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The biosorption properties ofCocos nuciferashell andMoringa oleiferaseeds for Pb(II) were investigated under batch mode. The optimum pH values obtained for the removal of Pb(II) by theCocos nuciferashell and theMoringa oleiferaseeds were 5 and 2, respectively. The equilibrium biosorption capacities obtained were 2.3 mg g−1 (Moringa oleiferaseeds) and 1.6 mg g−1 (Cocos nuciferashell). The Freundlich isotherm model described the removal of Pb(II) by the biosorbents better than the Langmuir model. TheCocos nuciferashell sorbed 83.34% of the Pb(II) ions in 30 min, while 94.03% was sorbed by theMoringa oleiferaseeds in the same time. The results indicated a fast kinetics for Pb(II) sorption by the biosorbents investigated. The biosorption of Pb(II) ontoCocos nuciferashell andMoringa oleiferaseeds followed the pseudo second-order kinetics withR2values of 0.9997 and 0.9999, respectively. The second-order rate constant (k2) obtained were 0.205 g mg−1min−1(Cocos nuciferashell) and 0.067 g mg−1min−1(Moringa oleiferaseeds). The results indicate that intraparticle diffusion controls the rate of biosorption in this study. This study shows thatCocos nuciferashell andMoringa oleiferaseeds can be important low-cost biosorbents for Pb(II) ions. [ABSTRACT FROM AUTHOR]

Adsorption kinetic studies are of great significance in evaluating the performance of a given adsorbent and gaining insight into the underlying mechanism. This work investigated the sorption kinetics of Cu(II) on to coconut shell and Moringa oleifera seeds using batch techniques. To understand the mechanisms of the biosorption process and the potential rate-controlling steps, kinetic models were used to fit the experimental data. The results indicate that kinetic data were best described by the pseudo-second-order model with correlation coefficients (R 2) of 0.9974 and 0.9958 for the coconut shell and Moringa oleifera seeds, respectively. The initial sorption rates obtained for coconut shell and Moringa oleifera seeds were 9.6395×10−3 and 8.3292×10−2 mg g−1 min−1, respectively. The values of the mass transfer coefficients obtained for coconut shell (1.2106×10−3 cm s−1) and Moringa oleifera seeds (8.965×10−4 cm s−1) indicate that the transport of Cu(II) from the bulk liquid to the solid phase was quite fast for both materials investigated. The results indicate that intraparticle diffusion controls the rate of sorption in this study; however, film diffusion cannot be neglected, especially at the initial stage of sorption. [ABSTRACT FROM PUBLISHER]