Heavy Metal Extraction from Aqueous Solutions using Three Novel 3-Hydroxy-2-Naphthoate-Based Task-Specific Ionic Liquids
- Author(s)
- Philip Pirkwieser, Jose A. Lopez-Lopez, Wolfgang Kandioller, Bernhard Keppler, Carlos Moreno, Franz Jirsa
- Abstract
Ionic liquids (ILs), which are salts with melting points below 100 °C, have been discovered as suitable alternatives for traditional chemical treatment of polluted water due to their favorable environmental and physico-chemical properties such as high thermal stability, very low vapor pressure and recyclability. Liquid-liquid extraction of metals from aqueous phases, however, revealed a major drawback regarding green applicability, i.e., the partial solution of the ILs during extraction, so-called leaching. Even if ILs display excellent extraction capabilities, strong leaching can limit their status as an environmentally friendly alternative. For this reason, three novel ILs based on 3-hydroxy-2-naphthoic acid were synthesized. Aiming to improve stability during liquid-liquid extraction while still achieving high selectivity towards heavy metal ions: trihexyltetradecylphosphonium- ([P66614]), methyltrioctylphosphonium ([P1888]) and methyltrioctylammonium 3-hydroxy-2-naphthoate ([N1888][HNA]). The impact of different alkyl chains and the central atom of the cation on physico-chemical properties, extraction efficacy and leaching were investigated. Extraction capabilities for Ag, Cd, Co, Cu, Mn, Ni and Pb were studied in pure water at pH = 8.0 and in water containing 30 g L-1 NaCl and/or 30 mg L-1 humic acid, as well as metal-spiked natural water samples. The natural waters included drinking water, an effluent from a wastewater treatment plant, and seawater as well as hypersaline water. The three ILs displayed extraction efficacies ≥ 90% for Cu and Pb after 24h. Overall, extraction efficacies for Ag, Cd, Cu and Pb were highest for drinking water samples. Extraction of Ag and Cd was increased by up to 41% in hypersaline samples using IL [P66614][HNA] compared with pure water samples. Leaching values were reduced down to 0.07% loss of the applied IL, which can be attributed to the hydrophobic character of 3-hydroxy-2-naphthoate. These results represent a positive development towards a greener extraction of heavy metals from natural waters.
- Organisation(s)
- Department of Inorganic Chemistry
- External organisation(s)
- University of Johannesburg (UJ), University of Cádiz
- Publication date
- 07-2018
- Austrian Fields of Science 2012
- 104003 Inorganic chemistry, 104023 Environmental chemistry
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/heavy-metal-extraction-from-aqueous-solutions-using-three-novel-3hydroxy2naphthoatebased-taskspecific-ionic-liquids(1e95700e-69fc-4b5a-89ea-833901f63557).html