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<p>Toxic dyes present in wastewater pose a severe threat to aquatic ecosystems, emphasizing the urgent need for eco-friendly and efficient remediation strategies. In this study, we report a novel rapid synthesis protocol for graphitic carbon nitride (g-C<sub>3</sub>N<sub>4</sub>) nanosheets via thermal polymerization of thiourea, followed by annealing in ambient air at 550&#xa0;°C for two hours. The resulting g-C<sub>3</sub>N<sub>4</sub> nanosheets were employed as adsorbents for the removal of methylene blue (MB) and rhodamine B (RhB) from aqueous solution. Comprehensive characterization using XRD confirmed the formation of a hexagonal crystalline phase, while FT-IR indicated the presence of nitrogen-rich heterocyclic structures. SEM and TEM images revealed the successful fabrication of few-layer nanosheets with edge thicknesses ranging from 6.9 to 20.88&#xa0;nm. BET analysis demonstrated a Type IV porous structure with a surface area of 101.2&#xa0;m<sup>2</sup>/g and an average pore diameter of 7.01&#xa0;nm. Adsorption experiments utilizing 20&#xa0;mg of g-C<sub>3</sub>N<sub>4</sub> nanosheets at an initial dye concentration of 25&#xa0;mg/L and a pH of 7.5 demonstrated a preferential affinity for RhB, achieving removal efficiencies of 99.80%, in contrast to 94.56% for MB. Kinetic and isotherm analyses revealed that dye adsorption conformed to the Freundlich and pseudo-second-order (PSO) models, indicating a spontaneous, endothermic process characterized by multilayer adsorption and increased interfacial disorder. Notably, the Freundlich isotherm predicted maximum adsorption capacities of 9.226 × 107&#xa0;mg/g for RhB and 2.251 × 107&#xa0;mg/g for MB, surpassing the estimations provided by alternative models. Reusability assessments demonstrated the g-C<sub>3</sub>N<sub>4</sub> nanosheets maintained over 85% removal efficiency after five cycles, highlighting their potential as a sustainable, cost-effective solution for dye remediation in wastewater treatment.</p>

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Rapid synthesis of graphitic carbon nitride nanosheets as an efficient adsorbent for removal of Methylene Blue and Rhodamine B from Aqueous Solutions

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年8月8日

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  • Rohit Madankar,
  • Mayuri Umekar,
  • Ganesh Bhusari,
  • Aniruddha Mondal,
  • Mohammad Raish,
  • Mohd Afzal,
  • Małgorzata Norek,
  • Ratiram Chaudhary

摘要

Toxic dyes present in wastewater pose a severe threat to aquatic ecosystems, emphasizing the urgent need for eco-friendly and efficient remediation strategies. In this study, we report a novel rapid synthesis protocol for graphitic carbon nitride (g-C3N4) nanosheets via thermal polymerization of thiourea, followed by annealing in ambient air at 550 °C for two hours. The resulting g-C3N4 nanosheets were employed as adsorbents for the removal of methylene blue (MB) and rhodamine B (RhB) from aqueous solution. Comprehensive characterization using XRD confirmed the formation of a hexagonal crystalline phase, while FT-IR indicated the presence of nitrogen-rich heterocyclic structures. SEM and TEM images revealed the successful fabrication of few-layer nanosheets with edge thicknesses ranging from 6.9 to 20.88 nm. BET analysis demonstrated a Type IV porous structure with a surface area of 101.2 m2/g and an average pore diameter of 7.01 nm. Adsorption experiments utilizing 20 mg of g-C3N4 nanosheets at an initial dye concentration of 25 mg/L and a pH of 7.5 demonstrated a preferential affinity for RhB, achieving removal efficiencies of 99.80%, in contrast to 94.56% for MB. Kinetic and isotherm analyses revealed that dye adsorption conformed to the Freundlich and pseudo-second-order (PSO) models, indicating a spontaneous, endothermic process characterized by multilayer adsorption and increased interfacial disorder. Notably, the Freundlich isotherm predicted maximum adsorption capacities of 9.226 × 107 mg/g for RhB and 2.251 × 107 mg/g for MB, surpassing the estimations provided by alternative models. Reusability assessments demonstrated the g-C3N4 nanosheets maintained over 85% removal efficiency after five cycles, highlighting their potential as a sustainable, cost-effective solution for dye remediation in wastewater treatment.