Bergaya F. Handbook of Clay Science

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9.5. CONCLUSIONS

Microorganisms are ubiquitous on the Earth’s surface. They are especially abun-

dant in bioﬁlms and microbial mats associated with ponds, hot springs, weathered

feldspar, deep-sea ﬂoor vents, and mine drainage areas. In these environments

microorganisms can synthesize many kinds of clay minerals, both inside and out side

their living cells. The study of biomineralization and the processes involved requires

a multidisciplinary approach and the application of a range of analytical and

instrumental techniques. At the same time, the results can provide valuable back-

ground information with respect to environmental protection, such as bioremedi-

ation of polluted sites, as well as an insight into the sustainable development of new,

clean energy sources, mineral resources, and biomedical technologies (Tazaki et al.,

2002).

REFERENCES

Asada, R., Tazaki, K., 2000. Observation of bio-kaolinite clusters. Journal of the Clay Science

Society of Japan 40, 24–37 (in Japanese with English abstract).

Brindley, G.W., 1980. Quantitative analysis of clay mixtures. In: Brindley, G.W., Brown, G.

(Eds.), Crystal Structures of Clay Minerals and Their X-ray Identiﬁcation, Monograph 5.

Mineralogical Society, London, pp. 411–438.

Guggenheim, S., Martin, R.T., 1995. Definition of clay and clay mineral: joint report of the

AIPEA nomenclature and CMS nomenclature committees. Clays and Clay Minerals 43,

255–256.

Mann, S., Sparks, N.H.C., Wade, V.J., 1990. Crystallochemical control of iron oxide bio-

mineralization. In: Skinner, H.C.W., Fitzpatrick, R.W. (Eds.), Biomineralization Processes

of Iron and Manganese—Modern and Ancient Environments. Catena suppl. no. 21,

pp. 21–49.

Moore, D.M., Reynolds, R.C. Jr., 1997. X-ray Diffraction and the Identiﬁcation and Analysis

of Clay Minerals. Oxford University Press, Oxford.

Morikawa, T., 2002. Bacterial Bio-Weathering of Feldspar at the Dam Reservoir. Graduate

thesis. Kanazawa University, Japan (unpublished, in Japanese).

Roh, Y., Zhang, C.L., Hali, H., Lauf, R.T., Zhou, J., Phelps, T.J., 2003. Biogeochemical and

environmental factors in Fe biomineralization: magnetite and siderite formation. Clays and

Clay Minerals 51, 83–95.

Schwertmann, U., Fitzpatrick, R.W., 1992. Iron minerals in surface environments. In: Skin-

ner, H.C.W., Fitzpatrick, R.W. (Eds.), Biomineralization Processes of Iron and Manga-

nese—Modern and Ancient Environments. Catena suppl. no. 21, pp. 7–30.

Simkiss, K., Wilbur, K.M., 1989. Biomineralization, Cell Biology and Mineral Deposition.

Academic Press, London.

Tawara, K., Yamamura, T., Tazaki, K., 1997. Microorganisms of hydrothermal vents at

Iheya Ridge. Journal of the Mineralogical Society of Japan 26, 81–85 (in Japanese).

Tazaki, K., 1997a. Biomineralization of layer silicates and hydrated Fe–Mn oxides in micro-

bial mats: an electron microscopically studies. Clays and Clay Minerals 45, 203–212.

Chapter 9: Clays, Microorganisms, and Biomineralization496

Tazaki, K. (Ed.), 1997b. A new world in the science of biomineralization: Environmental

biomineralization in microbial mats in Japan. Science Reports of Kanazawa University,

XLII, 1–65.

Tazaki, K., 1999. Architecture of biomats reveals history of geo-, aqua-, and bio-systems.

Episodes 22, 21–25.

Tazaki, K., Asada, R., 2003. Microbes associated with clay minerals: formation of bio-

halloysite. In: Dominguez, E.A., Mas, G.R., Cravero, F. (Eds.), 2001. A Clay Odyssey,

Proceedings of the 12th International Clay Conference, Bahia Blanca, Argentina. Elsevier,

Amsterdam, pp. 569–576.

Tazaki, K., Asada, R., Ikeda, Y., 2002. Quick occurrence of Fe-rich bioﬁlms on the water

surface. Journal of the Clay Science Society of Japan 42, 21–36 (in Japanese with English

abstract).

