Lu(in an Ti€n sf V(it ly

CHUaNG 1

MOT s6 VAN DE VE PHAN TICH." "

VANG VA PLATIN

-Chuang).. Mi)t so van tie ve phfmtich va!'-g va platin Luq.nan Tien sf Vq.tl'i 7

CHUONG 1: MOT s6 VANDE VE PHAN TicH

VANG VAPLATIN

1.1. NGUYEN TO VANG

Yang Ia mQt kim Ioc;ti qui d nhom 1, 6 thu 79 trong bang tu'an hoan

Mendeleev, co trQngIu'<Jngnguyen t\i'Ia 179,2, ty trQngd =19,3. Vang hoan toaD

nguyen cha't ra't hiSm. Trong tuy~t dc;tida s6 tru'ong h<Jp,yang tl! nhien Ia h6n h<Jp

d5ng hlnh voi bc;tc,chua bc;tctu 4-15% trQng Iu'<Jng.Loc;tichua bc;tcnhi~u bon thl

thanh mQtkhming v~t dQcI~p gQi Ia electrum. Yang tl! nhien co nhi~u thu: yang

I~nd5ng (cuproaurit) chua 20% trQngIu'<Jngd5ng; pocpexit Ia yang Ifin Pd Wi 5-

11% va bc;tcWi 4%; yang I~n Bi (bismutoaurit) chua Bi toi 4%. Ngoai ra yang con

d mQt s6 dc;tngsail: petzit (AgAu)2Te; caleverit AuTe2; crenerit AuTe2; sylvanit

AuAgTe4; nagyagit PbsAu(TeSb)4.[5,14]

Yang thu'ong hay cQng sinh voi cac thc;tchanh va cac suIfua, d6i khi voi Te,

bc;tc MQt d~c diSm mJa la co "vang nhln tha'y" thuQc Ioc;tikhoang v~t tach ra d

giai doc;tnsail cling thu'ong tha'y trong cac khe nha cua nhung khoang v~t da thanh

tc;tOtUtru'oc. Hinh 1.1 Ia khoang v~t yang nhln tha'y thuQc d~ an B5ng son [41]

du'<Jcchl;lPdu'oi kinh trQng sa dQphong dc;ti500 I'an.

mnh 1.1: Khoang v~ityang nhln tha'y thuQc d'e an B'ong son

ChUdng T:MQt so van ae v~ phan rich vimg va J!latin Lu~n an Tiin sf V~t ly 8

Ngoai yang nhin tha'y dU<;1C,con co yang lien ke't l§n trong cac sulfua nha't

la pyrit va arsenopyrit (FeAsS) chi Hm tha'y b~ng phuong phap phan tich hoa hQc.

Nguai ta dff Hm tha'y b:;tcvoi yang trong di~u ki<%nphong hoa mQt ph'an bi cuO'ndi

va do do yang d ngoai ria hay dQc theo cac khe nho thi tinh khie't bon. MQt d?c

di~m khac la yang dffi trong cac phu sa chila it b:;tcbon la yang d trong cac mo

nguyen thuy.

(j Vi<%tNam, yang du<;1ctha'y d ma'y lo:;tikhoang sang sail:

- Trong cac phu sa: thuang la cac vity nho litn trong cat soi d cac long song

ho?c tren cac th~m da't (My Bilc, MQ Son, Mi~n song Ba, song La, song Lvc

Nam, song Thuong).

- Khoang sang trong m:;tch:trong nhfi'ngm:;tchth:;tchanhco pyrit chua yang

(d PAcLan).

- Trong cac sulfua philc t:;tp: khoang san quail trQng la d B'Ong Mieu,?

Quang Nam d do co m:;tch th:;tch anh co pyrit litn yang xuyen qua da n~n va mica

phie'n th:;tch, khoang sang nay san xua't ra toi 200kg Yang, 78kg b:;tc nam 1936, va

110kg Yang, 49 kg b:;tcnam 1939.

- Trong qu?ng sAt: trong qu?ng oxyt sAt thuang co chua yang duoi d:;tng ra't

phan tan (mo sAtThai Nguyen).?

d tren the' gioi, n6i tie'ng nha't la mo yang Nitvattessan (Nam Phi). Truoc?

day mo nay san xua't40% ta't ca yang tren the' giOi.d Lien xo va My d~u co

nhfi'ngmo yang IOn.(j trQngsa dnh Victoria (Uc),nguai ta dfftim tha'ynhfi'ngcvc

yang n~ng Wi59,67kg (1958) va 68,08kg (1869).

Yang la mQt kim lo:;tinit qui vi no co mQt sO'tinh cha't d?c bi<%t:yang khong

bi tac dvng cua oxy ngoai khong khi va d nhi<%tdQ tha'p bon 1000oC, d'Ong thai

cling it bi tac dvng cua nhi~u cha't hoa hQc ngay ca acid m:;tnh (tnl h6n h<;$pHNO3

+ HCl). V~ m?t ly hQc, no cling co nhfi'ng Hnh cha't ra't qui. MQt gr yang co th~

Chlio'ng 1: MQt s{f van tie vi?phan tfch vang va piatin Lu(in an Tiin Sl V(it iy 9

keD S<;5ithanh day dai 3km, dat thanh la mong O,OOOlmm, nghla la nho hon s<;5i

toc cua con nguai Wi 500 l'an. Vi co nhfi'ng tinh chtt qui tren, nen yang co rtt

nhi~u cong dvng. Nguai ta thuang dung no dS lam d'o trang suc, m? nhi~u dvng

qt, d'ong thai dung trong mQts6 nganh cong nghi~p. Gia tri cua yang hi~n nay la

d~ trao d6i ti~n t~. Ham lu<;5ngyang co thS khai thac la tu I de'n 10g/t.

1.2. cAe PHUONG PHAp xAc DJNH v ANG

Cho de'n nay a Vi~t Nam ya tren the' gidi dfi co nhi~u phuong phap phan

tich xac dinh ham lU<;5ngyang trong m~u dia chtt [13]: phuong phap filing luy~n;

phuong phap hoa quang ph6 phat X? h'o quang; phuong phap di~n hoa; phuong

phap chie't-tri1c quang; phuong phap htp thv nguyen tli'; phuong filing luy~n-htp

thv nguyen tli'; phuong phap quang ph6 phat X? cam ung plasma ICP; phuong

phap kich ho?t notron; phuong phap trich ly b~ng xianua, phuong phap xac dinh

tren ray, dudi ray.

