Masaki Kawano

Bio: Masaki Kawano is an academic researcher. The author has contributed to research in topics: Sepiolite. The author has an hindex of 3, co-authored 3 publications receiving 13 citations.

Sepiolite from Sangju, Kyongsangpuk-Do, Korea

Abstract: Sepiolite specimen which was imported from Korea, as a sample of industrial materials, has been investigated by means of X-ray, thermal method and chemical analysis. It occurs near Sangju, Kyongsangpuk-Do, associated with tremolite and other minerals, and forms aggregates of fine fibers. The material has white colour, soft and pliable and looks like leather. It is difficult to grind into fine powder. The data of X-ray powder diffractions both on no treated material and heated materials in various temperatures suggest that the specimen is of well crystallized a-sepiolite, with unit cell parameters of a0=13. 50A, IN=26. 94A, and co=5. 28A, which is calculated in orthorhombic system. On the TGA curve for the sepiolite, the second and third weight loss of 5. 8% from 250•Ž to 450•Ž and from 450•Ž to 620•Ž correspond to dehydrations of bound water. The fi nal weight loss of 3. 3% between 620•Ž and 1000•Ž shows dehydration of hydroxyl water. The chemical compositions of the sepiolite is given in Table 4 and indicate that the material belongs to the common Mg rich sepiolite. The structural formulae calculated from the chemical analysis, on the basis of\" dehydration sepiolite \" after Brauner and Preisinger's formulae, is as follows, (Si11. 92A10.04Fe3+0.04)CFe3+0.06Fe2+0.01147.95) O32. The chemical compositions as well as thermal properties on the Sangju sepiolite support that the structure of sepiolite is suitable for the Brauner and Preisinger's model rather than that of Nagy and Bradley's model.

Advances in the Crystal Chemistry of Sepiolite and Palygorskite

Abstract: The structure and chemical composition of sepiolite and palygorskite are known from the first half of the twentieth century. Ideal palygorskite Si 8 O 20 (Al 2 Mg 2 )(OH) 2 (OH 2 ) 4 ⋅H 2 O) 4 has dioctahedral character, and sepiolite Si 12 O 30 Mg 8 (OH) 4 (OH 2 ) 4 (H 2 O) 8 is a pure trioctahedral mineral. In the two minerals, isomorphic substitutions in both tetrahedral and octahedral sheets are frequent. In addition, Mg-rich palygorskites, Fe-rich palygorskites and Al-rich sepiolites have been reported and it seems that the compositional limits accepted until now could be too narrow. Therefore, sepiolite and palygorskite can be classified into different types depending on the composition. In this chapter, the variations in the chemical composition of natural sepiolites and palygorskites as well as the limit of chemical composition of both minerals, if it exists, using the data from the literature available are established. Sepiolite can be classified into two types: sepiolite and Al-sepiolite. A limit for these two types can be established from the octahedral occupancy, and Al-sepiolites are those that have more than 10% of octahedral positions vacant and more than 0.5% VI Al atoms. On the other hand, palygorskite is classified into Ideal palygorskite with an octahedral composition near to the ideal palygorskite. Common palygorskite : where VI Al content is less than in the ideal formula and as a consequence that the Mg content is higher, but the number of octahedral cations is close to 4. Magnesic palygorskite is the most trioctahedral extreme, and Aluminic-palygorskite , which is defined by a total number of octahedral cations (p.h.u.c.) 3 ) > Mg. Magnesic palygorskite and aluminic sepiolite can have very similar chemical composition. There is no a compositional gap between the two minerals. Palygorskite can be so rich in Mg and sepiolite so rich in Al that is possible to affirm that a continuous composition series exist and all the intermediate compositions between the two extremes corresponding to the two pure minerals can be found. The intermediate compositions can be explained by intergrowths of sepiolite and palygorskite ribbons or polysomes.

Dissolution kinetics of sepiolite from Eskisehir (Turkey) in hydrochloric and nitric acids

Abstract: A B S T R A C T: Dissolution kinetics of sepiolite from Eskisehir (Turkey) have been investigated at various temperatures and particle sizes using dilute hydrochloric and nitric acids. Dissolution reaction rate constants were calculated and apparent activation energies were dependent on acid concentration. For both acids, apparent activation energy values reached a minimum of ~11 kcal/mol at an acid concentration of 0.75 u. For the second-order reaction which is independent of the acid concentration, the activation energy was 14.5 kcal/mol for both acids. The reaction rate constants were proportional to the acid concentrations, and inversely proportional to the square-root of the initial particle radii of the sepiolite. The activation of natural clay surfaces by acid treatment has been studied extensively. Dissolution of Mg from sepiolite mined at Eskisehir (Turkey) using dilute acids was first attempted by Abdul-Latif & Weaver (1969) who found that dissolution of palygorskite and sepiolite in excess hydrochloric acid was a first order reaction in terms of concentrations of A1, Fe and Mg. They also noticed that the dissolution reaction rate constant of Mg in sepiolite was 240 times that for Mgin palygorskite. Several studies of the acid activation of Spanish sepiolite have been carried out to

Sepiolite and Palygorskite in Japan

Abstract: Recent investigations on palygorskite and sepiolite from Japan are summarized in relation to their mode of occurrence and mineral genesis. Description of the Japanese palygorskites has been confined to only two specimens from the Kuzuu district, represented by “karst region” where a thick sequence of carbonate rocks crops out extensively. These two palygorskites occur along fissures or faults as fillings and are considered to have been formed by direct precipitation from an aqueous solution at earth-surface temperature. The solution rich in silica and magnesium with lesser amount of aluminium, resulted from the descent of meteoric water. Japanese sepiolites, on the other hand, show various modes of occurrence, and may be classified largely into four groups on the basis of their mode of occurrence; (1) sepiolite in serpentinite, (2) sepiolite associated with metallic mineral deposits, (3) sepiolite from the “karst region”, and (4) sepiolite (iron-rich variety) in Tertiary sediments. The sepiolites are considered to be of either hydrothermal or supergene origin, and to have been formed by direct crystallization from low-temperature hydrothermal solution and/or from supergene or marine water rich in silica, magnesium and other components. Palygorskite and sepiolite in Japan do not form sedimentary deposits of economical importance, and occur on a small scale. Intensive studies of clay mineral compositions in clay fractions of surface marine sediments in the oceans and seas in the environs of the Japanese Island Arc, have not confirmed so far the presence of palygorskite or sepiolite.

Chapter 1 An outline of clays and clay minerals in Japan

Abstract: Publisher Summary This chapter presents the studies on the clays and clay minerals of Japan. The chapter presents the research and discussion that includes: (1) the specific properties of clay minerals as revealed by X-ray; thermal, electron optical analyses, etc.; (2) some of the analytical procedures; (3) synthesis; (4) changes in the properties of clays and clay minerals on heating, grinding, and chemical treatment; and (5) miscellaneous items. The chapter surveys the mineralogical properties, modes of occurrence, and origin of the clays and clay minerals found in Japan. Throughout geological time, volcanic activity has frequently occurred in Japan, resulting in an abundance of clays and clay minerals that occur as hydrothermal alteration products of various rock types, and as weathering products of volcanic ashes and glassy tuffs. The chapter reveals the studies based on the exchange acidity (in modern terminology) confirming the release of alumina on treatment with neutral salt solution, and revealing the important role of alumina in the clay acidity.