Daphnia Pulex Toxicity Testing of Ethylenediaminetetraacetic Acid Tetrasodium Salt Dihydrate and the Wastewater Effluent from Extraction of Rhodium using Emulsion Liquid Membranes

Document Type : Original Research Paper


Faculty of Pharmacy, Rhodes University, P. O. Box 94, Grahamstown, 6140, South Africa


Ecotoxicity of rhodium (Rh) from the model of mining waste water side stream was examined
in this paper. Rh was extracted from the model of the mining waste water using an emulsion liquid membrane
(ELM). The extractions were done at pH of 1.87 and pH 2.92 and 41.6 % and 46.2 % of Rh was extracted
respectively. The side streams of pH of 1.87 and pH 2.92 after the extractions were examined for ecotoxicity
using Daphnia pulex in the acute toxicity testing. All test organisms died after 48 hours of exposure to the side
stream effluent with the original pH = 1.87, while 10-60 % survival rates were observed at the mining spent
effluent with original pH of 2.92 if the strength of the effluent ranged from 12.5 to 62.5 %. Results for
ethylenediaminetetraacetic acid tetrasodium salt dehydrate (EDTA) showed that an increase in concentration
of EDTA in the test concentrations lead to the death of D. pulex. It was concluded that the very dilute water
side streams are toxic hence the discharge of the spent Rh side-stream should thus be discouraged and
prevented at all costs.