Tazaki, K., Ishida, H., 1996. Bacteria as nucleation sites for authigenic minerals. Journal of

the Geological Society of Japan 102, 866–878.

Theng, B.K.G., Orchard, V.A., 1995. Interactions of clays with microorganisms and bacterial

survival in soil: A physicochemical perspective. In: Huang, P.M., Berthelin, J., Bollag,

J-M., McGill, W.B., Page, A.L. (Eds.), Environmental Impact of Soil Component Inter-

actions. Lewis Publishers, Boca Raton, FL, pp. 123–143.

Ueshima, M., Mogi, K., Tazaki, K., 2000. Microbes associated with bentonite. Journal of the

Clay Science Society of Japan 39, 171–183 (in Japanese with English abstract).

Ueshima, M., Tazaki, K., 1997. Bacterial biomineralization of clay minerals. Journal of the

Mineralogical Society of Japan 26, 87–92 (in Japanese with English abstract).

Ueshima, M., Tazaki, K., 1998. Bacterial bioweathering of K-feldspar and biotite in granite.

Journal of the Clay Science Society of Japan 38, 68–82 (in Japanese with English abstract).

Ueshima, M., Tazaki, K., 2001. Possible role of microbial polysaccharides in nontronite

formation. Clays and Clay Minerals 49, 292–299.

Yoshizu, K., Tazaki, K., 1997. Role of microorganisms in iron and manganese mineral for-

mation. Journal of the Mineralogical Science Society of Japan 26, 69–72 (in Japanese with

English abstract).

References 497

Handbook of Clay Science

Edited by F. Bergaya, B.K.G. Theng and G. Lagaly

Developments in Clay Science, Vol. 1

499

Chapter 10

CLAYS IN INDUSTRY

F. BERGAYA

, B.K.G. THENG

AND G. LAGALY

CRMD, CNRS-Universite

d’Orle

ans, Orle

ans Cedex 2, France

Landcare Research, Palmerst on North, New Zealand

Institut fu

r Anorganische Chemie, Universita

t Kiel, D-24118 Kiel, Germany

This composite chapter is concerned with the industrial applications of clays in

general. Conventional applications, as in ceramics and paper coating, are described

in Chapter 10.1. Catalysis by clay minerals, includi ng their use as catalyst supports,

has received much attention, and is discussed in Chapter 10.2. The versatility of clay

minerals is also reﬂected by their usage in the formation and preparation of

clay–polymer nanocomposites. As described in Chapter 10.3, these inorganic–

organic hybrid mate rials are the subject of intensive research because of their huge

potential for novel applications.

DOI: 10.1016/S1572-4352(05)01015-9

Handbook of Clay Science

Edited by F. Bergaya, B.K.G. Theng and G. Lagaly

Developments in Clay Science, Vol. 1

r 2006 Published by Elsevier Ltd.

501

Chapter 10.1

CONVENTIONAL APPLICATIONS

C.C. HARVEY

AND G. LAGALY

Institute of Geological and Nuclear Sciences, Wairakei Research Centre, Private Bag

2000, Taupo, New Zealand

Institut fu

r Anorganische Chemie, Universita

t Kiel, Otto-Hahn-Platz 6-7, D-24118

Kiel, Germany

Clays and clay minerals are extensively used in a wide variety of industrial ap-

plications (Grim, 1962; van Olphen, 1977; Lagaly and Fahn, 1983 ; Jepson, 1984;

Odom, 1984; Murray, 1986, 1999, 2000, 2003; Harvey and Murray, 1997). Their

usages fall into two contrasting broad classes:



Clays are used because of their inertness and stability. A large variety of industrial

uses are also related to the unique rheological properties of clay and clay mineral

dispersions.



Clays are used because of their reactivity and catalytic activity.

In the following section the various families of clays are discussed in terms of their

inert or reactive applications and their unique rheological properties. In many cases

the different clay types are modiﬁed to meet required speciﬁcations.

Pure clays do not usuall y occur in nature. In terms of tonnage used, we may

distinguish four classes of clay. The so-called ‘common clays’ enjoy the largest usage

in numerous engineering applications. These clays contain mixtures of different clay

minerals such as illite/smectites, kaolinites, smectites, micas and associated minerals.

This is followed by ‘industrial kaolins’ that contain relatively high amounts of ka-

olinite (kaolins), and sometimes a small proportion of high-quality kaolin minerals.

