## 3 Results and Discussion
Meanwhile, in the case of fly ash obtained during the incineration of household waste (sample 3) and after plasma-chemical treatment (sample 4), the characteristic compounds are CaSO\({}_{4}\), SiO\({}_{2}\), and CaO. The reasons for the formation of these compounds are the same as in the case of wood ash. In the case of slag obtained from household waste (sample 5) and material after the plasma-chemical  
Figure 5: The XRD research results of primary and post-plasma–chemical treatment materials. treatment of slag (sample 6), the predominant compounds, according to our XRD studies, are SiO\({}_{2}\) and CaO. The reasons for the formation of these compounds are the same as in the first two cases. However, in this case, a smaller variety of metals is observed. Analyzing the XRD studies, it became clear that the resulting fiber has an amorphous structure. It is likely that this happens because the vitrification process takes place during the formation of fibers, during which a disordered structure (resembling a homogeneous melt) and amorphous formations are formed [1; 2; 3; 4; 5; 6]. This fact was also partially confirmed by the TG studies, since there is almost no reaction with reactive gases and no mass loss is observed, which is characteristic of the structures formed during the vitrification process. Figure 6 shows the FTIR spectra of wood ash before plasma-chemical treatment and after it; fly ash obtained from the incineration of household waste before plasma-chemical treatment and after; slag primary materials and slag after plasma-chemical treatment; and the produced fiber. Figure 6: \(Cont.\)  
Several broad and high-intensity absorption peaks in the wavenumber range from 400 to 3700 cm\({}^{-1}\) were obtained. It has been shown that the stretching vibration of Ca-O bonds occurs at 700, 1050, and 1400 cm\({}^{-1}\). Meanwhile, absorption peaks were also obtained for Si=O at 650 and 1400 cm\({}^{-1}\). A C=O low-intensity peak at 1900 cm\({}^{-1}\) could also be observed. These discussed peaks of compounds are characteristic of wood ash both before and after plasma treatment. After the treatment, wood ash is also characterized by OH at 3600 cm\({}^{-1}\). While analyzing the FTIR spectra of fly ash (obtained by the incineration of household waste) both before plasma treatment and after treatment, it was observed that the same peaks are characteristic as in the case of wood ash, except that at 3400 cm\({}^{-1}\), for which the high-intensity CaSO\({}_{4}\) is observed; this peak basically coincides with the OH peak. Analysis of the FTIR spectra in the case of slag (obtained by burning domestic waste) before plasma treatment and after treatment, showed high-intensity peaks: CaSO\({}_{4}\) at 490 and 3400 cm\({}^{-1}\); Si=O at 650 and 1400 cm\({}^{-1}\); Ca-O bond stretching is obtained at 1400 cm\({}^{-1}\). These peaks of the FTIR spectrum are similar for the slag before plasma treatment and after it. The only essential difference is that at 3400 cm\({}^{-1}\), there is a peak characteristic of CaSO\({}_{4}\) slag before plasma-chemical treatment. It was possible to obtain fiber from slag during plasma-chemical treatment. The FTIR spectra of the fiber (obtained at 55.5 kW plasma torch power) show that the peaks of CaSO\({}_{4}\) at 490 and Si=O at 650 cm\({}^{-1}\) are characteristic, and there is also a peak at 1400 cm\({}^{-1}\) that is characteristic of Ca-O and Si=O. When the fiber was obtained at 74 kW plasma torch power, the obtained peaks of the FTIR spectrum were the same as those of the fiber obtained at 55.5 kW power. Figure 7 presents the BET results of fiber obtained by processing slag (obtained by burning household waste) by the plasma-chemical method. The fiber was obtained at 55.5; 55.6 and 74 kW, with a specific surface area of 11.9; 8.5 and 3 m\({}^{2}\)/g. The best-fit computational model for estimating the pore size distribution of the sample was the QSDFT, N2, carbon equilibrium transition core at 77.4 K based on the slot pore model, with a computational fit error of 3.27%.