Cellulose
7
5
4
3
6
2 1
0
before degradation sandy soil forest soil agricultural soil
-0,00008
5300
5050
4800
4550
4300
4050
wavenumber (cm -1 )
Fig. 3 Effect of soil type on the biodegradation of the recycled paper with addition of 5% wheat bran for 8 weeks
observed for commercial pots. Pots without additives (WP) possessed the highest mechanical resistance among all laboratory-manufactured products and any bran addition lowered the crushing strength. It was also found that paper pots with added peat were brittle, as did not retain any strength after first compression cycle. Conversely, pots manufactured from waste paper with added bran were elastic, maintaining integrity after several cycles.
degradation progress, where the evolution of the spectra acquired after degrading sample WP5W (waste paper with addition of 5% wheat bran) in various soils is presented. All peaks mentioned in Table 2, with exception of region 5464 cm - 1 (7)were affected by the degradation process. However, the spectra of paper placed in a sandy soil seems to be most similar to the control samples. It demonstrates that the sandy soil containing the lowest organic content and persistent low humidity has the lowest impact on the speed of degradation, as in Mostafa et al. (2010). In contrast, the agricultural and forest soil accelerated the degradation speed. Analyses of the chemical composition of the papers after degradation in agricultural soil for 8 weeks are summarized in Table 3. Cellulose changed consider- ably after degradation, including quality and quantity alterations, as observed also by Shogren (1999). The amount of cellulose decreased in all investigated cases, where major changes (over 12%) were observed for paper with rye bran and with 5% of wheat bran. Conversely, the cellulose polymerization degree PD drop was slightly higher for papers without any bran additives. The content of extractive components was higher after biodegradation, especially in the case of extraction in 1% H 2 SO 4 . It can be explained as a result of constitutive polymers degradation due to hydrolysis and biotic factors (Witkowska et al. 1989). Microscopic analysis allows the assessment of changes in the micro structure of cellulose fibres as results of the degradation. Selected SEM microscopic
Changes to paper due to biodegradation in soil
Degradation processes take place in the natural environment constantly and on a large scale (Pagga 1999). Biodegradation in soil is an important end-of- life option for bio-based materials used in agricultural applications. The rate of degradation can vary signif- icantly, depending not only on the molecular structure of the material, but also on soil characteristics and conditions (temperature, water and oxygen availabil- ity which influence microbial activity) (Briassoulis et al. 2014). Biodegradation occurs in two steps. First, the polymers are fragmented into lower molecular mass by means of abiotic reactions (oxidation, pho- todegradation or hydrolysis) or biotic reactions (degradations by microorganisms). Then the polymer fragments are assimilated and mineralized by microor- ganisms (Vroman and Tighzert 2009). The effect of soil type on the biodegradation of investigated papers was analysed by means of NIR spectroscopy. Figure 3 presents an example of
123
Made with FlippingBook - Online catalogs