CONVERSION OF CHRYSOTILE ASBESTOS TO SMECTITE MICHAEL C. CHESHIRE, B.A. A THESIS GEOSCIENCE

Transcription

1 NVERSION OF CHRYSOTILE ASBESTOS TO SMECTITE by MICHAEL C. CHESHIRE, B.A. A THESIS IN GEOSCIENCE Submitte t the Grauate Faculty f Texas Tech University in Partial Fulfillment f the Requirements fr the Degree f MASTER OF SCIENCE Apprve Chairpersn f the Cmmittee Accepte Dean f the Grauate Schl December,

2 ACKNOWLEDGEMENTS I v\ Lil like t thank Dr. Necip Guven fr the pprtunity t stuy with him. He has been a great mentr in life an in gelgy. Fr this I am eeply inebte t him. I am als appreciative f Dr. Mira Riley an Dr, Hal Karlssn fr all the help they have given me, I thank Dr, Dminick Casante, Dr. Zhengrng Li, an Lauren McPhersn fr their help an avice with the snicatin reactins. Mike Gwer, thank yu fr immense talent an patience fr keeping the X-ray iffractin machine up an running. I wul nt have been able t cmplete my wrk withut him. Drs. Thmas Lehman an Jim Barrick, thank yu fr yur cntinue interest an encuragement uring my unergrauate an grauate career. Owen Frst an Rusty Winn, there is nt enugh wrs t express hw much I appreciate all that yu have ne fr me. Yur enless genersity an kinness have meant the wrl t me. Russell Frst, Kelly Opre-Jnes, Mike Jnes, Brenan Hea, Michael Khl, Wayne Mark, an Hlly Wwar yur frienship an supprt thrugh the years have mae this experience in my life ne I will never frget. Mm, Da, Christie, an Dug, thank yu fr yu cntinue lve an supprt. I wul like t thank my Granma fr her lve an extreme genersity thugh ut the past six an a half years. I wul nt have been able t accmplish all that I have set ut t withut the supprt f my entire family an friens. Thank Yu!

3 TABLE OF NTENTS ACKNOWLEDGEMENTS ii TABLE OF NTENTS ui ABSTRACT iv LIST OF TABLES vi LIST OF FIGURES vii CHAPTER L INTRODUCTION n. OBJECTIVES OF THE INVESTIGATION m. EXPERIMENTAL PROCEDURES AND METHODS OF ANALYSES 6 IV. RESULTS U V. DISCUSSION 6 VL NCLUSIONS REFERENCES APPENDIX

4 ABSTRACT In the Unite States, chrystile asbests is legally eclare a carcingenic health hazar, which requires the remval f all frms f asbests in all public places. Upn remval, the chrystile is ispse in lanfills; thus mving the hazar t anther relatively secure lcatin. In this stuy, we are investigating the pssibility f altering chrystile t a nn-hazarus mineral, such as smectite, which ptentially may be ecnmically viable. Chrystile frm Thetfr Mines in Quebec, Canaa was treate first with mil rganic acis, such as frmic an xalic acis, at cncentratins.5 t.n at C in Tefln-line. ml Parr bmbs. Examinatin f the reactin pructs with X-ray iffractin an Analytical Electrn Micrscpy inicate a prly crystalline irn-bearing kerlite-type : layer silicate with a thin fily mrphlgy was fun t frm uring the aci pretreatment alng with significant amunts f amrphus silica. The magnetite impurity in the initial chrystile asbests serve as the surce f irn in the abve reactins. Kerlite seems t frm frm the fllwing reactin: Mg6Sii(OH)8(s)+ 6.H'(aq) +.5Fe^''(aq)» chrystile (Mg.6Fe%.5)Sii(OH)-nH(s) +.55Mg^*(aq) kerlite Subsequently, kerlite was reacte with.n NaOH fr 8 t 96 hurs at C. A highly crystalline smectite was fun t frm with the same fily mrphlgy as the kerlite precursr. X-ray spectral analyses f the kerlite precursr an smectite suggest the fllwing reactin t take place: iv

5 (Mg.6Fe^"'.5)Sii(OH)-nH(s) +.5Mg^%) -.5NaOH(aq) + G.OlFe^^aq)"» kerlite Na.5(Mg.99Fe^*O.Ol)(Si.6Fe'\5)Oi(OH) s)+.5si%aq) sapnite The reactin pructs, kerlite an smectite, efinitely pssess a nn-hazarus mrphlgy an has prmising ecnmic ptential.

