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The recycling of polystyrene wastes by precipitation from limonene solutions using CO2 as antisolvent is an alternative and original environmentally friendly route to recover high quality wastes. The most suitable working conditions to conduct the process are selected based on the accurate knowledge of the phase equilibrium for the ternary mixture. To maximize the recycling of polymeric wastes while the consumption of CO2 and limonene is minimized, high values of pressure (≥100 bar), low values of temperature (≤30°C) and moderated concentrations of polymer (≤0.4 g PS/ml limonene) are required.

Poly(d,l-lactide-co-glycolide), PLGA, is a biodegradable polyester with many medical applications. In this article, several catalysts are studied as potential substitutes of the conventional catalyst, tin (II) 2-ethylhexanoate (known as tin octoate, SnOct2). Namely, different metal carboxylates have been examined, in order to study the influence of the metal counterion. Among them, most promising results have been obtained when using zinc (II) 2-ethylhexanoate (ZnOct2) followed by potassium (I) 2-ethylhexanoate. Furthermore, in the case of ZnOct2, the use of alcohols as initiators was examined in order to improve reaction rate and to study their effect on molecular weight distribution, polymer microstructure, and side reactions, such as transesterification reaction.

Seventeen sediment samples from the Tinto and its main tributaries were analyzed for this study. For each of these samples, the association of metals (Cu, Zn, Cd, Pb, Fe, Ni, Cr and Co) was determi...

Supercritical carbon dioxide has been used as a solvent for the extraction of rock rose leaf (Cistus ladanifer L.). The aim of this work was to identify the best processing conditions to obtain rock rose essential oil. The operating variables were selected so that the only extracted compounds were essential oils and waxes (8–10 MPa and 30–60°C), avoiding the coextraction of high-molecular-weight compounds that do not contribute to fragance formation. Moreover, a two-stage separation procedure was used to separate the waxes from the essential oil. The supercritical extracts were characterized by gas chromatography (GC) to assess the presence of undesirable compounds and to obtain the detailed oil composition. The best oil was produced by extraction at 9 MPa and 40°C and fractionation of the product in two separators in series operating at P = 7 MPa, T = –10°C and at P = 2 MPa, T = 10°C, respectively. Organoleptic analysis confirmed the high quality of the product.

Les resultats de l'analyse montrent que les principales sources de particules en suspension sont: la poussiere du sol, le calcaire, l'incineration des dechets, les gaz d'echappement des automobiles, les particules marines et la combustion des carburants

Factor analysis and chemical element balance were employed to identify and quantify the major atmospheric deposition sources at 12 sampling stations in the “Campo de Gibraltar” Region. The data were best represented with 5 sources: soil, marine aerosol, residual fuel oil, refuse and limestone. Predicted concentrations account for about 80% of measured total deposition.

Nowadays there is an increasing interest in determining the origin of dustfall constituents, because in presence of an air pollution problem, its knowledge allows to detect the major emission sources and it helps to choose the adequate correcting measures. In this paper, with the help of a chemical element balance, we have determined the origin of several dustfall constituents of Seville City, as well as the relative contributions from the following sources: soil, marine aerosols, oil combustion, motor vehicles, cement manufacturing and refuse incineration. Therefore, dustfall samples at eleven locations in the City of Seville were taken for a year, and they were analyzed chemically, as well as the particle samples of emission sources mentioned above.

A study of the atmospheric pollution by suspended particulate lead in the city of Seville, Spain, was carried out during the period between March 1983 and February 1984. The results obtained from seven sampling stations allowed us to study the site to site variations; there are two locations with average annual concentrations higher than 2 micrograms X m-3. In one station, the meteorological and traffic effects and relationship with other traffic-related pollutants, were investigated. The regression analyses performed on the average monthly data have shown an inverse correlation with wind speed and temperature and a direct correlation with carbon monoxide and smoke concentrations, but no significant correlation was found with the lead deposition levels.

Total suspended particulates (TSP) and metal concentrations were determined from October 1982 to September 1983 in the “Campo de Gibraltar”, an Industrial zone where there are important residential areas. The data included in this paper provide basic information on concentrations of 13 elements (Al, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, V and Zn) in air to establish those areas where the major atmospheric levels of certain elements generally occur, to estimate the sources of such elements and to show their temporal variation.