Cadmium removal by the dry biomass of Sargassum polycystum

Abstract

This study was concerned with a biosorption by biomass of the brown marine alga Sargassum polycystum in a batch system. The optimum condition for cadmium removal was investigated by determination of cadmium uptake capacity of alga which were dried at different temperatures; 80 and 100°C. In each case of algal preservation, three different conditions of pH; 4.0, 4.6, and 5.6 were studied. A sodium acetate buffer was used in a system to maintain constant pH. The results showed that S. polycystum had the highest cadmium uptake at pH 4.0 at both different drying temperatures. The cadmium uptake capacity estimated from Langmuir isotherm were 103.36 and 95.49 mg Cd/g biomass for the alga dried at 80 and 100°C, respectively. The biomass which were dried at 80°C had a cadmium uptake capacity of 71.39 mg Cd/g biomass at pH 4.6 and 70.66 mg Cd/g biomass at pH 5.6. The cadmium uptake capacity of alga dried at 100°C in the conditions of pH 4.6 and 5.6 were 56.78 and 56.67 mg Cd/g biomass respectively. Alga dried at 80°C was found to have slightly higher cadmium uptake capacity per gram dry weight than that of alga dried at 100°C. The recovery of cadmium loaded alga with 0.2 M HCl resulted in no changes of the algal cadmium uptake capacity through five cycles of regenertion process. The dry biomass of S. polycystum exhibited high swelling volume. The values of distention index were 13.8 and 11.1 ml/g for alga dried at 80 and 100°C, respectively. These results indicated the low stability of biosorbent. However, its high cadmium uptake capacity and abundant availability indicated that S. polycystum can be used for the development of biosorbent for heavy metal removal from wastewater. © 1999 Elsevier B.V. All rights reserved.