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 Fe2O3 after FeOOH to Fe2O3 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 NO2 adsorption driven by crystalline Fe2O3 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.