Paper
Sulfonation of Microcapsules Containing Selective Extractant Agents
- Authors:
- Juan F. Rodríguez; Manuel Carmona; Antonio de Lucas; Ángela Alcázar; Angel Perez
- Abstract
- Microcapsules from P(St-EGDMA) and P(St-DVB) containing di(2-ethylhexyl) phosphoric acid (DEHPA) as core material has been prepared by suspension-like polymerization technique by using two different recipes. These materials were synthesized by using percentage mass ratios of 0.1 wt.% and 18.6 wt.% for EGDMA/St and DVB/St, respectively. Toluene was required as diluent to produce microcapsules from P(St-DVB) due to the high reactivity of the crosslinking monomer (DVB) since polymerization reaction without toluene yielded to compacted block. Microcapsules containing DEHPA were obtained using the above shell materials having a smooth and spherical shape, a particle size in the range of those reported for commercial resins but the amount of encapsulated DEHPA was larger when P(St-DVB) was used, 34.86 wt.% respect to the 28.15 wt.% obtained for the P(St-EGDMA). Attending to this higher DEHPA content, P(St-DVB) was selected as shell material to develop microcapsules combining the advantages and capabilities of the ion exchange and the solvent extraction technologies. Once the extractant agent has been encapsulated, different sulfonation agents -chlorosulfonic and sulfuric acid- and the applicability of swelling agents to minimize the sulfonation treatment impact on the microcapsules were carried out to attribute them ion exchange properties. Swelling agents release the DEHPA from the microcapsules whereas the chorosulfonation treatment leads to a cracked material. Thus, the effect of the sulfonation by sulfuric acid on DEHPA and sulfur contents and swelling degree of microcapsules as function on the particle size was studied. Sulfonation results showed that sulfuric acid at 50ºC did not damage the microcapsules but it had big influence on the DEHPA content. Results showed that sulfur and swelling increased whereas the DEHPA decreased in a linear way with the sulfonation time. From the slopes of these curves, it was found that sulfonation process was dependent on the particle size and DEHPA was less released from particles having a particle size of 500 m and incorporating an enough amount of sulfonic groups in the shell material (-6.43 gDEHPA/gS). Besides, attending to the low sulfonation required for this material, a maximum time of 20 min is recommended to introduce a 30% of the sulfonic groups commonly found in commercial resins.
- Keywords
- Microcapsules; Extractant Agent; Sulfonation; Suspension-Like Polymerization; Heavy Metals
- StartPage
- 25
- EndPage
- 38
- Doi