Sheep Wool Humidity under Electron Irradiation Affects Wool Sorptivity towards Co(II) Ions

Abstract

The effect of humidity on sheep wool during irradiation by an accelerated electron beam was examined. Each of the samples with 10%, 53%, and 97% relative humidity (RH) absorbed a dose of 0, 109, and 257 kGy, respectively. After being freely kept in common laboratory conditions, the samples were subjected to batch Co(II) sorption experiments monitored with VIS spectrometry for different lapses from electron beam exposure. Along with the sorption, FTIR spectral analysis of the wool samples was conducted for cysteic acid and cystine monoxide, and later, the examination was completed, with pH measuring 0.05 molar KCl extract from the wool samples. Besides a relationship to the absorbed dose and lapse, the sorptivity results showed considerable dependence on wool humidity under exposure. When humidity was deficient (10% RH), the sorptivity was lower due to limited transformation of cystine monoxide to cysteic acid. The wool pre-conditioned at 53% RH, which is the humidity close to common environmental conditions, demonstrated the best Co(II) sorptivity in any case. This finding enables the elimination of pre-exposure wool conditioning in practice. Under excessive humidity of 97% RH and enough high dose of 257 kGy, radiolysis of water occurred, deteriorating the sorptivity. Each wool humidity, dose, and lapse showed a particular scenario. The time and humidity variations in the sorptivity for the non-irradiated sample were a little surprising; despite the absence of electron irradiation, relevant results indicated a strong sensitivity to pre-condition humidity and lapse from the start of the monitoring.

Keywords: electron irradiation; humidity; keratin; modification; sheep wool; sorptivity.

Figure 1

Selected FTIR spectra of wool samples pre-conditioned at 10% RH taken 26 days (A) and 178 days (B) after irradiation.

Figure 2

Time development of sorptivity (A), relative content of cysteic acid and cystine monoxide (B), and cystine monoxide to cysteic acid ratio (C) for non-irradiated wool pre-conditioned at different RH. Measurements were performed after subsequent storage under laboratory conditions.

Figure 2

Time development of sorptivity (A), relative content of cysteic acid and cystine monoxide (B), and cystine monoxide to cysteic acid ratio (C) for non-irradiated wool pre-conditioned at different RH. Measurements were performed after subsequent storage under laboratory conditions.

Figure 3

Time development of sorptivity (A), relative content of cysteic acid and cystine monoxide (B), and cystine monoxide to cysteic acid ratio (C) for wool pre-conditioned at different RH and dosed 109 kGy. Measurements were performed after subsequent storage under laboratory conditions.

Figure 4

Time development of sorptivity (A), relative content of cysteic acid and cystine monoxide (B), and cystine monoxide to cysteic acid ratio (C) for wool pre-conditioned at different RH and dosed 257 kGy. Measurements were performed after subsequent storage under laboratory conditions.

Figure 4

Time development of sorptivity (A), relative content of cysteic acid and cystine monoxide (B), and cystine monoxide to cysteic acid ratio (C) for wool pre-conditioned at different RH and dosed 257 kGy. Measurements were performed after subsequent storage under laboratory conditions.

Figure 5

Time sorptivity variation with absorbed dose for wool pre-conditioned at 10% RH.

Figure 6

Time sorptivity variation with absorbed dose for wool pre-conditioned at 53% RH.

Figure 7

Time sorptivity variation with absorbed dose for wool pre-conditioned at 97% RH.

Figure 8

Variation of pH in 0.05 molar KCl extracts from wool depending on absorbed dose for different RH (%) in conditioning prior to irradiation. Measurements were performed 353 days after irradiation and subsequent free storage under laboratory conditions.

Figure 9

Variation of wool sorptivity 160 days after electron irradiation depending on RH under pre-exposition conditioning.