# Utilization of Natural Adsorbents in the Purification of Used Sunflower and Palm Cooking Oils
## 3 Results
### FT-IR Spectroscopy of the Analyzed Oils  
Figure 3 shows the FT-IR spectrum recorded for eight sunflower oil samples according to Table 1 (S1--fresh, S2--WCO by frying potatoes, S3--WCO by frying chicken meat, S4--WCO by frying a mix of animal and non-animal food, S5--S4 purified with NaCl 10%; S6--S4 purified with zeolite-NaCl, S7--S4 purified with zeolite-NaOH, S8--S4 purified with eggshell).  
In the case of sunflower oils, the results show that the band at the regions of 3008 cm\({}^{-1}\) (the unsaturated C-H functional group), 2922 cm\({}^{-1}\) (the saturated C-H functional group), and 2853 cm\({}^{-1}\) are associated with symmetric and asymmetric C-H of alkanes groups (stretching vibrations of C-H in CH\({}_{2}\) and CH\({}_{3}\) groups, respectively). The band of 1744 cm\({}^{-1}\) is because of the presence of C=O stretching vibration of carbonyl groups present in triglycerides and esters.  
Bands that appear between 1500 cm\({}^{-1}\) and 500 cm\({}^{-1}\) represent a complex spectral band due to the complicated stretching and bending in the substance molecule, which is also called  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Eggshell**} & \multirow{2}{*}{
\begin{tabular}{c} **Time**, \\ **min** \\ \end{tabular} } & \multicolumn{2}{c}{**AV, mg KOH/g**} & \multicolumn{2}{c}{**PV, mEqO2/kg**} & \multicolumn{2}{c}{**TPC, \%**} \\ \cline{3-8}  & & **EST 1** & **EST 2** & **EST 2** & **EST 2** & **EST 2** & **EST 2** & **EST 2** \\ \cline{2-8}  & **0** & \multicolumn{2}{c}{**3.40 \(\pm\) 0.10**} & \multicolumn{2}{c}{**40.5 \(\pm\) 0.82**} & \multicolumn{2}{c}{**43.0 \(\pm\) 0.01**} \\ \hline
5 & & 1.51 \(\pm\) 0.26 & 2.04 \(\pm\) 0.17 & 33.61 \(\pm\) 0.44 & 33.84 \(\pm\) 0.23 & 43.0 \(\pm\) 0.04 & 43.0 \(\pm\) 0.02 \\
10 & & 1.77 \(\pm\) 0.05 & 1.95 \(\pm\) 0.06 & 32.62 \(\pm\) 1.43 & 24.52 \(\pm\) 0.81 & 43.0 \(\pm\) 0.02 & 43.0 \(\pm\) 0.08 \\
20 & & 1.57 \(\pm\) 0.08 & 1.85 \(\pm\) 0.03 & 29.75 \(\pm\) 1.68 & 30.65 \(\pm\) 1.56 & 43.0 \(\pm\) 0.06 & 43.0 \(\pm\) 0.03 \\
30 & & 1.10 \(\pm\) 0.04 & 1.44 \(\pm\) 0.06 & 20.82 \(\pm\) 1.27 & 20.33 \(\pm\) 1.14 & 43.0 \(\pm\) 0.01 & 43.0 \(\pm\) 0.03 \\ \hline \hline \end{tabular} \({}^{1}\) EST—Thermally activated, 2 EG\({}_{\text{HCI}}\)—Activated with HCl; All values are means \(\pm\) standard deviations (\(n=3\)).  
\end{table}
Table 6: The values of the quality parameters of the sunflower—WCO treated with eggshell.  
Figure 3: FT-IR spectra of fresh sunflower oil (S1), WCO (S2, S3 and S4), and purified oils (S5, S6, S7 and S8).  
a \"fingerprint\" region [46; 47]. The band at 1463 cm\({}^{-1}\) region confirms the bending vibrations of CH\({}_{2}\) and CH\({}_{3}\) aliphatic groups, while the bending of HCH occurs at 1377 cm\({}^{-1}\) and CH\({}_{2}\) and scissoring at 1463 cm\({}^{-1}\), respectively. The bands situated in the region 1237 cm\({}^{-1}\), 1160 cm\({}^{-1}\), 1097 cm\({}^{-1}\) present the stretching vibration of C=O ester group.  
Figure 4 presents the FT-IR spectrum recorded for three palm oil samples (S9--fresh oil, S10--WCO by frying bakery and pastry products, S11--S10 purified with NaCl 10%). Since palm oil is semi-solid at room temperature and contains several saturated and unsaturated fats, only the treatment with 10% NaCl solution was analyzed by FT-IR.  
A similar trend is also observed in the case of palm oils. The absorption band of the carbonyl group C=O in saturated aliphatic esters usually appears at 1743 cm\({}^{-1}\). Stretching vibrations of groups C-H--Methyl (-CH\({}_{3}\)) and methylene (-CH\({}_{2}\)-), both symmetrical and non-symmetrical, are present at 2851, 2916, and 3038 cm\({}^{-1}\). The C-O stretching vibration at 1377 cm\({}^{-1}\) is also observed in the spectra of other organic compounds such as carboxylic acids, ethers or alcohols. Methyl esters belonging to long-chain fatty acids often give rise to absorption maxima at about 1177 cm\({}^{-1}\).