Valorization of orange peel via slow pyrolysis: Effect of particle size on biochar characteristics for wastewater remediation

Orange peels are forming a significant portion over global production of food waste generated in each year. As a byproduct of juice production, orange peel can be recycled into biochar a carbon-rich material for wastewater treatment. This study explored the conversion of orange peels into micro- and nanobiochar via pyrolysis at 500, 600, and 700 degrees C (5 degrees C/min for 1 hour). A comparative analysis of various physicochemical properties was conducted to evaluate the potential of micro and nano sized biochar that could be a sustainable adsorbent for wastewater treatment. The pyrolysis process enhanced key characteristics of the biochar, including BET surface area, carbon content, zeta potential, and fixed carbon content. However, increasing the temperature from 500 degrees C to 700 degrees C reduced 28 % to 13.5 % of biochar yield. Nanobiochar demonstrated superior properties compared to its microsized biochar. Specifically, nanobiochar at 700 degrees C exhibited the highest BET surface area of 295.7 m2/g, zeta potential of -44.03 f 0.5 mV, and fixed carbon content of 69.34 %, along with diverse carbon functional groups. Notably, nanobiochar generated at 600 degrees C exhibited similar performance characteristics, making it a promising alternative for sustainable wastewater treatment. To assess practical application, nanobiochar at 700 degrees C was tested for its adsorption capacity. It effectively removed 58.5 f 3.7 mg/g of lithium, 45.3 f 2.4 mg/g of methylene blue, and 46.1 f 3.5 mg/g of Eriochrome Black T. These results highlight the potential of orange peelderived nanobiochar as a sustainable adsorbent for wastewater treatment, promoting circular waste management and environmental remediation.