Exploratory synthesis of magnetic chitosan macrospheres

RIAL, JULIANA BELEN; FERREIRA, MARÍA LUJÁN

Ciudad Autónoma de Buenos Aires

Congreso; WCCE11 - 11th WORLD CONGRESS OF CHEMICAL ENGINEERING; 2023

Asociación Argentina de Ingenieros Químicos

The study of heterogeneous Fenton-like systems to remediate textile effluents with low-cost catalysts, has attracted great interest. A research topic of our group has evolved from the study of enzymes and biomimetics to inorganic mimetics (iron oxide nanozymes, IONzymes) [1]. In this context, a protocol for the synthesis of chitosan (CTS) magnetic macrospheres was established as a basis for the development of multicatalytic solids. First, CTS solution (2, 3.5 and 4% w/v in 5% v/v acetic acid) was dropped in 3.75 M NaOH, followed by a crosslinking with tripolyphosphate (5.5% w/v in 1M NaOH) for 1 h. Then, magnetite nanoparticles (MAG) (FeCl3.6H2O and FeSO4.7H2O as precursors with ferric/ferrous salt molar ratio equal to 2) were incorporated by (A) chemical precipitation in NaOH in presence of CTS spheres and (B) CTS-MAG co-precipitation. Both methods were performed under an inert atmosphere (N2) and followed by crosslinking. For the spheres synthesized using (B), the effect on structural stability of 10, 20 and 30% nominal MAG with respect to the total mass of the solid was studied. The best solid was characterized by XRD and SEM-EDX. The behavior of CTS-MAG spheres was evaluated under an external magnetic field and in the presence of H2O2. Chitosan concentration of 3.5% w/v proved to be the optimal concentration to obtain resistant spheres with approximately 2 mm in diameter (Fig.1a). The method (A) led to low MAG immobilization (Fig.1b), while (B) led to effective MAG entrapment in the solid (Fig.1c), confirmed by SEM-EDX. The presence of MAG was verified by XRD. The suitable MAG nominal percentage was 10%, since 20 and 30% led to fragmentation of spheres during handling. The CTS-MAG spheres showed superparamagnetic behavior (Fig.1d) and catalase mimetic activity decomposing hydrogen peroxide (H2O2) in H2O y O2. A simple synthesis procedure to obtain CTS/MAG spheres was developed. On this solid, hematin will be supported to obtain two immobilized radical-generation systems (associated to Fe2+/Fe3+ of MAG and to Fe3+ present in the porphyrin structure of hematin) with the use of H2O2 as oxidant.