Removal of Ni (II) and Pb (II) ions from aqueous solutions by grapefruit (Citrus paradisi) Mesocarp Biomass

Abstract

The surface characteristics of Citrus paradisi (grapefruit mesocarp biomass) on the biosorption of Ni (II) and Pb (II) ions from aqueous solution were studied adopting a batch reactor technique. The dried  grapefruit mesocarp biomass was characterized using phytochemical screening and Fourier Transform  Infra – Red (FTIR) Spectroscopy. The results of the characterization revealed the presence of alkaloids, tannins, saponins, cyanogenic glycosides. Furthermore, the FTIR spectrum pattern of the biomass  showed broad and sharp absorption peaks indicating the existence of functional groups like – OH, C=O, C-H, C-O, N-H, etc. The biosorption process was found to be pH, time and concentration dependent. The rate of biosorption was higher in Ni (II) ion than Pb (II) ion. The result of the  equilibrium modeling showed that the biosorption process fitted well with the Freundlich isotherm equation indicating a muiltilayer biosorption. The mechanism of the biosorption process followed pseudo – second – order kinetic model equation with correlation coefficient (R2) of 0.999 for Ni (II) ion and 0.991 for Pb (II) ion  respectively. Thermodynamic parameters determined showed that the biosorption of Ni (II) and Pb (II) ions on the surface of the biomass was an exothermic and spontaneous process. The rate of biosorption was found to decrease with increasing temperature. The results showed that the dried grapefruit mesocarp biomass was efficient and effective in the biosorption of Ni (II) and Pb (II) ions and is recommended to be applied in wastewaters.

Keywords: Citrus paradisi, biosorption, metal ions, characterization, mechanism.