One-step fabrication of hydrophobic photothermal pomelo peel biochar via copper-catalyzed carbonization for efficient viscous oil and organic solvents absorption

The leakage of hazardous chemicals and viscous crude oil represents one of the most pressing environmental challenges today. Developing efficient and eco-friendly approaches to facilitate organic solvents and oil absorption is crucial for addressing these issues. In this research, a hydrophobic photothermal biochar (Cu-PPC) was synthesized via catalytic carbonization of pomelo peel with copper ions and urea. The results indicate that Cu-PPC possesses outstanding hydrophobicity (with a water contact angle of 142.4°) and absorption capacity (up to 26.4 g/g), along with exceptional thermal stability and fire resistance. Additionally, Cu-PPC displays a remarkable photothermal effect, as the surface temperature rapidly reaches 89.1 °C within 5 min under solar irradiation of 1 kW/m². Leveraging this property, Cu-PPC effectively elevates temperature under illumination and successfully reduces the viscosity of surrounding silicone oil, thereby reducing the absorption time from 61 s to 41 s and achieving a 32.8% reduction. This biochar efficiently separates various oil-water mixtures, demonstrating outstanding cyclic absorption stability and broad application potential. This biochar absorbent is a novel method for treating agricultural waste and provides a simple, low-cost and efficient avenue for addressing organic solvents and crude oil spills.