A natural coagulant protein from copra (Cocos nucifera): Isolation, characterization, and potential for water purification

A natural coagulant protein was extracted from the endosperm of Cocos nucifera, and characterized by Fourier Transform Infrared Spectroscopy, size exclusion chromatography, potentiometric titration, electrophoretic mobility, and then tested for its coagulant properties using silica nanocolloids. The infrared spectra revealed predominant absorption bands at 1649 cm(-1) and 1536 cm(-1) characteristics of -C=0 in primary and secondary amides of proteins arranged into an alpha-helical secondary structure, and the presence of triolein when fat was not removed from the extract. The molecular weight determined by size exclusion chromatography was about 5.6 kDa, the charge density of the fat extracted protein being 1.05 meq g(-1), and the isoelectric point 7.5. The proteinous extracts behaved as effective coagulants of silica particles, the destabilisation mechanism being consistent with an heteroaggregation of oppositely charged colloids. Overall, the characteristics of that natural protein were closely similar to those of Moringa oleifera seed extract, thus suggesting that copra can be considered as a potential source of an efficient and sustainable coagulant for water treatment in emerging countries. (c) 2013 Elsevier B.V. All rights reserved.