Abdul Aji, Elsaday Br Purba, Demi Dama Yanti, Muhammad Yogi Saputra, Agustina Sus Andreani, Amalia Kurnia Amin
The growing contamination of water resources by hazardous dyes, such as Congo Red (CR), presents significant environmental and health challenges, underscoring the urgent need for the development of effective and sustainable remediation methods. This study presents the synthesis of a novel magnetically separable composite, iron oxide/hydrochloric acid-activated kaolin/silver nanoparticles (Fe3O4/HCl-AK/AgNPs), designed to enhance the photocatalytic degradation of CR through the Fenton process. The composite was synthesized via a co-precipitation method and comprehensively characterized using Vibrating Sample Magnetometry (VSM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy coupled with Energy Dispersive X-ray analysis (FE-SEM-EDX), thermogravimetric analysis-differential scanning calorimetry (TGA-DSC) and Diffuse Reflectance UV-Visible spectroscopy (UV-DRS). The Fe3O4/HCl-AK/AgNPs composite exhibited strong magnetic behavior, evidenced by a saturation magnetization (Ms) of 14.9 emu/g, thermal stability with a total weight loss of only 7.78% up to 1000 °C, and an optical band gap of 1.89 eV. The material showed a uniform hexagonal plate-like morphology with well-dispersed nanoparticles, and a pHpzc value of 7.16, favoring CR adsorption under acidic conditions. The degradation of CR was optimized using a Box-Behnken design (BBD), with the maximum degradation efficiency (99.23%) obtained at pH 4.02, an initial CR concentration of 23.88 mg/L, a catalyst dosage of 26.26 mg, and a reaction time of 90 min. Furthermore, the composite exhibited excellent recyclability, retaining 96.11% degradation efficiency after five successive cycles, underscoring its potential for sustainable and cost-effective wastewater treatment applications. This study underscores the significant potential of the Fe3O4/HCl-AK/AgNPs composite as an efficient, magnetically separable photocatalyst for the removal of organic pollutants, particularly CR, from aqueous environments. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.
Department of Chemistry, Faculty of Science, Institut Teknologi Sumatera, Lampung, Lampung Selatan, 35365, Indonesia; Research Center for Chemistry, National Research, and Innovation Agency (BRIN), Kawasan Puspiptek Serpong, Tangerang Selatan 15314, Banten, Indonesia