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چکیده
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In this study, an attempt was made for the first time to synthesize novel biophotocatalyst Cygnea/Fe3O4/TiO2 -based oyster shell (Andonata Cygnea). Different analyzes, including Fourier transform infrared spectroscopy (FESEM), High-resolution transmission electron microscopy (HRTEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Fourier-transform infrared spectroscopy (FTIR), Diffuse Reflectance Spectroscopy (DRS) and vibrating sample magnetometer techniques(VSM) were used to prove the successful synthesis of photocatalyst and coating of titanium dioxide on Cygnea /Fe3O4. The results showed the presence of iron and titanium dioxide in the synthesized magnetic Cygnea and photocatalyst, and the successful synthesis of the photocatalyst. In the following, synthetic photocatalyst was used to remove COD, NO3⁻, and PO4³⁻ from fish farm wastewater (FFW). The results of various analyzes have shown the success of the photocatalyst synthesis. The degradation efficiency was highly dependent on UVA6W exposure time, photocatalyst mass, temperature, and pH. At pH 5.5, a photocatalyst mass of 300 mg, a temperature of 37.5°C, and a UVA6W exposure time of 35 min, the optimal conditions for the treatment of FFW under UVA6W irradiation for the removal of 98, 95, and 98% of COD, NO3⁻, and PO4³⁻, were obtained respectively. Analyses of isotherms and kinetics revealed that the photodegradation kinetics best fit the Langmuir and pseudo-first-order models. Due to photocatalysis, the FFW's half-life was significantly reduced from hours to minutes. According to the thermodynamic analysis of activation parameters computed by the Eyring model and transition state theory (TST), an exothermic reaction with negative values for ΔH° (-69.421 kJ mol⁻¹) and ΔS° (-7.65 J/molK) both contribute to the achievement of negative values for ΔG° and a photocatalytic process. Consequently, Cygnea /Fe3O4/ TiO2 can be proposed as new, prospective alternatives for reducing FFW pollution from the fish industry.
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