# Variation of the Chemical Composition of Waste Cooking Oils upon Bentonite Filtration
## Materials and Methods
### Xrd  
X-ray diffraction (XRD) patterns of the bentonite samples were acquired with a Rigaku SmartLabpowder diffractometer, operating in Bragg-Brentano geometry, equipped with a Cu- rotating anode X-ray source (K\(\alpha\), \(\lambda\) = 1.5418 A) and a graphite monochromator mounted on the diffracted beam. The powders were dispersed and compacted into an amorphous glass sample holder and the measurements recorded in the angular range of 5-50 20 with a scan step of 0.05\({}^{\circ}\) per 4 s. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline
**PCA** & **RT** & **WCO** & **SD** & **WCO1** & **SD** & **WCO2** & **SD** & **RI** & **RI Literature** & \(\Delta\) & **Compound** \\ \hline V1 & 5.444 & 0.42 & 0.08 & 0.72 \({}^{\ast}\) & 0.14 & 0.96 & 0.08 & 702 & 700 & 2 & heptane \\ V2 & 5.573 & 0.89 & 0.03 & 0.28 \({}^{\ast}\) & 0.13 & 0.11 & 0.01 & 711 & 702 & 9 & acetaldehyde \\ V3 & 6.13 & 0.53 & 0.07 & 0.10 \({}^{\ast}\) & 0.07 & 0.13 & 0.02 & 748 & n.a. & Methylamine, N,N-dimethylly- \\ V4 & 6.881 & 1.12 & 0.26 & 2.22 \({}^{\ast}\) & 0.72 & 3.46 & 0.53 & 799 & 800 & 1 & octane \\ V5 & 9.65 & 0.20 & 0.04 & 0.10 \({}^{\ast}\) & 0.01 & 0.05 & 0.00 & 910 & 907 & 3 & 2-Butanone \\ V6 & 10.132 & 0.72 & 0.39 & 0.48 & 0.28 & 0.43 & 0.10 & 925 & 918 & 7 & Butanal, 3-methyl- \\ V7 & 10.579 & 0.14 & 0.00 & n.d. & & n.d. & & 939 & 971 & 32 & Butyl- cyclopentane \\ V8 & 12.109 & 1.00 & 0.19 & 1.18 & 0.28 & 1.54 & 0.33 & 988 & 979 & 9 & pentanal \\ V9 & 15.527 & 4.43 & 0.87 & 6.79 & 1.33 & 7.42 & 0.84 & 1091 & 1083 & 8 & hexanal \\ V10 & 18.842 & 0.26 & 0.03 & 0.47 & 0.22 & 0.53 & 0.01 & 1193 & 1182 & 11 & 2-Heptanone \\ V11 & 18.94 & 0.31 & 0.24 & 0.86 & 0.08 & 1.19 & 0.50 & 1196 & 1184 & 12 & Heptanal \\ V12 & 19.133 & 0.28 & 0.12 & 0.07 \({}^{\ast}\) & 0.01 & n.d. & & 1202 & 1185 & 17 & Pyridine \\ V13 & 19.404 & 0.23 & 0.09 & 0.42 \({}^{\ast}\) & 0.02 & 0.56 & 0.04 & 1211 & 1200 & 11 & Limnene \\ V14 & 19.997 & 0.42 & 0.20 & 0.06 \({}^{\ast}\) & 0.03 & n.d. & & 1230 & 1212 & 18 & Pyrazine \\ V15 & 20.184 & 0.50 & 0.14 & 0.24 \({}^{\ast}\) & 0.09 & n.d. & & 1237 & 1216 & 21 & 2-Hexanal, (E)- \\ V16 & 20.297 & 0.44 & 0.15 & 0.66 & 0.18 & 1.00 & 0.06 & 1240 & 1231 & 9 & Furan, 2-pentyl- \\ V17 & 20.675 & 0.56 & 0.21 & 0.66 & 0.06 & 0.53 & 0.09 & 1253 & 1250 & 3 & 1-Pentan \\ V18 & 20.884 & 0.48 & 0.17 & 0.56 & 0.02 & 0.70 & 0.09 & 1260 & 1246 & 14 & Y-trippinene \\ V19 & 21.500 & 0.20 & 0.15 & n.d. & n.d. & & 1280 & 1272 & 8 & Hexyl acetate \\ V20 & 21.728 & 0.81 & 0.15 & 0.06 \({}^{\ast}\) & 0.02 & 0.03 & 0.01 & 1287 & 1266 & 21 & Pyrazine, methyl- \\ V21 & 22.061 & 0.12 & 0.02 & 0.12 & 0.02 & 0.05 & 0.01 & 1298 & 1287 & 11 & 2-Octanone \\ V22 & 22.199 & 1.11 & 0.28 & 1.46 & 0.51 & 0.98 & 0.80 & 1303 & 1289 & 14 & Octanal \\ V23 & 22.841 & 1.16 & 0.25 & 0.20 \({}^{\ast}\) & 0.06 & n.d. & & 1325 & 1303 & 22 & 2-Propanone, 1-hydroxy- \\ V24 & 23.448 & 2.09 & 0.44 & 2.28 & 0.24 & 1.87 & 0.53 & 1346 & 1322 & 24 & 2-Heprenal \\ V25 & 23.632 & 0.27 & 0.09 & 0.43 & 0.10 & 0.26 & 0.05 & 1353 & 1338 & 15 & 5-Hepten-2-one, 6-methyl- \\ V26 & 23.821 & 0.81 & 0.08 & 0.10 \({}^{\ast}\) & 0.01 & n.d. & & 1360 & 1326 & 34 & Formamide, N,N-dimethylly- \\ V27 & 25.27 & 5.07 & 1.10 & 6.42 & 0.40 & 6.59 & 0.25 & 1410 & 1391 & 19 & Nonanal \\ V28 & 26.032 & 1.25 & 0.25 & 0.23 \({}^{\ast}\) & 0.08 & 0.38 & 0.00 & 1437 & 1414 & 23 & N,N-Dimethylacetamide \\ V29 & 26.305 & 0.22 & 0.08 & 0.19 & 0.04 & 0.12 & 0.02 & 1447 & 1441 & 6 & Ethyl octanoate \\ V30 & 26.463 & 0.79 & 0.08 & 0.69 & 0.04 & 0.56 & 0.20 & 1453 & 1429 & 24 & 2-Octanal, (E)- \\ \hline \end{tabular}
\end{table} 
Table 1: Main VOCs detected, tentatively identified, by HS-SPME GC/MS analysis of WCO, WCO1, and WCO2. The values expressed are the result of the average value of three independent replicates \(\pm\) SD of absolute total ion chromatogram (TIC) peak area (1E6).