Elimination of Harmful Heavy Metals from Sea Lettuce Enteromorpha sp. with Acid Treatment

Abstract

The elimination of harmful heavy metals (Cd, Cr, and Pb) from sea lettuce Enteromorpha sp. was evaluated in filtered seawater over a pH range of 2.0-4.0 using citric, hydrochloric, and nitric acids. We also evaluated the quality of sea lettuce samples after release of their internal constituents into seawater solutions containing acids. The heavy metals that accumulated in raw sea lettuce after incubation for 3 days in seawater containing Cd, Cr, and Pb were, in descending order, Pb (120.45 μg/g), Cr (86.04 μg/g), and Cd (18.35 μg/g). The rate of elimination of heavy metals from sea lettuce was higher at lower pH for all of the acids used. However, the color of the sea lettuce changed adversely at below pH 2.5. The heavy metals in sea lettuce samples after 10 min in seawater at pH 3.0 containing the three acids were eliminated in the order Pb (42.2-78.0%), Cd (51.8-55.3%), and Cr (14.0-32.8%). The quality of the sea lettuce was not affected when it was incubated for 30 min at pH above 3.0. The maximum elimination of heavy metals from sea lettuce occurred when it was soaked for 10 min in seawater at pH 3.0 containing citric acid.