Abstract This work reports the preparation of magnetic polymeric microspheres based on poly(methyl methacrylate) and the investigation of these materials as catalysts in heterogeneous Fenton processes for the decolorization of methyl orange (MO). The microspheres were prepared by polymerization of the magnetic material together with the monomers by aqueous suspension polymerization. The microspheres had specific surface area of 48.2 m2 g-1. Mossbauer data indicated that the magnetic material was a mixture of magnetite (31%), maghemite (21%), and goethite (48%). Fenton reactions were performed by varying the concentration of H2O2, pH, composite mass, and contact time. The highest color removal rates (around 80%) were reached at pH 3.0, 20% w/v of composite, 20 minutes contact time, and 10 ppm of H2O2. The composite could be reused during four cycles with removal efficiency above 50%. The results indicated that the adsorption and oxidation mechanisms act together determining the variation of the MO dye removal.

Abstract Preparation and characterization of polymeric microspheres based on poly(methacrylic acid-co-divinylbenzene) (P(MAA-co-DVB)) by precipitation polymerization are reported. The influence of the change in comonomer composition, crosslinking degree, ratio of total monomers/diluents by weight/volume (g/100 mL) and the volume ratio of diluents were studied. Spherical particles were obtained in the range from 1.42 to 8.41 µm. An increase in particle size and thermal resistance with decreasing molar fraction of methacrylic acid (MAA) were observed, associated with increases in critical chain length (CCL) and the number of crosslinks in this system, respectively. The analysis of particles with molar fraction of 50% MAA and acetonitrile/toluene volumetric ratio of 75/25 showed that larger particle size and yield were achieved with increasing ratio of total monomers/diluents (g / 100 mL). The particles prepared with 14% molar fraction of MAA obtained greater swelling ratios than the particles prepared with 50% MAA.

Abstract Core-shell magnetic polymer particles were synthesized by seeded suspension polymerization. The core was made of poly(methyl methacrylate-co-divinylbenzene) and a mixture of magnetite, maghemite and goethite (P(MMA-co-DVB)-M). The shell was composed of poly(glycidyl methacrylate-co-divinylbenzene) (P(GMA-co-DVB)). These particles were characterized by infrared spectrometry (FTIR), thermal analysis (TG), scanning electron microscopy (SEM), dynamic light scattering (DLS) and vibrating sample magnetometry (VSM). The results showed the formation of core-shells with good magnetic properties (≈7.1 emu/g) and good thermal resistance (≈300 ºC). The light scattering experiments showed that the particle size of these materials changed from 5-90 microns (core) to 5-120 microns (core-shell). Scanning electron microscopic images were useful to show the formation of P(GMA-co-DVB) shells on P(MMA- co-DVB)-M cores. The materials synthesized in this work have potential to be modified and employed in magnetic separation processes in the biotech and environmental fields.

Microesferas poliméricas à base de metacrilato de metila (MMA), divinilbenzeno (DVB) e material magnético foram preparadas via polimerização por suspensão. Foi estudada a influência da polimerização em suspensão ou semisuspensão, concentração de material magnético e concentração de divinilbenzeno sobre as características das microesferas obtidas. As partículas poliméricas foram caracterizadas por espectroscopia vibracional na região do infravermelho por transformada de Fourier (FT-IR), microscopia eletrônica de varredura, analisador de área específica e porosimetria, espalhamento de luz e magnetometria de amostra vibrante. O material magnético também foi caracterizado por FT-IR, além de difratometria de raios X e espectroscopia Mössbauer. Foram obtidas, com sucesso, microesferas poliméricas magnéticas à base de MMA e DVB (P(MMA-co-DVB)-M), contendo partículas magnéticas tanto na superfície quanto no interior da microesfera. As partículas obtidas através de polimerização em semisuspensão apresentaram tamanhos menores e distribuição de tamanhos de partículas mais estreita que as partículas obtidas através de suspensões convencionais. Os compósitos apresentaram um comportamento superparamagnético. As microesferas magnéticas sintetizadas neste trabalho têm potencial para serem modificadas e aplicadas como resinas de troca iônica ou suportes catalíticos.

Magnetic polymeric microspheres based on methyl methacrylate (MMA), divinylbenzene (DVB) and magnetic materials were prepared via suspension polymerization. We studied the influence of the suspension or semi-suspension polymerization, magnetic materials and divinylbenzene concentration on the characteristics of the microspheres. Polymeric particles were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy, accelerated surface area and porosimetry analyzer (ASAP), dynamic light scattering (DLS) and vibrating sample magnetometer (VSM). The magnetic materials were also characterized by FT-IR, X-ray diffraction and Mössbauer spectroscopy. Magnetic polymeric microspheres based on MMA and DVB (P(MMA-co-DVB)-M), containing magnetic particles on the surface or inside the microspheres, were successfully obtained. The polymer particles obtained through semi-suspension polymerization had smaller sizes and narrower particle size distribution than particles obtained by conventional suspension. The composites showed a superparamagnetic behavior. The magnetic microspheres synthesized in this work have potential to be modified and applied as ion-exchange resins or catalyst supports.