Determination of Traces of Metals in Industrial Wastes

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PU R D U E UNIVERSITY

T H IS IS TO C ER T IFY T H A T T H E T H E S IS P R E P A R E D U N D E R MY S U P E R V IS IO N

PH IL IP GUERNSEY BUTTS

BY

E N T IT L E D

DETHRMTTfAfpTON OF TRACES OF 1.ÎETALS IN

INDUSTRIAL

WASTES

C O M P L IE S W ITH T H E U N IV E R S IT Y R E G U L A T IO N S O N G R A D U A T IO N T H E S E S

A N D IS A P P R O V E D B Y M E A S F U L F IL L IN G T H IS P A R T O F T H E R E Q U IR E M E N T S

FOR THE DEG REE OF

Ph.D.

P r o f e sso r in C h a r g e o f T h e s is

H ea d o f S chool, o r D epartm ent

vT/

TO T H E L IB R A R IA N :---T H IS T H E S IS I S N O T TO B E R E G A R D E D A S C O N F ID E N T IA L .

P R O F E SS OH XX CH ARG E

G R A D * S C H O O L F O R M fl—3 - 4 9 —1M

DETERMINATION OF TRACES OF METAIS IN INDUSTRIAL WASTES A T h e s is S u b m itte d t o t h e F a c u l t y of P u rd u e U n i v e r s i ty by P h ilip

G u e rn se y B u t ts

I n P a r t i a l F u lf illm e n t o f th e R e q u ir e m e n t s f o r t h e D e g re e of D o c to r o f P h i l o s o p h y J u n e , 1950

ProQuest Number: 27712238

All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is d e p e n d e n t upon the quality of the copy subm itted. In the unlikely e v e n t that the a u thor did not send a c o m p le te m anuscript and there are missing pages, these will be noted. Also, if m aterial had to be rem oved, a n o te will ind ica te the deletion.

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ACKNOWLEDGMENT

T he a u t h o r d e s i r e s t o e x p r e s s h i s s i n c e r e a p p r e c i a ­ t i o n o f t h e i n t e r e s t a n d a s s i s t a n c e o f P r o f e s s o r M. G> M e llo n t h r o u g h o u t t h i s w o r k .

M r. A . R . G a h l e r m ade n u ­

m e ro u s h e l p f u l c o n t r i b u t i o n s i n t h e p l a n n i n g o f e x p e r i ­ m e n t a l w o rk .

Many s u g g e s t i o n s w e re a l s o

c o n trib u te d by

D r. W. D. H a t f i e l d , C h a irm a n o f t h e S t a n d a r d M e th o d s C o m m itte e o f t h e F e d e r a t i o n o f S ew age W orks A s s o c i a t i o n s , w h ic h a d m i n i s t e r e d t h i s p r o j e c t i n c o o p e r a t i o n w i t h t h e P u rd u e R e s e a rc h F o u n d a tio n .

F i n a n c i a l s u p p o r t w as p r o ­

v id e d by a g r a n t fro m th e N a tio n a l I n s t i t u t e XJ. S . P u b l i c H e a l t h S e r v i c e .

o f H e a lth ,

TABLE OF CONTENTS Page ABSTRACT............................................................................................................. PART I

i

COLORIMETRIC DETERMINATION OF METALS IN INDUSTRIAL WASTES.................................................................. I n t r o d u c t i o n ...............................................................................

1

P r e p a r a t i o n o f W a te r S a m p le s f o r A n a l y s i s . . .

4

R e m a rk s o n C o l o r i m e t r i c M e th o d s f o r M e t a l s . .

14

C o lo r im e tr ic D e te rm in a tio n

o f C o p p e r ................

17

C o lo r im e tr ic D e te rm in a tio n

o f C hrom ium

29

C o lo r im e tr ic D e te rm in a tio n

o f I r o n .....................

43

C o lo r im e tr ic D e te rm in a tio n

of L ead.

50

C o lo r im e tr ic D e te rm in a tio n

o f Z i n c ...............

........

