Catalytic activity of g-C3N4/SA and Ag0–Fe0-fabricated g-C3N4/SA composite beads towards dye-containing wastewater treatment: a comparative study

Abstract

BACKGROUND

Sodium alginate (SA)/carbon nitride (g-C₃N₄) composite beads loaded with silver (Ag) and iron (Fe) bimetallic nanoparticles (Ag⁰–Fe⁰/g-C₃N₄/SA) introduce a new approach in wastewater treatment. Ag⁰–Fe⁰ synergy is utilized to enhance reduction efficiency and ensure sustainable water purification. Composite beads of g-C₃N₄/SA were prepared and then introduced to a bimetallic solution of Ag and Fe and reduced to their zero valent state (M⁰) by treating it with sodium borohydride (NaBH₄). Ag⁰–Fe⁰/g-C₃N₄/SA was further used for the catalytic reduction of harmful compounds from water.

RESULTS

X-ray diffraction was used to analyze chemically synthesized composite beads. The high intensity of Ag peaks confirmed that the amount of loaded Ag was higher than Fe. Scanning electron microscopy showed the shape of Ag⁰–Fe⁰/g-C₃N₄/SA and g-C₃N₄/SA composite beads to be rough and granular. Atomic absorption spectroscopy confirmed that the composite beads exhibited higher adsorption capacity for Ag ions as compared to Fe ions. Fourier transform infrared spectroscopy confirmed the presence of OH, CN, CO, and CH functional groups in the sample. Catalytic reduction of Erichrome Black T (EBT), Methyl Orange (MO), Rhodamine B (Rh-B), and Reactive Black 5 (RB-5) was carried out using Ag⁰–Fe⁰/g-C₃N₄/SA and g-C₃N₄/SA as catalysts. Various parameters such as apparent rate constant (k_app), reduced concentration, percentage reduction, reduced time, and half-life were also studied to analyze the catalytic activity of both catalysts.

CONCLUSION

Overall, Ag⁰–Fe⁰/g-C₃N₄/SA showed the highest percentage reduction of 73%, 93%, 94%, and 92% for EBT, MO, Rh-B, and RB-5, respectively, and was effectively used for water treatment. © 2025 Society of Chemical Industry (SCI).