# Utilization of Natural Adsorbents in the Purification of Used Sunflower and Palm Cooking Oils
## 2 Materials and Methods
### Physicochemical Analysis of Vegetable Oil Samples  
Moisture content. About 5-20 g of the sample was accurately weighed to 0.0002 g in a flask brought forward to constant mass. It was then placed in an oven at 101 \(\pm\) 1 \({}^{\circ}\)C for 15 min, followed by cooling in a desiccator. The drying process was repeated until a constant weight was achieved [28]. Relative Density. The density was measured at 25 \({}^{\circ}\)C using a 50 mL bottle pycnometer, which had been washed with degreasing solution, water, and petroleum ether [29]. Refractive Index (RI). It was measured in triplicate with a Cell RX4 (Mettler Toledo, Shah Alam, Selangor, Malaysia) device [30]. Peroxide value (PV). The oil sample (2.5 \(\pm\) 0.1 g) was mixed with 10 mL of chloroform until complete dissolution; then, 15 mL of acetic acid and 1 mL of saturated potassium iodide solution were added. The sample was stirred for one minute and left to stand for 5 min. Then, 75 mL of distilled water was added, and the released iodine was titrated in the presence of starch, under continuous stirring, with 0.01 M sodium thiosulfate solution. All measurements were carried out in triplicate [31]. pH determination. The pH was measured using the pH-meter PHT 810 (1340-5810) (EBRO, Freiburg im Breisgau, Germany). All measurements were performed in triplicate. Viscosity. Viscosity was determined utilizing the viscometer _micro_VISC--M (RheoSense Inc., San Ramon, CA, USA) at 40 \({}^{\circ}\)C. All measurements were conducted three times. Acid Value (AV). A 5 \(\pm\) 0.01 g vegetable oil sample was dissolved in 50 mL of solvent while being stirred. (ether: 95% alcohol (Chempur, Piekary Slaskie, Poland)). The resulting mix was titrated with 0.1 M KOH solution (Merck, Darmstadt, Germany) in the presence \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample No.** & **Type of Vegetable Oil** & **Note** \\ \hline S1 & Fresh sunflower oil & - \\ S2 & WCO—sunflower oil from frying potatoes & 100 mL of oil \\ S3 & WCO—Sunflower oil from frying chicken & 100 mL of oil \\ S4 & WCO—Sunflower oil from frying a mix of potatoes and chicken & 10 g of sliced potatoes and 10 g of lean chicken meat in \\ S5 & S4 treated with 10\% NaCl sol. & - \\ S6 & S4 treated with zeolites activated with NaCl & - \\ S7 & S4 treated with 30 g zeolite activated with & - \\ NaOH/120 min & - \\ S8 & S4 treated with 30 g eggshell & - \\  & heat-treated/120 min & - \\ S9 & Fresh palm oil & - \\ S10 & WCO—palm oil from frying bakery products & 20 g of doughnuts in \\  & & 100 mL of oil \\ S11 & S10 treated with 10\% NaCl sol. & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The vegetable oil samples used and the treatments applied to them. of phenolphthalein (Merck, Darmstadt, Germany) until the pink turning point. The result was expressed in mg KOH/g [32]. Iodine value (IV)--Hanus method. An amount of 0.2 g of oil was dissolved in 20 mL of chloroform (Merck, Darmstadt, Germany). An amount of 25 mL of Hanus solution was added (10 g of iodine monobromide (Merck, Darmstadt, Germany) in 500 mL of glacial acetic acid (Chempur, Piekary Slaskie, Poland). After stirring, it was kept in the dark for 30 min. Ten mL of potassium iodine was added to the 15% flask solution (Merck, Darmstadt, Germany) followed by 100 mL distilled water. The mix was titrated with 0.1 M sodium thiosulfate solution (Univar, Seven Hills, Australia) until the yellow straw color was achieved. Starch was added (Merck, Darmstadt, Germany), and the titration continued, until the blue color disappeared. Two blank samples were performed in parallel with the same amounts of solvent and Hanus reagent but without oil. The result was expressed as grams of I\({}_{2}\) absorbed by 100 g oil [33]. Saponification value (SV). Two g of dry sample were mixed with 25 mL of the alcoholic potassium hydroxide solution (Merck, Darmstadt, Germany). An air cooler was installed, and the solution was boiled under reflux until complete saponification (about 1 h).