Abstract
Poly(acrylic acid)/montmorillonite (MMT) composites with various polymer contents were synthesized by in situ polymerization technique. The structure of obtained materials was characterized by powder X-ray diffraction and infrared spectroscopy (FTIR). It was found that only a limited amount of hydrogel could be introduced between the clay layers. The remaining part of polymer was deposited on the external surface of clay particles. The introduction of the polymer modifier significantly increased the adsorption capacity of MMT in the elimination of Fe3+ ions from aqueous solution. The thermal behavior of the samples before and after the Fe3+ adsorption was examined by thermogravimetry and differential thermal analysis. Moreover, the composition of gaseous products evolved during decomposition was determined by FTIR. The materials after Fe3+ adsorption exhibited different thermal stability in oxidizing atmosphere than the fresh samples. Fe3+ cations, forming FeOx species during thermal treatment, appeared to be effective catalysts of polymer oxidation.
Highlights
Modification of clay structure has attracted great attention due to the possibility of obtaining promising materials to new applications
For the MMT-poly(acrylic acid) (PAA)-20 sample containing the lowest amount of polymer, the d001 spacing increased to a lesser degree (1.64 nm) compared to other composites, which resulted from the intercalation of the lower amount of polymer into the interlayer space
PAA can be introduced into the MMT structure by in situ polymerization
Summary
Modification of clay structure has attracted great attention due to the possibility of obtaining promising materials to new applications. In the MMT structure, the sheet containing Al3? Cations by lower valency ions (mainly Mg2?) leads to the generation of negative charge on the clay layers, which is neutralized by hydrated, exchangeable cations (e.g., Ca2?, Mg2?, Na?, K?) located in the interlayer spaces. Such a structure causes that the interlamellar space of the natural clay can be functionalized through the replacement of interlayer ions by other species, for instance transition metal cations (or clusters), cationic surfactants, or monomers [12,13,14,15]
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