6 LIST OF TABLES.. Reactins at C fr frmic aci an alkaline (NaOH) treatments 9.. Reactins at C fr xalic aci an alkaline (NaOH) treatments.. Atmic ratis an basal spacings () fr the kerlite an smectite pructs frm frmic aci pretreatments... Atmic ratis an basal spacings () fr the kerlite an smectite pructs frm frmic aci an ultra-snicatin pretreatments... Atmic ratis an basal spacings () fr the kerlite an smectite pructs frm xalic aci pretreatments... Amunts f Magnesium leache frm chrystile with frmic an 6 xalic aci pretreatments at C an C. VI

7 LIST OF FIGURES.. Chrystile's curle sheets evelpe frm lateral misfits an crss sectin shwing Mg-ctaheral sheet verlying Si-tetraheral sheet (Bnneau et al., 986)... TEM image f fibers f Thetfr chrystile.. Spectral intensity ratis f the main elements in the chrystile fibers... Thin kerlite fils frming as extensins f chrystilefiberswith amrphus silica surruning the kerlite fils uring 8 hur l.on frmic aci pretreatment (Ma-6)... Clse up f smectite fils grwn frm renmant chrystile fibers uring 8 hur.n NaOH hyrthermal treatment (Ma-6)..5. Kerlite fils frming as extensins f chrystile 6 fibers uring 8 hur.n frmic aci pretreatment..6. Large kerlite fils ranging frm t micrns evelp 6 uring 8 hur.on frmic aci pretreatment..7. X-ray spectra an spectral intensity rati f the main elements 7 btaine frm (a) kerlite fils an (b) smectite fils..8. Hematites frming euheral hexagnal platelets 8.9. Small amrphus Mg-silicate glbules 8.. Large smectite fil frme uring 8 hur.n NaOH 9 hyrthermal treatment (Ma-7,7r,,5,56)... fils evelping as lateral extensins f renmant 9 fibers uring 8 hur.n NaOH hyrthermal treatment (Ma-7,7r,, 5,56)... Large smectite fils calescing frming large mats with resiual fibrils f chrystile uring.n NaOH an.% NaF hyrthermal treatment fr 8 hurs (Ma-69). vu

8 .. Large smectite fil frme uring 7 hur.n NaOH hyrthermal treatment (Ma-57)... fils extening frm a laterally fracture fiber fllwing minutes f ultra-snicatin an.n NaOH hyrthermalteeatmentfr 8 hurs (Ma- S#)..5. Large cluster f small smectite fils fllwing 6 minutes f ultra-snicatin an.n NaOH hyrthermal treatment fr 8 hurs (Ma-S#l)..6. Large kerlite fils extening frm resiualfibersafter 6 96 hur.n frmic aci pretreatment (Ma-)..7. Iniviual fils f kerlite evelp uring 7 hur 6.N frmic aci pretreatment (Ma-5)..8. Iniviual smectite fil evelpe frm 8 hur.n NaOH 7 treatment (Ma-5)..9. Very large smectite fil evelpe frm.n NaOH, 7.% NaF, an.% TMA hyrthermal treatment fr 8 hurs (Ma-)... Large kerlite fils extening frm resiualfibersevelpe 8 frm the hyrthermal treatment f. an. grams f chrystile in.n frmic aci fr 96 hurs (Ma-5 & 6)... STEM image f the kerlite fils frming uner same cnitins 8 as Figure.... fils evelping as extensins frm remnant fibers 9 uring 8 hur.n NaOH hyrthermal treatment (Ma-5 & 6)... Large iniviual smectite fil frming uner same cnitins 9 as Figure.... Kerlite clusters frme frm chrystile fibers hyrthermally treate in.5n xalic aci fr 8 hurs. Amrphus silica surruns the clusters (Ma-8). Vlll

9 .5. Kerlite clusters frme frm chrystile fibers hyrthermally treate in.n xalic aci fr 8 hurs (Ma-9 & 95)..6. Dense clusters f smectite fils evelpe frm.n NaOH hyrthermal treatment. Nte the platelets f hematite trappe within the fils f smectite (Ma-8)..7. Typical smectite fils evelpefrm.n NaOH an.% NaF hyrthermal treatment (Ma-98). A.l. XRD pattern f starting Thetfr Chrystile 5 A.. XRD pattern f the reactin pructs after the hyrthermal 6 treatments f chrystile first with l.on frmic aci fr 8 hur then with.n NaOH fr 8 hurs (Ma-6). A.. XRD pattern f the reactin pructs after the hyrthermal 7 treatments f chrystile first with.n frmic aci fr 8 hur then with.n NaOH fr 8 hurs (Ma-7). A.. XRD pattern f the reactin pruct smectite after the hyrthermal 8 treatments f chrystile first with.n frmic aci fr 8 hurs then witii.n NaOH fr 8 hurs (Ma-7r). A.5. XRD pattem f the reactin pructs after the hyrthermal 9 treatments f kerlite with.n NaOH fr 8 hurs (Ma-). A.6. XRD pattem f the reactin pructs after the hyrthermal 5 treatments f chrystile first with.on frmic aci fr 8 hur then with.n NaOH fr 8 hurs (Ma-5). A.7. XRD pattem f the reactin pructs after the hyrthermal 5 treatments f chrystile first with.n frmic aci fr 8 hur then with.n NaOH fr 8 hurs (Ma-56). A.8. XRD pattem f the reactin pructs after the hyrthermal 5 treatments f chrystile first with.n frmic aci fr 8 hurs then witii.n NaOH an.% NaF fr 8 hurs (Ma-69). A.9. XRD pattem f the reactin pruct smectite after the hyrthermal 5 treatments f chrystile first with.on frmic aci fr 8 hurs then with.n NaOH fr 7 hurs (Ma-57). IX

