The science of the total environment

Traditional and new applications for kaolin, smectite, and palygorskite: a general overview

Halloysite clay minerals are ubiquitous in soils and weathered rocks where they occur in a variety of particle shapes and hydration states. Diversity also characterizes their chemical composition, cation exchange capacity and potassium selectivity. This review summarizes the extensive but scattered literature on halloysite, from its natural occurrence, through its crystal structure, chemical and morphological diversity, to its reactivity toward organic compounds, ions and salts, involving the various methods of differentiating halloysite from kaolinite. No unique test seems to be ideal to distinguish these 1:1 clay minerals, especially in soils. The occurrence of 2:1 phyllosilicate contaminants appears, so far, to provide the best explanation for the high charge and potassium selectivity of halloysite. Yet, hydration properties of the mineral probably play a major role in ion sorption. Clear trends seem to relate particle morphology and structural Fe. However, future work is required to understand the possible mechanisms linking chemical, morphological, hydration and charge properties of halloysite.

Halloysite clay minerals — a review

Microbial carbonate precipitation in construction materials: A review

Clays and oxide minerals as catalysts and nanocatalysts in Fenton-like reactions — A review

The palygorskite-sepiolite group of clay minerals has a wide range of industrial applications derived mainly from its sorptive, rheological and catalytic properties which are based on the fabric, surface area, porosity, crystal morphology, structure and composition of these minerals. For assessing potential industrial uses, the mineralogical and chemical composition of the clay and its basic physical and physico-chemical parameters must be determined. Then some particular properties of commercial interest can be modified and improved by appropriate thermal, mechanical and acid treatments, surface active agents, organo-mineral derivatives formation, etc. In this paper, a revision of the principal characteristics of commercial palygorskite-sepiolite clays is presented, and potential uses are suggested according to these data. New products and applications are being investigated and those concerning environmental protection in particular, are noted. Finally, possible health effects of these elongate clay minerals are discussed. While commercial deposits of palygorskite and sepiolite are rare, these two clay minerals occur relatively frequently in sediments and soils. Both palygorskite and sepiolite clays are so- called 'special clays'. The annual production in the western world for the former is estimated to be around two million tonnes; production comes mainly from the southeastern USA (Miocene deposits in Florida and Georgia), about 1.8 million tonnes in 1989 (Ampian, 1991), and from Senegal, Spain, Australia, India, Turkey, South Africa and France to a much smaller extent. Sepiolite is less abundant than palygors- kite. The former is a typically Spanish mineral; in fact, over 90% of sepiolitic clays are produced in Spain (also from Miocene deposits). Other small operations are in Nevada (USA), Turkey and China. The annual production of sepiolite in Spain is close to 800,000 tonnes (O'Driscoll,

Properties and applications of palygorskite-sepiolite clays

Phyllosilicates, and among them clay minerals, are of great interest not only for the scientific community but also for their potential applications in many novel and advanced areas. However, the correct application of these minerals requires a thorough knowledge of their crystal chemical properties. This chapter provides crystal chemical and structural details related to phyllosilicates and describes the fundamental features leading to their different behaviour in different natural or technical processes, as also detailed in other chapters of this book. Phyllosilicates, described in this chapter, are minerals of the (i) kaolin-serpentine group (e.g. kaolinite, dickite, nacrite, halloysite, hisingerite, lizardite, antigorite, chrysotile, amesite, carlosturanite, greenalite); (ii) talc and pyrophyllite group (e.g. pyrophyllite, ferripyrophyllite); (iii) mica group, with particular focus to illite; (iv) smectite group (e.g. montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite); (v) vermiculite group; (vi) chlorite group; (vii) some 2:1 layer silicates involving a discontinuous octahedral sheet and a modulated tetrahedral sheet such as kalifersite, palygorskite and sepiolite; (viii) allophane and imogolite and (ix) mixed layer structures with particular focus on illite-smectite.

