Effect of oil extraction on the composition, structure, and coagulant effect of Moringa oleifera seeds

Moringa oleifera seeds contain cationic proteins that can be used for water and wastewater treatment; furthermore, the oil content of Moringa oleifera seeds is high, and the properties of this oil render it useful for many applications. In this study, it was investigated the effects of oil extraction on the structure, composition, and coagulant activity of Moringa oleifera seeds, and aimed to add value to the seed waste generated after oil extraction. The results revealed that the content of fatty acids and phenolic and aromatic compounds of the seeds decreased after oil extraction. However, the proteins, including those with coagulant properties, were retained in the oil-extracted seeds. Oil extraction increased the operating pH range of the natural flocculant derived from Moringa oleifera seeds from below 4.8 for the flocculant derived from oil-containing Moringa oleifera (M1) seeds to below 9.8 for the flocculant derived from oil-extracted Moringa oleifera (M2) seeds. Furthermore, the performance of the M1 and M2 seeds for water treatment via coagulation followed by dissolved air flotation was not significantly different, and their mean oil and grease removal efficiency was approximately 82.43 ± 0.70%. These results confirmed the promising use of Moringa oleifera seed waste for the removal of oil and grease from wastewater as a more affordable, sustainable, and natural alternative to commercial flocculants. In addition, the concomitant use of both the extracted oil and seed waste generated after oil extraction was facilitated. More studies should be performed to assess whether the performance of the M1 and M2 seed-derived flocculants could be improved at the pH values we determined to be optimal for the purification of the protein of interest, viz. 9.5 and 4.0, respectively.