Celso Gomes

Kaolinite to halloysite-7 Å transformation in the kaolin deposit of São Vicente de Pereira, Portugal

The transformation of kaolinite to halloysite-7 Å was identified in the kaolin deposit of São Vicente de Pereira (SVP), using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Both the 02, 1̄ and 13̄, 13 reflections show changes in the XRD patterns along the kaolinite to halloysite-7 Å transition, and the FTIR spectra show changes corresponding to both OH− and Si-O-stretching bands and Al-O-Si-bending vibrations. The interlayer water content in the kaolinite structure increases during transition. The two-layer periodicity of well-ordered kaolinite and rolling up of kaolinite plates are observed using high-resolution transmission electron microscopy (HRTEM). Long and short tubes exhibit halloysite-7 Å. No structural Fe was found in the kaolinite samples. Analytical electron microscopy (AEM) indicates no substitution of Al3+ for Si4+. The Si/Al ratio shows values of ∼1 for the kaolinite and rolled kaolinite plates. The 27Al magic angle spinning neutron magnetic resonance (MAS-NMR) spectra display a resonance centered at ∼1 ppm, assigned to six-coordinated aluminum. The transformation of kaolinite to halloysite-7 Å is controlled by surface reaction.

Chapter 11.5 Clays and Human Health

Publisher Summary This chapter describes the beneficial and harmful effects of clay mineral. Clay minerals can be beneficial to human health by serving as active principles or excipients in pharmaceutical preparations, in spas, and in beauty therapy medicine. In some cases, however, these minerals may be harmful to human health. In pharmaceutical formulations, spas and beauty therapy, clay minerals are used for therapeutic purposes and their beneficial effect on human health. In pharmaceutical formulations, these minerals are used as active principles (gastrointestinal protectors, antacids antidiarrhoeaics, dermatological protectors, cosmetics) and excipients (inert bases, delivery systems, lubricants, emulsifiers). In spas and beauty therapy, clay minerals are used in geotherapy, pelotherapy, and paramuds to treat dermatological diseases, alleviate the pain of chronic rheumatic inflammations, moisturize the skin, and combat compact lipodystrophies and cellulite. However, clay minerals can also have an adverse effect on human health when they are inhaled over a very long period. In the lung, clay minerals can cause diverse pathologies such as cancer, mesothelioma, or pneumoconiosis, but the toxicity of these minerals is generally related to the presence of quartz or asbestos from mining operations. The pathogenicity of fibrous clay minerals (sepiolite and palygorskite) is related to the geological conditions of formation.

Chapter 5.5 – Clays, Drugs, and Human Health

Abstract In this chapter, the beneficial and harmful effect of clays and clay minerals is described. Clays and clay minerals can be beneficial to human health by serving in pharmaceutical (as active ingredients and excipients) and cosmetic products (creams, powders and emulsions), in spas and beauty therapy (in pelotherapy to treat dermatological diseases, alleviate the pain of chronic rheumatic inflammations, moisturize the skin, and combat compact lipodystrophies and cellulite), or in other medical applications as diagnosis techniques. On the other hand, the toxicity of clay minerals is reviewed. Clay minerals can have an adverse effect on human health when they are inhaled over a very long period. Inside the lung, clay minerals can cause diverse pathologies such as cancer, mesothelioma, or pneumoconiosis, but the toxicity of these minerals is generally related to both the presence of quartz or asbestos from mining works, or with the geological conditions of formation.

Heavy elements in the phosphorite from Kalaat Khasba mine (North-western Tunisia): Potential implications on the environment and human health

Tunisia is one of the largest phosphate producers in the world (more than 10 million tons per year since the early nineties). The Kalaat Khasba mine (NW of Tunisia) has operated from 1893 until 1993 and data demonstrate that, in the phosphorites of Kalaat Khasba, Cd is enriched 105-208 times, when compared with shales, and U is enriched by a factor varying between 18 and 44. The general trend shows an increase in heavy elements content with decreasing particle size. On the other hand, concentrations of Sr, Cr and U exhibit the same distribution for the different size fractions. It was found that Cd concentrations exceed the allowed EC soil limits for growing crops. Hence, owing to the tailings exposure and to the mobilisation of the finest particles by rainfall and wind, Cd could have detrimental effects on human health and on the environment because a significant portion of Cd was found in the exchangeable form.