60

S t a t i s t i c a l A n a l y s i s o f C o l o r i m e t r i c M e th o d s

73

A n a l y s i s o f S y n t h e t i c W a ste S a m p le s .....................

75

Q u a l i t a t i v e T e s t s f o r M e t a l s ......................

90

PART I I POLAROCRAPHIC DETERMINATION OF METALS IN INDUSTRIAL WASTES.................................................................. I n t r o d u c t i o h .........................................................

95

C o m p a ris o n o f C o l o r i m e t r i c a n d P o l a r o g r a p h i c T e c h n i q u e s ...................................................................................

95

P r i n c i p l e s and T e c h n iq u e .

97

A p p a ra tu s .

.....................

............................................................................ 102

P o la r o g r a p h ic D e te rm in a tio n o f C opper an d I r o n .........................

103

P o l a r o g r a p h i c D e t e r m i n a t i o n o f C hrom ium

105

P o l a r o g r a p h i c D e t e r m i n a t i o n o f C adm ium , N i c k e l a n d Z i n c ...................

106

P ro c e d u re f o r th e P o la ro g ra p h ic A n a ly s is o f I n d u s t r i a l W a s t e s ........................................................

110

LITERATURE CITED......................................................................................

126

VITA

L IS T OF TABLES T a b le I

Page C o n c e n tr a tio n o f M e ta ls by I o n E xchange

7

o n a Colum n o f Domex 50 II

C o lo r im e tr ic D e te rm in a tio n o f C o p p e r ...

24

III

S ta b ility

32

o f C h r o m iu m - D ip h e n y lc a r b a z id e

C o l o r S y s te m IV

E f f e c t o f I r o n on th e I n t e n s i t y o f th e .

33

C h r o m iu m - D ip h e n y lc a r b a z id e C o l o r S y s te m i n HC104 V

D e t e r m i n a t i o n o f C hrom ium ...................................

38

VI

C o lo r im e tr ic D e te rm in a tio n o f I r o n . . . . .

47

V II

C o lo r im e tr ic D e te rm in a tio n o f L e a d . . . . .

V III

M a sk in g o f C o m p le x a tio n o f V a r i o u s

5 3 - 54 64

M e ta ls a n d D ith iz o n e IX

C o lo r im e tr ic D e te rm in a tio n o f Z in c

66

X

C o m p o s itio n o f S a m p le s f o r S t a t i s t i c a l .

76

S tu d y XI

S t a t i s t i c a l S tu d y o f th e D e te r m in a tio n .

77

o f C hrom ium X II

S t a t i s t i c a l S tu d y o f t h e D e t e r m i n a t i o n .

78

o f C opper X III

S t a t i s t i c a l S tu d y o f t h e D e t e r m i n a t i o n .

79

o f Iro n XIV

S t a t i s t i c a l S tu d y o f t h e D e te r m in a tio n o f L ead

81

XV

S t a t i s t i c a l S tu d y o f t h e D e t e r m i n a t i o n

83

o f Z in c XVI

A c c u ra c y a n d P r e c i s io n o f C o lo r im e tr ic

85

M e th o d s f o r M e t a l s X V II-X X

D e te r m in a tio n o f M e ta ls i n S y n th e tic ,*

86- 89

W a s te S a m p le s XXI

H a lf-W a v e P o t e n t i a l s o f M e t a l s i n

99

V a rio u s S u p p o r tin g E l e c t r o l y t e s X X II

D e t e r m i n a t i o n o f Z in c i n 1 M N H ^ - .. . • ♦

107

0 . 1 M NH4N03 X X III

P o la r o g r a p h ic D e te rm in a tio n o f M e ta ls .

1 1 0 -1 1 3

XXIV

P o la r o g r a p h ic D e te r m in a tio n o f M e ta ls

1 1 4 -1 1 9

i n S y n t h e t i c W a ste S a m p le s

L IS T OF FIGURES F o llo w s Page

F ig u re 1*

A p p a r a t u s f o r I o n E x c h a n g e .........................................

2.

S e p a r a t i o n C h a r t f o r P r e l i m i n a r y T r e a tm e n t P r o c e d u r e . .................................................................................

