Fabrication and characterisation of a Fe3O4/Raphia farinifera nanocomposite for application in heavy metal adsorption

Magnetite/Raphia farinifera nanocomposites of different magnetite to Raphia farinifera ratios of 2:1, 1:1, 1:2 and 1:3, designated as MRfA, MRfB, MRfC and MRfD respectively, were successfully prepared by chemical co-precipitation of magnetite precursors in a suspension of Raphia farinifera. The four nanocomposites, and the parent materials, Raphia farinifera and magnetite, were characterised and compared. It was seen that the properties of the nanocomposites were a reflection of the properties of magnetite to degrees which varied with the amount of magnetite. Increased magnetite content in the nanocomposites resulted in higher saturation magnetisation, larger surface area, better thermal stability and better crystallinity. On the other hand, the smaller the amount of magnetite, or the more Rf in the nanocomposites, the smaller the particle size, the better the dispersion or the lower the tendency for agglomeration. Scanning electron (SEM) microscopy showed that the nanocomposites have a morphology similar to that of magnetite, which is a pointer to the fact that the magnetite nanoparticles were successfully dispersed on the surface of the Raphia farinifera. Also, in terms of functionality, the Raphia farinifera enriched the surface of the nanocomposites with functional groups whose amount was determined by the Boehm titration. Both acidic and basic oxygen groups were present on the surface of the composite materials but only acidic groups were present on the Raphia farinifera biomass surface. The total number of acidic and basic oxygen functional groups followed the order: MRfD >Rf > MRfC > MRfB > MRfA. Of the two composites tested for heavy metal ion adsorption MRfD, that contained more biomass, performed better than MRfB. The adsorption of Pb2+ was particularly enhanced with an adsorption capacity of 63.8 mg g(-1). Thus, these magnetic nanocomposites show promise for the remediation of contaminated wastewaters. (C) 2018 Elsevier B.V. All rights reserved.