Synergistic sonophotocatalytic decomposition of pyrene using a recyclable C₃N₄/CoFe₂O₄@GO magnetic hybrid nanocomposite

Polycyclic aromatic hydrocarbons (PAHs) pose a huge threat to the water environment due to their carcinogenic, biotoxic, and hazardous nature. To eliminate such compounds, a novel and efficient CN-CFO/GO magnetic nanocomposite composed of graphitic–carbon nitride (CN) (0.0378 wt%) and Cobalt ferrite (CFO) nanoparticles (1 wt%) embedded on graphene oxide (GO) (0.0378 wt%) was synthesized via hydrothermal treatment at 170 °C for 6 h. The developed nanomaterials as sonophotocatalysts to degrade pyrene, which serves as a model for polycyclic aromatic hydrocarbons, were used. To understand how well these materials work and what properties they have, we analyzed them using several techniques, including X-ray Diffraction (XRD), Fourier-transform Infrared Spectroscopy (FT-IR), Ultraviolet-Visible Diffuse Reflectance Spectroscopy (UV–vis DRS), and Transmission Electron Microscopy (TEM) to assess their crystallinity, functional groups, energy levels, and overall shape. XPS data reveal significant electronic and chemical interactions between CN, CFO, and GO in the GO-CN/CFO composite, indicating charge redistribution, new interfacial bonding, and modified oxidation states. The CN-CFO/GO nanocomposite degraded 94.3 % of pyrene compared to pure GO (85.3 %), CN (80.9 %), and CFO (82.9 %). The kinetic results indicated that the reaction behaved according to a pseudo-first-order model. We observed the following order of rate constants: sonophotolysis had the lowest at 0.0098 min⁻¹, followed by CN at 0.014 min⁻¹, CFO at 0.0148 min⁻¹, GO at 0.0151 min⁻¹, and the combination of CN-CFO/GO at the highest rate of 0.0226 min⁻¹. The CN-CFO/GO nanocomposite, however, degrades up to 99.2 % of 10 mg/L pyrene under optimized conditions of pH 9, CN-CFO/GO dosage 80 mg/L, US power 50 W, sunlight-type white LED chips, within 120 min, suggesting its capability for the depollution of high molecular weight PAHs. Capturing experiments indicate that ∙$O_2^{-}$ $\text{and}{h}^{+}$ were the most dominant reactive species followed by ∙OH. The as-synthesized nanocomposite could be recycled five times with only 9.1 % decline in the degradation efficiency. The synergistic effect of CN-CFO/GO/LED/US (sonophotocatalytic) system (99.2 %) (0.0373 min⁻¹) was also found to be better than the binary CN-CFO/GO/LED (photocatalytic) (82.4 %) (0.0141 min⁻¹) and CN-CFO/GO/US (sonocatalytic) systems (90.9 %) (0.0188 min⁻¹). The mineralization efficiency of CN-CFO/GO/LED/US was also studied and could achieve 92.7 % TOC removal within 120 min under optimized conditions compared with CN-CFO/GO/LED (63.5 %) and CN-CFO/GO/US (72 %). The toxicity evaluation of the products of degraded pyrene and the effects of different anions on pyrene degradation were thoroughly examined.