Biosorption of heavy metal ions on peel of Artocarpus nobilis fruit: 2. Improvement of biosorption capacities of Ni(II) through different modifications
P. A. Kotabewatta, Namal Priyantha, Linda B.L. Lim
Abstract
ABSTRACT Processing of raw fruit peel (0.71 < d < 1 mm) of Artocarpus nobilis biosorbent using distilled water- washed peel (DWP), and modification with aqueous NaOH solutions (STP) of different concentrations enhances the extent of removal of Ni(II) as a result of increase in surface negative charges, porous nature and the mass to volume ratio. An increase in surface negativity is contributed by deprotonation of functional groups present in the biosorbent, and the cleavage of esters through saponification during the NaOH treatment. The surface area of the biosorbent is increased by breaking down of structural materials, such as lignin, during base treatment. The specific surface areas of DWP, and STP prepared by treatment with 0.10 M NaOH are 381.90 and 919.01 m 2 g –1 , respectively. The high surface area of STP is convinced by observing small cavities in scanning electron microscopy images. The optimum shaking and settling times are recorded as 2.0 h and 15 min, respectively, for both DWP and STP, while the ambient pH of Ni(II) solutions 5.0 leads to the maximum removal. Under these conditions, the maximum removal of 14.925 mg g –1 is obtained for STP3 from synthetic solutions at ambient solution temperature without any thermal treatment of the biosorbent. An important aspect of this biosorbent is that, although thermal treatment of DWP enhances its biosorption capacity, STP provides even higher capacity without any thermal treatment.