Abstract: To improve the regeneration efficiency of aged transformer oil, a polyaniline/lignin fiber-chitosan/bentonite composite adsorbent was prepared. The effects of adsorbent dosage, polyaniline/lignin fiber mass fraction, and treatment temperature on the dielectric properties of regenerated oil were investi-gated. Fourier-transform infrared and ultraviolet-visible spectroscopies were used to analyze the adsorption mechanism. Under optimal conditions (an adsorbent dosage of 4 g/L,a polyaniline/lignin fiber mass fraction of 20%, a temperature of 80 °C,an adsorption time of 1.0 h), the breakdown voltage increased from 5.66 to 47.36 kV, while the dielectric dissipation factor decreased from 0.215 to 0.009. The treated oil met the requirements of GB/T 7595—2017 for in-service transformer oils (≤220 kV) and for oil prior to commissioning. Spectroscopic results showed no formation of new substances, indicating that impurity removal mainly occurred through physical adsorption. The composite adsorbent features simple preparation and effective regeneration performance, offering a promising approach for the resource utilization of aged transformer oil.

Key words: aged transformer oil, adsorption regeneration, chitosan, bentonite, lignin fiber, polyaniline