The Lowdown on Nanofiltration

The benefits of using nanotechnology within packaging continue to be debated, with market experts, such as Kathy Groves from Leatherhead Food Research, questioning whether or not particles will come off onto food and if there is enough capacity to provide the necessary volume of packaging.

Aside from packaging, however, nanofiltration has been proving its worth for the filtration and separation aspect of food processing.

Using a membrane process that rejects particles of the size range of one nanometre, nanofiltration is classified as a process between ultra filtration and reverse osmosis. Frost & Sullivan’s report: "Nanofiltration – An Overview of Technology Development Status and Trends", reports that nanofiltration as the final process has become more popular in recent times "due to its potential application in new technical areas or as a replacement for other solutions such as reverse osmosis".

Despite being seen by some market commentators as a relatively recent development in membrane processes, nanofiltration has, according to Frost & Sullivan chemicals, materials, and food ingredient analyst Krzysztof Grzybowski, been in existence for a long time.

Frances Penwill-Cook: How popular is nanofiltration in the food processing industry?

Krzysztof Grzybowski: Nanofiltration is, in my opinion, quite popular in food processing. Separation technologies usually count for approximately 40% of processing costs within the food industry. So, if someone has the possibility of separating chemicals using a cheaper method such as membrane separation then this person will choose it. There are a few specific applications where nanofiltration is used.

FP-C: What are the benefits of nanofiltration implementation?

KG: Benefits include the reduction of cost due to energy savings compared with other technologies, and as it is a well-developed technology there is no problem with applicability and various differences. The food industry is not afraid of using it because compared to other separation techniques, for instance with the most demanding reverse osmosis, it uses less energy and provides the same effect and the same efficiency. So you can have the same separation effect at a lower cost.

FP-C: What is one of the most exciting developments on the scene?

KG: If you are talking strictly about nanotechnology, I would say there are interesting membranes developed by Lawrence laboratory that are built of carbon nanotubes. These guys have found that the friction of the internal surface is very small and there is a low pressure drop. It is really good material to use, but it must pass a validation procedure to be used in contact with food.

FP-C: How is nanofiltration likely to develop as we head towards the future in the food industry?

KG: I would rather speak in more general terms as the technology is also used in the water industry. There is a huge interest in water desalination and usually this is done by reverse osmosis – if we are talking about membrane separation there are some interesting applications, but there is a method for replacing monovalent ions in the solution (the most cost and energy demanding, separated usually by reverse osmosis), with higher ions like calcium during chemical reaction.

FP-C: Do you think nanofiltration could ever replace reverse osmosis?

KG: Nanofiltration is much cheaper in operation than reverse osmosis but you get the same effect, so nanofiltration could, in the future, replace reverse osmosis because of this and other advancements.

Better membrane structures mean that you have better and higher precision separation, which can be more precisely controlled. Better control on the content means better product quality.

FP-C: What are some of the disadvantages of using nanofiltration?

KG: If you have a less-demanding application you can use microfiltration and it will cost you less and also use less energy. Moreover most of the separation may be a group of polymers – the temperature threshold for polymers is approximately 80°C so it is difficult to use polymeric membranes over these temperatures.

People are fighting with these problems using various approaches, but often the polymers are sensitive and they can be destroyed, limiting their capability.

FP-C: How does nanofiltration reduce costs and is it more beneficial to the environment?

KG: Some companies will be able to recover waste water, which can be reused in the industrial process. This is crucial to the food industry as it produces a lot of waste water. If you have good membranes, you can control the stream of the water that is recovered from the processed water – therefore you are reducing the waste water and the bill for the water that is consumed in the process.