Sustainable Reclamation of Spent Transformer Oil Using Bentonite and Palm Kernel Shell: A Review

Abstract

Transformer oil plays a crucial role in ensuring the operational reliability of power transformers by providing electrical insulation and facilitating thermal management. Nevertheless, its deterioration owing to thermal, oxidative, and electrical stresses results in the emergence of contaminants, including sludge, acids, moisture, and dissolved gases, which subsequently undermine performance and present environmental hazards. Traditional treatment methodologies, although effective, frequently produce hazardous waste and incur substantial operational expenditures. This review explores the sustainable reclamation of spent transformer oil utilising various adsorbents, with a focus on bentonite clay and palm kernel shell due to their natural abundance, effectiveness, and sustainability. The investigation assesses the transformer oil composition and degradation products, the efficacy of various adsorbents, the activation methods, and the regeneration strategies. Modified bentonite, physically and chemically treated, exhibits superior adsorption efficiency. Similarly, palm kernel shell (PKS), recognised as a lignocellulosic agro-waste, demonstrates increased adsorption capacities for polar compounds due to its porous structure and carbon content. Integrated reclamation protocols encompassing heating, agitation, centrifugation, and adsorption methodologies effectively restore spent oil to a quality approaching its original state. Properties of transformer oil, such as dielectric strength, viscosity, acid number, moisture content, flash point, and fire point, improve after reclamation. The findings reinforce the viability of employing these cost-effective, environmentally benign adsorbents for sustainable transformer oil reclamation, offering a scalable solution suitable for industrial implementation.