Functionalization of microcapsules for the removal of heavy metal ions

Abstract

BACKGROUND: Solvent extraction and ion exchange technologies have been widely used for the recovery or removal of heavy metals from aqueous phases. However, different problems have been encountered on applying these techniques. Although the extractants are highly selective, this technique requires a high level of mechanical agitation to improve the kinetics of the process, a requirement that promotes leakage of the extractant from the aqueous/organic interface to the aqueous phase during separation of the two phases. On the other hand, ion exchangers can easily be regenerated but gel form resins have low selectivity and those with high selectivity (chelating resins) have low diffusion coefficients, a characteristic that leads to low mass transfer rates. An interesting alternative to overcome these limitations is the microencapsulation of extractants within a functionalized polymeric shell. This new type of material would be expected to combine the advantages of the aforementioned methods and improve selective removal of heavy metals from an aqueous phase.

Advancements in organic and inorganic shell materials for the preparation of microencapsulated phase change materials for thermal energy storage applications

“…prepared microcapsules exhibited excellent latent heat storage properties when embedded in the polypropylene matrix. Sánchez et al 143 synthesized microencapsulated paraffin using polystyrene as the wall material through the suspension polymerization technique and explored the effect of the mass ratio of paraffin wax to styrene, stirring rate, and reaction temperature on the properties of the prepared microcapsules. Emulsion polymerization is discovered to be the most popular Fig.…”

“…Mochane et al 142 developed a microencapsulated paraffin core using polystyrene as a shell material through the emulsion polymerization technique, and the prepared microcapsules exhibited excellent latent heat storage properties when embedded in the polypropylene matrix. Sánchez et al 143 synthesized microencapsulated paraffin using polystyrene as the wall material through the suspension polymerization technique and explored the effect of the mass ratio of paraffin wax to styrene, stirring rate, and reaction temperature on the properties of the prepared microcapsules. Emulsion polymerization is discovered to be the most popular encapsulation method for poly(styrene) shell-based MPCMs due to its simplicity of synthesis, absence of toxic organic solvents, and capacity to produce polymeric shells with desired mechanical properties along with the inexpensive nature of synthesis.…”

Sulfonated poly (styrene‐co‐ethylene glycol dimethacrylate) with attractive ion exchange capacity

“…heavy metals require hard agitation. 14 Hydrophobic cation exchange resins are required for this application due to its flexibility and low swelling in water, 15 which favors mechanical resistance. Hence, the use of a small and rigid molecule, such as DVB, as crosslinker, is the main issue to be discussed because absorbance of solvents and mechanical properties is affected by the crosslinker chain length.…”

“…17 The use of PS-EGDMA as a shell for polymeric ion exchange particles has been studied, and Symbology: DVB, divinilbenzene; EGDMA, ethylene glycol dimethacrylate; IEC, ion exchange capacity; N HCl , normality of HCl (N); Sw, swelling index;; V NaOH , volume of NaOH used (mL); V P , fixed pore volume (cm 3 /g); V t , volume of HCL titred; w s , weight of collected sample (g);; w sw , weight of swollen gel (g);; Y dma , molar fraction of crosslinker in the monomeric mixture; Y m , volumetric fraction of monomers in the organic phase; Y tol , volumetric fraction of toluene in the mixture toluene/heptane the results proved that this crosslinker can enhance the chemical and mechanical properties of particles. 14,16 Nevertheless, the literature is still very scarce on the use of EGDMA as crosslinker in sulfonated resins. In this sense, the present study aims to find the optimum process conditions for the production of sulfonated PS-EGDMA particles with attractive ion exchange capacity (IEC).…”