# Methods for Obtaining Humus Substances: Advantages and Disadvantages
## 3 Results and Discussion
### FT-IR Analysis  
To assess and analyze the interactions between HS and micropollutants, the IR spectrum of HS(A), HS(B), and HS(C) were created. These allowed us to determine the structure of HS samples, including the type of functional groups. Independently, the spectrum of fulvic acids extracted from treated municipal wastewater (FA1) was created to compare the results. The spectra are presented in Figure 5, and the results are in Table 3. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Wavenumber cm\({}^{-1}\)** & **HS(A)** & **HS(B)** & **HS(C)** & **FA1** & **Interpretation** \\ \hline \multirow{3}{*}{3650–3200} & \multirow{3}{*}{X} & \multirow{3}{*}{X} & \multirow{3}{*}{X} & \multirow{3}{*}{X} & Absorption in this range indicates the presence of an OH or NH group, v(OH) or v(NH) vibrations. A sharp band of medium intensity at 3300 cm\({}^{-1}\) corresponds to an ethylynyl group (-C\(\equiv\)C-H). \\ \cline{3-5}  & & & & & \\ \hline \multirow{3}{*}{3050–2900} & \multirow{3}{*}{X} & \multirow{3}{*}{X} & \multirow{3}{*}{X} & \multirow{3}{*}{X} & The occurrence of asymmetric and symmetric \\  & & & & & C-H stretches of the CH\({}_{2}\), O-H group. \\ \hline \multirow{3}{*}{1700–1650} & \multirow{3}{*}{-} & \multirow{3}{*}{-} & \multirow{3}{*}{X} & \multirow{3}{*}{X} & The bands at 1650 cm\({}^{-1}\), 1692 cm\({}^{-1}\), and 1700 cm\({}^{-1}\) are typical of C=O, C=C double bonds (stretching), bonds of ketones, aldehydes, esters, alkenes, in aromatic rings, including lignin structures, and C=N amide groups and other nitrogen-containing groups. \\ \cline{3-5}  & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Characteristic absorption bands of FA and HS [33; 39; 40; 41; 42; 43; 44]. Figure 4: Thermogravimetry (TG) curve of HS(C) sample. Comparative analysis indicates that they are broadly similar. Broad bands with peaks of 3370-3280 cm\({}^{-1}\) and 2920-2910 cm\({}^{-1}\) result from the stretching vibrations of the O-H group. Such a pattern is on brand for alcohols, phenols, and organic acids, and confirms the presence of aliphatic groups in HS samples (FA1, HS(A), HS(B), HS(C)). Three sharp bands of variable intensity are visible in the 1582-1500 cm\({}^{-1}\) region of the HS(A) spectrum. They correspond to the stretching vibrations of the aromatic ring [n(C=C)]. The simultaneous occurrence of the 1411 cm\({}^{-1}\) peak, resulting from the O-H deformation, CH\({}_{3}\) bending, OH phenolic stretching, and COO- antisymmetric stretching, confirms the presence of phenolic and carboxylic functional groups. The bands in the region of 1700-1650 cm\({}^{-1}\) of the FA1 and HS(C) are typical of double bonds C=O, C=C (their stretching vibrations) of ketones, aldehydes, esters, and alkenes in aromatic rings,  
Figure 5: IR spectra of the samples: HS(A), HS(B), HS(C), and FA1 (wastewater). \begin{table}
\begin{tabular}{c c c c c c} \hline
**Wavenumber** & **HS(A)** & **HS(B)** & **HS(C)** & **FA1** & **Interpretation** \\ \hline
1600–1500 & X & X & - & - & Aromatic rings, stretching vibrations of the ring \(\
u\)(C=C). \\ \hline
1420–1300 & X & X & X & X &
\begin{tabular}{c} O-H deformation, CH\({}_{3}\) bending, C-O stretching \\ of phenolic OH, and antisymmetric stretching COO- \\ \end{tabular} \\ \hline
1350–1000 & X & X & X & X &
\begin{tabular}{c} Fingerprint region. \\ \end{tabular} \\ \hline
770 & - & - & X & X &
\begin{tabular}{c} Deformation vibrations \(\delta\) NO\({}_{2}\), \\ out-of-plane deformation NH\({}_{2}\). \\ \end{tabular} \\ \hline \end{tabular}
\end{table} 
Table 3: _Cont._and indicate the presence of aromatic elements in the molecule [39; 40; 41; 42]. They occur only in FA1 and HS(C), which are extracted from municipal wastewater treatment products. No such bands exist in the HS(A) and HS(B) spectra. This means that HS(A) and HS(B) are not contaminated with toxic organic substances in municipal wastewater. The 1100 cm\({}^{-1}\) band occurs in the FA1, HS(A), HS(B), and HS(C) spectra. It is a band from the fingerprint region 1350-1000.