Magnetic resins

Micro-SMB separators have only been studied numerically (Subramani and Kurup, 2006), but one can think of ways to implement a real moving bed in a miniaturized version by applying a shifting magnetic field on, for example, magnetic resin beads or applying DEP on adsorbent particles, in a microchannel. 

The flocculating properties of resins from barium ferrite and y-iron oxide are similar. Even diough the magnetized resin is flocculated, the floes break up readily when stirred so that the particles react more rapidly than standard-sized resin beads which are 300-1200 pm in diameter (Fig. 2). The shell configuration of whisker-type resins also enhances reaction r tes. Because of the magnetic flocculation phenomenon the magnetized beads separate out much more rapidly than the unmagnetized ones (Fig. 3). 

Table 7. Comparison of typical dealkalization results obtained with the fluidized bed of whisker-type magnetic resin and a conventional contactor of Asahi type...

Fluidized bed of whisker-type magnetic resin Asahi-type resin... 

Bolto and Dixon advocated a system which involves a simple pipeline for the adsorption reaction, in which the magnetized resin and raw water are pumped through a pipe at such a flow rate that turbulence results and the floes are broken apart so that the reaction is complete when the mixture leaves the pipe. The slurry flows into a settling vessel, whereupon the magnetic floes reform and rapid sedimentation ensues. 

To eliminate the detrimental effect on ion-exchange capacity of turbidity and the formation of precipitates, a contacting method based on a fluidized-bed should be employed. Magnetic resins are of special interest in this regard,... 

Magnetic resins have been prepared in a variety of physical forms. 

Toner monocomponent magnetic resin styrene-acrylic d = 13 pm Tsoft = 100 °C... 

UF with a MWCO of 500 Da was used to desalt NOM concentrated with a magnetic resin but high losses of LMW NOM were reported (Hepplewhite (1995), Newcombe et al. (1996), Crum et al (1996)). UF of such a MWCO is also likely to retain salt to some degree. If fractionation is employed prior to desalting, the desalting step may be limited to the lowest MW fraction, thus minimising the loss of organic matter. 

MAGNETIC RESINS PRODUCTION Maghemite Nanoparticles Production... 

Donia, A.M., Atia, A.A., Daher, A.M., and Elshehy, E.A. (2011) Extraction and separation of zirconium (TV) and hafnium (IV) from chloride media using magnetic resin with phosphoric acid functionality. J. Dispersion ScL Technol, 32,193-202. 

The advantages of continuous contactors based on magnetic resins are that the amount of resin needed is only 25-33% of that required in other systems, the equipment is smaller and simpler, and there is no necessity for a prior filtration step. Magnetic resins can also be used to detoxify sludges and slurries, when employed in large bead form so that separation from the gelatinous sludge is facilitated (11). 

In recent years, interesting works have been focused on the amino polysaccharide chitosan-based microspheres. The chitosan microspheres have been applied in diversified fields, such as food processing, water treatment and biological fields. To bring new or improved properties, the chemical modification of chitosan based microspheres is of rapidly growing interest. After chemical modification, chitosan based microspheres can be used as functional materials with modified properties, such as adsorption resins, magnetic resins and nanocomposites, for specific end use in food industry. This paper presents a review of the developments in the preparation and applications of chitosan-based microspheres. The main objective of this review is to provide recent information and to show the development trend about chitosan-based microspheres. 

Chitosan can dissolute in acidic solutions, so it is hard to recycle from acidic solution. It is thus necessary to stabilize it chemically for the recycling in acidic solutions. Several processes have been developed to stabilize chitosan, such as suspending cross-linked technique, emulsification technique and spray drying technique [10]. Through stabilization, chitosan can be prepared as microspheres, easily separated from solutions. To get new or improved properties, chitosan-based microspheres have been researched recently. In addition, to expend the range of chitosan applications, chitosan-based microspheres can be used as functional materials with modified properties, such as adsorption resins, magnetic resins and nanocomposites, etc. The preparation and application of different kinds of chitosan-based microspheres are reviewed in this paper. 

---