1.2.1.Phuong phap nung luy~n (Phuong phap yang nghi~m) (FA)

Day la phuong phap c6 diSn nhtt song do tlnh u'u yi~t cua no nen y~n du<;5C

sli'dvng a nhi~u nudc tren the' gidi nhu : Dc, Nga, Phap...

NQi dung phuong phap: m~u qu(mg ydi lU<;5ngm~u can tu 25 -IOOg dem

filing chay ydi h6n h<;5pcac hoa chtt g'om natri cacbonat, oxi chi, borac, tinh bQt...

trong 10 a nhi~t dQ 1100 -1200°C se thu du<;5cnv chi g'om Pb + Au + Ag. Dem

cupen a 850°C se thu du<;5Ch?t h<;5pkim Au + Ag. Dung axit nitric hoa tan Ag se

con l?i h?t Au dem xac dinh tren can yi lu<;5ng.

Phuong phap co u'u di~m la dung lu<;5ngm~u can lOn, h?n che' du<;5canh

huang phan b6 khong d'ong nhtt cua yang trong m~u, h?t yang thu dU<;5Cnhin thty

b~ng melt thuang, qua tr'inh tie'n hanh xac dinh du<;5cca yang ya b?c. Nhu<;5cdiSm:

h?t yang thu dU<;5Ckhong phai la tinh khie't ma con co ca Pt, Jr, Rh di theo cung

Chucmg 1: Milt s{f vdn aev'eEblin tich vimg va platin Lu~n an Tiin sf V~t ly 10

yoi Au khong tach ra duQC,vi ham luQng cua cac nguyen to' nay ra"tnho nen ta

thuongbo qua. Hoa cha"toxyt chi dung trong qua trlnh na"uchay thuong hay chila

cae t~p cha"tnhu Au, Ag nen dS lam tang ke't qua cua Au, Ag (ne'u khong ki€m

ITaxii'19 tu truoc).

Phuong phap filing luyt$n thuong duQc dung d€ xac dinh Au ham luQng lOn,

gioi h~n xac dinh tha"pnha"tla O,4g/t

Hit$n nay ngoai thi truong tt,i do nguoi ta dang sii' dl:mg phuong phap filing

luyt$nd€ phan tich va thu h6i vang tu quiling va sa khoang duoi 1 ten gQi khac -

phuong phap cupen th6i. Qua trlnh phan tich khong tie'n hanh hang lo~t ma chi

lam tung m~u me)tvoi khO'iluQng m~u tu 1.000g toi me)tvai kg hoilichang ch\lc

kg. Truoc khi filing chay thuong lo~i bot anh huang cua As, Sb biing natri

hydroxit + natri sunfua, lo~i bot anh huang cua Cu, Fe biing axil sunfuric + axil

oxalic. Do phuong phap tie'n hanh hoan loan thu cong, hoa cha"t la"y khong dinh

luQng ma ang chung, 10 bS, d\lng C\l thi nghit$m tho so nen c~c ke't qua phan tich

thu duQc chi a milc de)dinh luQng g'an dung.

1.2.2. Phtidng phap hoa - quang ph6 phat x~ h'o quang (C-ASES)

Day la phuong phap ke't hQp: giai do~n boa tan m~u la hoa hQc, giai do~n

Ido ham luQng la quang ph6 h6 quang.

Ne)i dung cua phuong phap: m~u quiling voi luQng can tu 5 - 109 duQc boa

tan biing cuong thuy. Yang boa tan duQc ha"pth\l biing than ho~t tinh hay ce)ng ke't

biing telua. LQc, tro hoa va nh6i VaGdit$n ct,ic, dO'ttren quang ph6 h6 quang, xac

dinh ham luQng theo de) den cua cuong de) v~ch ph6 phat x~ [44]. Gioi h~n xac

dinh tha"pnha"tde'n 0,01 g/t, nhung khong 6n dinh, de)l~p l~i kern. Tu khi co cac

phuong phap phan tich hit$nd~i xua"thit$nthi nhi~u nuoc tren the' giOicling da:bo

phuong phap hoa - quang ph6 nay.

Chl1dng1,' M(Jt so van tie v~ phan rich vimg va platin LUtJnan Tiin sf V(1tly 11

1.2.3.Phuo'ng phap di~n hoa (ECA)

M~u qu~ng voi kh6i lu'Qngdin 5g du'Qcboa tan b~ng cu'ong thuy. Au va Ag

tan trong dung dich du'QCtach b~ng nhl)'a anionit DOWEX AD-1.8. San khi giai

hffpxac dinh ham lu'Qng cua chung b~ng ky thu~t von-ampe boa tan an6t. GiOi

h~n xac dinh tha'p nha't la 0,08g/t. Phu'dng phap dil dung d~ xac dinh ham lu'Qng

Au,Ag trong m~u dia cha't.

Uu di~m cua phu'dng phap la sii'dvng hoa cha't, thie't bi ddn gian. Song do

luQngm~u din nho khong baa dam tinh d£;lidi~n.

1.2.4. Phuo'ng phap chie't -trdc quang (ESA)

NQidung phu'dng phap : m~u qu~ng tU 10 - 20g boa tan b~ng cu'ong thuy.

Au tan trong dung dich du'QCtach ra b~ng cach cho t£;lophilc lien hQp voi mQt

thu6c thii' r6i chie't b~ng mQt dung moi thich hQp. Cu6i cung do ham lu'Qng Au

tren may tr~c quang. Cac thu6c thu va dung moi thu'ong du'Qcdung la: rhodamin

B trong toluen, thu6c thii'PAN trong ru'Quisoamylic... Phu'dng phap du'Qcnghien

CUuva cong b6 trong nhung nam g'an day d~ ap dvng cho phan tich m~u qu~ng

voi lu'Qngmftu can tu 10 - 20g va giOih£;lnphat hi~n tha'p nha't la 0,05 - O,lg/t.

Phu'dng phap nay cling nhu' phu'dng phap di~n hoa chu'a du'Qcap dvng ph6

bie'n.

