Synthesis and Swelling Behavior of Carrageenans-Graft-Poly(Sodium Acrylate)/Kaolin Superabsorbent Hydrogel Composites
In the present paper, a novel superabsorbent hydrogel composite based on carrageenan have been prepared via graft copolymerization of acrylic acid (AA) in the presence of kaolin powder using methylenebisacrylamide (MBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator. The certain variables of the graft copolymerization (i.e. the monomer, the initiator and the crosslinker concentration as well as kaolin/carrageenan weight ratio) affected on the ultimate water-swelling capacity were optimized. The composite structure was confirmed using FTIR spectroscopy. A new absorption band at 1707 cm in the 1 composite spectrum confirmed kaolin-organic polymer linkage. The effect of kaolin amount and MBA concentration showed that with increasing of these parameters, the water absorbency of the superabsorbent composite was decreased. Because of their exceptional properties, i.e. anhydrogalactose units (13). The types of carrageenans biocompatibility, biodegradability, renewability and differ only in the position and number of ester sulfate non-toxicity, polysaccharides and proteins are the groups. Following a continuous research on modification main part of the natural-based superabsorbent of carrageenans (14), in this work, we attempt to hydrogels. The higher production cost and low gel synthesize and characterize new superabsorbent strength of these superabsorbents, however, restrict composites based on carrageenan in the presence of their application widely. To improve these limitations, kaolin particles. The preparation of the biopolymer-based inorganic compounds with low cost can be used. The superabsorbent composites can also improve the introduction of inorganic fillers to a polymer matrix mechanical properties of materials and can lower the cost increases its strength and stiffness properties. of the finished product compared with the synthetic Among inorganic compounds, special attention has counterparts as well as providing biodegradable been paid to clay minerals in the field of nanocomposites characteristics.
Synthesis and characterization of modified carrageenan microparticles for the removal of pharmaceuticals from aqueous solutions.
In the present study, carrageenan microparticles were synthesized using spray-drying method and used as biosorbents for the removal of pharmaceutical compounds. The cross-linking reaction of iota-carrageenan (iCAR) and kappa-carrageenan (kCAR) with glutaraldehyde (GLA) at different concentrations (2.5% or 5% (w/w), mass of GLA per mass of CAR) was studied (iCAR/GLA2.5, iCAR/GLA5, kCAR/GLA2.5, kCAR/GLA5). The physicochemical properties of the novel cross-linked polymers were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Swelling studies were in accordance with the polymer properties, showing the lowest swelling degree (19%) by using the iCAR/GLA5 microparticles. The optimal kCAR/GLA5 microparticles were successfully employed for the removal of Metoprolol (MTPL) from aqueous samples. The adsorption capacity of the adsorbents was investigated using a batch adsorption procedure and the kinetics and thermodynamics of the adsorption process were further investigated. It was found that the adsorption isotherms agree well with the Langmuir-Freundlich model. The maximum adsorption capacity (Qm) was achieved in pH 6, whereas an increase of Qm was observed increasing the temperature (from 109 at 20°C to 178 mg/g at 40°C). Kinetic studies showed that the adsorption process on iCAR/GLA5 microparticles followed pseudo-second-order rate mechanism. Finally, a new phenomenological model of the adsorption process was proposed in order to extract information on the relevant sub-processes.
Semicontinuous emulsion copolymerization of ethyl acrylate and butyl acrylate at high conversions
Semicontinuous emulsion copolymerization of ethyl acrylate and butyl acrylate was studied at conversions higher than 0.9. It was found that, in the cases in which the mole fraction of ethyl acrylate in the reaction mixture was over 0.65, the copolymerization diagram differs from the one given by the reactivity ratios. It was suggested that this deviation was caused by the diffusion control of the process. This suggestion was also supported by the differences in the free-monomer composition of the systems with and without seed latex, respectively, at the beginning of the copolymerization.