Adsorption of cadmium and lead ions from aqueous solution by brown algae Cystoseira indica

This research aims at investigating the biosorption of cadmium and lead cations from aqueous solution using brown alga، Cystoseira indica. Adsorption capacity of this alga affected on pH concentration، when pH of solution increases، the amount of both metals adsorptions by alga rise. Generally، the most suitable pH for biosorption of the alga ranges between 6 and 7، more specifically، the maximum adsorption rate for Cd (II) and Pb (II)، for 1 g and 2. 5 g were 79. 1%، 89. 2% and 73. 2%، 69. % respectively. The other environmental factors which influence the adsorption of this alga include the time of adsorbent contact and environment temperature، when time increased from 10 to 40 minutes، the amount adsorption increased too. The maximum capacities of adsorption for both metals were in temperatures between 40 and 50 °C. This research also examined the effect of biomass concentration alga on the adsorption capacity. The obtained results indicated that there was no significant change in adsorption capacity. In addition، kinetic investigations showed that speed pseudo-second-order model equation of both metals for 1 and 2. 5 g of alga biomass with constant speed were 11. 14،12. 1*10-3g mg-1 min-1 and 12. 41،8. 96*10-3 g mg-1 min-1 for cadmium and lead respectively. The results show that kinetic data fallow speed pseudo-second-order model. Experimental equilibrium data was fitted by Freundlich isotherm more than Langmuir isotherm. The results show that the alga Cystoseira indica can be used for treatment of aqueous solutions containing cadmium and lead as a low cost adsorbent.