Biogenic growth of magnetic retrievable Ca4Fe9O17 anchored on rice husk biochar for methylene blue degradation through persulfate activation

The presence of dyes in wastewater has gained significant attention due to rapid industrialization. Methylene blue (MB) is a widely used cationic dye in the textile industry, but it poses several issues due to its toxicity and persistence in the environment. Herein, the Ca4Fe9O17/biochar (CFO/BC) nanocomposite by the coprecipitation method for persulfate activation have been successfully fabricated. The as-synthesized catalyst shows effective removal of MB dye with 96.33% efficiency in just 40 min. The fabricated catalyst shows 54% total organic carbon removal of MB dye. The catalyst is characterized by Fourier-transform infrared spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller analysis, scanning electron microscopy, and vibrating-sample magnetometer. The average crystalline size and crystallinity of the CFO/BC nanocomposite are found to be 31.74 nm and 49%, respectively. The mechanism of MB degradation by CFO/BC nanocomposite follows both the electron-transfer pathway and radical pathway, as shown by the scavenging test. The scavenger study shows the presence of reactive species such as sulfate radical (SO4•−), hydroxyl radical (•OH), and electrons for the degradation of MB dye. The liquid chromatography-mass spectrometry analysis is used to investigate the possible degradation pathway of MB dye. Moreover, the catalyst shows four-time reusability, highlighting its practical potential.