In this work, we have reported a low-cost and environmentally friendly Fe3O4-modified activated kaolin (AK-Fe3O4) composite for efficient Fenton-like degradation of 4-nitrophenol (4-NP) and optimization of the degradation variables. The AK-Fe3O4 composites were characterized by Fourier transform infrared spectroscopy, powder x-ray diffraction, scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). X-ray diffraction confirms the syntheses of pure phases of Fe3O4 and AK-Fe3O4. The SEM image of the AK-Fe3O4 composite reveals the formation of a highly porous surface. The room temperature VSM analysis describes the superparamagnetic nature of AK-Fe3O4 composites with 25 emu/g magnetization values. Response surface methodology coupled with Box-Behnken design was used to optimize the 4-NP degradation (%) variables such as contact time (10-90 minutes), 4-NP concentration (10-30 mg/L), and pH (3-8). The high regression value ( R² = 0.9964 and adjusted R² = 0.9917) and analysis of variance ( P < .0001) show that the quadratic model can sufficiently explain the 4-NP degradation (%). The optimum 4-NP degradation was found to be 96.01% ± 1.89% using 1 mg/mL of AK-Fe3O4, 20 mg/L of 4-NP, 97.9 mmol/L of H2O2, and pH of 3 at the end of 75 minutes of reaction time. Moreover, the catalyst shows good recyclability and stability after 5 successive degradations of 4-NP. In general, a low-cost and magnetically separable AK-Fe3O4 composite is an effective Fenton-like catalyst for the degradation of 4-NP.
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