Removal of Hazardous Heavy Metals (Cd, Cr, and Pb) from Laver Pyropia sp. with Acid Treatment

Abstract

We examined the removal of hazardous heavy metals (Cd, Cr, and Pb) from laver Pyropia sp. using citric, hydrochloric, and nitric acids. Under the same conditions, the quality of the laver samples was also evaluated using the variation in absorbance and major mineral levels. The heavy metals that accumulated in raw laver samples after 3 days in seawater included Pb (117.79 μg/g), Cr (33.53 μg/g), and Cd (10.54 μg/g) in descending order. The rate of heavy metal removal from laver was higher at lower pH for all acids used. However, its color changed unsatisfactorily at pH 2.0. After 10 min in seawater at pH 2.5, the heavy metals in laver were eliminated in the order Cd (68.7-81.6%), Pb (57.7-67.0%), and Cr (31.9-49.4%) using the three acids. The differences in heavy metal removal among acid types were not significant. The laver quality was not affected after 20 min at the pH range of 2.5-4.0. The maximum removal of heavy metals was from laver soaked for 10 min in seawater at pH 2.5 using the organic acid, citric acid.

Health Functionality and Quality Control of Laver (Porphyra, Pyropia): Current Issues and Future Perspectives as an Edible Seaweed

“…By contrast, since reducing the heavy metal content of laver can lower the risks, intervention technologies for the elimination of heavy metal contaminants were developed. Cadmium, chromium, and lead can be removed by immersion of laver in acid solution (citric, hydrochloric, or nitric) of pH 2.5-4.0 for 20 min, and this method could be applied because laver undergoes color changes only in more acidic conditions (pH 2.0) [111]. Heavy metal contents of processed (roasted or seasoned) laver products indicate a reduction in the levels of lead, mercury, and cadmium during the cooking process [40].…”