Optimization of copper sorbing-desorbing cycles with confined cultures of the exopolysaccharide-producing cyanobacterium Cyanospira capsulata

ABSTRACT: The aim of the study was to compare the copper removal capacity of the cyanobacterium Cyanospira capsulata confined in various filtering systems and to assess whether the same culture could be reused for more than one metal sorbing-desorbing cycle. C. capsulata cultures were confined in three dialysis devices (tubing with two diameters, cassettes) and two hollow fibre systems with different surface to volume ratios, and were then dipped into 10 mg l-1 Cu solutions. Significant differences were found between filtering systems. The greatest amount of Cu (124  10 mg (g protein)-1) was removed by the C. capsulata biomass confined into dialysis cassettes in 4 h, followed by that in the two dialysis tubing systems (which removed about 110 mg of Cu (g protein)-1 in10-12 h), and lastly by the two hollow fiber systems (which removed around 23 mg Cu (g protein)-1, in 24 h). In subsequent multiple sorbing-desorbing cycle experiments carried out with the dialysis tubing systems, NaOH and HCl 0.1 mol l-1 were found to be the most effective desorbing agents, allowing the same biomass to be reused for eight consecutive sorbing-desorbing cycles, with copper uptake in subsequent cycles being only about 10-15% less that what it had been in the first cycle.