Preparation and Characterization of Mn0.4Zn0.6Fe2O4 Nanoparticles Supported on Dead Cells of Yarrowia lipolytica as a Novel and Efficient Adsorbent/Biosorbent Composite for the Removal of Azo Food Dyes: Central Composite Design Optimization Study

The removal of hazardous dyes is of great importance to making healthy and drinkable water. Here, a new ferro-magnetic composite based on Mn0.4Zn0.6Fe2O4 nanoparticles (NPs) supported on dead Yarrowia lipolytica ISF7 (D-YL-ISF7) was prepared. Nanoparticle aggregation was inhibited using D-YL-ISF7, which causes the availability of more active sites. The dead D-YL-ISF7-supported Mn0.4Zn0.6Fe2O4 nanoparticles (NPs) were characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX), Brunuaer-Emmett-Teller (BET), and vibrating sample magnetometer (VSM) analysis and used as robust adsorbents/biosorbents to simultaneously remove tartrazine (TA) and ponceau 4R (P4R) azo food dyes in their binary solution. First order derivative spectrophotometry was implemented for the simultaneous analysis of dyes in binary mixtures. Central composite design (CCD) was used to evaluate the influence of pH, sonication time, Mn0.4Zn0.6Fe2O4-NPs-D-YL-ISF7 mass, and initial TA and P4R concentrations on the efficiency for the removal of the studied dyes. At optimum conditions (pH 2.0, sonication time 5 min, Mn0.4Zn0.6Fe2O4-NPs-D-YL-ISF7 mass 0.015 g, TA concentration 12 mg and P4R concentration 16 mg L-1 high removal efficiencies (>99.0%) were obtained for TA and P4R dyes, reasonably well predicted by the model. The CCD allowed the optimization and the scale-up of the process, which presented a good correlation between large and small scales. Adsorption isotherm data fitted well to the Langmuir model. Under ultrasound, the Langmuir adsorption capacity of MMn0.4Zn0.6Fe2O4-NPs-D-YL-ISF7 was obtained to be 90.827 mg g(-1) for TA and 101.461 mg g(-1) for P4R. A pseudo-second-order reaction model was chosen for kinetic study.