it from all other chemicals which are present as impurities. Examples can include production of pharmaceutical compounds or food items.
The most common separation process is distillation, which consumes high amounts of energy. Researchers in fact estimated that distillation accounts for about 53 % of the energy used for all separation processes.
Different Distillation Technology – Membranes
A different way to separate two or more different compounds, that uses much less energy, is by using membranes. Membranes are materials with pores of appropriate sizes that act like filters; a separation can be achieved as some chemical compounds can pass through the pores (permeate or filtrate) while some others do not (retentate).
Membranes technology has evolved remarkably in recent years; Professor Glenn Lipscomb, PhD, from the University of Toledo (US) presented a summary of the latest development in the 19th Annual Green Chemistry and Engineering Conference in Maryland (US), on the 16th of July 2015.
Membranes Success for Waters
In his presentation, Dr. Lipscomb gave some examples of the successful use of membranes in industrial processes. Membranes are widely used, for instance, for water desalination; water filtering using appropriate membranes can remove all unwanted minerals from the water, making it drinkable.
According to published data, membranes are used to produce 63.7 % of desalinated water, while thermal methods such as distillation provide only 34.2 % of the water.
It is interesting to note that in the past it was the opposite, as thermal methods were more used than membrane filtration; this change was possible due to the developments of the membrane technology and the corresponding decrease in the costs.
Indeed, science has made substantial progress in the materials used for the membrane manufacture, and in the membrane process design. This increased membrane use led to substantial savings in energy consumption.
Applications to Liquids and Gases
Membranes are used also for the separation of different gaseous compounds. An example at industrial level is nitrogen (N2) production from air. To do this, air is passed through appropriate membranes which separate N2 from the other gases present in air, i.e. oxygen (O2), water vapor, carbon dioxide (CO2), etc..
Other membrane applications include the separation of different hydrocarbons derived from oil (separation of propene from propane), and the production of pure ethanol (elimination of water residues, for application as biofuel).
Membranes in Science: The Challenges
Decoded Science spoke to Dr. Lipscomb about the future challenges for more widespread membrane use. He tells us:
“Membranes demonstrated the ability to reduce the energy consumption and the total costs in desalination and nitrogen production. Similar reductions are possible in the chemical and pharmaceutical industries, if we can develop membranes that withstand the aggressive chemical and thermal conditions of these processes”.
To do this, research is essential, to find new materials and designs which could be suitable in more robust conditions. Indeed, many researchers are working in this field; this is confirmed by the increasing number of scientific publications.
Scientists are particularly investigating innovative materials, with advanced performance. These include carbon nanotubes, graphene and traditional materials (polymers and ceramics) but with increased porosity.
Technology for More Sustainable Industry
The use of membranes in some industrial processes already showed the potential for substantial energy savings. Widening the applications in which we use membranes presents challenges, which can only be met with more research and investment.
The development of this technology is essential for a more sustainable industry.
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