3.

11

S p e c t r o p h o o m e t r i c C u rv e s f o r C u p r i c b i s (2 - h y d r o x y e t h y l ) d i t h i o c a r h a m a t e C om plex

4.

7

19

C o m p a ris o n o f C u rv e s f o r C u p r i c - D i e t h y l d i th io c a rb a m a te and C u p ric -b is (2 -h y d ro x y e t h y l ) d i t h i o c a r h a m a te C o m p le x e s ..........................

5.

A b s o rb a n c y -C o n e e n tra tio n C u rv e s f o r C u p r ic b i s ( 2 - h y d r o x y e t h y l ) d i t h i o c a r h a m a t e C o m p lex

6*

30

A b s o r b a n c y - C o n c e n t r a t i o n C u rv e s f o r C hrom ium D i p h e n y l c a r b a z i d e S y s t e m .

8.

.............

103

P o l a r o g r a m o f C h ro rn ate i n 1 M NaOH S a t u r a t e d w i t h C u (0 H )g ...................................................

10.

34

P o l a r o g r a m o f a M ix tu r e o f C o p p e r and I r o n i n 0 . 5 M HC104 .......................................................................

9.

23

A b s o r b a n c y - C o n c e n t r a t i o n C u rv e f o r C h ro m a te i n NaOH...................................................................

7*

20

P o l a r o g r a m o f Cadm ium , N i c k e l , a n d Z in c

105

in

1 M NH40 H -0 • 2 M S o d iu m P o t a s s i u m T a r t r a t e . .

109

DETERMINATION OF TRACES OF METALS IN INDUSTRIAL WASTES P . G. B u t t s w i t h M. G. M e llo n

AN ABSTRACT

P o llu tio n o f s u rfa c e w a te rs a s a r e s u l t o f th e d is ­ c h a rg e o f m e ta l- b e a r in g w a s te s fro m e l e c t r o p l a t i n g p l a n t s a n d o t h e r m e t a l p r o c e s s i n g i n d u s t r i e s h a s becom e a t r o u b l e ­ som e p r o b le m t o p u b l i c h e a l t h a u t h o r i t i e s i n m any a r e a s . I n v e s t i g a t i o n s o f t h e p r o b le m h a v e g e n e r a l l y b e e n h a n d i ­ c a p p e d b y a l a c k o f s a t i s f a c t o r y a n a l y t i c a l m e th o d s f o r d e te rm in in g th e h eav y m e ta ls r e s p o n s ib le f o r p o l l u t i o n . A t t e m p t s t o a p p l y e x i s t i n g c o l o r i m e t r i c m e th o d s f o r

su ch

i o n s a s c h ro m iu m , c o p p e r , i r o n , l e a d , a n d z i n c i n w a t e r ( 1) h av e f a i l e d

i n m any c a s e s ;

due t o th e f a c t th e s e

m e th o d s a r e u s u a l l y s u b j e c t t o i n t e r f e r e n c e b y e v e n m o d e r a te c o n c e n tra tio n s o f o th e r h eav y m e ta ls , and i t

is n o t un­

common t o f i n d s e v e r a l s u c h c o n t a m i n a n t s p r e s e n t i n a p p r e ­ c i a b l e c o n c e n t r a t i o n i n a s i n g l e s a m p le o f w a t e r . R i e h l (1 6 ) h a s d i s c u s s e d t h i s p r o b le m i n c o n n e c t i o n w i t h a s t u d y o f t h e i n h i b i t i n g e f f e c t o f t o x i c m e t a l s i n se w a g e d i g e s t i o n . He w as f o r c e d t o e m p lo y s e v e r a l m o d i f i e d p r o c e d u r e s f o r e a c h m e ta l t o

be d e te r m in e d , th e c h o ic e o f th e p r o p e r p ro c e d u re

b e in g d e p e n d e n t upon th e c o n c e n tr a ti o n o f t h e d e s i r e d co n ­ s t i t u e n t and th e n a tu r e o f th e i n t e r f e r i n g io n s p r e s e n t .

