The effect of process parameters on kinetics and mechanisms of Co2+ removal by bone char.
Bone char powder, composed mainly of poorly crystalline hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2)), carbon and CaCO(3), has potential applicability in the removal of Co(2+) ions from contaminated effluents. In the present study, the influence of process parameters: particle size, agitation speed, initial pH and initial sorbate concentration, onto kinetics and mechanism of Co(2+)sorption was studied and discussed. In order to describe and compare time evolution of the process under different conditions, the experimental data were analyzed using pseudo-first, pseudo-second and Vermeulen's kinetic models. Generally, experimental results were best fitted with the pseudo-second-order model, which accurately predicted the equilibrium sorbed amounts. The pseudo-second-order rate constant was the most influenced by variations in initial metal concentration and pH, in the investigated ranges. The conclusions about sorption mechanism were derived based on Co(2+) amounts sorbed during time, as well as considering solution pH changes, changes of Ca(2+) amounts released into liquid phase and Ca(2+)/Co(2+) molar ratios. It was concluded that rapid sorption stage was governed by surface complexation reactions, whereas the contribution of the ion-exchange mechanism increased with time and became more significant in the second, slower phase. Experimentally determined maximum sorption capacity towards Co(2+), under optimal conditions, was found to be 0.38 mmol/g. The results show that bone char represents cost-effective alternative to synthetic hydroxyapatite sorbent.
University of Belgrade, Vinča Institute of Nuclear Sciences, Belgrade, Serbia.
Slavko D
SD
Dimović
Ivana D
ID
Smičiklas
Marija Z
MZ
Sljivić-Ivanović
Ilija B
IB
Plećaš
Latinka
L
Slavković-Beškoski
D000327:Adsorption; D001842:Bone and Bones / Q000737:chemistry*; D002119:Calcium Carbonate / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D002606:Charcoal / Q000737:chemistry*; D003035:Cobalt / Q000737:chemistry* / Q000302:isolation & purification; D017886:Durapatite / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D010316:Particle Size; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000302:isolation & purification; D018508:Water Purification / Q000379:methods*
D014874:Water Pollutants, Chemical; D002606:Charcoal; D003035:Cobalt; D002244:Carbon; D017886:Durapatite; D002119:Calcium Carbonate