Cu(II) binding by dried biomass of red, green and brown macroalgae

Dried biomass of the marine macroalgae Fucus spiralis and Fucus vesiculosus (brown), Ulva spp. (comprising Ulva linza, Ulva compressa and Ulva intestinalis) and Ulva lactuca (green), Palmaria palmata and Polysiphonia lanosa (red) were studied in terms of their Cu(II) biosorption performance. This is the first study of its kind to compare Cu(II) uptake by these seaweeds in the South-East of Ireland. Potentiometric and conductimetric titrations revealed a variety of functionalities on the seaweed surface including carboxyl and amino groups, which are capable of metal binding. It was also found that, of the seaweeds investigated, F. vesiculosus contained the greatest number of acidic surface binding sites while Palmaria palmata contained the least. The metal uptake capacities of the seaweeds increased with increasing pH and kinetic behaviour followed a similar pattern for all seaweeds: a rapid initial sorption period followed by a longer equilibrium period. P. palmata reached equilibrium within 10 min of exposure while F. vesiculosus required 60 min. Correlation was found between the total number of acidic binding sites and the time taken to reach equilibrium. Fourier transform infra-red (FTIR) analysis of the seaweeds revealed the interaction of carboxyl, amino, sulphonate and hydroxyl groups on the seaweed surface with Cu2+ ions while time course studies established the relative contribution of each of these groups in metal binding.