Elena Diacu

Calixarene derivatives as carriers in liquid membrane transport

The liquid membrane transport of some biogenic amines (n-buthylamine, hexylamine) and aromatic amino acids methylesters by p-tert-butylcalix[n]arenes (n = 6.8) were investigated. The transport driving force was the pH gradient between the source and the receiving phases. The complexation properties of the calixarenes under study towards amines and amino acids were evaluated. Several factors influencing the transport through liquid membrane were considered aiming to develop a mechanism model. The effect of the type of p-tert-butylcalixarene on the transport was also investigated. The results showed that the inclusion abilities of the investigated hosts were correlated with their conformational properties.

Aided phytostabilization using Miscanthus sinensis × giganteus on heavy metal-contaminated soils

A field experiment was carried out to evaluate the use of red mud, a by-product of the alumina industry, as a soil amendment on highly contaminated soils in the vicinity of a former Pb-Zn smelter in Copșa Mică (Romania). Changes in the distribution of Zn, Cd and Pb in various soil fractions, mobility of heavy metals in the soil, and their uptake and effects on growth and productivity of Miscanthus sinensis × giganteus were evaluated. Uptake of Zn, Cd and Pb was determined in different tissues of M. sinensis × giganteus cultivated in field plots situated at increasing distance from the pollution source and with different levels of contamination and metal availabilities. Soluble metal concentrations were determined in centrifugates, whereas potentially soluble fractions were analyzed by diffusive gradients in thin films. In terms of the biomass productivity there were significant differences among the plants obtained in plots with different characteristics and pollution levels. Bioconcentration factors were much lower than 1, indicating that M. sinensis × giganteus is an excluder of heavy metals, especially Pb. Amending soils with red mud reduced the exchangeable or phytoavailable fractions of Zn, Cd and Pb. Overall the results suggest that M. sinensis × giganteus is a valuable energy plant and can be successfully grown on heavily contaminated soils with Zn, Cd and Pb. Moreover, the addition of red mud to these soils can lead to a significant decrease in the concentration of heavy metals in the soil and in metal uptake by plant tissues.

Extraction and transport behaviour of aromatic amino acids by modified cyclodextrin

The extraction efficiency together with the active transport assisted by the pH gradient through liquid membrane of some aromatic native and derivative amino acids by using heptakis (2,3,6-tri-O-acetyl)-β-cyclodextrin as extractant agent or carrier has been studied. The modified cyclodextrin extracted aromatic amino acids, native (l-tryptophane, l-phenylalanine, and l-tyrosine) and their methylester derivatives from aqueous phase into the organic phase. Moreover, the modified cyclodextrin exhibits the carrier abilities for amino acid methylesters through liquid membrane. In the case of transport processes involving liquid membranes, the physicochemical properties of the solvents play an important role in membrane stability. The results demonstrated that the inclusion properties of the investigated host are correlated with the structural properties of amino acids, and they also suggest further possibilities for optimal separation of amino acids derivatives. Extraction and active transport through liquid membrane of some aromatic amino acids by using modified cyclodextrin.

Anion influence on extraction and transport of amino acid methyl esters by functionalised calix[4]arene

The liquid–liquid extraction of a series of amino acid methyl esters has been carried out with functionalised calix[4]arene (5,11,17,23-tetrakis(N-methylpiperazino)-25,26,27,28-tetrahydroxycalix[4]arene) from an aqueous phase into a chloroform phase as ion pairs in the presence of picrate ion or tropaeolin 00 as counter ion in order to study the molecular recognition properties of this receptor. The active transport assisted by pH gradient of amino acids as ion pairs through liquid membrane employing the functionalised calix[4]arene as carrier has been investigated. The results showed that the receptor exhibits good extractability towards amino acids and it can also act as carrier through liquid membrane aiming to the separation of amino acids. It was highlighted that the anion nature used as counter ion, the structure of calix[4]arene, and the structure of amino acids are responsible for the experimental results obtained. High yields in both amino acids extraction and transport were obtained for picrate ion used as counter ion.

Assessment of Water Quality in the Lakes Along Colentina River

The purpose of this study is to evaluate the water quality in the lakes along Colentina River according to Romanian regulations referring to the norms on surface water quality classification, MO 161/2006. To achieve this goal, two sampling sections (entry and exit points) for each lake have been established, and the following indicators have been determined: pH, water temperature, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, nitrites, nitrates and ammonium nitrogen, total nitrogen, orthophosphates, total phosphorus, electrical conductivity, filterable residue, chlorides, sulphates, calcium, magnesium and sodium. Following this study, the variation of the concentrations of determined indicators in the two sampling sections for each lake has been assessed, as well as the classification into quality classes according to the before mentioned order.