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<p>Biochars produced from sawdust (SD) and manure pellets (MP) at pyrolysis temperatures of 300, 500, and 700 °C, with and without steam activation, were evaluated for their adsorption characteristics for methylene blue (MB) and methyl orange (MO). The physicochemical characteristics and surface functionalities of the biochars, previously studied as part of a larger project, provided insights into their dye adsorption behavior in this work. Increasing the pyrolysis temperature significantly increased the surface area of SD biochars, primarily due to devolatilization and pore development, with a further increase observed under steam activation. In contrast, MP biochars exhibited no significant changes in surface area, likely due to pore blockage by ash formed from mineral components. Scanning electron microscopy (SEM) confirmed enhanced porosity at higher temperatures, and X-ray diffraction (XRD) revealed amorphous structures in SD biochars and crystalline inorganic&#xa0;phases in MP. Fourier-transform infrared spectroscopy (FTIR) indicated a reduction in surface functional groups with increasing pyrolysis temperature, while steam activation at 500 °C may retain sufficient surface functionalities that contribute to dye adsorption. Biochars produced at 500 °C demonstrated the highest adsorption performance, reflecting a favorable balance between surface area and functional groups. Steam activation further increased dye adsorption by improving pore accessibility and introducing more&#xa0;active sites. Despite having lower surface areas, MP biochars exhibited competitive adsorption, likely due to their mineral-rich surfaces contributing to dye interactions. Adsorption followed the Langmuir isotherm model and pseudo-2nd-order kinetics, indicating monolayer chemisorption on homogeneous surfaces. These findings highlight the interplay between thermal processing and feedstock composition in governing adsorption behavior, providing design strategies for an efficient biochar-based dye adsorption system for environmental remediation.</p> Graphical abstract <p></p>

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Adsorption of dyes by engineering biochars produced under different feedstocks and temperatures with steam activation

  • 期刊论文

  • 发表日期：

    2026年5月12日

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  • H. Roy,
  • M. N. Asif,
  • J. H. Kwak,
  • S. X. Chang,
  • Md. S. Islam

摘要

Biochars produced from sawdust (SD) and manure pellets (MP) at pyrolysis temperatures of 300, 500, and 700 °C, with and without steam activation, were evaluated for their adsorption characteristics for methylene blue (MB) and methyl orange (MO). The physicochemical characteristics and surface functionalities of the biochars, previously studied as part of a larger project, provided insights into their dye adsorption behavior in this work. Increasing the pyrolysis temperature significantly increased the surface area of SD biochars, primarily due to devolatilization and pore development, with a further increase observed under steam activation. In contrast, MP biochars exhibited no significant changes in surface area, likely due to pore blockage by ash formed from mineral components. Scanning electron microscopy (SEM) confirmed enhanced porosity at higher temperatures, and X-ray diffraction (XRD) revealed amorphous structures in SD biochars and crystalline inorganic phases in MP. Fourier-transform infrared spectroscopy (FTIR) indicated a reduction in surface functional groups with increasing pyrolysis temperature, while steam activation at 500 °C may retain sufficient surface functionalities that contribute to dye adsorption. Biochars produced at 500 °C demonstrated the highest adsorption performance, reflecting a favorable balance between surface area and functional groups. Steam activation further increased dye adsorption by improving pore accessibility and introducing more active sites. Despite having lower surface areas, MP biochars exhibited competitive adsorption, likely due to their mineral-rich surfaces contributing to dye interactions. Adsorption followed the Langmuir isotherm model and pseudo-2nd-order kinetics, indicating monolayer chemisorption on homogeneous surfaces. These findings highlight the interplay between thermal processing and feedstock composition in governing adsorption behavior, providing design strategies for an efficient biochar-based dye adsorption system for environmental remediation.

Graphical abstract