10 A.. XRD pattem f the reactin pructs after the hyrthermal 5 tireatinents f chrystile with.n frmic aci fr 8 hurs then with.n NaOH fr 8 hurs with 5 minute ultra-snicatin betweenfreatments (Ma- S#). A.. XRD pattem f the reactin pructs after ie hyrtiiermal 55 ti:eatments f chrystile with.n frmic aci fr 8 hurs then with.n NaOH fr 8 hurs with minute ultra-snicatin between treatments (Ma- S#). A.. XRD pattem f the reactin pructs after the hyrthermal 56 treatments f chrystile with.n frmic aci fr 8 hurs then with.n NaOH fr 8 hurs with 6 minute ultira-snicatin Ijetweenfreatments (Ma- S#I). A.. XRD pattern f the reactin pructs after the hyrthermal 57 treatments f chrystile with.n frmic aci buffere t ph=. (Na-frmate) fr 8 hurstiienwitii.n NaOH fr 8 hurs (Ma-59). A.M. XRD pattem f the reactin pructs after the hyrthermal 58 treatments f chrystile first with.on frmic aci fr 7 hur then witii.n NaOH fr 8 hurs (Ma-5). A. 5. XRD pattem f the reactin pructs after the hyrthermal 59 treatments f chrystile first with.n frmic aci fr 96 hur tiien witii.n NaOH fr 8 hurs (Ma-6). A. 6. XRD pattem f the reactin pructs after the hyrthermal 6 treatments f chrystile fu:st with.n frmic aci fr 96 hur tiien witii.n NaOH,.% NaF, an.% TMA fr 8 hurs (Ma-). A. 7. XRD pattem f the reactin pructs after the hyrthermal 6 treatment f. grams f chrystilefirstwith.n frmic aci fr 96 hurs then witii.n NaOH fr 8 hurs (Ma-5). A. 8. XRD pattem f the reactin pructs after the hyrthermal 6 treatment f. grams f chrystilefirstwith.n frmic aci fr 96 hurstiienwitii.n NaOH fr 8 hurs (Ma-6). A. 9. XRD pattem f the reactin pructs after the hyrthermal 6 treatment f chrystile first with.5n xalic aci fr 8 hurs then with.n NaOH fr 8 hurs (Ma-8).

11 A.. XRD pattem f the reactin pructs after the hyrthermal 6 freatment f chrystile first with l.on xalic aci fr 8 hurs tiien witii.n NaOH fr 8 hurs (Ma-9). A.. XRD pattern f the reactin pructs after the hyrthermal 65 freatment f chrystile first with l.on xalic aci fr 8 hurs tiien witfi.n NaOH an.% NaF fr 8 hurs (Ma-95). A.. XRD pattem f the reactin pructs after tiie hyrthermal 66 treatment f chrystile first with.n xalic aci fr 8 hurs tiien witti.n NaOH fr 8 hurs (Ma-). A.. XRD pattem f the reactin pructs after the hyrthermal 67 treatment f chrystilefirstwith.n xalic aci fr 8 hurs tiien witii.n NaOH an.% NaF fr 8 hurs (Ma-98). XI

12 CHAPTER I INTRODUCTION Asbests is an inustrial term use t escribe a grup f silicate minerals that are heat resistant, chemically inert, an exhibit asbestifrm mrphlgy (Zltai, 98). Minerals having asbestifrm mrphlgy are escribe as exhibiting strng, flexible, hair-like fibers that ccur in bunles (Zltai, 98). Due t these prperties, asbests has been applie t ver, uses, mstly in brake linings, fire prfing, heat insulatin an textiles with nyln, cttn, plyester, r metal wires interwven. There are tw mineralgical types f asbests: () serpentine (chrystile) asbests an () amphible asbests. Bth serpentine an amphible asbests have been ascribe t the cntributin f numerus respiratry iseases, hwever current stuies suggest serpentine asbests pses n health risk in nnccupatinal envirnments (Churg, 99; Mssman et al., 99). The serpentine asbests, als knwn as chrystile r "white asbests," cnstitutes 95% f all use asbests (Abelsn, 99). The Unite States gvernment, ignring the ifferent pathlgic effects f the chrystile an amphible asbests, has manate the remval f all frms f asbests frm public places. This manate was calle by Abelsn (99) as the 'Asbests Remval Fiasc' that may cst up t $5 billin, an its ispsal in lanfills may a abut $ per tn (Mssman et al., 99). The current ispsal prceure nly places the asbests t a relatively secure lcatin; it es nt eliminate the prblem.

