Abstract: In this study, activated clay was used as an adsorbent in the bleaching process of transformer oil, and the effects of adsorption temperature, amount of activated clay and adsorption time on the oil color were discussed. The color changes of the oil samples were analyzed by colorimeter and spectrophotometer, and the structures of the activated clay before and after adsorption were characterized by infrared spectroscopy (IR), thermogravimetry analysis (TG) and scanning electron microscopy (SEM). The results showed that the activated clay had excellent decolorization effect on transformer oil. At the conditions of activated clay amount of 5%, the adsorption temperature 90 ℃ and the adsorption time of 1.5 h, the color number of transformer oil could decrease from 9 to 1 and the light transmittance was over 90%. The breakdown voltage increased by 56.64%, the dielectric loss factor decreased by 18.81%, and the moisture content decreased by 25.69%.

Key words: activated clay, transformer oil, bleaching, adsorption