1.2.5. Phuo'ng phap ha'p th1,1nguyen to'

Bay la mQt trong nhung phu'dng phap phan tich hi~n d£;lico dQ nh£;lyva

chQnlQccao. Tuy thuQcvao tung phong thi nghi~m, phu'dng ti~n va hoa cha't hi~n

co, tinh nang va milc dQ hi~n d£;licua tUng may ha'p thv nguyen tii' ma phu'dng

phap nay co nhi'eu ky thu~t phan tich khac nhau. Cac ky thu~t nay thu'ong t~p

trung chu ye'u (j hai khan tach lam giau va do ph6 xac dinh ham lu'Qng.

aH:fi<H-:-TIJNHI~ .TI-UI VIEN

, T,

000920

Chu(Jng1.. M()t s6 win ae v~ phan rich vang va platin Lu(in an Tiin sf V(it l2 12

Khau tach lam giau ra't da d<;lngtuy thuQc vao hoa cha't, phuong ti~n va

trlnh dQ cua m6i phong thi nghi~m. Co noi tach b~ng cQng k€t telua, tach b~ng

each chi€t voi mQt dung moi hU'uco thich hQP.

Khau do ph6 thuong co 2 cach: do b~ng ky thu~t ngQn hl'a va ky thu~t

khong ngQn hl'a, trong do ky thu~t khong ngQn hia qui trlnh phuc t<;lPbon, gia

thanh cao bon nhu'ng giOi h<;lnxac dinh l<;licao hang chvc va hang tram fan so voi

do b~ng ky thu~t ngQn Ilia.

1.2.5.1. Ky thui;it tach v~mg b~ng telua kim lo~i (Te-F.AAS, Te-GF.AAS)

M~u qu~ng 25g boa tan b~ng cuong thuy. Au tan trong dung dich duQc

tach va lam giau b~ng cQngk€t voi telua. Hoa tan tua b~ng cu'ong thuy, du6i NO3

r6i do ph6 xac dinh ham luQng Au b~ng may ha'p thu nguyen tU'.N€u do ky thu~t

ngQn IU'athi giOi h<;lnxac dinh d€n 0,1 g/t. N€u c'an phan tich ham luQng nhi) bon

thi do ky thu~t khong ngQn Ilia, giOi h<;lnxac dinh d€n 0,020 g/t. [25]

1.2.5.2. Ky thui;it tach b~ng chie't vO'idung moi MIBK (F.AAS- MIBK,

GF.AAS-MIBK)

M~u qu~ng 25g boa tan b~ng h6n hQp 3 axil (HCL + HNO3 + HF) trong

binh teflon. Au trong dung dich duQc chi€t b~ng dung moi MIBK r'oi do ham

lu'Qngcua no b~ng may ha'p thv nguyen tU'[1]. N€u do ky thu~t ngQn lira thi gioi

h<;lnxac dinh la 0,2g/t. Do b~ng ky thu~t ngQn lli'a voi gioi h<;lnxac dinh d€n 0,010

- 0,020g/t.

Phuong phap co de)nh~yva de)chinh xac cao ra't phil hQpvoi m~u qu~ng

chua hiQng IOn th<;lchanh.

1.2.5.3. Ky thui;it tach b~ng chie't vO'i dung moi TBP (F.AAS-TPB, GF.AAS-

TPB)

ChUdng1:}19J~q~~t0 de v~ phdn tich vimg va platin Lul;tn an Tiin sf Vl;ttly 13

Qua trlnh phan tich cua phuong phap gi6ng nhu phuong phap AAS-MIBK

(fiVC1.2.5.2) chi khac thay dung moi chie't MIBK b~ng TBP [I]. Ne'u do lIen

kh6i ngQn Ilia thl gioi h~n xac dinh la O,lg/t. Ne'u yell c'au ham luQng nho hon thl

do ky thu~t khong ngQn Ilia voi giOi h~n xac dinh de'n O,OO5g/t. Phuong phap

phan tich nay chua duQc ph6 bie'n.

1.2.5.4. Ky thu~t tach bAng chie't voi dung moi NB (F.AAS-NB, GF.AAS-NB)

Mau qu~ng 109 boa tan b~ng cuong thuy. Au tan trong dung dich cho lac

dvng voi FeII_phenanthrolin r'oi chie't b~ng dung moi nitrozo benzen. Do ham

hiQngAu b~ng may ha'p th\l nguyen tli. GiOih~n xac dinh ky thu~t ngQn Ilia la

O,lOg/tva khong ngQnIlia la O,Olg/t.

1.2.5.5.Ky thu~t tach bAng chie't voi dung moi E.A (F.AAS-EA)

Mau qu~ng 25g boa tan b~ng cuong thuy. Au boa tan trong dung dich duQc

chie'tb~ng dung moi EA (etyl axetat). Dung moi chie't dem boa tan b~ng cuong

thuy dS chuySn v~ moi truong nuoc. Do ham luQngAu b~ng may ha'p th\l nguyen

tti'ky thu~t ngQn Ilia.

Phuong phap do Trung tam Phan tich va Moi truong Vi~n Cong ngh~ x~

hie'm nghien CUllva cong b6 nam 1998. Do moi chi thvc hi~n lIen kh6i ngQn Ilia

lien gioi h~n phat hi~n chi khoang O,lg/t. Chua co nhi~u mall dia cha't phan tich

b~ngphuong phap nay lien chua du co sd daub gia.

1.2.5.6. Ky thu~t tach bAng chie't vOi dung moi DIBK (TOMAC.DIBK-

F.AAS, TOMAC.DIBK-GF.AAS)?

0 mQt s6 nuoc dil sli dvng phuong phap chie't vang tU dung dich, trvc tie'p

b~ng dung moi DIBK (tuong tv nhu MIBK m\lc 1.2.5.2). Phuong phap co u'udiSm

la h~n che' duQc hi~n tuQng cQng chie't cua mQt s6 kim lo~i n~ng nhung van bi anh

huang nhi~u khi mall chua luQng IOnFe va Cu.[16]

