Purification of Produced Water by Solvents to Enhance Oil Recovery and Reuse Separated Droplets Aljadiri, Aqeel Shaikhah Arafat Bailón Moreno, Rafael Produced water Purification of produced water Oil Petroleum Complex emulsions This work has been carried out as part of the research of the doctoral thesis of Aqeel Shaikhah Arafat Aljadiri, directed by Rafael Bailón-Moreno. The doctoral thesis belongs to the Doctoral Program in Chemistry of the University of Granada (codes ISCED 1 Chemistry and ISCED 2 Physical, Chemical, Geological Sciences), International Postgraduate School of the University of Granada). The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/app15041700/s1. Supplementary Document S1: Toxicity of Xylene, Cyclohexane, and Tetrahydrofuran. In crude oil production, large volumes of produced water are generated as a highly polluting waste byproduct. On average, at least two barrels of produced water are generated for every barrel of oil. This water contains oil traces in stable and complex emulsions. To purify it, a method is proposed based on breaking these emulsions using solvents that induce the coalescence of oil droplets, facilitating their separation from the water. The method has two main objectives: (1) To identify the characteristics a solvent must have to effectively break oil emulsions according to the Hansen solubility parameter (HSP) model. (2) To select, from 40 solvents of different chemical families, the most suitable ones based on efficiency, low toxicity, industrial availability, and cost. The experimental procedure included the following steps: (1) Contacting the solvent with produced water containing 150 ppm of oil under agitation. (2) Allowing the mixture to rest until a layer of recovered oil formed. (3) Spectrophotometric analysis of the residual oil. Three distinct HSP solubility spheres were identified, within which the most effective solvents were xylene (99.4% recovery), cyclohexane (99.5% recovery), and tetrahydrofuran (100% recovery). Their high efficiency not only facilitated oil separation but also made the recovered oil suitable for commercialization. 2025-03-07T09:38:13Z 2025-03-07T09:38:13Z 2025-02-07 journal article Aljadiri, A.S.A.; Bailón-Moreno, R. Purification of Produced Water by Solvents to Enhance Oil Recovery and Reuse Separated Droplets. Appl. Sci. 2025, 15, 1700. https://doi.org/10.3390/app15041700 https://hdl.handle.net/10481/102907 10.3390/app15041700 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional MDPI