SOLUTION AND PARTICLE EFFECTS ON THE BIOSORPTION OF HEAVY-METALS BY SEAWEED BIOMASS

Biosorption of cadmium (Cd), cobalt (Go), copper (Cu), nickel (Ni), le ad (Pb), and zinc (Zn) by six fractions of particle sizes, ranging fro m 0.063 to 1.4 mm of dry marine algal biomass of Sargassum fluitans an d Ascophyllum nodosum, is examined. Equilibrium metal uptake by larger particles was higher than that by smaller particles in the order of P b > Cd > Cu > Co > Zn > Ni for both biomass types, with S, fluitans so rbing slightly more than A. nodosum. Uptakes of metals ranged from the highest, q(max) = 369 mg Pb/g (particle size 0.84-1.00 mm), to the lo w Zn and Ni uptakes, q(max) = 77 mg/g (size 0.84-1.00 mm) for S, fluit ans. A. nodosum adsorbed metals in the range from q(max) = 287 mg Pb/g (particle size 0.84-1.00 mm) to q(max) = 73 mg Zn/g (particle size 0. 84-1.00mm). Harder stipe fractions of S. fluitans demonstrated general ly higher metal uptakes than the softer fractions derived from its bla des (leaves). The pH dependence of the Zn uptake by S, fluitans exhibi ted a S-shaped curve between pH 1.5 and pH 7, with 50% of the maximum (pH 7.0) uptake at pH 3.5. Monovalent Na and K ions at higher concentr ations inhibited the biosorption of Zn by S. fluitans. A significant i nhibition started at 50 mM potassium chloride or sodium acetate, and a t 1M the biosorption was completely blocked.