Assessment of aquatic toxicity of the caffeic acid complexed with Cr(III) and Pb(II) in the flotation process

Abstract

The use of the metals collectors reagents in the flotation process, applied in the aim of the aqueous systems remediation, require an ecotoxicity assessment on aquatic organisms. For this purpose, laboratory experiments were performed in order to determine the toxicity indices expressed by: median lethal concentration values (LC50 / EC50), effects generated on the aquatic organisms and the estimation of biodegradability degree of the resulted effluents.The acute toxicity of caffeic acid (reagent collector) and the effluents obtained after two different flotation processes(ionic and precipitation) containing Pb(II) and Cr(III) was assessed.The biological material consisting in different aquatic organisms such as fish Cyprinus carpio, planktonic crustaceans Daphnia magna, green algae Selenastrum capricornutum, luminescent bacteria Vibrio fischeri and other gram + and gram - bacteria). The organisms were exposed to different concentrations of the caffeic acid (0 to 100 mg/L) and to various dilutions of effluents containing Pb(II) and Cr(III) respective (6.25% to 100% vol.). The caffeic acid shows no toxicity on the studied aquatic organisms(CL 50/CE50> 100 mg/L). In both flotation process, the effluents containing Pb(II) present a high toxicity compared to the effluents containing Cr(III) for crustaceans and bacteria. From the point of view of the flotation processes, it is noted that precipitate flotation effluents were less toxic, this process being more efficient in terms of the effects on aquatic organisms.The most sensitive aquatic organisms were crustaceans and luminescent bacteria. On the fish, algae and gram positive and negative bacteria no toxic effects were observed.