Study on iron anchoring methods for magnetic biochar: Characterization, functional mechanism, and RBBR dye removal

Abstract Magnetic biochar (MBC) is a novel bio‐metallic composite material with high potential in sustainable water cleaning. Iron anchoring is critical in forming iron‐based MBC and will fundamentally impact its characteristics and functionality in dye removal applications. However, the mechanism is not well‐revealed. To understand the iron anchoring mechanism and to identify the most efficient strategy, this study developed and compared three methods for preparing MBC, including impregnation pyrolysis, post‐treatment with Fe salts, and one‐step co‐pyrolysis using maple wood and different types of Fe‐containing chemicals, including FeO, FeSO 4 , and FeCl 3 , and the products were characterized comprehensively and evaluated for the adsorption of Remazol Brilliant Blue R (RBBR) dye. Key results of this study indicate that the one‐step co‐pyrolysis method yields the highest adsorption efficiency, with MBC produced at 700°C exhibiting optimal performance. The adsorption capacity of RBBR dye was found to be highest at acidic pH levels, with the 1:1 FeO to biomass ratio achieving a removal efficiency of 100% at a dosage of 0.4 g. Kinetic studies revealed that adsorption follows a pseudo‐second‐order model, suggesting chemisorption as the primary mechanism. Isotherm analysis indicated that the Langmuir model best describes the adsorption process, with a maximum adsorption capacity of 11.33 mg/g. This study provides new insights into the critical step of iron anchoring design and optimization of MBC synthesis for environmental applications, which could help address growing concerns about water pollution.