13 This investigatin explres the pssibility f altering serpentine asbests t an ecnmically valuable material r at least t a legally 'nn-hazarus' frm. The alteratin prcess f the serpentine asbests will cnsist f a series f chemical treatments t initiate a recrystallizatin r a sli-state transfrmatin reactin. Serpentine Asbests Chrystile is a : trictaheral phyllsilicate with a frmal chemistry f MgSi5(OH). This : phyllsilicate is mae f ne Mg-ctaheral sheet bne with an unerlying Si-tetraheral sheet. These sheets exten infinitely in the X an Y crystallgraphic irectins. Within chrystile's structure, magnesium reacts in tw mes: tw-thirs f the Mg^"^ is easily leache in aciic slutins while the remaining ne-thir es nt reaily react in aciic slutins (Vaillancurt, 997; Barbeau, 979). An ieal Mg-ctaheral sheet has a lateral imensin f b = 9.A an an ieal silxane tetraheral sheet has a lateral imensin f b = 9. A (Wicks & O'Hanley, 988). This size ifference yiels a lateral misfit between the tw sheets alng the X an Y irectins (Veblen & Wylie, 99 an Wicks & O'Hanley, 988). T partially cmpensate fr this misfit the larger ctaheral magnesian sheet curls ver the smaller silxane sheet (Figure.), prucing chrystile's fibrus mrphlgy. The uter surface f the fiber therefre expses hyrxyl ins (OH) f the ctaheral magnesian sheet (Bnneau et al., 986). Chrystile's tubular stmcture pruces fur reactive sites: () uter hyrxyl layer, () ens f the fiber, () lege f the curle sheet, an () insie the hllw central channel (Chwhury, 975; Chi & Smith, 97).

14 Chrystile was reprte t mainly frm ue t hyrthermal alteratin f peritites r reactins between lmite an silica-rich fluis (O'Hanley, 996). Majr epsits f chrystile asbests are in Canaa (Quebec), Russia (Urals), an sme minr epsits in Califrnia (Abelsn, 99; Veblen & Wylie, 99). V OH OH OH OH, OH JD «/ J\, - "" s». '^Ht \ \ n i» V '% Figure.. Chrystile's curle sheets evelpe frm lateral misfits an crss sectin shwing Mg-ctaheral sheet verlying Si-tetraheral sheet (Bnneau et al., 986).

15 CHAPTER n OBJECTIVES OF THE INVESTIGATION There have been numerus stuies ealing with the ispsal f chrystile. Manley (998) use electric plasma t breakwn chrystile fibers. This meth use high temperatures ( C) t melt the asbests. Althugh this prcess estrys the asbests, it is nt energy efficient an the bypructs are f nn-cmmercial value. Anther stuy (Heasman an Balwin, 986) use inustrial waste acis t leach apprximately 8-9% f the magnesium frm the structure. This reners the chrystile fibers nn-hazarus an recycles ther wastes, but es nt yiel an ecnmical bypruct. Vaillancurt et al. (997) estrye chrystile asbests by aci isslutin an then use the amrphus silica resiue fr the synthesis f zelites. The aim f the present stuy is t evaluate a meth fr altering cmmn chrystile asbests t a pssible ecnmical an nn-hazarus mineral. Magnesium smectites have bth chemical an structural similarities t chrystile; an pssess nnhazarus mrphlgies. Natural an synthetic smectites are use cmmercially in a wie variety f inustries such as in paper inustry, cleaning agents, washing etergents, re pructin, ceramics, agriculture, rilling mus, an thers. ften precipitate frm alkaline slutins, but such slutins prvie a chemically stable envirnment fr chrystile. T initiate the alteratin f chrystile t smectite, abut half f the magnesium in chrystile will be partially isslve in frmic aci (OH) r xalic aci (H) slutins. Frmic an xalic acis are use in this

16 stiiy because bth acis are abunant in nature an are envirnmentally safe. Frmic aci is a mnprtic mil rganic aci tiiat ecmpses at C (Bell et al., 99). The frmic aci issciatin equilibrium is represente as the fllwing HOH(aq) ^ H (aq) + HO (aq). Oxalic aci is a iprtic merately strng aci that ecmpses at 75 C (Kettler et al., 99). The xalic aci issciatin equilibrium is represente as the fllwing HC(aq) ^ HC(aq) ^ H (aq) "H H (aq) H (aq) - - (aq). By varying the cncentratin f frmic an xalic acis, the ptimal cnitins fr selectively remving magnesium frm chrystile is etermine. The secn aim f this stuy is t etermine the effects f temperature, time, ultra-snicatin, an crystallizing agents n the recrystallizatin f aci resiue when treate in alkaline slutins. Ultra-snicatin uring the crystallizatin f uble-layere hyrxies has shwn t increase the crystallite size an crystallinity (Seia et al., ). Als, the presence f crystallizing agents, such as NaF an Tetramethylammnium chlrie (TMaCl), has been reprte t enhance the crystallizatin f smectite (Klprgge et al., 999).