The third class is ‘bentonite’ with a high montmorillonite (smectite) content. The

fourth class is the ‘palygorskite-sepiolite clays’ that have many sim ilarities to bent-

onites and are specifically used because of their surface properties and reactivity.

The world production of processed kaolins is about 20 million tons/year and that

of bentonites is 13 million tons/year, while palygorskite-sepiolite production is

around 2 million tons/year. The amount of common clays used worldwide is difﬁcult

to estimate since there are no statistics. However, it is likely to exceed many hun-

dreds of millions tons/year. There are also a few deposits of high-purity clays, such

as halloysite (used in high-quality porcelain and catalysis) and hectorite (used

in cosmetics and pharmaceuticals). Their peculiar properties classify them as

DOI: 10.1016/S1572-4352(05)01016-0

high-quality additives rather than bulk industrial minerals. In addition, some ﬁnely

ground minerals with similar properties to some industrial clays are frequently in-

cluded in industrial clay surveys. They include vermiculite, mica, talc and pyrophyl-

lite. A brief summary of their uses is included here.

10.1.1. INDUSTRIAL USES

A. Common Clays

Although the technologies associated with the engineering properties of clays are not

covered in this chapter, large tonnages of common clays are used in a wide variety of

engineering applications including road construction, ﬁll, dam construction and in

waste containment. The mineralogy and particle size distribution determine their

engineering properties.

Large tonnages of common clays are used in ceramic production (bricks, tiles,

terracotta, earthenware, stoneware, sewer pipes, paving bricks, refractory bricks,

etc.). Although these clays are typically impure, they contain sufﬁcient clay minerals

to cause them to develop plastici ty and to produce adequate strength, porosit y and

other properties to justify their use. These raw materials may contain high amounts

of mixed-layer clay minerals, notably illite/smectite. As illite/smectite particles can

delaminate to a certain extent depending on their layer charge distribution (see

Chapter 5), the type of illite/sm ectite may inﬂuence the ceram ic properties of com-

mon clays, and their behaviour in dispersions (for casting processes, etc.). A small

amount of smectite can be tolerated or is added to improve plasticity. Large amounts

of smectite would give undesirable shrinkage and drying properties. The pre sence of

kaolinite is not desirable in clays used for bricks and tiles because kaolinite would

increase the ﬁring temperature and a light burning colour is not required (Grim,

1962).

B. Kaolins

Kaolins as Filler and Coating Particles

Table 10.1.1 provides a gen eral summary of the uses of clays as inert components in

industrial systems (Murray, 1986, 1999, 2000; Harvey and Murray, 1997; Harvey,

1997). Amongst the earliest industrial uses of clays are water-based systems such as

paper or water-based paints where the hydrophilic nature of clays enables them to

readily disper se in such systems. However, kaolins were long used a s ﬁllers for

plastics and rubber. To make the hydrophilic surface of the clay mineral compatible

with the organic material, the surface is modiﬁed by reacting with organic com-

pounds, in most cases by grafting (see Chapter 7.3). If the clay mineral particles are

highly dispersed in the polymer matrix and the adhesion between the ﬁller particles

Chapter 10.1: Conventional Applications502

and the matrix is good, the ka olinite particles act as active ﬁllers, i.e., they improve

certain mechanical properties of the polymers (Lagaly, 1999).

Modern developments in this ﬁeld not only aim to increase the bonding strength

between the ﬁller particles and the polymer matrix but also to produce clay min-

eral–polymer nanocomposites where the fully delaminated mineral is dispersed in the

matrix (see Chapter 10.3).

Kaolin, bentonite, palygorskite and sepiolite are used as carri ers and diluents of

pesticides (insecticides, fungicides, herbicides). Enhanced application of herbicides

requires particular formulations based on modiﬁed clay minerals (see Chapter 11.2).

The largest amounts of processed kaolins (more than 60% of the word produc-

tion) are used in the paper industry as ﬁllers within the network of cellulose ﬁbres

and as coating particles. The technical requirements for ﬁller clays are significantly

less than for kaolinite particles in the coating colours. Gloss, brightness, opa city and

smoothness generally improve with increasing coat mass and decreasing particle size.