ChUdng1: M()t so' van ae v~phan rich vimg va pia tin LuQnan Tiln sf VQtif 14

Hit$n nay me)t s6 phong thi nghit$m khong dung cach chi€t tnlc ti€p nhu

tren ma di theo huang tach chi€t phlic lien hQp ion trong do thu6c thU'd~ t<:lOphlic

lien hQp la trioctyl amonium clorua (TOMAC) va dung moi chi€t diisobutyl

ketone (DIBK). Ti€p theo do ph6 cua yang tren may h1p th\l nguyen tU'b~ng ky

thu?t ngQn lU'a va khong ngQn lU'a. Mfiu qu~ng voi kh6i luQng 2Sg sau khi filing

d6t (j 600°C boa tan voi HCl r6i b~ng cuang thuy, co du6i bot HNO3. Dung dich

dinhmlic trong blnh 2S0ml voi tinh toan th€ nao d~ n6ng de)HClla 2M va HNO3

khong qua 0,2M. D~ lclng trang, hut SOmlvao phiSu chi€t dung tich 60ml. L1y

vao phSu me)t luQng chinh xac Sml dung moi DIBK co chlia 1% TOMAc. D~y

na:pphSu, lclc chi€t trong 1 phut. Sau khi thao b6 pha nuoc rU'adich chi€t b~ng

SOmldung dich HCl 10%. Lclc d'eu trong 30 gHiy, chuyen pha hU'uco vao 6ng

nghit$md~ do ph6 h1p th\l cua yang tren may h1p th\l nguyen tU'b~ng ky thu~t

ngQnlU'ava khong ngQn lU'agiOi h<:lnxac dinh d€n 0,01 g/t.

1.2.6. Phuong phap nung luy~n - ha'p tht;t nguyen tii' (FA-F.AAS, FA-GF.AAS)

Day la phuong phap ph6i hQp d~ lQi d\lng u'u di~m cua 2 phuong phap:

Giai do<:lnd'au la filing luyt$n con giai do<:lnsau la do tren may h1p th\l nguyen tU'.

Phuong phap chi th\l'c hit$n (j cac phong thi nghit$m vila co 10 filing luyt$n vila co

may h1p th\l nguyen tU'.[29]

Vu di~m cua phuong phap la xac dinh duQc d6ng thai ca Au, Pt, Pd. Gioi

h<:lnxac dinh voi Au khi do ngQn lU'ala O,OSg/tva do khong ngQn lU'ar1t nh<:lYla

O,OOS- O,OSO g/t.

1.2.7. Phuong phap quang ph6 plasma (ICP-AES)

v'e ban ch1t day la phuong phap d\l'a tren nguyen ly phat X<:lnhung khac

voi phuong phap quang ph6 hit$nco la : ngu6n kich thich d~ nguyen tU'hoa khong

phai la ngu6n h6 quang ma Ia ngu6n plasma caD t'an cam ling voi nhit$t de)plasma

ra't caD til 7.000 - 10.000°c. Voi nhit$t de) nay h'au h€t cac nguyen t6 d'eu bi

Chuclng 1: M(Jt s6 van ae v~_ph(tnJich wIng va Elatin Lw?n an Ti€n sf Vt;ltIf 15

nguyentii'boa, cuong dQphat X(;lit bi anh huang cua dung dich n~n ngay ca khi

n5ng dQ HNO3 d€n 1M.

Qui trlnh ti€n h~mhtom dt nhu san: 25g mfiu qua75ng san khi Dung do't a600°C se boa tan b~ng HCl r6i b~ng cuong thuy. Dinh muc blob 250ml, hUt50ml

d6 co du6i HNO3oChuySn v~ moi truong HCl 2M va ti€n hanh cQng k€t vang VaG

ke't tua telua. LQc va boa tan tua Te-Au b~ng cuong thuy r6i ch€ hoa dung dich

doph6 co thS phan tich 10ml voi n6ng dQ HClla 2M va HNO3 duoi 1M. [15]

Phuong phap co gioi h(;lnph<ithi~n duoi la 0,05 g/t con gioi h(;lntren co thS

de'nhang tram g/t ma kh6ng din phai pha loang dung dich do ph6.

1.2.8. Phuong phap kich ho~t neutron (NAA) va phuong phap kich ho~t

neutronhoa phong x~ (R.NAA)

Nguyen t~c chung: khi phong VaGmfiu qu~ng mQtchum h(;ltnotron tu cac

maygia to'ccua 10philo ung h(;ltnhan thl nguyen tii'cua cac nguyen to'chua trong

m~u chuySn thanh nhung ph'an tii' co ho(;lt tinh phong X(;lra't m(;lnh. Ho(;lt dQng

ph6ng X(;lnay ty l~ voi kho'i luQng cua chung trong mfiu va do duQc b~ng cac may

do X(;lchuyen d1;lng.[23,42,43]

Voi ky thu~t NAA chi c'an luQng can mfiu nho O,lg, giOi h(;ln xac dinh toi

O,OOlg/t.Song do luQngmfiu qua nho nen k€t qua phan tich Au kh6ng mang tinh

d(;lidi~n duQC.

Voi ky thu~t R.NAA c'an phai them mQt giai do(;lnhoa hQc dS boa tan, tach

va lam giau Au tu kho'i luQng mfiu khoang 20g. Au tan VaGdung dich dem ha'p

th1;1lennh1;l'aSBW. Lam kh6 nh1;l'ava chi€u x(;llen nh1;l'anay, san do do ho(;ltdQng

ph6ng X(;lcua d6ng vi 198Au. GiOi h(;lnxac dinh O,Olg/t.

1.2.9. Phuong phap trich ly b~ng xianua ( BLEG-BCL)

Mfiu qu~ng co kho'i luQng IOn tu 500g - 10kg dem ngam chi€t trong dung

dich xianua. Au tan trong dung dich duQc tach va lam giau b~ng than ho(;lt tinh,

ChU(fng1..MQt so win ae v~phan rich vang va platin Lu(in an Tiin sf V(it ly 16

kern kim lo~i ho~c mQt dung moi hUllco thich hQp. Bo ham luQng cua no tren

mayha'pth1,lnguyen tti' [24]. Tuy theo kh6i hiQngm~u phan tich ma gidi h~n xac

dinh giao dQng trong khoang 0,001 - 0,010g/t. Co th~ noi day la mQt phuong

phap co dQnh~y caD ga'p vai ch1,lcfan dSn vai tram fan so vdi cac phuong phap

khac va kh~c ph1,lcduQc hi~n tuQng phan b6 khong d6ng nha't cua yang trong

mftu.Tuy nhien phuong phap rung co mQt sO'nhuQc di~m la: khong xac dinh

duQct6ng luQng Au co trong m~u VI xianua chi co th~ boa tan duQc cac h~t yang

tho hay mill dff duQc giai phong khoi cac khming v~t khi gia rang m~u. Do kh6i

luQngm~u ldn nen gia thanh caD ga'p vai fan so vdi cac phuong phap khac.

