Comparison of the retention of cadmium and lead in plant tissues of aquatic macrophytes water hyacinth (Eichhornia sp.) and cattail (Typha sp.) by biosorp-tion and phytoremediation

Abstract

Alternative technologies such as biosorption and phytoremediation are effective for removing metals form water. In order to compare these two technologies, in laboratory scale, the present work had as objective to evaluate the mass retention of the toxic metals Cd and Pb in the plant tissues of two species of aquatic macrophytes, Water hyacinth (Eichhornia sp.) and Cattail (Typha sp.). In the biosorption the dry biomass of aquatic macrophytes Eichhornia sp. and Typha sp. remained in contact with solutions contaminated with Cd (4 mg L^-1) and Lead (4 mg L^-1) isolated at different time intervals, up to 24 hours. The samples were collected, filtered and analyzed by ICP OES. In the phytoremediation assay, the mother plants remained in acclimatization process in nutrient solution. After acclimatization, daughter plants were collected and conditioned in polyethylene bottles with nutrient solutions contaminated with the same concentrations of Cd and Pb isolated. Throughout the test period, aliquots of the solution were collected, filtered and analyzed in ICP OES. To evaluate the concentration of metals accumulated in plants tissues, after 21 days of contact with contaminated solutions, the plants were removed from the flasks, washed and dried for Nitro-Perchloric digestion followed by ICP OES analysis. For both treatments, the tests were performed in triplicates and for the statistical analyzes, the ANOVA and the t-Test were used with a significance level of 5%. The metals retained in plant tissues (q) of Water hyacinth had the maximum values of 18.8 mg g^-1 (Cd) and 8.6 mg g^-1 (Pb) and  Cattail  15.0  mg ^-1 (Cd) and 4.6 mg g^-1 (Pb) in the biosorption. In the phytoremediation, the concentration of metals in plant tissues of Water hyacinth was 3.2 mg g^-1 (Cd) and 4.28 mg g^-1 (Pb) and 5.0 mg g^-1 (Cd) and 2.3 mg g^-1 (Pb) in Cattail. Apparently, dry biomass exhibits better performance in Cd and Pb removal.