Abstract

Although Zn2+ and Cd2+ ions in waters are pollutant with a large amount due to mining and industrial activities, information relating to the
use of marine microalgae Nannochloropsis salina to absorb both types of metals is still very little. A marine microalga, N. salina, was used
as biosorbent for the metal ions in water. Concentration of each ion (Zn2+ and Cd2+) was 10 mg L–1
and the concentration ratio of Zn2+ to
Cd2+ in the two-metal system (a combination of Zn2+ and Cd2+ in the culture medium) was 1:1. Experimental conditions were as follows:
salinity = 25 ‰, temperature = 20 ºC, and pH = 7. Addition of each ion individually or the combination of ions was conducted when the
optimum growth of microalgae was achieved (i.e. at the 8th day after cultivation). The N. salina growth after the exposure of metal ions was
observed daily and the metal ion concentration adsorbed was determined by using atomic absorption spectrophotometer. Results showed
that N. salina can be used as biosorbent for Zn2+ and Cd2+ both in single metal ion and two-metal system. Biosorption of Zn2+ by N. salina
was higher than that of Cd2+ in the single metal ion. The amount of Zn2+ adsorbed in the two-metal system was higher than the one in the
single metal ion. However, the opposite trend was observed in the case of Cd2+ ion.

Key words: Nannochloropsis salina, zinc, cadmium, two-metal system, Conwy, biosorption