1.2.10.Phu'dng phap xac dinh yang tren rilY va du'm.rilY

Nhu dff biSt nSu qu~ng yang thuQc lo~i xam tan tho thl theo qui trlnh gia

rang thong thuong va la'y luQng m~u can khoang 25 - 30g la khong d~i di~n va

ke'tqua phan tich ham luQngyang m6i hic mQtkhac.

B~ kh~c ph1,lchi~n tuQng nay, cac nha ph an tich nghien cUu qui trlnh phan

tich tren ray dudi ray [29] vdi kh6i luQng m~u khong phai la 25g ma t6i thiSu Ia

lOOOg(Q). M~u qu~ng sau khi nghi~n dSn co h~t 0,25mm se ray toan bQ tren co

ray O,2mm rho dSn khi nao tren ray chi con l~i mQt kh6i luQng m~u tho Ql ~ 50g.

Luc nay m~u se chia thanh 2 ph'an :

- Ph'an tren ray vdi kh6i luQng QI ~ 50g se chua cac h~t yang ho~c v§:y

v~mgtho khong IQt duQc qua ray 0,20mm. Bern QI phan tich filing luy~n se tinh

duQcham luQng yang tho trong m~u (Q)

- Ph'an dudi ray la Q2 :::0950g chua yang mill va sieu mill -0,20mm. TrQn

d'eula'y 200g/950g nghi~n tiSp dSn -O,O74mmr6i la'y m~u can 25g d~ phan tich

Au b~ng phuong phap ha'p th1,lnguyen tti' hay quang ph6 ICP. Ham luQng yang

trongm~u se la t6ng cua ham luQngyang tren ray va ham luQngyang dudi ray.

Chli(Jng1: M(}t so'van de v~phan tfch vang va platin LuQn an Tien sf VQt ly 17

Thtfc ra day khong phai la phuong phap mdi ma la mQt qui trlnh t6ng hQp

cua cac phuong phap dii co, dBng thai co kern theo mQtgiai do~n xU'ly mall d~c

bi~td~ thau tom duQcttt ca cac h~t yang tho va yang mill chua trong kh6i luQng

mh phan tich lkg (ho~c ldn bon) nen ke't qua se mang tinh d~i di~n bon va chinh

xac bon. Tom t.1tcac phuong phap phan tich yang dang duQc ap dvng duQc cho

trong phV Ivc 1.

1.3.sTj KHONG ON DfNH CUA KET QUA PHAN TicH VANG

1.3.1.Stj khong 6n djnh cua ke't qua phan tich yang

Nhung nam g'an day, cac Lien doan Dia chtt cung nhu cac Gongty khoang

san a trung uong va dia phuong co nhi~u mall gU'iphan tich xac dinh ham luQng

v~mg.Nhi~u phong thi nghi~m a cac noi,. k~ ca cac phong thi nghi~m khong

chuyenv~ mall dia chtt dii thong baa cho khach hang ho~c gidi thi~u lIen cac t~p

chikhoa hQcv~ kha nang phan tich yang a don vi minh. Hang ngan ke't qua phan

tich dii duQCsU'dvng vao cac mvc dich l~p d~ an xin ma nhi~m vv Hm kie'm tham

do v~mg ho~c danh gia tru luQng va chtt luQng cac vling mo, cac di~m qu~ng

chila yang a Vi~t Nam.

Songco mQtso'nh~nxet chungla: ke'tqua phan tich ham luQngyang trong

mQts6truang hQp khong 6n dinh. Cling mQt mall qu~ng yang gU'iphan tich nhi~u

ndi cho cac ke't qua khac nhau, k~ ca cac mall duQc phan tich a nudc ngoai. Dung

phuong di~n qUail ly cila Nha nudc, de'n nay van chua co mQt co quail nao duQc

giao lam trQngtai d~ khing dinh mUGdQdung sai cila cac ke't qua phan tich ham

lu<,jngyang giua cac phong thi nghi~m [13].

MQt so' ke't qua phan tich l~p ham luQng yang duQc trich tu lo~t mall phan

tich nghien CUlldQ khong 6n dinh 39M/98 va 40M/98 cila Trung tam Phan tich

Thinghi~m Lien doan Ban dBDia chtt Mi~n Nam duQccho lIen bang 1.1.

Chlidng1: M(jt so win de v~ phan rich wlng va platin Lu~n an Titn sf V~t ly 18

Bang 1.1: Ke't qua phan tich l~p ham 1u'Q'ngyang (j m{)t s6 miiu yang co xam

hin tho biing phu'o'ngphap ha'p thl,l nguyen til' [41]

£>Ql~ch chu~n cua mQt miu thli j la Sj:

n 1 n 2

~)Xl) - - LX;)n .Sj = n -1

£>Ql~ch chu~n tu'dng dO'icua mQt miu thli j la RSDj:

S.RSD % = ~* 100} -

x.}

voi: Xij: tri sO'do l'an i cua miu j

n : sO'1'ando

Xj : sO'do trung blnh cua miu j

Ten miuHam lu'Qngyang (g/t)

Sttfan 1 l'an 2 l'an 3 l'an4 l'an 5

1 RL-52 1.36 29.84 1.38 20.24 5.68

2 5B-28 28.79 12.18 22.85 47.22 16.65

3 5E-2 0.14 9.30 0.10 0.65 2.34

4 5E-8 63.95 54.82 18.75 122.01 47.65

5 9B3-2 0.76 0.88 1.35 0.54 1.79

6 5C-14 0.36 <0.10 0.20 1.56 4.54

7 HMR -71/2 8.5 0.42 0.72 1.65 3.54

8 MR-1055/2 0.4 0.12 <0.10 1.02 0.56

9 MR-488 1.8 1.5 1.3 0.9 2.2

10 MR-71/5 0.2 4.0 4.3 0.2 0.41

r Chudng1.jdi)t sf)'van de v~phan rich vang va piatinLugn an Tiln sf Vgt iy 19

DQ l<%chchu§:n tuong d6i cua tung m§:u d~u vuQt rc1t xa dQ l<%chchu§:n

tu'dng d6i cho phep theo qui dinh xii'ly [4], ki@mtra m§:u dia chc1tva khoang san

rAncua nganh dia chc1t(bang 1.2)

Bang 1.2: Sj, RSDj, va RSDj tho phep

Khi g~p nhung m§:uco yang xam tan tho sl! khong 6n dinh cua ke't qua

dlllg tang cao. R5 rang c'an phai co mQtphuong phap phan tich kha thi d@kh~c

phl;lChi<%ntuQng nay. Phuong phap phan tich tren ray duoi ray dil duQc ap dl;lng

[25,30] d@giai quye't vc1nd~ nay.

