Revisiting the persulfate activation performance of seaweed derived biochars: The composition and origin of pollutant degradation activity

A steady increase in seaweed production necessitates effective strategies to manage its post-production waste and its associated CO₂ emission. Biochar formation stand out as a promising option, offering significant advantage for persulfate-activated water remediation processes. Herein, we investigated and compared the performance of two seaweed-derived biochars, focusing on their physical characteristics, heteroatoms, and chemical composition in activating persulfate (PS). Although, both seaweeds (Capsosiphon fulvescens (CF) and Undaria pinnatifida (SW)) that studied are edible, they exhibit unique catalytic activity towards simazine (SIM) degradation. The differences in SIM degradation activity observed in these biochars were primarily attributed to the description of metal active sites rather than its chemical composition and specific surface area of the biochars. The identification of these active sites was achieved through various physical characterization tools (XRD, XPS, BET) and by examining the adsorption models and degradation patterns of simazine under different conditions. Our results demonstrate that the biochar derived from CF (100 % removal) seaweed having metal active centres is more catalytic than SW (58.4 % removal) derived biochar. ROS quantification and electrochemical studies suggest that simazine degradation occurs through different mechanisms in these biochars. Therefore, the CF-derived biochar catalytic system was optimized for simazine oxidation, with studies focusing on its degradation pathway, intermediate toxicity, and catalytic stability. Thus, the present study outlines the significance of seaweed biomass selection for optimal catalytic activity in the persulfate-based oxidative process.