The p2 mm fraction is particularly important in coating kaolins and high-glossing

paint kaolins. More than 70% (w/w) of the coating particles should be smaller than

2 mm. Very ﬁnely divided kaolins can cause technical problems. Filler clays typically

Table 10.1.1. Uses of clay minerals as inert components

Clay family Industry Use

Kaolin Paper, plastics, rubber Filler

Pesticides Carrier, diluent

Vermiculite Building industry Heat insulation, sound dissipation

Package industry Shock proof materials, thermal

protection, liquid absorption

Foundries thermal protection

Mica Electrical industry Insulation

Paints UV-, heat-stable and under-water

paints

Cosmetics Nacreous pigments

Coating Corrosion proof, polymer coatings,

underseal

Talcum, pyrophyllite Plastics, rubber, paper

industry

Filler

cosmetics, pharmaceutics Powders, pastes, ointments, lotions

refractory industry Refractories

Palygorskite, sepiolite Pesticides Carrier for insecticides and

herbicides

Chemical industry Catalyst carrier, ﬁlter material,

anti-caking agent

Cosmetics, plastics Filler

10.1.1. Industrial Uses 503

have 50–70% particles >2 mm(Jepson, 1984; Murray, 1986, 1999, 2000), the op-

timum particle size for lodging within paper ﬁbres being 5–7 mm. Typical particle size

distributions of industrially processed ﬁller and coating kaolins from the sedimentary

kaolin deposits in Georgia (USA) are illustrated in Fig. 10.1.1.

Coating of paper is done at very high speeds (1200 m/min and even more), and

using large machines (Bundy, 1993). As such, it requires an exact tuning of the

rheological properties of the highly concentrated slurries. In blade coating the rate of

shear can reach 10

1

along the line of contact of the blade with the paper. The

relation between bulk kaolin properties and coating colour rheology is complex.

Particle shape, size, size distribution and particle packing are critical factors. For the

same clay content, dispersions of thin, large particles have higher viscosities than

those of blocky particles. The more platy the particle shape, the lower is the shear

rate at which shear thickening starts.

To prepare homogeneous slurries of kaolin with up to 70% (w/w) solids, anionic

macromolecules, mainly polyphosphates and polyacrylates,

are added. This en-

hances the negative charge density at particle edges, providing steric stabilisation to

the dispersion (see Chapter 5). It is necessary to select appropriate size fractions and

particle shapes to obtain the required rheological properties (yield value, viscosity,

thixotropy). One also has to consider the interaction of the coating particles with the

thickeners (often carboxy methylcellulose and starch) as this plays a key role in

controlling the rheological and dewatering properties (Li et al., 2001).

filler

coating

thick particles

thin particles

325 mesh

mass percent finer than

uivalent s

herical diameter (

Fig. 10.1.1. Typical particle size distribution of ﬁller and coating grade kaolins. From

Murray (1986).

Some polyphosphate containing kaolin slurries can form gels within a few hours if left undisturbed

producing discharge problems. Gelation is retarded or impeded by adding sodium polyacrylates.

Chapter 10.1: Conventional Applications504

Kaolins in Ceramics

A major use for high-purity kaolins is for ceramic products such as porcelain, bone

china, vitreous sanitary ware and earthenware. Low-quality kaolins are also used as

ﬁllers in a wide range of ceramic products including brick, pipes and tiles. Refractory

clays are dominantly composed of kaolins with low levels of iron, alkali and alkaline

earth cations. High levels of such metals would reduce the fusion point.

Delamination of kaolinite particles

improves the quality of porcelain. This re-

action was used by Chinese ceramists to produce very thin (‘egg-she ll’) porcelain of

high mechanical stability (see Chapter 7.3). Delamination was also used in the pro-

duction of speciality paper clays. Delamination of large particle-size kaolin stacks

can convert ﬁller clay into high-surface area platelets with superior opacity in light-

weight coatings (Bundy, 1993).

The presence of smectit es in commercially exploited kaolin resources is undesir-

able for most industrial applic ations. The smectites may therefore have to be re-

moved in order to meet the required speciﬁcations. As these minerals are generally

concentrated in the ﬁnest size fractions (o 0.5 mm) of kaolins (Fig. 10.1.2), size

fractionation can help to reduce the smectite content. Chemical modiﬁcation of the

smectites was also proposed to reduce their negative effect (Jepson, 1984).

Historically, mainly in China and Eastern Asia, clays and kaolins for the pro-

duction of ﬁne ceramics were traditionally matured by placement in humid pits for

several years. The improvement in properties is caused by the modiﬁcat ion of par-

ticle size (and possibly composition) through the action of microorganisms. This

100 10 1 0.1

uivalent s

herical diameter (

composition (% mass)

Fig. 10.1.2. Variation in mineral composition with particle size for Cornish kaolin. F ¼ feld-

spars; Q ¼ quartz; M ¼ mica; S ¼ smectite; K ¼ kaolinite. From Jepson (1984).

