Document VJZM4DdL7d38jaYkR29wKR5gj

FILE NAME: Marley (MAR) DATE: 1969 Nov DOC#: MAR026 DOCUMENT DESCRIPTION: Technical Bulletin from Nicolet CHRYSOTILE ASBESTOS C hem ical and M ineralogical P ro p erties as R elated to B eh avior in Aqueous Media Richard C. B reiner Novem ber, 1969 NICOLET INDUSTRIES, INC, MARDEP0443 November 10, I969 Behavior of Chrysotile Asbestos in Aqueous Media Suspensions of Chrysotile asbestos in water are generally believed to carry a positive charge, whereas the Amphibole grades result in negative potentials in water. Upon opening of Chryso tile fibers in water, polyvalent metal ions are released which cause coagulation of anionic additives in papermaking. The sur face area of asbestos which is believed to have a strong bearing on zeta potential is approximately 130,000 to 220,000 sq./cm/gm. (As noted in another section of this report, the general formula for Chrysotile asbestos is Mg^SigOc (0H)i*. Th Mg (0H)2 portion of the molecule is closest to the fiber surface, whereas the sili con-oxygen part is "inside." Note: The former has been cited as the reason for the poor acid resistance of Chrysotile. The Amphi bole varieties of asbestos have the silicon-oxygen layer on the outside. . < The magnesium ions and hydroxyl ions of Chrysotile asbestos dissociate in water. More hydroxyl ions probably dissociate, since the Chrysotile grade has been reported to carry a negative charge in carbon-dioxide-freewater ; the charge, however, becomes positive as pH increases-- i.e., Chrysotile possesses a positive charge in ordinary distilled or tap water. MARDEPO0O44'4 November 10, 199 Physical Properties of Chrysotile Asbestos Chrysotile asbestos is found in fibrous form grades ranging from powder form to over 3/^ inch staple and classi fied by Canadian Standards from 7 grade to Number One grade with various subclassifications; most papermaking applications, however, utilize grades 5 through 7* Asbestos fiber is gen erally found in a green to gray color with a soft to harsh 'texture-- depending upon where mined d General physical properties of asbestos are noted below: . Crystal Structure . ' > Monoclinic Hardness * - 2.5-k.O "" ']' V;. Specific Gravity Refractive Index Tensile Strength (psi) Fusion Point (F) 2.U-2.6 1 .50-1.55 82^,000 max 2770 ^ . '-V Resistance to Heat Good but brittle above 900f Filtration Properties Slow 'Fiber Diameter .(inches) .000000706 to .00000118 ; 7*o6 X 10"7 1.18 X lo"6 ' -MRDEP000445.. - November 10, 1969 Mineralogical Properties of Chrysotile Asbestos i ; Chrysotile asbestos is a hydrous silicate of magnesia found in three forms-- i.e., cross fiber, slip fiber and mass fiber. The former is generally a shorter fiber, since fiber is arranged normal to vein wall and limited to vein width, whereas slip fiber lies in the same plane as the vein; mass iiber is interlaced and unoriented. As noted previously, Chrysotile has the general formula an^ consists essentially of Mg (OH)^ layers condensed into silicon-oxygen tetrahedra. Mineralogical pro perties are noted below: "Essential Composition 'Hydrous silicate of magnesia Crystal Structure Fibrous and asbestiform Crystal System Monoclinic and orthorhombic^- Mineralogical Structure In veins of serpentine, etc. Mineral Association In altered peridotite adjacent to serpentine and limestone near contact with basis igneous rocks . : Veining . Cross and slip fibers V Luster , Silky ih'VV Hardness ph , . '. :. Specific Gravity Cleavage Optical Properties 2.5-h.O ' '' 9 .2-9.8 i . > v '; 2.H-2.6 " ' 0.0 perfect Biaxial positive, extinction parallel . .... Refractive Index ; 1.50-1.55 ' . . b. ' V 1 .MARDP''00446 November 10, 19^9 General . : Asbestos fiber, unlike standard papermaking (cellulosic) grades, is of mineral origin. Although found in six major forms, only Chry- sotile asbestos is of major importance in papermaking. The Chrysotile fiber, as it is known today, is the highly fibrous portion of Serpentine rock; picrolite and common Serpentine make up the remaining portion of the rock, but represent little commercial value. Other grades of as bestos, referred to as amphiboles, include Crocidolite, Amosite, Antho- phyliite, Tremolite and Actinolite. The three former grades have some use in papermaking and general building products, whereas the latter two are in short supply and have little significant commercial value. Most of the Chrysotile fiber referred to in the literature is mined in Quebec, Canada, although the Soviet Union also produces large Quantities of this variety; smaller deposits also exist in Vermont, Arizona and California in-the U.S.A. Africa produces Amosite and Crocidolite, whereas Anthophyllite is obtained primarily from Finland. Prior to its use in papermaking, the fiber must be removed from the rock.by several techniques--i.e., crushing, defiberizing, screening, grading ana packing. After separation, the fiber is shipped to the mills for processing into product forms.' Due to its mineral origin, however, the fiber is a chemical complex and presents a particular problem when 'used in aqueous media . In view of the above, asbestos suspensions in water present an interesting study. The discussions on the attached pages represent a summary of the salient properties of asbestos and a brief synopsis of the behavior of this mineral fiber in papermaking .systems. - -. ' ... ... ... KJ MARDEP000447 November 11, 1969 -Chemical Properties of Chrysotile Asbestos " . .. A typical chemical analysis of Chrysotile asbestos is noted below. Primary differences between the Chrysotile (Serpentine) grade and the Amphpboles is higher magnesium oxide ' content and higher water of crystallization in the former. All . of the Amphiboles contain relatively high iron content in their chemical structure except Tremolite; paradoxically, Chrysotile, with no iron.in the chemical structure, contains the highest per centage of magnetic (tramp) iron. . Generally defined, Chrysotile asbestos is a hydrous silicate of magnesia with a theoretical formula of 3MgO, 2SiC>2 2H2O or Kg3Si20ij (OH)i|. The fibers consist of layers of silicon- oxygen 'tetrahedras condensed into magnesium hydroxide layers. No chemical binding exists between the layers. Chrysotile can be considered as a magnesium hydroxide layer on a silicate sub strate. It is as strong a base as magnesium hydroxide,and its hydroxyl ions dissociate the same as magnesium hydroxide. Acid resistance of Chrysotile is poor (as opposed to all Amphiboles where acid resistance is fair to good), but alkali resistance of - the Chrysotile is excellent. . . y < MARDEP000448 Typical Analysis of Chrysotile Asbestos November 10, 19^9 Silica (SiOg) Alumina (Al^Og) Ferric oxide ^ 020^) Ferrous oxide (FeO) Magnesia (MgO) Iiime (CaO) Sodium oxide (Na20) Combined water (H2O) Alumina, Calcium, Water, etc Sulpher Phosphorus ^Canadian (Thetford)