Recovery of magnesium from industrial waste streams
My name is Coco and for my bachelor thesis, I was very lucky to participate the experimental campaign at the University of Palermo (UNIPA) in Sicily.It is part of the European project ZERO BRINE. ZERO BRINE integrates innovative technologies to recover minerals and water of sufficient quality.
The experimental campaign which I participated in was focused on the recovery of magnesium from a saline impaired stream also known as brine. Magnesium is classified as being one of the most critical raw materials in the Europe, which means that 96% of the magnesium is imported from other countries. At the same time, it is one of the discharged ions in high concentrations in the brine streams of various industries, such as pharma, chemical, food and textile industry. This highlights the importance of the search for methods of magnesium recovery from the industrial waste streams.
Crystallization is the used method to recover magnesium from industrial brine water during my research. The challenge for my research is to shorten the filtration time of the crystallized magnesium and to obtain a good quality of magnesium. This is done by doing experiments with an imitation brine stream and using a seed suspension. The seed suspension consist seeds of magnesium hydroxide and water. The new formed crystals will ‘grow’ on the existing seeds, which will make the filtration time shorter. The first step is to choose an experimenting method that is similar to the pilot system of the ZERO BRINE project and also is easy to control. These requirements are such as processing rate of the brine stream and the dimensions of the pilot system. This is why the semi batch system is chosen with a needle injection. The second step was to obtain a good ratio between seed suspension and the imitation brine, during the crystallization of magnesium hydroxide. More seed suspension during crystallization leads to lower filtration times, but also makes the experiment more expensive. So the challenge is to find the balance between the two. The third step is to check the quality of the crystallized magnesium hydroxide.
The quality of the crystallized material has to be high, in order to have commercial values. This is done by using ionic chromatography and granulometric analysis. This experimental study has indicated that using a semi batch system to recover magnesium hydroxide with initial seeding is promising for potential application in the experimental campaign of UNIPA. The optimal conditions were found to be a [1:10] brine to seed-suspension ratio with an injection time of 68 seconds. The produced product shows a promising purity of magnesium hydroxide of 95.8%. What I have found in this research was promising for the future of the experimental campaign of UNIPA. My research describes only a first step in experimental campaign. The results can be optimized by further experimentation.