In a strength sense ‘delamination’ describes the disarticulation of the particles into single silicate layers

(see Chapter 5). In industrial applications ‘delamination’ stands for the dissociation of aggregates into

single particles or smaller aggregates.

10.1.1. Industrial Uses 505

beneﬁciation process is currently attracting the attention of scient ists (Groudeva and

Groudev, 1995; Lee et al., 2002).

Ceramic masses can be shaped because of the unique ability of clay mineral

particles to form card-house or band-type networks (see Chapter 5). On the other

hand, the ease with which clay minera l particles form stable colloidal disper sions also

allows the production of ceramics by casting, especially porcelain and vitreous san-

itary ware. The deﬂocculated slip (total solid content X70% (w/w) is poured into a

porous plaster mould so that a ﬁlter cake builds up on the plaster surface. The mould

is inverted, and the excess slip is allowed to drain. After de-watering in the mould,

the cast is removed, and, after a few further steps, is sprayed with glaze and ﬁred

(Jepson, 1984). This technique needs ﬂuid colloidal dispersions with clay contents as

high as possible. Liquefaction requires the addition of sodium salts and a pH above

6. At the same water content, a sodium kaolinite dispersion can be ﬂuid whereas

calcium kaolinite forms a plastic mass (see Chapter 5). This behaviour was ﬁrst

described by Justus von Liebig (1865). Fine ceramics produced by slip casting com-

monly have a higher dry breaking strength than shaped ceramics. The ﬁlter cake

built up during slip casting consists of kaolinite particles that are more densely

packed in parallel orientation as compared with moulded plastic masses in the

presence of calcium ions (Hofman n, 1962a).

In technical processes the charge on particle edges is changed from positive to

negative by addition of multivalent anions, particularly oligo- and poly-phosphates

as well as polyanions like polyacrylate and less well-deﬁned macromolecular com-

pounds such as humic substances. These additives often impart a certain amount of

steric stabilization to the dispersion (see Chapter 5). One of the most effective dis-

persants for modern high-performance ceramics is oxidized ﬁsh oil (Bo

hnlein-MauX

et al., 1992). Liquefaction of a mass of 100 g kao linite (‘China clay’) in 200 ml water

by 1 g tetrasodium diphosphate (Na

10 H

O) is illustrated in Fig. 10.1.3. The

ﬂuid dispersion can sti ffen again by the addition of salts such as KCl (in this case

3 g/100 g clay), causing the clay mineral particles to coagulate (ﬂocculate).

C. Bentonites

World production tonnages for bentonites are very difﬁcult to obtain. Our best

estimate is 13 million tons and the major usages are iron ore pelletizing, foundry

mouldings and oil well drilling (Fig. 10.1.4). However, the use of bentonite in nu-

merous environmental applications is growing fast. Large volumes are needed for

ﬁltering, decolourizing and clarifying (mostly in form of bleaching earths), pelletising

animal feed, as pet litter adsorbent,

pesticide carrier and oil and grease adsorbent.

Smaller amounts of bentonites are needed for paints, pharmaceutical and cosmetic

uses, waste disposal, lubricants, as additives for cement and mortar, as catalysts and

The effectiveness of clays for pet litter may also be related to the deactivation of enzymes that convert

urea to ammonia (W. P. Moll, personal communication, see Chapter 11.1).

Chapter 10.1: Conventional Applications506

foundry

23.5%

adsorbents

29.4%

refining

3.1%

agronomy

7.3%

building industry

3.4%

other

6.9%

drilling fluids

13.2%

iron ore pelletising

13.3%

Fig. 10.1.4. Use of bentonite. World production may be 13 million tons in 1993 (Courtesy N.

Schall, Su

d-Chemie AG, Germany).

0 50 100 150

shear stress (Pa)

500

100

shear rate (s

-1

)

100g

Fig. 10.1.3. Liquefaction of kaolin by tetrasodium diphosphate. A 100 g China Clay in 200 ml

water. B Liquefaction by addition of 1 g Na

10 H

O, C again stiffening by addition of 3 g

KCl. Data from M. Mu

ller-Vonmoos, ETH Zurich. From Jasmund and Lagaly (1993).

10.1.1. Industrial Uses 507