Kinetic Modeling of Cd Biosorption from Aqueous Solution by Inactive Biomass of Nannochloropsisoculata Microalgae

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