Efficient removal of dibutyl phthalate from transformer oils by iron/activated carbon adsorbent

Capturing dibutyl phthalate (DBP) impurities from transformer oils and purifying them is crucial for maintaining long-term sustainable transformer operation. Furthermore, this process significantly reduces the generation of waste from aged transformer oils, thereby contributing to environmental protection and sustainable development. In this study, various metal ion-modified wood activated carbons (ACs) were prepared using the wet impregnation method. The adsorption isotherms and adsorption kinetics studies reveal that Fe/AC exhibits a significant enhancement of more than 40% in DBP adsorption capacity compared to the original AC. Consequently, Fe/AC is the material with the highest adsorption capacity for DBP in transformer oils up to now. Furthermore, the desorption activation energy of DBP on Fe/AC was 46.623 kJ/mol, 1.73 times higher than original AC. Ultimately, the adsorption mechanism was explained using the Hard-Soft-Acid-Base (HSAB) principle, which demonstrated a stronger interaction between hard base DBP and Fe/AC due to the hard acidic nature of Fe3+ and therefore a higher capture capacity of DBP by Fe/AC. The simplified preparation method and enhanced adsorption capacity of the modified Fe/AC make it an efficient and cost-effective approach to ensure reliable and sustained transformer operation, while also minimizing the generation of waste transformer oils.