Abstract

With the growing emphasis on environmental sustainability, the proper treatment of industrial wastewater and the protection of groundwater resources have become pressing global concerns. Congo red (CR), a widely used azo dye, enters water bodies via wastewater discharge, posing persistent ecological risks to surface and groundwater systems. Adsorption, as a direct and sustainable remediation approach, necessitates the development of high-performance adsorbents to inhibit CR migration into groundwater. In this study, a Fe2O3/γ-Al2O3 composite was synthesized via sol-gel method for efficient CR adsorption, thereby mitigating groundwater contamination risk. The composite exhibited a high specific surface area (246.22 m2/g) and a maximum adsorption capacity of 1027.72 mg/g. Adsorption behavior followed the pseudo-second-order kinetic and Langmuir isotherm models, consistent with chemisorption-driven monolayer adsorption. The Weber–Morris intraparticle diffusion model confirmed rapid initial surface adsorption, beneficial for practical groundwater remediation. pH-dependent adsorption efficiency further indicated the role of electrostatic interactions, informing process optimization under varying groundwater chemistries. DFT calculations demonstrated that Fe2O3/γ-Al2O3 possesses a higher adsorption affinity for CR than γ-Al2O3. Collectively, Fe2O3/γ-Al2O3 shows strong potential as a novel, efficient adsorbent for CR interception and groundwater quality protection.

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