PFAS remediation using engineered shrimp waste biochar: Rapid PFOA removal with mechanistic validation in synthetic and real wastewater

Shrimp waste was utilized to produce biochar for perfluorooctanoic acid (PFOA) removal, a highly persistent per- and polyfluoroalkyl substances (PFAS) characterized by strong C–F bonds and resistance to conventional treatment. The persistence of PFAS demands adsorbents that combine rapid kinetics, high capacity, and stability under real environmental conditions features often limited in bio-based materials due to insufficient textural parameters and poor surface chemistry. To bridge this gap, an engineered shrimp waste biochar was developed as a modified biochar (M-BC) protonated sorbent, with textural properties and surface chemistry. Batch experiments in synthetic and real wastewater demonstrated rapid equilibrium within 5 min, and near complete PFOA removal at 1 and 10 mg/L concentrations (0.5 g/L dose). Kinetic data followed the pseudo-first order (PFO) model, indicating a rapid surface process. Adsorption isotherms fitted Sips and Freundlich models, while Langmuir analysis revealed a maximum adsorption capacity of 192.18 mg/g. The removal mechanism involved a synergistic combination of electrostatic attraction (at pH ˂ pH PZC ), hydrophobic interactions, hydrogen bonding, and pore filling, with possible anion exchange mechanism. Minimal interference from co-existing ions and natural organic matter confirmed robust performance under competitive conditions. The M-BC achieved 99.7% PFOA removal in real wastewater and demonstrated over 89% efficiency after five consecutive adsorption/desorption cycles. A preliminary production cost for M-BC was estimated at 3.61 USD/kg under laboratory-scale conditions, highlighting its potential as a cost-effective solution for PFAS remediation. • Engineered shrimp waste biochar (M-BC) prepared via pyrolysis and acid modification. • M-BC yields a 12-fold surface area increase and protonated sites for PFOA uptake. • M-BC rapidly removed PFOA within 5 min, reaching a maximum capacity of 192.18 mg/g. • Adsorption driven by electrostatic attraction, hydrophobic effects and pores. • 99.7% PFOA removal achieved in real wastewater with stable reusability.