il

T he a p p a r e n t n e e d f o r v e r s a t i l e c o l o r i m e t r i c p r o c e d u r e s a p p l i c a b l e i n th e p r e s e n c e o f an y l i k e l y c o m b in a tio n o f i n t e r f e r i n g i o n s t h a t m ay b e e n c o u n t e r e d i n s a m p le s o f se w a g e o r i n d u s t r i a l w a s t e s h a s p r o m p te d t h e i n v e s t i g a ­ t i o n o f s u c h m e th o d s f o r s e v e r a l o f t h e m ore i m p o r t a n t i n d u s t r i a l m e t a l s . T h i s p a p e r p r e s e n t s m e th o d s f o r c h ro m iu m , c o p p e r, ir o n , le a d and z in c . I n v i e w o f t h e d i v e r s e n a t u r e o f s a m p le s t o w h ic h t h e s e m e th o d s m ig h t u l t i m a t e l y b e a p p l i e d , t h e f o l l o w i n g r e q u i r e m e n t s w e re c o n s i d e r e d t o b e e s s e n t i a l t o a s a t i s ­ f a c t o r y s o l u t i o n o f t h e p r o b le m : 1#

B a c h m e th o d s h o u l d p e r m i t t h e a c c u r a t e

d e te rm in a tio n

o f t h e d e s i r e d m e t a l a t a n y c o n c e n t r a t i o n down t o 0 . 1 p . p . m . , a n d p r e f e r a b l y t o 0 .0 5 p . p . m . o r l e s s . 2.

T he

m e th o d s s h o u l d b e a p p l i c a b l e i n t h e

p re se n c e o f

an y o f th e fo llo w in g c a tio n s a t c o n c e n tr a tio n s a t l e a s t 200 t i m e s t h a t o f t h e d e s i r e d

c o n s titu e n t:

Na+ , K * , Cat t , c a + t , C u*- , Mg*'*', Mn**" , Ni** , P b * * , Zn*f , A I*** , Cr*** , V e**¥ .

T hey s h o u ld l ik e w i s e

a l l o w f o r t h e p r e s e n c e o f se w a g e o r o t h e r o r g a n i c m a t t e r , a n d o f a n i o n s s u c h a s C l- , CN’*, » £ 3.

T he

SON- , F " ,

, NOrf , COjf , S % S03s , SgO-f, a n d P 0 45 . m e th o d s s h o u ld b e r e a d i l y a d a p t a b l e

t h e c o m m e rc ia lly a v a i l a b l e p h o t o e l e c t r i c

to any of filte r

p h o to m e te rs o r s p e c tr o p h o to m e te r s . I n a d d i t i o n t o t h e s e o b j e c t i v e s , a n o p tim u m b a l a n c e w as s o u g h t b e tw e e n a c c u r a c y a n d s i m p l i c i t y ;

th u s , a s h o rt and

ill

r a p i d p r o c e d u r e w a s f a v o r e d o v e r a l o n g e r , m o re p r e c i s e o n e , p r o v i d e d t h a t t h e a c c u r a c y o f t h e c h o s e n m e th o d w as a t l e a s t

5% o f t h e c o r r e c t v a lu e *

P r e l i m i n a r y T r e a tm e n t o f W a te r S a m p le s B e f o r e c o l o r i m e t r i c m e a s u re m e n t o f t h e m e t a l l i c s t i t u e n t s o f a w a t e r s a m p le c a n b e a t t e m p t e d , i t s a r y t o re m o v e o r g a n i c m a t t e r a n d t o

con­

is n eces­

e lim in a te t h e a n io n s

w h ic h f o rm p r e c i p i t a t e s o r c o m p le x i o n s w i t h t h e common heavy m e ta ls .

