Search results for "Exchange"

Economia della condivisione e antropologia dello scambio

2017

The article analyses the distinctive economic models based on sharing that proliferated with the rise of web 2.0 (or social web). In particular, it analyzes what sharing means in different contexts (material and immaterial goods, and services) and it questions whether sharing can be seen as a discrete category, different from both market exchange and gift. Finally, the article questions the role of law with respect of these new economic activities.

Transnational Organized Crime and European Union: Aspects and Problems

2014

The fight against criminal organizations and their ability to carry out illegal activities beyond the national borders has represented a “bridge head” in the European path towards the harmonization of criminal laws in the member states. After considering the role played by the harmonization of criminal law in the European Union treaties, the study underlines how the difficulty in defining the concept of transnational organized crime could result in an excessive European intervention. In order to avoid such a risk, it is useful to refer to other relevant international sources, like the 2000 Palermo UN Convention, and also to recent European documents on the matter (in particular, a Resolutio…

Financiación de asociaciones: examen especial del ejercicio de actividades económicas

2019

The economic crisis has led to an increase in the funding needs of associations and at the same time, a decrease of its resources. In view of this situation, we will examine the different existing possibilities to obtain a stable financial framework and, in light of the limitations which other systems suffer from, we will conclude that implementation of economic activities will prove to be the most practical solution. However, this exercise faces the disapproval of the Administration which considers, in many cases, that said alternative leads to the loss of its declaration of public utility and subsequently the possibility of opting for the privileged tax regime inherent in Law 49/2002 on T…

NOVEL TOOLS FOR THE MECHANICAL ANALYSIS OF THIN PLATES AND RELEVANCE ON MEMBRANE-BASED TECHNOLOGIES

2020

Adsorption and separation of black liquor-derived phenol derivatives using anion exchange resins

2017

Abstract Kraft black liquor is the major waste stream of the paper pulping industry. This stream is usually directly incinerated in such facilities for energy production and recycling of the inorganic chemicals involved. However, lignin and other low molecular organic fragments dissolved in black liquor give rise to a large variety of aromatic fine chemicals. Energetic use of black liquor and its components prevents the removal of these valuable compounds from the waste stream. We present an easy protocol for adsorption and selective desorption of low molecular phenol derivatives from black liquor depending on the composition of the desorption system. Furthermore, adsorption experiments in …

Electrochemical characterization of iron sites in ex-framework FeZSM-5

2002

Abstract The electrochemical response of FeZSM-5 prepared by an ex-framework method has been studied using Paraloid B72 polymer film electrodes immersed in aqueous media using H2SO4, HCl, Na2EDTA and NaCl electrolytes. The ex-framework method comprises the hydrothermal synthesis of isomorphously substituted FeZSM-5, followed by calcination at 823 K and subsequent steam treatment (300 mbar H2O in N2) at 873 K. During this process iron is extracted to extra-framework positions. Also partial dealumination of the zeolite framework takes place. Characteristic voltammetric responses in the +1.0 to −0.6 V versus SCE potential range have been recorded and were used to characterize the iron species …

The influence of an ion-exchange resin on the kinetics of hydration of tricalcium silicate

2010

The addition of a finely-ground ion-exchange resin makes it possible to modify the hydration kinetics of C3S pastes. Analyses of the liquid phase in pastes and more dilute suspensions show that the resin exchanges calcium ions for sodium ions very rapidly during the early stage of hydration and therefore the concentration of silica in solution increases. The resin impacts the hydration of C3S by other mechanisms which depends on the resin quantity added. For a high resin quantity, the induction period is very short, but the longer-term hydration is enhanced compared to a reference sample without resin. We hypothesize that the surface of the resin can provide sites for the nucleation and gro…

Adsorption of water vapor on X and Y zeolites exchanged with barium

2001

Abstract The adsorption of water vapor on BaY and BaX zeolites is studied by thermogravimetry and calorimetry under isothermal or isobaric conditions. The faujasite zeolite exhibits a stronger adsorption affinity for water molecules with barium than with sodium or potassium as exchangeable cations. The adsorption–desorption isotherm at 150°C shows a hysteresis loop attributed to the migration of compensating cations during their interaction with water molecules. Calorimetric measurements and the Dubinin–Radushkevich’s model both show that the adsorption of water occurs via a three-step mechanism: adsorption on compensating cations, formation of a monolayer on the walls and multilayer adsorp…

Space charge effect on competitive ion transport through ion-exchange membranes

2002

A mathematical model of the competitive electro-transport of two counter-ions through an ion exchange membrane based on the Nernst-Planck and Poisson equations is developed. A three-layer system is considered: the membrane and two adjacent diffusion layers. Concentration profiles in the three layers, effective transport numbers as functions of the current and current-voltage characteristics are calculated. Deviation from the local electroneutrality in space charge region near the depleted solution/membrane interface is taken into account. It is shown that the space charge region grows with the voltage applied. However the fluxes of the competitive counter-ions at over-limiting currents are …

Ion-exchange fibers and drugs: a transient study.

2003

The objective of this study was to theoretically model and experimentally measure the kinetics and extent of drug release from different ion-exchange materials using an in-house-designed flow-cell. Ion-exchange fibers (staple fibers and fiber cloth) were compared with commercially available ion-exchange materials (resins and gels). The functional ion-exchange groups in all the materials were weak -COOH or strong -SO3H groups. The rate and extent of drug release from the fibers (staple fiber>fiber cloth) was much higher than that from the resin or the gel. An increase in the hydrophilicity of the model drugs resulted in markedly higher rates of drug release from the fibers (nadolol>metoprolo…