Eleusine coracana silica immobilised spirogyra rhizobrachiales adsorbent for biosorption of Ni2+ and Pb2+ ions
Ruwocha, Patty Tariro.
MetadataShow full item record
The Spirogyra rhizobrachiales was embedded in Eleusine coracana silica to combine the mechanical stability and porosity of the silicate with the algae’s compatibility for the biosorption for heavy metals. The functional groups and sorption capability of such algae silicate materials were investigated by FTIR spectrophotometer and it showed that carboxyl, ether, alcoholic and amino groups are responsible for the binding of the metal ions. Comparative equilibrium sorption experiments were performed batch wise and for Ni2+ the best conditions for adsorption were: adsorbent dosage of 20 mg, initial metal ion concentration of 80 ppm agitated for 20 mins at a pH of 5 and for Pb2+ were: 10 mg adsorbent dosage, initial metal ion concentration of 60 ppm agitated for 40 mins at a pH of 6. The adsorption kinetics was also described, using a pseudo-first-order model and pseudo-second-order models. The results show strong correspondence to a pseudo-second-order kinetics model for Pb2+ with an R2 value of 0.9748 and pseudo-first-order kinetics model for Ni2+ with an R2 value of 0.9936. Another key part of the analysis was the use of the Langmuir and Freundlich isotherm models to determine the adsorption isotherms. The experimental data were in strong correspondence with Langmuir’s isotherm model with R2 for lead (II) and nickel (II) ions being 0.9949 and 0.9404 respectively. The maximum sorption capacities of the adsorbent with respect to nickel (II) and lead (II) ions were 13.6 mg/g and 50.0 mg/g respectively. The adsorption capability in the presence of other ions was determined and adsorption was reduced by 15 % for nickel ions and 4.2 % for lead ions. The adsorbent can be successfully regenerated. KEY WORDS: Biosorption, Immobilisation, Heavy metals, Eleusine coracana, Spirogyra rhizobrachiales.