Kaolin deposit of Mevaiela (Angola), alteration product of anorthosite: assessment of kaolin potentialities for applications in paper

Abstract The Mevaiela kaolin deposit located near the village of Quihita in southwestern Angola resulted from the alteration of anorthosite in the Kunene Complex; its mineralogy was determined by XRD, FTIR, DTA, DTG, TEM and XRF. The Mevaiela kaolin, even in its raw state, is quite pure, being composed of kaolinite and halloysite. Several properties considered as pre-requisites for applications in paper, such as grain size distribution, brightness, rheology and abrasivity, have been assessed and the results obtained are clearly favourable for applications of the Mevaiela kaolin both, as a filler and as a pigment.

Healing and edible clays: a review of basic concepts, benefits and risks

The use of clay by humans for medicinal and wellness purposes is most probably as old as mankind. Within minerals, due to its ubiquitous occurrence in nature and easy availability, clay was the first to be used and is still used worldwide. Healing clays have been traditionally used by man for therapeutic, nutritional and skin care purposes, but they could impart some important health and skin care risks. For instance, clay particles could adsorb and make available for elimination or excretion any potential toxic elements or toxins being ingested or produced, but they could adsorb and make available for incorporation, through ingestion or through dermal absorption, toxic elements, e.g. heavy metals. Edible clays, a particular case of healing clays, have been traditionally used by man for nutritional and therapeutic purposes. Geophagy, the deliberate soil eating, earth eating, clay eating and pica (medical condition or eating disorder shown by individuals addicted to eat earth substances), has been observed in all parts of the world since antiquity, reflecting cultural practice, religious belief and physiological needs, be they nutritional (dietary supplementation) or as a remedy for disease. This paper pretends to review historical data, basic concepts and functions, as well as benefits and risks of the use of healing clays, in general, for therapeutic and cosmetic purposes, and of edible clays, in particular, for therapeutic purposes.

Manufacture of Ceramic Bricks Using Recycled Brewing Spent Kieselguhr

In the brewing process, kieselguhr performs as a filtration medium and one generated by-product is a sludge containing kieselguhr, which is mainly composed of fragmented diatom frustules associated to organic material retained during the clarification process. The physic-mechanic tests were performed on assemblages with brick composition and brewing spent kieselguhr containing 3, 9, and 15 wt% incorporation levels of sludge, being extruded and dried (105°C) before being submitted to slow firing at 900°C, 950°C, and 1000°C. The obtained results showed that, even when at its maximum incorporation level, the spent kieselguhr for all firing temperatures do not cause important losses on the properties exhibited by the clay paste without kieselguhr incorporation and the best incorporation levels are 4.2 wt% when fired at 900°C, 9.8 wt% when fired at 950°C, and 13.4 wt% when fired at 1000°C. When fired at 950°C, 15 wt% addition of spent kieselguhr increased by 27% the open porosity and decreased by 10% the bulk density of the brick paste. Furthermore, physic-mechanic tests and ecotoxicity evaluation on semi-industrial brick manufactured with 9 wt% of brewing spent kieselguhr were accessed. The results do no show any constrain concerning mechanical properties, and the ecotoxicity evaluation shows the safety of the brewing spent kieselguhr incorporation in ceramic products.

Clays and Health

First book in English which describes the pharmaceutical and therapeutic benefits of clays in terms of their physical and physicochemical properties. Provides a concise history of the use of clay in human health practices. Unlike popular texts, this book describes the customary applications of clays and explains the mode of action causing the palliative effect

General Information on Clay Applications for Health and Well-Being

This chapter reports on the ordinary clay applications in the field of health: first, the function of the nature of the pathologies to be treated, second, the function of the clay potentialities to treat certain pathologies, and third, the function of the principal reactivity domains pertaining to clay and living organisms.

Historical Aspects of a Natural Pharmacopeia: Clay in the Corpus of The Medieval Pharmacopeia Written in Arabic

This chapter opens with an historical presentation of some translations of Ancient Greek medical texts. They reached us partly thanks to translations into Arabic carried out during the Middle Ages. These texts were progressively enriched and thereafter evolved autonomously. Stories of conquests and religions, both ancient and medieval, are superimposed on the evolution of this knowledge, without being the exclusive causes. Therapies based on clay and its various daily uses are described in the corpus of profane texts of pharmacy, pharmacopeia, medicine, and rules for healthy living. In this chapter these points, disclosed in chronological order and by topics, are dealt with, concentrated only on some fundamental studies in medicine and pharmacy.