I n m any c a s e s i t

i s a ls o d e s ir a b le to con­

c e n t r a t e t h e s a m p le s o a s t o p e r m i t a m o re a c c u r a t e d e ­ t e r m i n a t i o n o f c o n s t i t u e n t s p r e s e n t i n t r a c e a m o u n ts* T h e s e s t e p s a r e m o st e a s i l y a c c o m p l i s h e d b y e v a p o r a t i n g a m e a s u r e d v o lu m e o f t h e s a m p le i n t h e p r e s e n c e o f a m i x t u r e o f s u l f u r i c and n i t r i c

a c i d s u n t i l fu m e s o f SO3 a p p e a r *

M o st o f t h e o b j e c t i o n a b l e a n i o n s a r e d i s t i l l e d

o r d e s tro y e d

d u r i n g t h e e v a p o r a t i o n , a n d s m a l l a m o u n ts o f o r g a n i c m a t t e r a r e o x id iz e d by th e h o t a c i d s .

The r e s u l t i n g s o l u t i o n i s

t h e n d i l u t e d t o a d e f i n i t e v o lu m e a n d a l i q u o t s a r e t a k e n f o r th e i n d iv i d u a l c o lo r i m e t r ic a n a l y s e s . I t i s a d v a n ta g e o u s to s u b s titu te p e rc h lo ric a c id f o r s u lf u r ic o rg a n ic

c o n te n t o f t h e

s a m p le i s

a c i d when t h e

l a r g e , o r w hen l e a d i s t o

be d e te rm in e d . P ro c e d u re .

A g ita te th e

s a m p le t o

o b t a i n a h o m o g en e o u s s u s ­

p e n s i o n o f s o l i d s , t h e n m e a s u re o u t a o n e l i t e r u s in g a v o lu m e tric f l a s k an d tr a n s f e r to a la r g e

s a m p le

iv

e v a p o r a t i n g d i s h * A c i d i f y t h e s a m p le w i t h 5 ml* o f c o n c e n tra te d n i t r i c

a c id a n d e v a p o r a te o n a s te a m

b a t h t o 1 5 -2 0 ml* T r a n s f e r t h e

s o lu tio n , to g e th e r

w i t h a n y s o l i d s r e m a i n i n g i n t h e d i s h , t o a 1 2 5 ml* c o n i c a l f l a s k , a n d a d d 5 m l. a d d i t i o n a l n i t r i c

a c id ,

10 m l* o f c o n c e n t r a t e d s u l f u r i c a c i d , a n d a f e w g l a s s b e a d s o r c a rb o r u n d u m c h i p s t o p r e v e n t bum ping* E v a p ­ o r a t e o n a h o t p l a t e u n t i l d e n s e w h i t e fu m e s a p p e a r i n t h e f l a s k , b u t do n o t c o n t i n u e t h e h e a t i n g b e y o n d t h is p o in t.

I f t h e s o l u t i o n i s n o t c l e a r , 10 m l.

a d d i t i o n a l BNQg a r e a d d e d a n d t h e e v a p o r a t i o n t o SOg fu m e s i s

re p e a te d *

a tu r e and c a r e f u lly

C o o l t h e s o l u t i o n t o ro o m t e m p e r ­ d i l u t e t o a b o u t 50 m l. F i l t e r

th ro u g h a s in te r e d g la s s f i l t e r o r p o r c e la in f i l t e r c r u c i b l e a n d w a s h t h e r e s i d u e w i t h tw o s m a l l p o r t i o n s o f w a te r , th e n t r a n s f e r th e f i l t r a t e

t o a 100- m l .

v o l u m e t r i c f l a s k a n d d i l u t e t o v o lu m e . The r e s u l t i n g s o l u t i o n i s a b o u t 3 N i n a c id * A liq u o ts o f t h i s

s o lu ­

t i o n a r e ta k e n f o r t h e d e te r m in a tio n o f m e ta ls * I f th e o rg a n ic m a tte r i s d i f f i c u l t to if

le a d i s

a c id

is

o x id iz e , o r

t o b e d e t e r m i n e d , 10 m l. o f 60% p e r c h l o r i c

s u b s titu te d f o r s u lf u r ic a c id . A f te r e v a p o ra t­

i n g t o d e n s e fu m e s o f H C IO ^, t h e s o l u t i o n i s d i l u t e d t o a b o u t 50 m l . , b o i l e d t o e x p e l c h l o r i n e , t h e n c o o l e d , filte re d ,

and d ilu te d to

100 m l.

t i o n i s a b o u t 0 ,8 N i n a c i d .