1.3.2.Phep phan tlch phu'dng sai

Co th@thc1ysl! khong 6n dinh cua phep phan tich yang la do ye'u to' ng§:u

nhien va ye'u to' h<%th6ng. Phuong sai t6ng So2 b~ng t6ng cua phuong sai la'y m§:u

Stt Ten m§:u Sj RSD. RSDj cho phepJ

1 RL-52 12.76 109.09 20

2 5B-28 13.65 53.45 12

3 5E-2 3.91 155.85 30

4 5E-8 37.85 61.61 9

5 9B3-2 0.50 47.22 30

6 5C-14 1.88 138.80 30

7 HMR -71/2 1.26 87.82 30

8 MR-1055/2 0.38 85.82 30

9 MR-488 0.49 32.01 30

10 MR-71/5 2.13 116.88 30

ChUdng 1.. MQt so van de v~ phan rich vang va platin Lu(m an Tien sf V(lt Ii 20

s/ va phuong sai qui trlnh phan tich sa2,tuan theo lu~t cQng tinh cua phuong sai2 2 2 C

""h ? d '

h.' d ? 3 h . 2 2 2 v.,.. d '

h.'

So =Sa + Ss. an p al an gla uQc ca p uong sat So , Ss , Sa. l~C an gla

c'and1!avao chuffn th6ng ke Fisher. Phep ANOV A la cong Cl;lth6ng ke dS th1!c

hi~nnhi~m Vl;lnay [19]

1.3.2.1. Ynghia cua cae phIidngsai

Ye'u to'ng§u nhien la ye'u t6t6 hQpcua ra't nhi'eu lac dQngng§u nhien khac

nhauma thong co lac dQng nao chie'm u'u the'. Bay la ye'u to' Juan Juan co m~t,

gayra mQtthanh ph'an e6dinh trang ba't ell mQtphuong sai t6ng nao. Thanh ph'an

nay cling co thS gQi la phuong sai tai hi~n. Tuy nhien, tuy thuQc vao tlnh hu6ng

thlfcnghi~m, dS nha'n m~nh di'eu ki~n Cl;lthS cua s1!tai hi~n nhu trang bfli loan

phan tich phuong sai dS phat hi~n tinh thong d'ong nha't cua v~t li~u, phuong sai

taihi~n duQcgQila phuong sai qui trlnh phan tich hay phuong sai NQibQcac m§u

PIN, ky hi~u la Sa2 hay s/. Co thS hiSu day la phuong sai m§u d cong do~n thi

nghi~ml~p l~i sau chat, no dff duQc tach ra dQc l~p, thong bi pha trQn voi cac

phuong sai m§u khae.

Ye'u to' h~ th6ng la ye'u to' co nguyen nhan ra rang va co thS phat hi~n

ngu'ong6c phat sinh ne'u no gay ra lac dQng vUQttrQi ye'u to' ng§u nhien. Trang

bai loan phan tich Yang, ye'u to' h~ th6ng la tinh thong d'ong nha't cua m§u lam

phat sinh thanh ph'an phuong sai la'ym§u, ky hi~u la s/. Phuong sai la'y m§u phat

sinh tu ba't Cllye'u to'h~ th6ng nao luon luon bi pha trQnvoi phuong sai m§u phat

sinh tu ye'u to' ng§u nhien. Theo thu~t ngii' cua phep phan tich phuong sai thl

phuong sai m§u pha trQnnay co ten gQirieng la phuong sai Giii'a cac m§u PTN,

ky hi~u la SI2..

Chuang 1: MQt sff van de v~ phan rich vcmg vCl_platin Lu(in an Tiin Sl V(it ly 21

1.3.2.2.Mo hinh tht1c nghi~m

f)~ ph an tich phuong sai, thi nghi~m dU<;1Cho~ch d!nh nhu sau (hlnh 1.2):

M~u 1 M~u2 M~u 3 M~u4

xI

xI

x11 12 13

X21

X22

X23

X24

X25

X31

X32

X33

x:w

X35

X44

X45

Cac gia tr! do du<;1cky hi~u Ia Xji; yoi j = 1,..., k; i = 1,...,n

IDnh 1.2: Mo hinh tht1c nghi~m

1.3.2.3. Cong thuc tinh

T'h

'h

. Z ZIII cac p uong sa! Sl ,sz

Phuong sai Iffy m~u du<;1ctinh d\la theo thu~t toan Anoya:Z Z Z

S1 =Sz + nss

Tli d6 tinh dU<;1Cphuong sai t6ng

Z Z ZSo =Sa + Ss

D~t:

k n

SSI= LLX~ij=l i=l

k n

ssz = (l/n)ICIXjJ2j=l i=l

k n

SS3 = (1/kn)CIIXjJj=l i=l

Tinh dU<;1Ccac phuong sai: s/ =(SSl- ssz)/k(n-l)

s/ =(SS2- ss3)/(k-l)

Soz =(SSl-Ss3)/(kn-l)

ChIiO'ng1: MQt s5 van ae ve phan rich vang va platin Luq.n an Titn sf vq.t ly 22

D~ quye't dinh xem Sl co IOnhon dang k~ voi S2hay khong, ta so sanh gia

triFTNvOigia tri FLTtra trong bang thO'ngke. Trang do sli'dl,mgchu~n F tinh gia

tri FTN=S12/S/ (j day chQn gia tri FLTling vOi xac sua't mQt phia P=O.95. Ne'u

FTN>FLTthl sllon hon dang k~ S2, tuc la co sai bi~t dang k~ giua Sl va S2.NguQC

l~i, ne'u FTN<FLTthl giUa chung khong co sai bi~t dang k~.

1.4.GIOIH~N PHAT HI~N vA Y NGHIA THTjCTn~N

Gioi h:~lllphat hi~n la thong sO'co y nghla thvc ti~n ra't IOn. Thuong nguoi

ta phan bi~t hai gioi h~n phat hi~n khac nhau nhu sail: gioi h~n phat hi~n do thie't

bi do d~c, d day Ia may ha'p thv nguyen tli' va giOi h~n phat hi~n cua phuong phap

phan tich.

