Removal of copper from aqueous solution by Ascophyllum nodosum immobilised in hydrophilic polyurethane foam

The seaweed Ascophyllum nodosum was pre-treated by successive washes in distilled water and dilute acid, dried, and pulverised to produce particles of <150 μm. These were immobilised during the manufacturing process of Hypol 2002 polymer to form a biomass/polymer matrix that was stable and easy to handle. In making the composite a mixing speed of 360 rpm for 20–30 s with 2% (w/w) addition of surfactant to pre-polymer was found to be ideal. The average pore sizes for different water polymer mixes (expressed as volume ratios) were 1.66 mm±0.98 (ratio 0.75:1), 1.58 mm±0.76 (ratio 1:1), 1.64 mm±0.6 (ratio 1.5:1) and 1.11 mm±0.615 (ratio 2:1). omass/polymer was used alongside free native biomass in an initial adsorption experiment using a 0.0315 mmol dm−3 Cu (II) solution and gave a copper uptake capacity (qmax) of 0.037 mmol Cu g−1 dry weight seaweed in both cases which represented approximately 85% of total initially available copper. In later adsorption isotherm experiments using Cu concentrations between 0.0315 and 0.944 mmol dm−3 at pH 5.0 and immobilized biomass over five consecutive adsorption/desorption cycles the biomass/polymer showed an initial lowering of adsorption capacity but stabilised at 0.23 mmol g−1 dry weight by the third re-use. The qmax of the immobilised biomass decreased from 0.55 and 0.416 mmol of Cu g−1 dry weight when pH was lowered from 4.0 to 3.0, and increased from 0.576 mmol g−1 dry weight (biomass) at 283 K to 0.636 mmol g−1(biomass) at 303 K.