(175c) Adsorption of Harmful Algal Bloom Toxins Onto Commercially Available Biochar: An Exploration on the Mechanisms and Factors Influencing Adsorption

Harmful Algal Bloom (HAB) events involve the growth of microalgae which release lethal toxins into fresh and brackish water bodies due to climatic and anthropogenic activities. Some common HAB examples are red tides, blue-green algae, and cyanobacteria, which are known to lyze neurotoxins and hepatotoxins during blooms causing massive fish kills, and serious threat to human life. These outbreaks have terrorized Great lakes and coastal waters such as Lake Erie, Lake Okeechobee, Florida’s Coasts and Gulf of Maine, negatively impacting marine ecosystems, fisheries, and the economy. To mitigate the release of these toxins, physical water treatment such as adsorption with the use of biochar provides a low-cost solution with high removal efficiency. This study investigates the effectiveness of commercially available pine derived biochar for adsorption of HAB toxins: Brevetoxin (PbTx-3), Microcystin-LR (MCLR) and Saxitoxin (STX). Material characterization of the biochar presented positively charged with high carbon content, high porosity (S_BET = 261.06 m²/g) with substantial oxygen functionality (941.33 μmol/g). Dosage, equilibrium and kinetic study were performed on PbTx-3, MCLR and STX under ambient conditions with commercial biochar. Enzyme-linked Immunosorbent Assay (ELISA) analysis and high -performance liquid chromatography (HPLC) was used for adsorption analysis of the investigated toxins. From the dosage reports all three toxins experienced high percent removal (> 90 %) at a dosage rate of 0.4 g/L. High adsorption capacities were observed for the target toxins which fitted well with the combined Langmuir-Freundlich adsorption model and Pseudo-Second Order and Elovich kinetic model. The results support possible adsorption mechanisms such as electrostatic attraction, pi-pi stacking, ion exchange, hydrophobic interactions, and more which is explored in detail. Thus, commercial provides as a high removal efficiency solution for the mitigation HAB toxins.