Structure and Mineralogy of Clay Minerals

Publisher Summary This chapter describes structures and mineralogy of clay minerals. Phyllosilicates considered in this chapter ideally contain a continuous tetrahedral sheet. Each tetrahedron consists of a cation, T, coordinated to four oxygen atoms and linked to adjacent tetrahedra by sharing three corners (the basal oxygen atoms, Ob) to form an infinite two-dimensional hexagonal mesh pattern along the a, b crystallographic directions. The free corners (the tetrahedral apical oxygen atoms, Oa) of all tetrahedra point to the same side of the sheet and connect the tetrahedral and octahedral sheets to form a common plane with octahedral anionic position Ooct. Ooct anions lie near to the center of each tetrahedral 6-fold ring, but are not shared with tetrahedra. The 1:1 layer structure consists of the repetition of one tetrahedral and one octahedral sheet, while in the 2:1 layer structure one octahedral sheet is sandwiched between two tetrahedral sheets. In the 1:1 layer structure, the unit cell includes six octahedral sites (i.e., four cis and two trans-oriented octahedral) and four tetrahedral sites. Six octahedral sites and eight tetrahedral sites characterize the 2:1 layer unit cell. Structures with all the six octahedral sites occupied are known as “trioctahedral.” If only four of the six octahedra are occupied, the structure is referred to as “dioctahedral.” The structural formula is often reported based on the half unit-cell content—that is, it is based on three octahedral sites.

Chapter 2 Structures and Mineralogy of Clay Minerals

Sepiolite and palygorskite

Brindley et al. (1951) reported the earliest efforts to obtain international collaboration on nomenclature and classification of clay minerals, initiated at the International Soil Congress in Amsterdam in 1950. Since then, national clay groups were formed, and they proposed various changes in nomenclature at group meetings of the International Clay Conferences. Most of the national clay groups have representation on the Nomenclature Committee of the Association Internationale pour l’Etude des Argiles (AIPEA, International Association for the Study of Clays), which was established in 1966. The precursor committee to the AIPEA Nomenclature Committee was the Nomenclature Subcommittee of the Comite International pour l’Etude des Argiles (CIPEA, International Committee for the Study of Clays). The AIPEA Nomenclature Committee has worked closely with other international groups, including the Commission on New Minerals and Mineral Names (CNMMN) of the International Mineralogical Association (IMA), which is responsible for the formal recognition of new minerals and mineral names, and the International Union of Crystallography (IUCr), which considered extensions to the nomenclature of disordered, modulated and polytype structures (Guinier et al. , 1984) published earlier by a joint committee with the IMA (Bailey, 1977). In contrast to the other national clay groups, however, The Clay Minerals Society (CMS) Nomenclature Committee, which was established in 1963 at the same time as the CMS and predates the AIPEA Nomenclature Committee, remains in existence and occasionally produces recommendations. The precursor to this committee was the Nomenclature SubCommittee, which was organized in 1961 by the (US) National Research Council. The Chair of the AIPEA Nomenclature Committee is a standing member of the CMS Nomenclature Committee so that the committees are in close contact.

The purpose of the AIPEA Nomenclature Committee has been to make general and specific recommendations concerning: (1) definitions of mineralogical and crystallographic clay-related terms; (2) classification and terminology …

/pdf/summary-of-recommendations-of-nomenclature-committees-1599cngqau.pdf

Summary of recommendations of nomenclature committees relevant to clay mineralogy: report of the association internationale pour l’etude des argiles (aipea) nomenclature committee for 2006

Emilio Galán

Papers

Properties and applications of palygorskite-sepiolite clays

Structure and Mineralogy of Clay Minerals

Chapter 2 Structures and Mineralogy of Clay Minerals

Sepiolite and palygorskite

Summary of recommendations of nomenclature committees relevant to clay mineralogy: report of the association internationale pour l’etude des argiles (aipea) nomenclature committee for 2006