Removal of Copper, Chromium, and Arsenic by Water Hyacinths

Abstract

The removal of different concentrations of toxic metals by water hyacinths (Eichhornia crassipes) from a simulated aqueous environment was studied in an outdoor experiment. The hyacinth’s tissues were analyzed to evaluate the removal of copper (Cu), hexavalent chromium (Cr VI), and arsenic (As) from CCA (Chromated Copper Arsenate) contaminated water (5, 10, and 20 mg/L arsenic content, 7, 14, and 28 mg/L chromium concentration, and 2.5, 5, and 10 mg/L copper concentration) over a 17 day period. The vigor of the plants was also recorded during this period. The results showed that the hyacinth was not a suitable plant to remediate arsenic and copper. Arsenic removal for 5, 10, and 20 mg/L concentrations were 4.8, 4.7, and 0% respectively and copper removal for 2.5, 5, and 10 mg/L showed 53, 0, and 0% respectively. However, water hyacinth did show promising results as a hyper-accumulator of chromium. Percent chromium removal for 7, 14, and 28 mg/L contaminated water was 72.3, 21, and 19% respectively. The amount of copper in the containers with water hyacinths present was higher than the containers without plants (controls) indicating that the water hyacinth exudates might cause copper to stay in aqueous solution longer. As for the vigor of the plants, 5 and 10 mg/L arsenic concentrations damaged the plants somewhat over the 17 day period but overall these plants remained alive for the duration. Plants that were treated with 20 mg/L arsenic began to wilt and change color after day 1 and by the end were lifeless.