Magnetic field induced zinc ferrite distribution in mixed matrix membrane for phenol removal

Abstract

The mixed matrix membrane typically has the particles randomly dispersed within the membrane. The random particle dispersion will reduce the adsorption and photocatalytic performance because the optimum position for particles in the membrane is near the membrane surface. At the optimum position, the particles will easily interact with the incoming targeted molecule, i.e., phenol. One of the methods to disperse the particles near the membrane is by magnetic induce casting. Hence, the first objective was to analyze the effect of magnet arrangement in magnetic induced casting on zinc ferrite distribution in the membrane for phenol adsorption. Next, was to elucidate the impact of different zinc ferrite dosage on magnetic induced casting at varied initial phenol concentrations via adsorption kinetic, isotherm, and diffusion model. The final objective was to investigate the effect of varied magnetic strength on the distribution of zinc ferrite particles in the membrane for photocatalytic degradation of phenol. The particle in this work refers to zinc ferrite, while the magnetic induced casting refers to a step during the membrane fabrication in which the cast film was exposed to magnets in different arrangements with a unique magnetic field for inducing particle distribution and migration. The membrane performance was tested by water flux, phenol adsorption, regeneration while the adsorption data were fitted into adsorption isotherm and kinetic model. For testing the hypothesis, the magnetic induced casting was carried out by arranging the magnets into the rod, circular (MB), and chain (MC) pattern while the zinc ferrite composition was varied at 3, 12 and 30 wt%. The distance between the magnet and cast film was varied to 10, 15 and 40 mm to study the influence of magnetic strength. The findings show that magnet arranged in a chain and circular pattern produced a membrane with high phenol adsorption, fast water flux and stable performance after three regeneration cycle. Circular/12wt% ZnFe (MB12) membrane reported 30.4 L/m2.h water flux with a phenol adsorption capacity of 415 mg phenol/g ZnFe (mg/g). Meanwhile, the finding shows that membrane with 3 wt%/total solid has a stable performance compared to other compositions of zinc ferrite. In studying the effect of zinc ferrite composition, the magnetic arrangement was fixed to a MC and MB pattern. Circular/3wt% ZnFe (MB3) membrane possessed a balanced water flux and phenol adsorption performance with both registering ~27 L/m2.h and ~303 mg/g, respectively. The adsorption kinetic model revealed that the diffusion in the MB3 membrane was propelled by intraparticle diffusion due to low external mass transfer coefficient, Ks = 0.000633, while the chain/3wt% ZnFe (MC3) membrane was rate-limited by external diffusion with Ks of 0.00254. The zinc ferrite adsorption stage implied that the MB3 membrane possessed a zone IV: drastic kinetic, the fastest adsorption rate, while the MC3 membrane exhibited zone III: quick kinetic, a moderate adsorption rate. Furthermore, varying the distance between magnetic and cast film revealed that the circular/12wt% ZnFe/15mm gap (MB1215) membrane demonstrated the highest photocatalytic performance with a stable photodegradation after three regeneration cycles at 1736, 1706, and 1693 mg/g phenol degradation capacity per cycle. A prolonged photocatalytic run indicated the MB1215 degraded ~98% phenol after 510 min.