17 CHAPTER ni EXPERIMENTAL PROCEDURES AND METHODS OF ANALYSES Chrystile in this stuy is frm the Thetfr Mines in Quebec, Canaa an was btaine frm War Gelgical Supplies (#9-5865). An 88% frmic aci slutin (Mallinckrt) an crystalline frm f xalic aci (Alfa-Aesar) were use t make aciic slutins. The chrystile samples were first brken up an then cut t abut -5 mm length with scissrs. These cut fibers are then grun in an autmate cffee griner t separate the fibers. These chrystile fibers were subjecte t a series f hyrthermal treatments in a. ml Tefln line Parr bmbs at C. First,. t. grams f chrystile fibers were pretreate in. ml f a ilute rganic aci (. t.n) fr varius peris f time (8 t 96 hurs). After aci pretreatment the intermeiate pructs (precipitates) were centrifuge t remve the remaining aci an magnesium in slutin. The intermeiate pructs then were hyrthermally treate in. ml f.n NaOH fr 8 t 96 hurs. The specific experimental cnitins are summarize in Tables. an.. After each hyrthermal treatment, reactin vessels were cle t rm temperature (5 C). Slutin ph was taken at 5 C with a Fisher Accumet ph Meter, Mel 6. Sme samples were subjecte t ultra-snicatin after the aci treatment. (R) Snicatin was prefrme in a Cle Parmer 7 series 6 W Ultrasnic Hmgenizer fr 5 t 6 minutes, perating at khz an C. Fllwing snicatin, the intermeiate pructs unerwent hyrthermal treatment in. ml f.n NaOH.

18 Bth the intermeiate an final hyrthermal pructs are examine with X-ray iffractin an Electrn Micrscpy. X-rav Diffractin Analysis X-ray iffractin analyses were carrie ut with a Phillips-Nrelc X-ray iffractmeter with CuKa-raiatin (k =.58 nm) generate at kv an 5 ma. Samples were smeare n a glass slie an were scanne frm 9 t 6 at a rate f 6 per minute. Samples were then saturate with ethylene glycl an scanne frm 6 t e t etermine if any expanable cmpnent is present. Patterns were recre an analyze using XRD Acquisitin an Prcessing prgrams evelpe by Guven an Subei () with Natinal Instrument's Lab VIEW 5. prgramming sftware. Analytical Electrn Micrscpy Electrn Micrscpic examinatin was carrie ut with a JEOL CX Analytical Electrn Micrscpe perate at kv an (la. The hyrthermal pructs were ilute in istille an einize water with traces f tertiary butylamine. A rp f this ispersin was rie n a slim bar cpper gri cate with a Frmvar substrate. The gris were subsequently cate with carbn an platinum. Bth transmissin electrn micrscpy (TEM) an scanning-transmissin electrn micrscpy (STEM) were use t etermine mrphlgy f the reactin pructs. Energy-ispersive analysis f the X-ray spectra (EDAX) prvie chemical analysis f the iniviual

19 particles. Specfral intensities f the cmmn elements were cllecte by a KEVEX micranalyzer with a Si(Li) sli-state etectr. The spectral intensity ratis were nrmalize fr Si an the Mg/Si an Fe/Si atmic ratis were calculate by the thin-film apprximatin (Glstein, 979). Atmic ratis were cnverte frm the spectral intensity ratis using crrectin factrs erive frm talc stanar fr Mg/Si (fc=.7) an frm annite fr Fe/Si (fc=.7). EDTA Titratins The ttal amunt f Mg^"^ remve uring the aci pretreatment was etermine by titratin with isium-ethyleneiaminetetraacetic aci (EDTA) as escribe by Harris (99). Five milliliters f the sample were ilute in 5 ml f einize (DI) water which was buffere t a ph f with NHOH. Six rps f a.% Erichrme Black T were ae t the slutin as the inicatr (re slutin). The buffere slutin was titrate witii a.6n EDTA slutin until equilibrium was reache (blue slutin). Each sample was repeate three times an average. The results are tabulate in Table..