1.4.1. GiO'ih~n phat hi~n do thie't bi do

Gioi h~n phat hi~n la'mQt mesurand ra't quail trQng va duQCphan bi~t theo

2lo~i LoD va LoQ. LoD dung cho phan tich ban dinh luQng va LoQ la giOi h~n

phat hi~n dinh luQng dung cho phan tich dinh luQng. GiOi h~n phat hi~n chili tac

dQngra't IOnbdi thanh ph'an n'en nen thuong khong tuan theo phan bO'chu~n ho~c

ba't cll'mQt phan bO'ly thuye't naG. Duong nhien tin hi~u phat hi~n XPHva tin hi~u

dinh luQng XDLphai IOn hon tin hi~u n'en XNEN.V~y phai IOnhon co baa nhieu d~

sl1phat hi~n co xac sua't tin c~y caD. [19]

Gia thli' co mQt d~i luQng ng~u nhien ma ky vQng la ~ va dQ l~ch chu~n

t6ng th~ la cr. Til' do Tchbytchev l~p ra mQt d~i luQng ng~u nhien d~n xua't, ky

hi~u la hTRE, tinh theo cong thuc sail:

hTRE = I (X-~)/cr I

Tchbytchev dii chung minh ding khi hTRE> 1 thl xac sua't tin c~y d~ cho dQ

l~ch chu~n tuy~t dO'i I X-~ I nho hon ho~c b~ng d~i luQnghcr phai IOnhon gia tri

(l-I/hTRE2),ba't lu~n d~i luQng ng~u nhien X co phan bO'naG. Co th~ bi~u di~n

phat bi~u cua Tchbytchev duoi d~ng mQt ba't ding thuc:

ChUdng1: Mf)t srI van de v~ phan tich vang va platin Lu(in an Titn sf V(it ly 23

P{ I x-Ill::; hTREcr} > (1-1/hTRE2)

Vdi bc1td~ng thilc tren, ta chi c'an cho tru'ck gia tfi hTRE la dff co thS dV

dmin xac suc1tP ma khang c'an bitt d~i Iu'Qng ng~u nhien X tuan theo phan bO'

nao.

DO'i vdi XPH va X£)Lv-e nguyen t~c ta co thS ap dvng bc1t d~ng thilc

Tchbytchev dS dv doan xac suc1ttin c~y ling vdi khoclng tin c~y cho tru'dc. Theo

tieu chuffn cua khO'iEC ngu'oi ta chQn hTRE=3 khi tinh XPH va chQn hTRE= 10 khi

HnhX£)L:

XPH =XNEN + 3crNEN

X£)L = XNEN + 10crNEN

Vi~c Iva chQn tren tu'dng ling vdi xac suc1t sail:

ChQn hTRE=3.0 thi it ra phcli co P > (1-1/32) =0.888 ~ 90%

ChQn hTRE=10 thi it ra phclico P > (1-1/102)= 99%.

Thu'ong gidi h~n ph:it hi~n la cd sa dS nha phan tich dinh ra phu'dng phap

pha m~u co lien quail trvc titp dtn trQng Iu'Qngdin ban d'au va thS tich dinh milc.

1.4.2. GiOi h~n phat hi~n ciia phtidng phap phan tlch

Day 1a gidi h~n phat hi~n nguy_en to'thvc tt trong di-eu ki~n phu'dng phap

dang stl' dvng. Gidi h~n ph:it hi~n nay thay d6i tuy trQng Iu'Qngcan ban d'au va thS

tich dinh milc.

PhV 1vc 1 thO'ng ke tom t~t cac phu'dng phap phan tich yang va gidi h~n

phat hi~n cua cac phu'dng phap phan tich.

1.4.3. Ynghla thtfc ti~n ciia gioi h~n phat hi~n ciia phtidng phap phan tlch

Khang thS nghien CUumQt nguyen to' nao do khi ma ham Iu'Qngcua no

luau thc1phdn gidi h~n ph:it hi~n cua phu'dng phap dang stl'dvng. Di-eunay d~t ra

mQt vc1nd-echo nha nghien cUu, do la phcli chu dQng tim dung phu'dng phap phan

tich dS gtl'i m~u. R6 rang khang thS gtl'i m~u phan tich yang b~ng phu'dng phap

ChurJng1: M()t srI van de v~phan tich vang va platin LuQn an Titn sf VQt ly 24

nung 1uyt$ndS Hm kie"m thilm do Yang. Va cfing khong c'an thie"t ph~h sa d1;lng

phuong phap phan tich yang b~ng 10 graphite dS cling dip cac s6 1it$ucho khai

thac mo. Ynghla th1.fctiSn cua gioi hC;tnphat hit$n 1a qua ra: no co tac d1;lngchi ra,

phuongphap c'an phai sa d1;lngdS phan tich dS dC;ttdU<;1cbai toan cua th1.fctiSn

nghienCUllva san xutt. Theo th1.fcte"va kinh nghit$m cua cac nha nghien cUu

Yang,thuong phai chQn phuong phap co gioi hC;tnphat hit$n t6t hon 10 1'annguong

quail tam cua mlnh [81]. Co nghla 1a ne"u d~ tai nghien CUllquail tam de"n ham

lU<;5ngyang tu Ippm, thl phai chQn phuong phap phan tich co giOi hC;tnphat hit$n

0.1ppm.

Trang khai thac ma Yang, (j Dc nguoi ta quail tam tu ham 1U<;1ng3 ppm,

ngay nay voi ky thu~t tien tie"nthong s6 nay da giam con 0.3ppm, (j Vit$tNam

chua co s6lit$u cong b6, dan thuong khai thac vo tQi VC;t(j cac ham 1U<;1ngrtt cao

hang ch1;lcppm. Day Ia s1.fphung phi rtt IOn [5].

1.4.4. Cae giOi h~n phat hi~n yang du'Q'esii' dQ.ng

Trang thilm do Hm kie"m khoang san, cac gia tri tu 0.1ppm dU<;1cghi nh~n.

Trang nghien cUu dia hoa Yang, ham 1U<;1ngyang du<;1cquail tam tu co ppb. Trang

cae d~ an v~ yang Lam D6ng do cong ty Kim Resources, d~ an Honmo do cong

ty Pacific Basin Graup d~u cua Dc th1.fchit$nphan tich (j cac phong thi nghit$m(j

Dc cho thty hQ quail tam de"nt~n ham 1U<;1ngppt (cac m~u phan tich cho ke"tqua

theo don vi ppt). Cong ty Chernex cua Canada cfingquail tam t~n ham 1u<;1ngco

1O0ppt.DS dC;ttdu<;1cke"tqua nghien CUucac d~ an yang nay, nguoi ta c'an phai co

phuong phap co gioi hC;tnphat hit$n co ppt.

