Mechanism of retention of hydrocarbons in reservoir rocks. Role of polar compounds and effect of additives

Evidence is given for the involvement of hydrophobic interactions in the retention of hydrocarbons in oil fields. A prerequisite is that the surface of the reservoir rock has to be hydrophobic. This was obtained through adsorption of lipophilic polar compounds. The isotherms for the adsorption of dodecylamine hydrochloride and N-hexadecylpyridine hydrochloride were plotted. The treated quartz could take up large amounts of toluene. The relationships between some features of the isotherms and the retention phenomenon have been analysed. The effect of water-structuring additives (e.g. LiF, CaCl₂, NaF and guanidine hydrochloride) on the recovery of hydrocarbons was investigated by means of static and dynamic methods.     

Analysis of muscle length effect on an S type motor-unit fractional multi-model

Muscle models are useful in bio-inspired robotic, because they allow to reproduce accurately natural motion. When they are used for robotic issue, they need to be compact and embeddable. The non-integer model order has the advantage to ensure a parametrical parsimony that permits to implant it easily on an embedded system. Thus, a fractional multi-model of muscle was identified and presented in later paper. This model is able to predict the response of a motor unit to an electrical stimulation, considering isometric contractions (that is to say, muscle length is constant). There are three different physiological types of motor unit (FR, FF, and S). The aim of this work is to study muscle length impact on the multi-model and the limitations of the linear multi-model. Previous paper was published using FR type motor unit. In this paper, the results of the study using S type motor unit are presented.     

Lead isotopes reveal different sources of lead in balsamic and other vinegars

Fifty-eight brands of balsamic vinegars were analyzed for lead concentrations and isotopic compositions (²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb) to test the findings of a previous study indicating relatively high levels of lead contamination in some of those vinegars — more than two thirds (70%) of them exceeded California's State Maximum Level (34 μg/L) based on consumption rates ≥ 0.5 μg Pb per day. The Lead isotopic fingerprints of all those vinegars with high lead concentrations were then found to be primarily anthropogenic. This isotopic analysis unquestionably reveals multiple contamination sources including atmospheric pollutant Pb and an unidentified contamination source, likely occurring after grape harvest. Organically grown grape vinegars display the same Pb content and isotopic signatures as other vinegars. This implies that pesticides might not be a significant source of pollutant Pb in vinegars. A significant post-harvest contamination would be inherited from chemicals added during production and/or material used during transport, processing or storage of these vinegars. This is consistent with the highest Pb levels being found in aged vinegars (112 ± 112 μg/L) in contrast to other vinegars (41.6 ± 28.9 μg/L) suggesting contamination during storage. It is, therefore, projected that lead levels in most vinegars, especially aged balsamic and wine vinegars, will decrease with improvements in their manufacture and storage processes consequential to recent concerns of elevated levels of lead in some vinegars.     

Spatial heterogeneity of personal exposure to airborne metals in French urban areas

The spatial distribution of urban population exposures to ambient air particles was investigated as part of the Genotox'ER study conducted in four metropolitan areas (Grenoble, Paris, Rouen and Strasbourg) in France. In each city, 60 to 90 non-smoking adult and children volunteers were selected. Subjects lived in three different urban sectors: one highly exposed to traffic emissions, one influenced by local industrial sources, and a background urban environment. The Harvard Chempass multi-pollutant personal sampler was used to sample PM10 and PM2.5 particles during 48 h during two different seasons ('hot' and 'cold'). The elemental composition of the filters was analysed by Particle-Induced X-ray Emission (PIXE). Sixteen elements were found to be over the method detection limits: Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Pb. The relative concentrations of elements of crustal origin (Si, Al, Ca) were higher in the coarse fraction of PM10 filters, while elements associated with combustion processes (traffic emissions or industrial combustion) presented higher relative concentrations in the PM2.5 fraction (S, Ni, V, Pb). Spatial heterogeneity of elemental exposures by urban sector is substantial for some metals of health concern, with 20% to 90% greater exposure values, on average, in the traffic proximity or industrial sectors, compared to the background sector, for Fe, Zn, Cu, V and Cr. This spatial heterogeneity should not be overlooked in epidemiological or risk assessment studies.     

Selection of an adsorbent for lead removal from drinking water by a point-of-use treatment device

The removal of lead from drinking water was investigated to develop a point-of-use water filter that could meet the regulation imposed by the new European Directive 98-83 lowering lead concentration in drinking water below 10 μg L⁻¹. The objective of this research was to assess the potential of different adsorbents (zeolites, resins, activated carbon, manganese oxides, cellulose powder) to remove lead from tap water with a very short contact time. To begin, the repartition of the lead species in a tap water and a mineral water was computed with the computer model CHESS. It showed that in bicarbonated waters lead is mainly under lead carbonate form, either in the aqueous or in the mineral phase. Batch experiments were then conducted to measure the equilibrium adsorption isotherms of the adsorbents. Then, for five of them, dynamic experiments in micro-columns were carried out to assess the outlet lead concentration level. Three adsorbents gave rise to a leakage concentration lower than 10 μg L⁻¹ and were then selected for prototypes experiments: chabasite, an activated carbon coated with a synthetic zeolite and a natural manganese oxide. The proposed method clearly showed that the measurement of equilibrium isotherms is not sufficient to predict the effectiveness of an adsorbent, and must be coupled with dynamic experiments.     

Catalytic oxidation of anisole over titanium silicalite-1

The reaction of anisole hydroxylation with hydrogen peroxide to form methoxyphenols over TS-1 was studied. Four C1-C3 alcohols and the two aprotonic solvents acetone and acetonitrile were used. Product conversion was almost proportional to the titanium content of the catalyst sample. The highest conversion and p-selectivity were observed in ethanol. Some speculations, based on the formation of substrate-solvent or titanium-solvent-oxidant complexes, about the role of the solvent are presented. It was found that in all the solvents studied the p/o ratio increased with time.