Biosorption of Cu2+ and Ni2+ by Arthrospira platensis with different biochemical compositions

This study is focused on copper and nickel biosorption onto Arthrospira platensis biomass of different biochemical compositions. Four types of A. platensis were employed, namely: (1) typical dry biomass (TDB), (2) carbohydrate-enriched dry biomass (CDB), (3) typical living biomass (TLB), and (4) carbohydrate-enriched living biomass (CLB). The CDB was produced using a cultivation mode where phosphorus was the limiting nutrient. The biosorption of both metals investigated was shown to be very fast. Most of the metal sorption capacity of the biomass was filled within 15-30 min, and equilibrium was achieved within 30-60 min. The cultivation conditions (nutrient repletion or depletion) did not affect the pattern of copper and nickel biosorption kinetics. The capacity for copper ions biosorption was significantly positively affected by the accumulation of carbohydrates in the dry biomass, but was negatively affected by the accumulation of carbohydrates in the living biomass. For nickel ions, the alteration of biomass had a little but positive effect on the dry biomass, and a greater negative effect (about 30% lower biosorption capacity) on the living biomass. Living biomass exhibited a higher biosorption capacity than dry biomass, for both metals. The biosorption of copper and nickel onto A. platensis biomass occurred mainly due to the mechanisms of ion exchange and complexation, and less to physical adsorption.