Universidade Estadual de Londrina

About: Universidade Estadual de Londrina is a education organization based out in Londrina, Brazil. It is known for research contribution in the topics: Population & Context (language use). The organization has 13052 authors who have published 19291 publications receiving 212123 citations.

Study on the cross-linked molecularly imprinted poly(methacrylic acid) and poly(acrylic acid) towards selective adsorption of diuron

Abstract: In the present study new molecularly imprinted adsorbents based on poly(methacrylic acid) and poly(acrylic acid) have been synthesized, characterized and evaluated as selective materials for the adsorption of diuron. Morphological, textural data and the presence of functional groups in the polymer have been evaluated by means of SEM, nitrogen adsorption–desorption assays and FT-IR, respectively. Two functional monomers were evaluated for the MIP synthesis, methacrylic acid (MIP MAA ) and acrylic acid (MIP AA ), and the first one showed higher selectivity and better adsorption towards diuron in the presence of competitor molecules, carbofuran and 2,4-D. The experimental adsorption isotherm of diuron has been obtained at pH 7.0 in phosphate buffer (0.05 mol L − 1 ):acetonitrile (1:2, v / v ) medium and equilibrium time of 180 min. The respective maximum adsorption capacities (MAC) of MIP MAA and MIP AA were found to be 14.58 and 7.32 mg g − 1 . One should note that MAC of MIP AA and its respective blank polymer (NIP AA ) was very similar to each other, while for the MIP MAA its MAC was significantly higher (14.58 mg g − 1 ) than the MAC of NIP MAA (6.12 mg g − 1 ). Such result demonstrates the great influence of monomer on the adsorption and selectivity of MIP. Adsorption kinetic data were well fitted to pseudo-first-order and intraparticle diffusion models, while the adsorption isotherms showed good fit to the isotherm of Langmuir–Freundlich for two sites (LF-2) and one site (LF-1), but the former one allowed insight into the adsorption mechanism with more details.

Ocorrência e ecologia trófica de quatro espécies de Astyanax (Characidae) em diferentes rios da bacia do rio Tibagi, Paraná, Brasil

Abstract: Stretches of the Rivers Fortaleza, Iapo and Tibagi were monthly sampled with gillnets of different mesh sizes and castnets from May 2001 to April 2002 in the Tibagi River basin. Specimens of four species of the Astyanax genera were captured. In order to assess how they use habitat and food resources in the different rivers, their constancy was calculated and the number of specimens was compared by using the Bray-Curtis similarity analysis. The composition (percentage) of food items consumed was ordered by using the Principal Components Analysis (PCA). The proportion of different food items in the diet was assessed and classified according to type (animal or plant material) and origin (allochtonous or autochtonous). The low similarity and constancy showed differences in the type of habitat preferred by the four fish species. Astyanax altiparanae Garutti & Britski, 2000 and A. fasciatus (Cuvier, 1819) were present in the large rivers but were constant only in the Tibagi River. Astyanax eigenmanniorum (Cope, 1894) was present in all rivers but prefers habitats in the mouth of affluents of large rivers. Astyanax scabripinnis (Jenyns, 1842) was restricted to Fortaleza River, a small Tibagi River affluent. The number of food items consumed by the different species varied from 11 to 23. Among the main food, three items were common for the four species: 1- plant residuals (leaves and seeds from the earth community of plants), 2- insect residuals (from different origins and unidentified) and 3- aquatic vegetation. So plants and insects were the main food consumed by all the species. Astyanax eigenmanniorum showed the highest distinction in the diet composition among the species studied. Such distinction was due to its ability of exploring an abundant food resource: the aquatic plants that were consumed together with portions of coal/sediments near the rocky shores at the Iapo River. The similarity of the origin and type of food consumed by the four species and the differences in terms of the habitat occupied may explain why one species is abundant and constant in only one of the river stretches studied.