Improving the Performance of a Liquid-Liquid Extraction Unit By Using Optimum Solvent

The Polytechnic University of Puerto Rico stopped the use of the Liquid-Liquid Extraction (LLE) Unit at the chemical engineering laboratory because it threatened the health of the operators and people near the area. The reason of this issue was the solvent used with this particular equipment, because it is hazardous to health, emits a strong odor and also causes corrosion in the equipment. Therefore, substituting this toxic solvent became a priority.
The LLE is a mass transfer operation unit based on the dissolution of one or more components of a liquid mixture in a selective solvent. This process consists in putting together a liquid mixture with a liquid solvent which is immiscible with this mixture and, by means of a good agitation, the solvent is put in contact with all the components of the mixture and selectively extracts the components that are more soluble in it than in the mixture. LLE has many applications in different industries such as: metallurgical extractions, pharmaceutics, fuel oil extractions, and environmental industry. It is an important process of the chemical engineering industry and if the students can learn more about it, the better; that is why this project is so important for the community and the institution. In this research, an optimum non-hazardous solvent to be used in the LLE Unit was found. Moreover, three Standard Operating Procedures (SOP) of LLE experiments were designed using this safe solvent.
The first phase of the research were to analyze the common solvents available to be used with this liquid-liquid extraction unit, and it was concluded that none of these solvents were suitable for solving the actual problem. All of them were dangerous for the health, and also had a low permitted exposure limit, established by regulatory agencies, for an operator to handle them without a fume hood. Because of this matter, the next phase of the project was searching for non-common alternative solvents to perform the experiment without harm. Green solvents are those non-toxic, biodegradable, reusable, and easy to separate solvents that can be used in industrial procedures without affecting human health or environmental safety. After a rigorous research, an optimum solvent was found in this category, meeting all the required specifications.
In the final phase, three new experiments were designed with their respective SOPs, in order to test the selected solvent. It was proposed to work at the following concentrations: 50% chosen solvent, 40% water and 10% solute. The selected concentrations were the appropiate ones, based on the literature review, in order to prevent any damage to the equipment and promote a good extraction. As future work, the validation of each SOP is required to confirm that the proposed concentrations are the most favorable.