The Institut Laue-Langevin, the global centre for neutron research in Grenoble, has announced a study relevant to mineral processing and based on the properties of extracts from seeds of the Moringa oleifera tree – the so called ‘miracle’ tree which is thought to be responsible for biblical stories of a tree turning ‘bitter waters sweet’ and is native to some of the poorest areas of Asia and Africa. The seeds are already a source of food and fuel, and have recently been revealed as a natural, low-cost sustainable alternative to removing toxins from drinking water. Now research suggest the same seeds could also be used as a natural low-cost alternative to synthetic chemicals in the separation and purification of metals in the mining industry.

Previous studies have shown that the extracts from seeds of the Moringa oleifera tree can be used for water purification. In a new study, researchers from Uppsala University show that the Moringa seeds can also be used for separation of different materials in the mining industry. Moringa trees are known as ‘miracle’ trees because of their many uses as food and as a source of oil. The special properties of the protein in the seeds have been studied by a group from Uppsala University in collaboration with the Polytechnic of Namibia, Windhoek, and the Institut Laue-Langevin.

The results, published in the Journal of Colloid and Interface Science, were obtained from neutron reflectometry experiments carried out at the Institut Laue Langevin. Dr Rob Barker, one of the study’s co-authors, said “What makes neutrons particularly valuable for experiments of this kind is their ability to examine interfaces buried below the surface layer. They are able to penetrate deep into the solution and extract critical information about properties such as density and thickness that would otherwise be extremely difficult to measure.” Protein from crushed seeds of Moringa bind to particles in water and cause them to aggregate. They can then be removed easily by filtration or settling. Choosing the right quantity of Moringa proteins avoids leaving unnecessary protein in purified water. The amount that saturates the surface is markedly less for alumina than for silica.

“The results can help us to find the optimum amount of Moringa seeds to purify water”, says Dr Maja Hellsing, one of the researchers behind the study. Experiments with detergents added to the bound protein showed that the behaviour changes for different materials. A cationic detergent, widely used as a disinfectant, causes the protein to detach from the surface of alumina. This discovery allows control of aggregation and is therefore a method to separate different materials. “Combining the protein with detergents offers new ways to use this natural material in mineral industries that are important in many countries where Moringa grows well”, says Professor Adrian Rennie, who led the study.