# Application of Ultrafiltration for Recovery of Bioactive Phenolic Compounds from Rose Wastewater
## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Solution type:**} & **Membrane** & **1 kDa** & **10 kDa** & **25 kDa** \\ \hline \multicolumn{5}{c}{**Flavonoid phenolic compounds, mg/dm\({}^{3}\) quercetin**} \\
1 & Initial rose wastewater & 529.03 \(\pm\) 8.89 a & 529.03 \(\pm\) 8.89 a & 529.03 \(\pm\) 8.89 a \\
2 & Retentate at VRR 2 & 531.22 \(\pm\) 4.83 a,A,B & 541.70 \(\pm\) 20.95 a,b,A & 503.52 \(\pm\) 14.20 b,B \\
3 & Retentate at VRR 4 & 700.43 \(\pm\) 22.87 b,A & 563.64 \(\pm\) 8.63 b,B & 503.73 \(\pm\) 9.87 a,C \\
4 & Retentate at VRR 6 & 700.93 \(\pm\) 11.56 c,A & 564.00 \(\pm\) 13.12 b,B & 521.58 \(\pm\) 1.61 b,C \\
5 & Retentate at VRR 8 & 767.83 \(\pm\) 32.55 d,A & 600.76 \(\pm\) 6.47 c,B & 608.63 \(\pm\) 1.38 c,B \\
6 & Permeate & 448.03 \(\pm\) 8.87 e,A & 382.04 \(\pm\) 18.09 d,B & 423.38 \(\pm\) 3.22 d,C \\ \hline \hline \end{tabular} Note: The different lowercase letters (a, b, c, d, e) show statistically significant differences in the column (by solution type); different capital letters (A, B, C) show statistically significant differences in the row (by membrane), at a significance level \(\alpha<0.05\).  
\end{table} 
Table 1: _Cont._  
Figure 3: Rejection (%) of total phenolic compounds, phenolic acids, and flavonoid phenolic compounds compared to the volume reduction ratio. material but on the molecular weight cut-off of the membrane. [PERSON] et al. [37] used membranes from 1 to 150 kDa and found that the membrane with a nominal molecular weight cut-off of 2 kDa showed the highest anthocyanin flux at 2 MPa and was classified as the most promising membrane for the fractionation of polyphenolic compounds. Changes in the antioxidant activity of retentates during the ultrafiltration of rose wastewater are presented in Figure 5. The highest antioxidant activity was established at a VRR of 8 with the 1 kDa membrane; the smallest was at a VRR of 2 with the 25 kDa membrane. Similar to the content of total phenolic compounds, phenolic acids, and flavonoid phenolic compounds, antioxidant activity increased with a decrease in the molecular weight cut-off of the membrane. A linear diminution in the total anthocyanins and total ellagitannins in blackberry juice (_Rubus adenotrichus_ Schltdl. ), with an increase in the molecular weight cut-off of the membranes, was found by [PERSON] et al. [37]. After observing the results obtained for permeate flux, energy demand, rejection, concentration factor, and antioxidant activity, we recommend using a VRR of 8, a transmembrane pressure of 0.5 MPa and a 1 kDa membrane. These working conditions will be used in our future investigations to obtain extrudates from rice semolina enriched with ultrafiltered rose wastewater. The chromatograms of the initial rose wastewater (A) and retentate at a VRR of 8 (B) with the 1 kDa membrane are presented in Figure 6. It can be seen that the main compounds presented in the initial rose wastewater are gallic and rosmarinic acids. Regarding the retentate at a VRR of 8 with the 1 kDa membrane (Figure 7), the main compounds are gallic acid and routin. An increase in the content of protocatechuic and vanillic acids was observed in the retentate, while the other compounds decreased in retentate compared to the initial rose wastewater. The rejection of phenolic acids depends on the type of initial solution, as well as the molecular weight cut-off of the membrane. [PERSON] and [PERSON] [37] studied 5, 10, and 50 kDa membranes for the ultrafiltration of broccoli juice and found that rejection with the 10 kDa membrane toward chlorogenic acid, sinapic acid, kaempfer, quercetin, and rutin was in the range of 4.2-44%. The most retained phenolic  
Figure 4: Concentration factor of total phenolic compounds, phenolic acids, and flavonoid phenolic compounds compared to the volume reduction ratio. compound was rutin, which could be explained by the higher number of benzene rings on the molecular structure and higher acidity coefficient.