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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]

Sorption is a viable treatment technology for copper-rich gold mine tailings wastewater. For continuous application, the sorbent should be regenerated with an appropriate desorbent, and reused. In this study, the sequential sorption/desorption characteristics of Cu(II) on coconut shell (CS) and iron oxide coated sand (IOCS) were determined. In batch assays, CS was found to have a Cu(II) uptake capacity of 0.46 mg g−1and yielded a 93% removal efficiency, while the IOCS had a Cu(II) uptake capacity and removal efficiency of 0.49 mg g−1and 98%, respectively. Desorption experiments indicated that HCl (0.05 M) was an efficient desorbent for the recovery of Cu(II) from CS, with an average desorption efficiency of 96% (sustained for eight sorption and desorption cycles). HCl (0.05 M) did not diminish the CS's ability to sorb copper even after eight sorption/desorption cycles, but completely deteriorated the iron oxide structure of the IOCS within six cycles. This study showed that CS and IOCS are both good sorbents for Cu(II); but cyclical sorption/desorption using 0.05 M HCl is only feasible with CS. [ABSTRACT FROM PUBLISHER]