Cadmium Removal from Contaminated Sediment Using EDTA and DTPA with Water Hyacinth

Abstract

Chelating agents and pH play a significant role in affecting heavy metal availability contaminated sediment. Water hyacinth was studied for efficiency of cadmium (Cd) uptake using EDTA, DTPA, and a mixture of EDTA/DTPA at various pH values. Experiments were conducted by adding 2 mg/L of EDTA, DTPA, and EDTA/DTPA at pH 4, 5, 7, and 9. Plants were submerged in water containing 80 mg/kg of Cd-contaminated sediment and harvested at 30, 60, 90, and 120 days to measure the Cd concentrations in two parts, including the above-water part (stems and leaves) and underwater part (roots). The results showed that Cd accumulation in the plants with added EDTA and DTPA was higher than that in the control sets, indicating that EDTA and DTPA enhanced Cd uptake by water hyacinth. However, the pH-dependent results with EDTA and DTPA amendment did not significantly differ in terms of Cd uptake. The Cd concentrations in underwater part (roots) with EDTA and DTPA were 62.53 and 61.17 mg/kg, respectively. The above-water part could accumulate Cd at lower levels than the underwater part by a factor of approximately 10 for both EDTA and DTPA. Cd accumulation in the underwater part was significantly (P < 0.05) higher than that in the above-water part. For the EDTA/DTPA treatment, the average Cd accumulation in the underwater part (112.73 mg/kg) was higher than that in the above-water part (14.23 mg/kg) at 90 days. The appropriate condition for reducing Cd concentrations in contaminated sediment by the uptake of Cd in water hyacinth is the synergistic mechanism of EDTA/DTPA at pH 5, which provides a Cd-removal capacity from sediment of more than 0.51% within 3 months.