A composite adsorbent of alginate and nanosized graphite carbon (NGC) was used for the removal of Co(II) and Ni(II) from aqueous solution. The sorption capacity of calcium alginate bead containing immobilized NGC(NCB) and alginate bead (AB) were assessed in batch mode for different contact time and initial metal ions concentration. Adsorption experiments were conducted in a shaker at 100 rpm using 50 mL capped glass tubes. For kinetic studies, 0.2 g of the adsorbent was equilibrated with 20 mL of adsorbate solution (10 mg/L). The concentrations of Co(II) and Ni(II) in aqueous solution were analyzed using inductively coupled plasma (ICP, Thermo Jarrell Ash). Kinetic studies revealed that the adsorption reached an equilibrium at 8 h, with a Co(II) and Ni(II) removal of 0.80 and 0.87 mg/g by AB, and 0.84 and 0.90 mg/g by NCB, respectively. The experimental results indicated that the adsorption fitted well in the pseudo-second-order model. The maximum uptake capacity for Co(II) and Ni(II) by AB and NCB were 8.12 and 9.01 mg/g, and 8.87 and 10.74 mg/g, respectively, at pH 5.0. NCB showed a higher sorption capacity of Co(II) and Ni(II), which might be due to presence of additional sorption sites provided by the impregnation of NGC. The adsorption isotherms of Co(II) and Ni(II) onto NCB were well depicted by the Freundlich model. A linear relationship was observed between the amounts of calcium ions released and the heavy metals adsorbed with a stoichiometric ratio of approximately 1:1, suggesting that the ion exchange reaction was the predominant sorption mechanism.

Mechanism of Co(II) and Ni(II) adsorption on the nanosized carbon impregnated alginate beads

248th National Meeting (2014)

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