Kinetic Modeling of Cd(Ⅱ) and Pb(Ⅱ) Biosorption from Aqueous Solution by Inactive Biomass of Nannochloropsis oculata Microalgae

摘要

The development of heavy metal treatment technologies plays a crucial role in avoiding contamination of water bodies. Nannochloropsis oculata biomass was used for Pb~(2+) and Cd~(2+) biosorption. The biosorption capacity (g metal ×g biomass"') was determined by evaluating the effects of pH and biomass amount. The maximum biosorption capacities for Pb~(2+) and Cd~(2+) were 1087.20 ±9.12 mg g~(-1) and 934.44+ 12.84 mg g~1, respectively. The pH for the highest biosorption of Pb~(2+) was 5.0, and it was 4.0 for Cd~(2+). The optimal amount of biomass needed to remove 100 ppm Pb~(2+) was 0.05 g, and it was 0.3 g for 100 ppm Cd~(2+), which suggests that microalgae showed greater capacity for removal of Pb~(2+) than Cd~(2+). The sorption rates for Cd~(2+) and Pb~(2+) were fitted with the pseudo-second-order kinetic model, and q_e values of 94.33 mg g~(-1) and 88.49 mg g~(-1), respectively, were obtained. Cd~(2+) reached equilibrium in the medium faster than Pb~(2+). The mechanism for adsorption of Pb~(2+) and Cd~(2+) is not controlled by intraparticular or film diffusion. FTIR results showed that Pb~(2+) and Cd~(2+) occupy the same carboxyl, amide, and hydroxyl functional groups.