20 ) O < a u O O n C O a t OS H TO "D '(/) Q O TO tsf E TO i_ C "TO.^ < O "( (/) c E (D QI X O < "ut.c J -I-?x Q. Q- < ^ O) h- "" 5 z X ^ O cn ^-' Z x: x DL CL * ^ < O! Li. ^^.S O ^~. U5 cr.c O Q E 5 t csi ^ c\i ^ ^~ CX t (» i 'P ^ ( ^ ^ CNI csi ^,,- C5 c\i ^ T ^ IT)., cn CM T-^ ^ *' CNJ ti; h~" 6 "^ rji ^ CN S ID '< r ^ '- lvj Csi ^ T 'vf., -^.,-: CM T-^ ^ ^.^ c E ^-^ 5 t in co ^ T '^ in r~.r^ Cvj T-^ ^ ^..^ c E ^ ' CM % 6 ^ ^ CM ^~ h- Cvi ^ T * in r^.r^ CM T- ^ 'c~ E in CM tt W ^ cn in <- T a> csi ^ T CM h~ C^J 't O cn.r.: CN T ^ in 6 '^ q in (N ^ ' ^ > in,r.: CM T- T 6 s CM h- J ^~ 't Csi ^ T t in,r^ C\l T- T t^ in 6 ( ^ ^ ^.,- (5 csi ^ ^~ ^ ID c\i CM T- r (y> in 6 5t csi ^ ^ r^ csi ^ '~ * Cvj, <y> T-^ CM T-, 5 6 ( ^ LO csi ^ T- Csi ^ T O cn CM ^ ^,r-^ CM T- ^ ^ T- 6 ( ^ CM ^ ^ h- Cvi ^ ^~ CJ in t^ T^ CM T- Csl in -^ 6 <f in \~^ C5 Csi ^ ^^ T C5,r^ CM T- c O ' 6 ^ c CN -a CJ,n ij-i kh ^ Q c -n erse CX -a CTS Mat ) - c n J u e niu ylamm -C S "S J' u ^~~* a a i_> (N " CJ C < 5 H

21 (D U X -a c c^ u X a u O O CN ^» c«c _ " (L> Pi (N (U C\l.«_i ( ;g (/) L_ ^ u M i "c ^- E k. c ".i: < p CM u> c E :rea prel T Aci (/) _.c.^.^j t -r (^ 9? I Q. Q- LL.^ zs * X ^ 9 ' ^- z,, (/).c " «j -r x Q. Q- *.. _ 5 ^^ ^.c % CL E ^ q. T ' ^~. j T ; T ^ <t in ; ' CvJ 6 ^ ^ q Csi T T ^ ^ q en CvJ 6 ( ' *! in Cvj t r-- Csi T ' i i O; '^'. * r^ CM ^ cn. q' ^ ; ; in CJ5 6 ^ t i j ^, c: T i O' eg; ' ^ ' ^ cn; in ^ CM in' 6 S * in in csi T ^ 5- '^ q CM in C5 6 ^ _ CN Q c -a (D C/ i-, <U,- g- (J U

22 CHAPTER IV RESULTS Thetfr Chrystile X-ray iffractin analysis inicates the Thetfr Chrystile is a clinchrystile (Mci) with small impurities f magnetite an brucite (Figure A. ). 's cncentratin remains arun -5% thrugh ut the starting material with sme hematite precipitating as catings n magnetite uring the hyrthermal reactins. Cncentratin f brucite varies greatly in the starting materials an thse with substantial amunts f brucite were nt use in this stuy. Micrscpy shws chrystile with a typical fibrus mrphlgy with an average fiber iameter f. micrn (Figure.). ED AX ata inicate a structural frmula f Mg6Sii(OH)8 with trace amunt f Fe^"^ in the ctaheral psitins (Figure.). Reactin Pructs f Chrystile Pretreate with Frmic Aci l.on Frmic Aci Pretreatment fr 8 Hurs Chrystile treate with l.on frmic aci fr 8 hurs yiels a prly crystalline kerlite with t % f chrystile remaining unreacte. Kerlite has a basal spacing f.99 nm (Figure A.). Kerlite ccurs mstiy as thin fils extening laterally frm remnant chrystile fibers with sme kerlite fils etache frm the fibers (Figure.).

23 Figure.. TEM image f fibers f Thetfr chrystile. secns Vert* 9 cunts Disp«Preset* Elapse sees 9 sees THETFOPD CHRV&OTILE Ranse-. kev. - Figure.. Spectral intensity ratis f the main elements in the chrystile fibers

24 . nm Figure.. Thin kerlite fils frming as extensins f chrystile fibers with amrphus silica surruning the kerlite fils uring 8 hur.on frmic aci pretreatment (Ma-6).. iin Figure.. Clse up f smectite fils grwn frm remnant chrystile fibers uring 8 hur.n NaOH hyrthermal treatment (Ma-6).

