Biosorption of cobalt(II) and nickel(II) by seaweeds: batch and column studies

Six species of green, brown and red seaweed were compared for their biosorption abilities in the uptake of cobalt(II) and nickel(II) from aqueous solutions containing 100 mg/l initial metal concentrations. Batch experiments showed that the pH influenced the metal uptake of all seaweeds examined. In general, brown seaweeds were performed well with Sargassum wightii outperformed all seaweeds with an uptake of 20.63 mg Co(II)/g at pH 4.5 and 18.58 mg Ni(II)/g at pH 4. Batch desorption and regeneration experiments revealed that 0.1 M CaCl2 (in HCl) performed well in eluting cobalt(II) and nickel(II) and caused least damage to S. wightii biomass. The ability of S. wightii to biosorb cobalt(II) and nickel(II) in a packed column was investigated as well. The design parameters such as bed height and flow rate affected the biosorption characteristics of the biomass. The column was regenerated using 0.1 M CaCl2 (in HCl) solution and sorption-desorption studies were carried out for five cycles. During regeneration cycles, a decreased breakthrough time and an increased mass transfer zone were observed as the cycles proceeded. However, S. wightii maintained a relatively consistent biosorption capacity of approximately 50 mg Co/g and 39 mg Ni/g during regeneration cycles.