Síntese de caracterização de membranas de troca iônica a partir de copos e pratos de poliestireno descartados

Abstract

In this work, membranes of sulfonated polystyrene were produced through the recycling of post-consumption plastic cups and plates. The polystyrene was chemically recycled through the reaction of sulfonation of the aromatic rings, which added active (SO3H) groups into the material. In order to compare, sulfonated virgin polystyrene membranes were also produced. Such membranes were characterized through water sorption, water flux, viscosity, ion exchange capacity (IEC) and infrared spectroscopy. When comparing the ion exchange resin Amberlite IR 120 and the membranes’ infrared spectra, one can notice that the resin absorption bands attributed to the out-of-plane C-H bending and to the symmetric SO2 stretching are dislocated. These dislocations are probably due to the existing cross-links in the resin structure, which were produced by the cross-link agent divinylbenzene (DVB). The resin which was mentioned above was used as a parameter of comparison in order to characterize the ion exchange membranes. We concluded that the difference between the IEC values of the membranes and the resin is about 40%. However, it also should be noticed that the difference concerning to the sulfonic group percentage is about 35% in the commercial ion exchange resin, while in the membranes this value is lower than 25%. Thus, it can be said that there is practically no difference between the ion exchange capacity of the resin and that of the membranes. The ‘first Fick’s law’ was used to analyze the transport data for the membranes. These investigations showed that the solubility coefficient for the PSSR membrane is higher than the one for PSSv due to the lower coiling of the macromolecule chains, which is caused by the lower molar weight. The lower molar mass was verified through the lower intrinsic viscosity value obtained for PSSR, since the intrinsic viscosity is directly related to the molar weight of polymers, The coefficient of water permeability through the sulfonated polystyrene membranes is ten times higher than through the PS membranes, what confirms that the sulfonation reaction increases the membrane permeability. This is due to the introduction of the active $03H groups which make the PSS hydrophilic since they have a great affinity to the water. It was verified that the coefficient of water diffusion for the membranes is lower than for the recycled polystyrene membrane. The factor that leads to this result is the higher water percentage of the PSSR membranes, which cause a diminishing in the coefficient of diffusion due to the production of clusters.