25 Aciificatin has generate large amunts f amrphus silica. The Mg/Si atmic ratis are much lwer than is expecte fr kerlite (Mg/Si(keriite) =.75) ue t the amrphus silica intimately mixe with the fils (Table.). (Fe^'T'e^"^) was fun t be partially xiize frming small amunts f hematite (Fea^^Os). Treating the kerlite with.n NaOH fr 8 hurs generates a prly crystalline smectite with a basal spacing f.59 nm that expans t.9 nm upn glyclatin (Figure A.). fils have retaine kerlite's riginal thin fily mrphlgy an remains as lateral extensins frm the resiual chrystile fibers (Figure.). fils exten laterally larger than.5 micrns. Recrystallizatin f kerlite t smectite invlve an increase in the Mg/Si an Fe/Si atmic ratis in the fils (Table.). Apprximately t 5% resiual fibrils an small amunts f hematite remain thrughut the final pruct..n Frmic Aci Pretreatment fr 8 hurs Chrystile treate with.n frmic aci fr 8 hurs pruces a priy crystalline kerlite phase with an average basal spacing f.99 nm (Figures A. - A.9). Kerlite fils seem t frm as lateral extensins frm resiual fibers, extening lnger than. micrns (Figure.5). In sme reactins kerlite fils aggregate frming large interwven mats extening t mre than micrns (Figure.6). During the crystallizatin prcess apprximately t 5% f tiie ttal magnesium is lst. The Mg/Si atmic ratis are much lwer than is expecte fr kerlite prbably ue t the excess f amrphus silica (Figure.7). XRD pattems inicate that resiual fibrils are

26 amrphus. During aciificatin, minr amunts f newly frme hematite an amrphus Mg-silicates were fun t precipitate glbulesfrm. t. micrns in size (Figures.8 an.9). Treating chrystile witii.n frmic aci fr 8 hun es nt cnsistentiy yiel kerlite fils. After hyrthermalti%atinentwitii.n NaOH fr 8 hurs, kerlite seems t cnvert t smectite with n change intiiefily mrphlgy. XRD pattems inicate that the smectite is highly crystalline in cnfrast ttiiepriy crystalline kerlite precursr. has an average basal spacing f.6 nm that expans t.78 nm upn glyclatin (Figures A. - A.7). s fils isplay very similar mrphlgical features as the kerlite fils (Figures. an.). Mst f the thin smectite fils exten laterally mre than 5. micrns an have significantiy higher Mg/Si an Fe/Si atmic ratis than thse f kerlite (Table.) (Figure.7). Aing.% NaF t the 8 hur.n NaOHtireatinentyiels littie imprvement n the crystallinity f the smectite, which has a basal spacing f.5 nm that expans t.7 nm upn glyclatin (Figure A.8). The smectite fils evelp as small iniviual fils, but ften ccur as aggregates greatertiians.o micrns in size (Figure.). The Mg/Si an Fe/Si atmic ratis nt shw any significant changes frm the ratis btaine intiiesmectite fils escribe abve (Table.). Small amunts f iniviual silicafibrils,hematite, an small granular precipitates remain tiirughut tiie pruct. 5

27 Figure.5. Kerlite fils frming as extensins f chrystile fibers uring 8 hur.on frmic aci pretreatment. Figure.6. Large kerlite fils ranging frm t micrns evelp uring 8 hur.on frmic aci pretreatment. 6

28 LAecutin time = secns v^rt> 8 cunts Disp" Pireset* Elapse sees sees SI I --. (a). Range-. kev i:. - Aia t-kecutiu/i vifii Vert«cunts Disp«Pireset" Elapse sees sees (b). Range-. kev. -^ Figure.7. X-ray spectra an spectral intensity rati f the main elements btaine frm (a) kerlite fils an (b) smectite fils. 7

29 . i^m Figure.8. Hematites frming euheral hexagnal platelets. Figure.9. Small amrphus Mg-silicate glbules 8

30 .5 fjvf\ Figure.. Large smectite fil frme uring 8 hur,n NaOH hyrthermal treatment (Ma-7, 7r,, 5, 56)../ym Figure.. fils evelping as lateral extensins f remnant fibers uring 8 hur.n NaOH hyrthermal treatment (Ma-7, 7r,, 5, 56), 9

31 kj. il Figure.. Large smectite fils calescing frming large mats with resiual fibrils f chrystile uring.n NaOH an.% NaF hyrthermal treatment fr 8 hurs (Ma-69).. nm Figure.. Large smectite fil frme uring 7 hur.n NaOH hyrthermal treatment (Ma-57).

32 . nm Figure.. fils extening frm a laterally fracture fiber fllwing minutes f ultra-snicatin an.nnaoh hyrthermal treatment fr 8 hurs (Ma- S#). ^PP^"'. nm Figure.5. Large cluster f small smectite fils fllwing 6 minutes f ultrasnicatin an,n NaOH hyrthermal treatment fr 8 hurs (Ma- S#l).

