The Water Hyacinth Eichhornia Crassipies (mart) Solms as a Biosorbent for Cadmium (II) and Lead (II) Removal: Kinetic and Equilibrium Studies
Murithi, Leonard Genson
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Presence of heavy metals in aquatic systems has become a serious problem. As a result there has been great attention given to new technologies for the removal of heavy metals from contaminated waters. Biosorption is one such emerging technology that utilizes naturally occurring biomass or waste materials to sequester heavy metals from industrial wastewater. Currently, water hyacinth, Eichhornia crassipes, is of low economic value and is available abundantly in some of Kenya's inland water systems. The aim of the present study was to assess the suitability of Eichhornia crassipes root biomass as a biosorbent for heavy metals from aqueous system. The adsorption of lead (II) and cadmium (II) ions by the water hyacinth Eichhornia crassipes roots has been studied. The abilities of Eichhornia crassipes roots to remove lead (II) and cadmium (II) ions from aqueous solutions were compared. Batch adsorption studies were carried out to examine the influence of various parameters such as the initial pH, contact time. adsorbent dose, initial metal ion concentration, temperature and agitation speed on the metal ion uptake. Uptake of lead (II) and cadmium (II) ions on the Eichhornia crassipes roots showed a pHdependent profile. The maximum metal uptake values were 163.90 mg/g and 104.16 mg/g for lead (II) and cadmium (II) ions respectively. Both Langmuir and Freundlich models fitted the experimental sorption equilibrium data, with Langmuir providing the best fit (R2 > 0.99). The biosorption kinetics was determined by fitting first-orderLagergren and Pseudo- second- order models to the experimental data. It was found that the data was better described by the pseudo- second- order model (R2 > 0.99) than the first- order- Lagergren. FTIR analysis suggested the possibility of the participation of carboxyl groups in metal uptake. Calcium and Magnesium nitrate salts were found to affect considerably the metal ion biosorption. A comparison of the maximum sorption capacity of several untreated biomaterial based residues showed that Eichhornia crassipes roots are suitable candidates for use as biosorbents in the removal of heavy metal ions from aqueous solutions.