CoFe2O4@MC/AC as an efficient and recyclable magnetic nanohybrid adsorbent for the metronidazole removal from simulated wastewater: bioassays and whole effluent toxicity

CoFe 2 O 4 @methylcellulose (MC)/activated carbon (AC) as a novel magnetic nanohybrid adsorbent was synthesized and characterized with field-emission scanning electron microscope, energy-dispersive X-ray-mapping and linescan, X-ray diffraction, Fourier-transform infrared spectrometer, vibrating sample magnetometer, and Brunauer-Emmett-Teller techniques. Then, on synthetic and real samples, the adsorption process of metronidazole was investigated, and the parameters affecting the adsorption process were optimized. Finally, the toxicity of the effluent from the process was investigated. The maximum removal efficiency of metronidazole for synthetic and real wastewater samples was 93% and 85%, respectively, under optimal conditions of pH 3, adsorbent dose of 2.5 g/L, 10 mg/L initial concentration of metronidazole, temperature 25C, and contact time of 20 min. The adsorption of metronidazole by CoFe 2 O 4 @MC/AC followed pseudo-second-order kinetic (R 2 = 0.999) and Freundlich isotherms (R 2 = 0.972). Furthermore, the thermodynamic findings of the process revealed H = -19.82 (kJ/mol) and S = -53.57 (J/molK), as well as negative Gibbs free energy values, indicating that the process was spontaneous and exothermic. After four regeneration cycles, the CoFe 2 O 4 @MC/AC was able to remove 66% of metronidazole while maintaining high chemical stability. The effects of effluent toxicity on Daphnia and Artemia were enhanced by increasing effluent concentration and exposure duration, according to the LC 50 values. However, the mortality rate for Daphnia and Artemia after 72 h at the maximum effluent concentration (100% by volume) was 33.3% for Daphnia and 26.6% for Artemia, according to the results. According to the findings, CoFe 2 O 4 @MC/AC can be employed as a novel magnetic nanoadsorbent with a high adsorption ability to eliminate pharmaceutical pollutants from aqueous solutions.