Comparative Evaluation of Mineral-Modified Biochar: Process Tunability, Characteristics, and Sustainable Application Potential

Mineral-modified biochar serves as a multifunctional catalyst for environmental remediation; however, the impact of the synthesis pathway on mineral speciation, pollutant removal, and sustainability remains less understood. This study fills this gap by synthesizing and comparing the iron-rich laterite biochar composite through two routes, evaluating the structure−function relationship: (i) a one-pot biomass-modification method yielding the post-pyrolyzed composite (PLBC) by precipitating hydrolyzed acid-leached laterite (HALL) on raw biomass before pyrolysis and (ii) a sequential biochar modification method producing a pre-pyrolyzed composite (LBC) via HALL precipitation on preformed biochar. Comprehensive characterization (EDS, XRF, XRD, FTIR, XPS) revealed FeOOH in LBC, whereas PLBC contained Fe 2 O 3 after FeOOH to Fe 2 O 3 conversion. HALL treatment of biomass significantly modified its morphology during pyrolysis, resulting in lower surface area, pore volume, and pore width. Functionally, PLBC demonstrated enhanced NO 2 adsorption driven by crystalline Fe 2 O 3 and enhanced electron transfer, whereas LBC exhibited higher arsenic uptake, enhanced surface area, and recalcitrance due to FeOOH shielding. Life cycle assessment identified HCl and NaOH as primary emission sources; however, biochar’s carbon sequestration potential presents a viable offset. Economic analysis revealed a 26.30% ROI and a 3.8-year payback, confirming feasibility. This work elucidates the relationship between structure, function, and sustainability, advancing the design of scalable composites.