ABSTRACT
Lanthanides are critical elements, and their recovery from wastewater increases the availability of these elements and reduces their impacts on the environment. In this study, tentative approaches to extract lanthanides from low-concentration aqueous solutions were investigated. PVDF membranes soaked with different active compounds or synthesized chitosan-based membranes containing these active compounds were used. The membranes were immersed in 10-4 M of aqueous solutions of selected lanthanides, and their extraction efficiency was assessed using ICP-MS. The PVDF membranes showed quite poor results, with only the membrane with oxamate ionic liquid giving some positive results (0.75 mg of Yb, 3 mg of lanthanides per gram of membrane). However, the chitosan-based membranes led to very interesting results, with the maximum concentration factor for the final solution relative to the initial solution being 13 times higher for Yb, which was obtained with the chitosan-sucrose-citric acid membrane. Several of the chitosan membranes, namely the one with 1-Butyl-3-methylimidazolium-di-(2-ethylhexyl)-oxamate, could extract around 10 mg of lanthanides per gram of membrane, with the better one being the membrane with sucrose/citric acid that achieved more than 18 mg/g of membrane. The use of chitosan for this purpose is a novelty. Since these membranes are easily prepared and have a very low cost, practical applications can be envisaged after further studies to better understand the underlying mechanism.
ABSTRACT
The Ardley Cove area (located on the Maxwell Bay shoreline, Fildes Peninsula, King George Island, Antarctica) is characterized not only by its high biodiversity, but also by a high density of scientific stations, making it potentially one of the most impacted areas of Antarctica. In order to assess the source, contamination levels, distribution and availability of several trace elements (Cr, Ni, Cu, Zn, As, Pb, Cd and Hg) in and around Maxwell Bay, soil and seawater samples were collected. Soil samples were also collected in the study reference site near the Bellingshausen Dome area, as it lies far from centers of human activity and associated infrastructure. Enrichment factors (EFs) and sequential extractions were also used to assess the degree of contamination and availability of the trace elements under investigation. The results obtained in this study pointed to the existence of several contamination hotspots, mainly related to high levels of Zn, Pb, Cd, Cr and Ni. Comparison of the contaminant distribution patterns with data from earlier studies allowed the identification of anthropogenic sources. Use of the EF approach and sequential extractions confirmed these findings. In particular, higher extraction proportions were obtained for Zn and Pb (68 and 71%, respectively), which were also the same elements where the highest EFs were determined. The results obtained in this study clearly point to human impact on the natural environment in this region of Antarctica and we recommend the implementation of appropriate contamination control and remediation methods.