33 Alkaline reactins (ph =.) ver 7 hurs enhance the crystallinity f the smectite even in tiie absence f NaF. evelps a sharp basal reflectin f.5 nm tiiat expans t.7 nm upn glyclatin (Figure A.9). Mst f the smectite fils have aggregate int large interwven mats greater than pm in size (Figure.). The Mg/Si an Fe/Si atmic ratis nt shw any significant change frm the ratis btaine in tiie smectite fils escribe abve (Table.). Small amrphus glbules f Mg-silicates, hematite, an thin amrphus silica-rich fibrils remain as impurities thrughut the final pruct. Snicatin Pst.N Frmic Aci Pretreatment Snicatin f kerlite prir t alkaline treatment severely ecreases the crystallinity f smectite. Kerlite snicate fr 5 minutes yiels a g crystalline smectite with a basal spacing f.9 nm that expans t.69 nm upn glyclatin (Figure A. ). Snicatin fr minutes ecreases the crystallinity t a merately crystalline smectite with a basal spacing f. nm that expans t.78 nm upn glyclatin (Figure A. ). Further snicatin up t 6 minutes yiels a prly crystalline smectite with a basal spacing f.7 nm that expan t.5 nm upn glyclatin (Figure A. ). Mst smectite fils ccur iniviually with sme fils as lateral extensins frm resiual fibers (Figure.). Snicatin increase the cncentratin f smaller fils extening t n mre than 5. micrns (Figure.5). The Mg/Si an Fe/Si ratis f the smectite fils are cnsistent with the smectites btaine abve (Table.). is cntinue t be xiize t frm hematite.

34 Buffere.N frmic aci Pretreatment fr 8 hurs Buffering tiie frmic aci pretreatment t a ph f. with.9 grams Na-frmate generates a priy crystalline kerlite with t % resiual chrystile. Kerlite has a basal spacing f.8 nm (Figure A. ). Micrscpy es nt shw any kerlite fils an chrystile ccurs mstiy as fraye an fracture fibers. The aciic slutin pruce an excess f amrphus silica. Treatment with NaOH fr 8 hurs yiels a merately crystalline smectite with a basal spacing f. nm that expans t.7 nm upn glyclatin (Figure A. ). Chrystile remaine unreacte thrugh ut the sample an retaine it riginal fibrus mrphlgy, an n smectite was fun. is cntinue t be xiize prucing hematite..n Frmic Aci Pretreatment fr 7 an 96 hurs Increasing the aci pretreatment t 7 hurs yiels a prly crystalline kerlite with a basal spacing f.975 nm (Figure A. ). Further increase in aci pretreatment t 96 hurs es nt pruce a significant imprvement in the crystallinity f the kerlite. Kerlite frme in 96 hurs es shw a slight increase average basal spacing f. nm (Figure A. 5 an A. 6). Kerlite fils, ranging frm 7. t. micrns in size, cntinue t crystallize as extensins frm remnant fibers an as iniviual fil (Figures.6 an.7). The aciic slutin an leaching f magnesium frm the chrystile structure causes an excess f amrphus silica. The excess silica causes the Mg/Si rati t be much lwer than is expecte fr kerlite (Table.). Micrscpy shws evience

35 tiiat magnetite has partially xiize frming minr amunts f hematite. Increasing uratins f the aci pretreatment (7 an 96 hurs), hwever, es cnsistently generate kerlite fils. Treating tiie 7-hur kerlite pructs in.n NaOH fr 8 hurs evelps a well crystalline smectite with a basal spacing f. nm that expans t.76 nm upn glyclatin (Figure A. ). The 96-hur kerlite pructs when treate uner the same cnitins evelp a slightly mre crystalline smectite with a basal spacing f.9 nm that expans t.7 nm upn glyclatin (Figure A. 5). Mst f the smectites ha crystallize as iniviual clusters 5. micrns an larger in size with sme fils extening frm resiual fibers (Figure.8). Treatment in alkaline cnitins causes a large increase in the Mg/Si an Fe/Si ratis (Table.) Aing.% NaF an.% tetramethylanunnium chlrie (TMaCl) t the 8 hur.n NaOH treatment shwe a ecrease n the crystallinity f the smectite, which has a basal spacing f.5 nm that expans t.8 nm upn glyclatin (Figure A. 6). The smectite fils ften ccur as aggregates greater than 5. micrns in size, but als ccurs as iniviual fils smaller than 5. micrns (Figure.9). The Mg/Si an Fe/Si atmic ratis nt shw any significant changes frm the ratis btaine in the smectite fils escribe abve. Small amunts f iniviual silica fibrils, hematite, an small amrphus Mg-silicates remain thrughut the pruct.