Brine is water with a high concentration of salt that is generated in the seawater desalination process to make it suitable for human consumption, irrigation or industrial uses, and that is returned to the sea.
But, in addition to salt – let's say common -, brine also contains other minerals that are also present in seawater, such as calcium, magnesium, lithium, potassium, boron and rubidium. High-value minerals, strategic in various industrial uses and whose land reserves are beginning to be very limited. In fact, the EU has classified some of them as critical raw materials.
So the possibility of extracting them for their use appears as a sustainable formula for obtaining, outside of traditional mining, with high environmental impact, these scarce elements and raw materials, as well as a way to reduce external dependence.
A mine in the desalination plant
The minerals contained in sea water come mainly from rivers that, for millions of years, have been pouring into it the particles produced by the erosion of rocks. However, there are regions in which there may be a different presence of one or the other.
In this context, Acciona is carrying out the Minerals project to develop and validate the most effective and efficient technologies and procedures to separate and extract critical minerals from brine before returning it to the sea.
“Most of these minerals are in small concentrations, so until now with existing materials and technologies they either could not be recovered, or it was not economically viable,” explains Lyvia Mendes, head of the Minerals project at Acciona. «The key is that, after the seawater desalination process, we have them concentrated in the brine; which, in addition, no longer has elements such as algae or other suspended solids, because they have already been eliminated. Which is an added advantage,” Mendes emphasizes.
The Minerals project led by Acciona will last three years, the Leitat technology center also participates in it and has financing from the European Union within the framework of the Next Generation projects.
Laboratory, first; demonstration plant after
It is currently in its first phase, in which “the entire global process of the project is designed and validated,” explains Olga Ferrer, head of desalination innovation at Acciona, “and when it is decided what technologies will be used, what membranes we will use to separate those minerals, the operating conditions, etc. Everything in the laboratory. With these tests, which will last approximately one year, it will be possible to check the degree of compliance with the estimates “of the quantities of each mineral that can be obtained, degrees of purity, consumption of reagents and energy, etc., to make a first technical balance,” predicts Ferrer.
The separation and extraction of minerals from brine is another industrial process and will require a specific plant, which will be designed based on the results of the first phase. The first installation will also be experimental in nature and it will be possible to verify that the process tested in the laboratory works correctly on a demonstration scale.
Strategic project
Obviously, this is a strategic and long-term project, which requires significant investments. An effort that will allow us to know if it responds to the forecasts of a project with which, additionally, desalination will be opened to the circular economy, since “some of the extracted minerals, such as calcium and magnesium, could later be used in the process of remineralization of drinking water,” says Olga Ferrer.
For this technique, “it is an interesting project because there is a great demand for all these minerals. As we treat enormous flows of water, after a year a considerable amount of it passes through a desalination plant. “It represents an opportunity to recover resources to the maximum and have security of supply.” An a priori calculation by Acciona estimates that about 28 tons of lithium per year could be extracted from the brine generated in the Torrevieja desalination plant. Or what is the same: enough quantity for the batteries of 1,800 electric cars. Having these raw materials could provide significant additional income to the company.
Precisely, the launch of the pilot plant, which will be an additional installation in an already operational desalination plant that will carry out an independent process, will allow “the definitive evaluation of the project and the processes be considered valid. From that moment on, costs can be optimized much more and the installation can be replicated in other plants, since in all of them, regardless of the desalination technology, the brine produced will contain high-value minerals susceptible to recovery.