Solvent-Aided Crystallization for Biodiesel Purification: A Review of the Technique's Proficiency

Traces of impurities encountered after purification processes compromise biodiesel's stability, longevity, and quality performance. Techniques, such as wet washing, adsorbents, and membranes, have been extensively explored; however, they grapple with several challenges, including wastewater generation, time-demanding tasks, and environmentally unfriendly protocols. This study presents a comprehensive overview of solvent-aided crystallization (SAC) as a plausible biodiesel purification option that offers economic and environmental benefits through efficient solvent recovery and minimal waste generation. A total of 23,009 documents published between 2004 and 2024 in the Scopus database were analyzed using a bibliometric approach. This gives insight into research trends, identifies the most extensively explored techniques, highlights countries with a well-established research base in this domain, and offers a guide for evaluation and preference selection for a particular technique. Although conventional methods have been acknowledged for showing great promise in removing impurities such as glycerol and free fatty acids from biodiesel achieving about 98 %, SAC was reported to achieve 99.8 % purity. Moreover, the analysis presented herein underscores the fundamental principles of SAC, factors influencing its efficiency, and the role of selective solubility in enabling effective purification. Finally, it highlights the critical role of strengthened policy action and continued research as key elements, offering researchers valuable insights for advancing the broader adoption and commercialization of SAC.