Urea/acrylamide-assisted nitrogen-functionalized rice husk biochar for Cd(ii) removal: adsorption performance and interaction insights.
- 1Department of Chemistry, Faculty of Science, King Khalid University P. O. Box 9004 Abha 61413 Saudi Arabia [email protected].
Abstract
Cadmium-bearing wastewater remains a major environmental concern, requiring effective sorbents that can operate under complex aqueous conditions. Herein, urea/acrylamide-assisted nitrogen-functionalized activated rice husk biochar, denoted UA-NARB, was synthesized through preliminary carbonization followed by K₂CO₃-assisted activation and nitrogen functionalization using urea and acrylamide as nitrogen-containing precursors. XRD, FTIR, SEM, N₂ adsorption-desorption, DLS, and zeta potential analyses revealed a heterogeneous carbon-mineral sorbent with disordered carbon domains, O-/N-containing functionalities, accessible mesoporosity, and a moderately negative surface charge. Cd(ii) adsorption was strongly pH-dependent, reaching 94.5% removal at pH 6, which was selected as the working condition. A sorbent dose of 2.0 g L⁻¹ provided an effective balance between Cd(ii) removal and material utilization. Kinetic analysis showed rapid initial uptake followed by gradual equilibration, with the pseudo-second-order model providing the best empirical description. Equilibrium adsorption exhibited saturation-type behavior and was well described by the Langmuir model, with a maximum adsorption capacity of 14.6 mg g⁻¹. Thermodynamic parameters indicated spontaneous and endothermic Cd(ii) uptake. From an application perspective, UA-NARB showed efficient regenerability, with 1.0 M H₂SO₄ desorbing 92.7% of adsorbed Cd(ii), and maintained 80.7% Cd(ii) removal from synthetic multimetal wastewater. The adsorption process is proposed to proceed through cooperative contributions from pH-regulated electrostatic attraction, interactions with polar surface functionalities and mineral-associated sites, and diffusion through accessible mesoporous domains. These results position UA-NARB as a rice-husk-derived sorbent with practical potential for Cd(ii)-contaminated wastewater treatment.
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BibTeX
@article{elzahhar2026ureaacrylamideassisted,
title = {{Urea/acrylamide-assisted nitrogen-functionalized rice husk biochar for Cd(ii) removal: adsorption performance and interaction insights.}},
author = {Adel A El-Zahhar and Majed M Alghamdi},
journal = {RSC advances},
year = {2026},
month = oct,
doi = {10.1039/d6ra08271h},
url = {https://europepmc.org/article/MED/42852000},
note = {CC BY},
}
RIS
TY - JOUR
TI - Urea/acrylamide-assisted nitrogen-functionalized rice husk biochar for Cd(ii) removal: adsorption performance and interaction insights.
AU - Adel A El-Zahhar
AU - Majed M Alghamdi
PY - 2026
DA - 2026/10/08
JO - RSC advances
DO - 10.1039/d6ra08271h
UR - https://europepmc.org/article/MED/42852000
AB - Cadmium-bearing wastewater remains a major environmental concern, requiring effective sorbents that can operate under complex aqueous conditions. Herein, urea/acrylamide-assisted nitrogen-functionalized activated rice husk biochar, denoted UA-NARB, was synthesized through preliminary carbonization followed by K₂CO₃-assisted activation and nitrogen functionalization using urea and acrylamide as nitrogen-containing precursors. XRD, FTIR, SEM, N₂ adsorption-desorption, DLS, and zeta potential analyses revealed a heterogeneous carbon-mineral sorbent with disordered carbon domains, O-/N-containing functionalities, accessible mesoporosity, and a moderately negative surface charge. Cd(ii) adsorption was strongly pH-dependent, reaching 94.5% removal at pH 6, which was selected as the working condition. A sorbent dose of 2.0 g L⁻¹ provided an effective balance between Cd(ii) removal and material utilization. Kinetic analysis showed rapid initial uptake followed by gradual equilibration, with the pseudo-second-order model providing the best empirical description. Equilibrium adsorption exhibited saturation-type behavior and was well described by the Langmuir model, with a maximum adsorption capacity of 14.6 mg g⁻¹. Thermodynamic parameters indicated spontaneous and endothermic Cd(ii) uptake. From an application perspective, UA-NARB showed efficient regenerability, with 1.0 M H₂SO₄ desorbing 92.7% of adsorbed Cd(ii), and maintained 80.7% Cd(ii) removal from synthetic multimetal wastewater. The adsorption process is proposed to proceed through cooperative contributions from pH-regulated electrostatic attraction, interactions with polar surface functionalities and mineral-associated sites, and diffusion through accessible mesoporous domains. These results position UA-NARB as a rice-husk-derived sorbent with practical potential for Cd(ii)-contaminated wastewater treatment.
SN - 2046-2069
ER -