Micro-nanobubble assisted photocatalytic and antibacterial activity of ZnFe2O4/g-C3N4/rGO nanocomposite

Abstract

Addressing the ongoing challenge of water pollution by synthetic dyes requires advanced approaches. This study examines the improved degradation of Indigo Carmine (IC) dye using a ternary nanocomposite made of ZnFe₂O₄, g-C₃N₄, and reduced graphene oxide (rGO), in combination with micro-nanobubble technology. The nanocomposite was synthesized using hydrothermal method, promoting effective interaction between ZnFe₂O₄, g-C₃N₄, and rGO, which enhances photocatalytic performance. The ZnFe₂O₄/g-C₃N₄/rGO nanocomposite (ZGR NCs) exhibited a 92 % degradation efficiency of IC dye within 60 min, significantly outperforming ZnFe₂O₄ (49 %), ZG (59 %), ZR (64 %), and ZGR without MNB (72 %). The photocatalytic process followed pseudo-first-order kinetics with a high correlation coefficient (R² ∼ 0.9789–0.9968), demonstrating the efficiency of charge separation and transfer facilitated by rGO. ZnFe₂O₄ excels in absorbing visible light, g-C₃N₄ serves as a capable photocatalyst with a suitable bandgap for visible light, and rGO further facilitates electron mobility, minimizing charge recombination. Also, the combination of ZnFe₂O₄, rGO, and g-C₃N₄ generates a synergistic effect that significantly boosts photocatalytic activity. This interaction leads to more effective production of reactive oxygen species, which are essential for degrading pollutants. The nanocomposite also exhibited excellent reusability, retaining 88 % of its initial efficiency after five cycles. Additionally, antibacterial studies revealed strong inhibition zones against Streptococcus mutans (18–22 mm) and Enterococcus faecalis (14–20 mm), attributed to ROS-induced bacterial membrane disruption. These findings highlight the multifunctionality of the ZGR nanocomposite-micro-nanobubble (MNBs) system, offering a promising approach for sustainable wastewater treatment and antibacterial applications.