Nhu v~y, co thS kh~ng dinh vit$cnghien cUu phuong phap cai thit$n giOi

hC;tnphat hit$n yang mang mQt y nghla khoa hQC va th1.fctiSn.

ChUdng 1: M9t so van de ve phan tich)JqYlg va platin Lu()n an Tien sf V()t ly 25

1.5.NGUYEN TO PLATIN

1.5.1.Nguyen to' platin

Platin va cac nguyen to' nhom platin co lien quail dia hoa voi da't da sieu

bazicva bazic. Chungthuong co trong cac m~u thien nhien rieng bi~t nhu yang

nguyensinh, mQtvai qu~ng sulfit nhu pyrotin, penlandit, pyrit co chlia niken...va

trongcae san ph§:mky thu~t. [3,45]

Platin tVsinh co trong cae da sieu bazic va d6i khi trong da bazic. Platin tV

sinhcon co trorig sa khoang va trong doi oxi boa. Khoang v~t platin ngoai h<;1p

ph'an IOn nha't chlia 80-98% Pt con chlia Pd, Fe, Ir, Cs, Cu, Ni, Rh, Au ke't tinh

trong ~~ l~p phuong, t~p h<;1pd"mg xam tan, yay, ke't h~ch, mall tdng b~c, anh

kim lo~i, dQ cling 4, ty trQng 21.5, nhi~t dQ Dong chay 1769°c. Cac khoang v~t

khac la cuperit (PtS) voi 85% Pt, sperilit (PtAs2) voi 56.5% Pt, moncheit (PtTe2)

voi 43.3% Pt. Ham IU<;1ngtrung blnh cua platin trong vo trai da't theo Clark va

Washington la n.l0.7% va trong cac lo~i da nhu sail: trong thien th~ch 2.10-4%,

trong da sieu bazic 2.10'5%, trong da bazic 1.10.5%.

1.5.2. Cae phuo'ng phap xae tqnh cae nguyen to' platin

Cac phuong phap xac dinh cac nguyen to' platin dU<;1Ctom ttlt duoi day:

- Cac phuong phap boa: nguyen to' phan tich Pt thuong dU<;1ct~o thanh

phucco mall. Sa dvng phuong phap so mall d cac buoc song nha't dinh. Vi dV,t~o

phuc Pt mall yang trong m6i truong HCI voi SuCh, ion cloroplatin ha'p thv buoc

song 403nm, ho~c ha'p thv buoc song 398nm trong acetatamine. DQ phat hi~n

thuong d co l/lg/ml. Cling co th~ sa dvng phuong phap clJ'cph6 d~ xac dinh cac

nguyen to' nay d dQphat hi~n tuong tlJ'nhu tIeD. Noi chung cac phuong phap hoa

c6 di~n co qui trlnh phlic t~p va kh6ng thich hQpvoi phan tich vi IU<;1ng.

- Phuong phap quang ph6 phat x~: M~u phan tich trQn theo ti l~ 1:3 voi

cha'td~m g'om 75% bQtthan va 25% SrCO3co them 0.05% ruteni ho~c 0.03% Zr.

Chztclng1.. M()t s5 win tie v~ phan rich wIng va platin Lu~n an Titn sf V~t ly 26

Zircon duQc dung lam lieu chuffn trong. Gioi h(;ln phcH hit%ntheo phuong phap

dinh luQng nay la Pt 10ppm [79]

- Phuong phap ha'p th\1 nguyen tU':Phuong phap ha'p th\1 nguyen tU'truy'en

th6ng kh6ng c6 u'u tht trong ph an tich nguyen to' nay do bdi kh6 khan trong khan

phan buy m§:u thanh dung dich d~ do. Mu6n h(;lgiam dQ ba't 6n thudng phai thl!c

hi~n cac c6ng do(;ln xU'ly h6a hQc phuc t(;lp.DQ phat hit%ncac nguyen to' nay do

theo ky thu~t ngQn IU'aco 1.2 mg/I. C6 th~ ktt hQp voi lam giau b~ng filing chay,

du'ah~t kim duQc lam giau v'e d(;lng dung dich va do ha'p th\1 nguyen tU'.Gioi h(;ln

phathit%ncho m§:utrong trudng hQpnay co ppb.

- Phuong phap quang ph6 plasma: Nhd ngu'on plasma nhit%tdQ cao, v~ch

phatx~ c6 nh~y bon so voi phuong phap ha'p th\1nguyen tU'.DQnh(;lyphat x~ cho

Pt la 0.2 mg/l [76].

- Phuong phap kich ho~t neutron: Day la phuong phap phan tich kha nhanh

va reoDQphat hit%nla Ippm. Tuy nhien, trQngluQngm§:udem phan tich kha nho

co Ig nen ktt qua mang tinh d(;li dit%nkh6ng cao. Phuong phap phan tich kich

ho~t neutron don thu'an thudng kh6ng phat hit%nduQc cac nguyen to' nay do n'en

caDche la'p cac dinh nang luQng hoi:ic gay ra sl! ch~p dinh d cac muc nang luQng

g'an trung nhau duOi muc phan giai cua detector. D~ lam tang dQ nh(;ly, ngudi ta

co th~ ap d\1ng cac thu thu~t tach h6a hQCtrong xU'ly m§:u truoc va san khi chitu

x~ va duQCgQi la kich ho~t h6a ph6ng X(;l.DQ phcHhit%nPt theo ky thu~t nay la

lppb [21,22]

C6 th~ nh~n xet r~ng, cac nguyen to' platin dti duQc phat hit%ntli' ra't Ian.

Tuy nhien cac ky thu~t phan tich vi luQng chung con gi:iPnhi'eu kh6 khan cho dtn

nay do bdi sl! phan tan cua chung trong tl! nhien, dQ phcH hit%ncua phuong phap

rhein tich chua dap ung duQc, vit%cboa tan m§:u thanh dung dich d~ do kha phuc

t~p va trQng luQng phan tich c6 giOi h(;lnkhitn tinh d~i dit%nkh6ng cao.