Combination of reduction with metallic sodium and adsorption with mesoporous materials for re-refining of used insulating oil via experimental design

In this study, re-refining of used insulating oil by mesoporous silicate material (MCM-41) and metallic sodium was investigated. Also, the effect of silicate absorbents which was synthesized and functionalized with aluminum (Al-MCM-41) was studied (18 wt% and 36 wt%). The physical and structural properties of Al-MCM-41 were characterized by FT-IR, BET, XRD, FESEM and the obtained results illustrated a successful synthesis of the mesoporous material. The refined oil was treated by MCM- 41 adsorbent. After that, total acid number (TAN) of used insulating oil was effectively reduced by metallic sodium. The effect of some parameters such as contact time, temperature and the dosage (sodium and adsorbent to oil ratio) was designed and optimized by response surface method (RSM). The results showed that the acid number incredibly decreased at 150, 60 min and 2% of sodium to oil. The color of the re-refined oil was significantly reduced. The factors such as, time, temperature and dosage was statistically studied by ANOVA. The adsorption of MCM-41 was also studied by this way. Based on proposed procedure, the modeling was carried out. Treating of oil with MCM-41 after using metallic sodium causes lower color of oil.