Moringa oleifera for drinking water treatment: influence of the solvent and method used in oil-extraction on the coagulant efficiency of the seed extract

Abstract

[EN] Moringa oleifera seeds contain a cationic coagulant protein that can be used either for drinking water clarification or wastewater treatment. The seeds contain 30-40% (w/w) oil, which represents a valuable resource with industrial, food and renewable energy applications. However, the oil also increases the organic matter added to water and avoids storage of treated water and its consumption within 24h. So oil extraction is recommended as a way to purify the extract. This work proposes solvent extraction using three solvents (hexane, acetone, ethanol) and two procedures (batch and Soxhlet) and analyses for the first time the influence that these factors have on the coagulant efficiency of the extract prepared using defatted seeds. Results show that solvent-defatted seed extracts have a coagulant efficiency comparable to that observed for polyaluminium chloride coagulant (up to 88%), while non-defatted seed extract efficiency is 30% lower. Moreover, ethanol and Soxhlet method for oil extraction allows obtaining a defatted extract that requires doses of coagulant protein 5-33 times lower than hexane or acetone defatted extract to clarify turbid water, reducing in consequence the organic load added. SDS-PAGE analysis showed no influence of the solvent on the nature of the coagulant protein present in the extracts. The results of the study provide an oil extraction procedure that recovers M. oleifera oil for industrial purposes and enhances the defatted seeds obtaining an improved coagulant for drinking water treatment.