Comparative Hg(II) Adsorption on Coffee Husk and Sugarcane Bagasse Biochars: Structure–Function Relationships
4 affiliations
- 1Grupo de Investigación de Materiales, Ambiente y Desarrollo (MADE), Programa de Química, Facultad de Ciencias Básicas, Universidad de la Amazonia, Florencia 180002, Colombia
- 2Grupo de Investigación en Química Aplicada a Procesos Ecológicos (QUAPE-UT), Facultad de Ciencias, Universidad del Tolima, Ibagué 730006, Colombia
- 3Centro de Investigaciones en Catálisis (CICAT), Parque Tecnológico Guatiguará, Universidad Industrial de Santander, km 2 vía el Refugio, Piedecuesta 681011, Colombia
- 4Biodiversity, Biotechnology and Bioengineering Research Group—GRINBIO, Department of Engineering, University of Medellin, Medellín 050026, Colombia
Abstract
Mercury contamination in water poses a significant environmental and public health concern because it is toxic, persistent, mobile, and bioaccumulative. This study investigated biochars derived from the perisperm (silver skin) fraction of coffee husk (CH) and sugarcane bagasse (SB) as sustainable adsorbents for Hg(II) removal from water. The biochars were produced at 800 °C, characterized by N2 adsorption–desorption measurements at approximately −198 °C, SEM–EDS, XRD, XRF, FTIR, and XPS, and evaluated through kinetic, equilibrium, and thermodynamic studies of Hg(II) adsorption. SB exhibited a higher BET surface area (599 vs. 525 m2 g−1), larger pore volume (0.298 vs. 0.216 cm3 g−1), and lower micropore fraction (63.4 vs. 86.3%) than CH. These textural differences were consistent with the faster Hg(II) adsorption observed for SB. The Avrami and Elovich models best described the adsorption kinetics (R2 = 0.980–0.996). At the same time, Freundlich and Langmuir adequately described the equilibrium data; their relative performance depended on biochar type and temperature. The Langmuir-estimated maximum adsorption capacity (qm) increased with temperature, reaching 45.05 mg g−1 for SB and 45.25 mg g−1 for CH at 318.15 K. The thermodynamic analysis yielded negative enthalpy and Gibbs free-energy changes for both biochars, with ΔH° values of −71.4 and −52.8 kJ mol−1 and ΔG°(298) values of −39.3 and −37.6 kJ mol−1 for SB and CH, respectively. FTIR and XPS supported the involvement of oxygen-containing surface environments in Hg(II) retention.
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BibTeX
@article{gomezrojas2026comparative,
title = {{Comparative Hg(II) Adsorption on Coffee Husk and Sugarcane Bagasse Biochars: Structure–Function Relationships}},
author = {Jairo F. Gomez-Rojas and César Jaramillo-Páez and Oscar A. Gamba and Jorge L. Gallego and Lis Manrique-Losada},
journal = {Molecules},
year = {2026},
month = oct,
doi = {10.3390/molecules31213914},
url = {https://www.mdpi.com/1420-3049/31/21/3914},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Comparative Hg(II) Adsorption on Coffee Husk and Sugarcane Bagasse Biochars: Structure–Function Relationships
AU - Jairo F. Gomez-Rojas
AU - César Jaramillo-Páez
AU - Oscar A. Gamba
AU - Jorge L. Gallego
AU - Lis Manrique-Losada
PY - 2026
DA - 2026/10/30
JO - Molecules
DO - 10.3390/molecules31213914
UR - https://www.mdpi.com/1420-3049/31/21/3914
AB - Mercury contamination in water poses a significant environmental and public health concern because it is toxic, persistent, mobile, and bioaccumulative. This study investigated biochars derived from the perisperm (silver skin) fraction of coffee husk (CH) and sugarcane bagasse (SB) as sustainable adsorbents for Hg(II) removal from water. The biochars were produced at 800 °C, characterized by N2 adsorption–desorption measurements at approximately −198 °C, SEM–EDS, XRD, XRF, FTIR, and XPS, and evaluated through kinetic, equilibrium, and thermodynamic studies of Hg(II) adsorption. SB exhibited a higher BET surface area (599 vs. 525 m2 g−1), larger pore volume (0.298 vs. 0.216 cm3 g−1), and lower micropore fraction (63.4 vs. 86.3%) than CH. These textural differences were consistent with the faster Hg(II) adsorption observed for SB. The Avrami and Elovich models best described the adsorption kinetics (R2 = 0.980–0.996). At the same time, Freundlich and Langmuir adequately described the equilibrium data; their relative performance depended on biochar type and temperature. The Langmuir-estimated maximum adsorption capacity (qm) increased with temperature, reaching 45.05 mg g−1 for SB and 45.25 mg g−1 for CH at 318.15 K. The thermodynamic analysis yielded negative enthalpy and Gibbs free-energy changes for both biochars, with ΔH° values of −71.4 and −52.8 kJ mol−1 and ΔG°(298) values of −39.3 and −37.6 kJ mol−1 for SB and CH, respectively. FTIR and XPS supported the involvement of oxygen-containing surface environments in Hg(II) retention.
SN - 1420-3049
ER -