Preparation of a novel magnetic calcium-based biochar for arsenic removal: Behavior and dominant mechanism

Engineered biochar as conventional adsorbents, was typically fabricated by pyrolyzing waste biomass first and then modified with reagents or techniques. In this work, the carbothermal reduction method was employed to produce magnetic calcium-based biochar composites (MCBB) by combusting shrimp shells impregnated with FeCl3 solutions at 800 °C. The adsorption capacity of MCBB3 for As(V) exceeded that of many conventional adsorbents, reaching 119.7 mg/g. The spontaneous and endothermic nature of the As(V) adsorption process by MCBB3 was confirmed, and both the Freundlich model and pseudo-second-order model adequately described the adsorption data. The potential adsorption mechanism was investigated and analyzed according to the results of the characterization. The removal of As(V) was achieved through surface complexation and electrostatic attraction, while the deposition occurred by substituting the hydroxyl group on the MCBB3 surface with Fe and Ca to generate bidentate complexes. Moreover, MCBB3 exhibited exceptional performance in various water matrices, establishing its potential as a promising adsorbent for the remediation of As-containing water in environmental applications. The proposed MCBB adsorbents manufactured via a pyrolysis-loading approach, provide new insights into design facile production.