The water-soluble iron-containing polyacrylic acid (Fe-PAA) obtained from acrylic acid

In the present work we used Mossbauer spectroscopy to investigate a sample of Fe-PAA which had been dried in air at 70~ and had a concentration of iron equal to 0.12 wt. % (A) and lyophilized samples of Fe-PAA with concentrations of iron equal to 0.12 (BI), 0.2 (B2), and 0.9 wt. % (B3). All the samples of Fe-PAA were synthesized in the presence of Mohr's salt enriched with the STFe isotope (the degree of enrichment was 95%). The Mossbauer spectra were obtained on an instrument of the electrodynamic type operating under constant acceleration conditions. The source was STCo in a chromium matrix. The spectra of the powdered samples of Fe-PAA were recorded at two temperatures: 80 and 300 K. The data were treated on a BESM-6 computer according to a program which was developed at the Institute of Chemical Physics of the Academy of Sciences of the USSR. The isomer shifts were determined relative to sodium nitroprusside. The error in the determination of the isomer shift 6 did not exceed 0.04 mm, and the errors in the determination of the quadrupole splitting & and the linewidth were no greater than 0.06 mm/sec. The Mossbauer spectra of the Fe-PAA samples obtained shortly after their synthesis have the form of a doublet with the parameters presented in Table i, and the spectra of samples B1 and B2 at 80 K display not only a doublet, but also an additional line of low intensity at a distance of 2.4 mm/sec from the center of the doublet. The low-temperature spectra of samples B1 and B2 can be described by the sum of two doublets; the parameters of one of them are presented in Table i, and the parameters of the other are 6 = 1.64 mm/sec and & = 3.1 mm/sec. The partial area of the second doublet amounts to no more than 8% of the total area of the spectrum. The isomer shift and the quadrupole splitting of the intense doublet in the spectra of the freshly prepared samples of Fe-PAA (see Table i) are characteristic of ions of trivalent iron in the high-spin state [4]. The doublet of lines with a lower intensity in the spectra of samples B1 and B2 has parameters which are characteristic of ions of divalent iron in the high-spin state [4].