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Rebelo M.,University of Aveiro | Viseras C.,University of Granada | Viseras C.,Andalusian Institute of Earth science | Lopez-Galindo A.,Andalusian Institute of Earth science | And 2 more authors.
Applied Clay Science | Year: 2011

In order to be used in therapeutics, geological materials must comply with a number of specifications. In particular, clays used as pharmaceutical raw materials must be safe. As a product to be manipulated during the manufacture of drug dosage forms, they are also required to satisfy a number of technological features, including flowability and texture. With these premises, this work aimed to characterize mineralogical, textural and technical properties of Portuguese clayey raw materials belonging to well known formations (from Upper Jurassic to Miocene in age). Some of these materials are used in particular beaches for their therapeutic properties. The present study showed that mineralogical and chemical compositions of the samples allow for their safe therapeutic application. Nevertheless, in some particular samples, it could be necessary to reduce the quartz content and coarse particles before use. Bulk samples showed better flow patterns than the < 63-μm samples. For that, the use of bulk samples is preferred over separated samples. The most suitable materials for medical hydrology applications were those belonging to Freixial, Aveiro, Barracão, Luz, Xabregas and Serra de Dentro Bentonite formations. © 2010 Elsevier B.V. Source


Rebelo M.,University of Aveiro | Viseras C.,University of Granada | Viseras C.,Andalusian Institute of Earth science | Lopez-Galindo A.,Andalusian Institute of Earth science | And 2 more authors.
Applied Clay Science | Year: 2011

Tailored peloids are prepared by the maturation of selected clay minerals mixed with thermo-mineral waters. These dispersions are topically applied to the skin to treat different ailments because of their unique rheological and thermal properties. Colloidal dimensions of the dispersed clay mineral particles yielded stable and viscous dispersions capable of flowing when spread and stand in the area to be treated without flowing away. To be easily handled and cause a pleasant sensation during application, the clay mineral dispersions must have good consistency and cause no abrasion. As thermotherapeutic agents, these systems are heated before application being important to ensure that the clay paste has heat retention capacity and adequate cooling kinetics.On the basis of a previous detailed characterization of Portuguese clayey materials for medical hydrology applications, six clay raw materials were selected as candidates to be used in the preparation of tailored peloids. This study aims to obtain tailored peloids with suitable technical, rheological and thermal properties. Samples from "Serra de Dentro" and "Barracão Clays" formations exhibited adequate abrasivity and consistency. Regarding sedimentation volume and apparent viscosity, the majority of samples showed some difficulties as they were coagulated in the absence of a dispersing agent. Specific heat and cooling rate were adequate in samples from "Serra de Dentro" and "Luz Clays" formations. © 2011 Elsevier B.V. Source


Aguzzi C.,University of Granada | Capra P.,University of Pavia | Bonferoni C.,University of Pavia | Cerezo P.,University of Granada | And 5 more authors.
Applied Clay Science | Year: 2010

Biocomposites of chitosan (CS) and montmorillonite (VHS) were prepared by solid-liquid interaction of the components. The resultant composites were characterized by thermal analysis and the cation exchange capacity of the clay mineral was compared to polysaccharide retention. The composites were loaded with 5-amino salicylic acid (5-ASA), comparing the drug loading capacity and drug release behavior with those of the interaction products prepared with the drug and chitosan or montmorillonite alone. The results showed that chitosan was effectively retained by montmorillonite particles through cation exchange. In comparison with interaction products prepared using the drug and the individual components, there was a synergic effect between the clay mineral and the polysaccharide regarding both their ability to retain drug molecules, and also the control of drug release in acidic medium. In particular, the 5-ASA/CS/VHS composites showed higher drug loading and slower drug release compared to both 5-ASA/VHS and 5-ASA/CS interaction products, with almost linear release profile throughout test. According to the results, biocomposites of chitosan and montmorillonite were promising supports for modified formulations of 5-amino salicylic acid. © 2010 Elsevier B.V. Source


Urena C.,University of Granada | Azanon J.M.,University of Granada | Azanon J.M.,Andalusian Institute of Earth science | Corpas F.,University of Jaen | And 3 more authors.
Construction and Building Materials | Year: 2013

The improvement in physical properties of expansive soils after addition of non-conventional additives is studied. The tested agents were magnesium hydroxide, seawater and olive mill wastewater. The use of these materials, which can be obtained from natural sources or as by-products derived from industrial processes, can lead to greater sustainability of the construction process. In the case of olive mill wastewater, its management is still an issue in many regions where production of olive oil is a main economic activity. The untreated soil used was a sample of pure bentonite. To evaluate the effects of the additives, the physical properties of the soil such as compaction, consistency, bearing capacity and swelling pressure were studied. The mineral compositions of the treated soils were evaluated by XRD tests. Test results showed that the non-conventional additives tested reduced the plasticity and the swelling potential of the soil. Indeed the tested agents proved to be very effective to produce reductions in the swelling pressure of 60-87% in comparison with the original swelling pressure of the untreated bentonite. X-ray diffraction tests proved that magnesium hydroxide, seawater and olive mill wastewater promoted mineral changes within bentonite, especially smectite to illite conversion. This conversion is due to the alterations promoted by the additives on conditions such as pH and concentration of different cations (magnesium, calcium, potassium, etc.) The mineral modifications occurred are behind the sharp reductions in swelling pressure and plasticity of bentonite. © 2013 Elsevier Ltd. All rights reserved. Source


Aguzzi C.,University of Granada | Viseras C.,University of Granada | Viseras C.,Andalusian Institute of Earth science | Cerezo P.,University of Granada | And 3 more authors.
Colloids and Surfaces B: Biointerfaces | Year: 2013

This paper investigates desorption of 5-aminosalicilyc acid (5-ASA) adsorbed onto halloysite (HL). Desorption isotherms were fitted according to kinetic laws obtained considering release of 5-ASA from HL as the phase of desorption of the previously adsorbed drug molecules both inside the nanotubes of HL as onto the surface of clay particles and/or in the inter-particle spaces of their aggregates [28]. Desorption isotherms has been also fitted with other equations frequently used in drug release kinetics studies. The best fitting corresponded to the kinetic model proposed; in agreement with the results of adsorption [28]. © 2013 Elsevier B.V. Source

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