Development of g-C3N4/CaCO3-Derived from Eggshell for Efficient Photocatalytic Wastewater Treatment

Abstract

Rapid industrialization has led to the increasing release of persistent organic pollutants into aquatic environments, posing significant environmental and public health challenges. In this study, eggshell waste was valorized as a sustainable CaCO3 source to synthesize CaCO3/g-C3N4 (Ca/gCN) composites through a co-thermal polymerization process. The successful fabrication of the composites was verified by comprehensive characterization of their structural, morphological, optical, and interfacial properties. The synthesized materials were subsequently applied as photocatalysts for the degradation of Rhodamine B (RhB), a representative organic dye pollutant in wastewater. Among the prepared samples, 2.5Ca/gCN exhibited the highest photocatalytic performance, achieving a RhB degradation efficiency 2.28 times greater than that of pristine gCN after 300 min of irradiation. The degradation efficiency was highly dependent on solution pH, with the optimum performance observed under acidic conditions (pH 3). The enhanced photocatalytic activity was attributed to improved light-harvesting capability, increased specific surface area, higher electron density associated with nitrogen defects, and efficient interfacial electron transfer through heterojunction formation, which effectively suppressed electron–hole recombination. Radical scavenging experiments identified •O2⁻ as the predominant reactive species responsible for RhB degradation. In addition, the photocatalyst retained excellent activity over five consecutive cycles, demonstrating excellent stability and reusability. These findings demonstrate the potential of eggshell waste valorization for the development of efficient Ca/gCN photocatalysts for wastewater treatment while promoting a circular economy approach to waste utilization.