Efficacy of Immobilized Biomass of the Seaweeds Ulva lactuca and Ulva fasciata for Cadmium Biosorption

The removal efficiency for Cd (II) by the marine algae Ulva fasciata and Ulva lactuca was studied at different culture conditions. The maximum biosorption capacities were 8.353 and 8.804 mg g−1 dwt for U. fasciata and U. lactuca, respectively, at optimum conditions for each alga. Ten milliliters of 4% calcium alginate immobilized different algal weights. Effect of different factors such as pH, temperature, contact time, biosorbent dose, and agitation speed on Cd (II) biosorption was examined. The results demonstrated the highest absorption efficiency obtained by using 0.05 and 0.15 g for U. fasciata and U. lactuca, respectively, as compared with the control. The results of Fourier transform infrared analysis for the fresh algae and pretreated algal biomasses demonstrated that hydroxyl, amide with hydrogen bond, and carbonyl extension in carboxyl groups played a significant role in biosorption. The biosorption mechanism was also investigated by energy-dispersive X-ray analysis; the results showed the presence of cadmium ion signal at 3.1 keV after the biosorption process. Immobilization of different weights of algae by using calcium alginate enhanced the biosorption capacity in case of low weight. Comparison of immobilized algal beads before and after Cd (II) biosorption showed morphological changed as shown by SEM. Ion exchange was the mechanism involved in Cd (II) biosorption by algae as elucidated by EDX analysis.