Biochars from Cardboard as an Alternative adsorbent for the Removal of Pesticides from the Water Environment

Abstract Hydrothermal carbonisation (HTC) is a promising method for converting biomass into carbonaceous materials with high adsorption capacity. This study examines the effect of various HTC conditions on the production of hydrochars from egg cardboard waste and their efficiency in removing metribuzin from aqueous environments. The results showed that temperature and HTC time significantly influenced biochar yield, organic carbon content, and sorption efficiency. The highest yield, 68.18 %, was achieved at 200 °C, whereas at 240 °C, the yield dropped to 23.08 %. Conversely, higher temperatures (220-240 °C) enhanced the retention of organic carbon, contributing to improved sorption properties. Morphological analysis via SEM confirmed that higher temperatures and longer reaction times promote the formation of a porous structure, which is crucial for adsorption applications. At 240 °C, the biochar exhibited substantial fragmentation and increased surface heterogeneity, indicating a high degree of carbonisation. Biochar produced at this temperature achieved the highest metribuzin removal efficiency, exceeding 60 % after 5 hours of contact, underscoring the importance of optimising production conditions to maximise sorption capacity for organic pollutants. These results contribute to a better understanding of the relationship between hydrochar production conditions, organic carbon content, and adsorption properties, which is important for future applications in water treatment and environmental engineering.