<p>The investigation of efficient biocarbon adsorbents for the separation of crude oil from water has garnered considerable attention from researchers. In this study, we successfully synthesized potassium-based-modified bio-adsorbents using K₂C₂O₄, K₂CO₃, and KOH from date palm seed for oil–water separation. The influence of various parameters such as modification temperature (600, 700, 800 and 900°C), adsorption temperature (10,25 and 50°C), adsorption kinetics and oil viscosity on the performance of bio-adsorbent was examined. Additionally, the mechanism of oil adsorption was evaluated. The synthesized biochar (BC7), prepared at 700°C for 1.5 h, and KOH-modified biochar (MBC7-8), prepared at 800°C for 2 h, were characterized using FESEM, EDX, FT-IR, XRD, and BET-BJH analysis. The results show that KOH-modified biochar has the higher oil adsorption capacity than K₂CO₃- and K₂C₂O₄-modified biochar. The results revealed that MBC7-8 exhibits a honeycomb-like structure and possesses functional groups with a high specific surface area 349.23m²/g. Adsorption studies of BC7 and MBC7-8 fit the pseudo-second kinetic model well (R² &gt; 0.99). BC7 and MBC7-8 demonstrated an exceptional oil adsorption capacity of 1726 and 3127mg/g. This enhanced capacity is attributed to the interaction between carbon-KOH at high modification temperature, which causes an increase in surface area, surface functional groups, and consequently, oil sorption capacity. Also, findings indicate that increasing the ambient temperature and oil viscosity has a positive impact on the performance of BC7 and MBC7-8, leading to an increase in their adsorption capacity. With its unique structural and surface properties, MBC7-8 holds immense potential as a cost-effective and efficient porous bio-adsorbent for oil spill clean-up.</p>