T he r e s u l t i n g s o l u ­

I f le a d i s p r e s e n t,

th e

V

r e s i d u e o n t h e f i l t e r m ay c o n t a i n P bS O ^; t h i s i s

d is ­

s o l v e d b y a d d i n g 50 m l. o f h o t 4 0 $ ammonium a c e t a t e t o t h e f l a s k i n w h ic h t h e e v a p o r a t i o n w as c a r r i e d o u t , t h e n d r a w in g t h i s s o l u t i o n t h r o u g h t h e f i l t e r . filtra te ,

C ool th e

t r a n s f e r t o a 100-m l* v o l u m e t r i c f l a s k , d i l u t e

t o v o lu m e , a n d s e t a s i d e f o r t h e d e t e r m i n a t i o n o f le a d #

D e te rm in a tio n o f C opper D ith iz o n e i s a s a t i s f a c t o r y r e a g e n t f o r th e ric

c o lo rim e t­

d e t e r m i n a t i o n o f m in u t e a m o u n ts o f c o p p e r ( 1 7 ) , a n d i t

h a s b e e n a p p l i e d t o t h e a n a l y s i s o f se w a g e a n d i n d u s t r i a l w a s t e s b y Swope ( 2 1 ) . U n d e r p r o p e r c o n d i t i o n s t h e c o p p e r d ith iz o n e r e a c t i o n i s

q u i t e s p e c i f i c ; u n f o r t u n a t e l y , how ­

e v e r, th e a n a ly tic a l p ro c e d u re i s

q u ite te d io u s and th e

f i n a l m e a s u re m e n t m u s t be m ade o n a m i x e d - c o l o r sy s te m # I t w as d e s i r e d t o s i m p l i f y t h e a n a l y s i s b y e m p lo y in g o n e o f th e o th e r h ig h ly s e n s i t i v e r e a g e n ts f o r c o p p e r such a s d ith io o x a m id e

(2 3 ), d ie th y ld ith io c a rb a m a te

b i s ( 2- h y d r o x y e t h y l ) d i t h i c a r b a m a t e

(1 7 ), o r

( 2 5 ) . S tu d y o f t h e l i t e r ­

a t u r e show ed t h a t a l l t h e s e r e a g e n t s w e re s u b j e c t t o i n t e r ­ f e r e n c e b y m o d e r a te a m o u n ts o f o t h e r h e a v y m e t a l s s u c h a s ir o n , n i c k e l, and z in c ,

i n d i c a t i n g t h a t som e m eans o f i s o ­

l a t i n g s m a l l a m o u n ts o f c o p p e r w o u ld b e S e p a ra tio n o f C opper

re q u ire d .

I n v e s t i g a t i o n w as l i m i t e d t o

se p a ra ­

t io n s in v o lv in g p a r t i t i o n e x tr a c ti o n , s in c e p r e c i p i t a ­ tio n o r e le c tro ly tic w hen a p p l i e d t o

s e p a ra tio n s a re s u b je c t to

lo s s e s

t r a c e a m o u n ts . C h lo r o f o r m e x t r a c t i o n o f

vi

t h e c o p p e r - «4 3

72

88

Table XU D eterm ination of Metals in S ynthetic Waste Sample Following Evaporation and D igestion w ith HCIO^

Ion

Added

PeP.flU From Sewage*

T otal

Found

Recovery

Ctt**

27.0

0 , 02

27,0

27,0

100$

Or*3

58, 8

0,02

58,8

57.0

97

re* 3 ZntA

1*00 12,0

0,80

1,80 12,1

0,14

1.90 12.2

105 101

♦ions were added to 500 ml, sewage (Sample B), then so lu tio n was d ilu te d to 1 l i t e r w ith d i s t i l l e d water# The follow ing co n cen tratio n s o f d iv erse ions were a lso added: Ion PbA1 Ba Ga+z Cd/i Ni+* ON" C itra te

S04 2

P.p.m . 15 50 660 added a s BaClpCi 50 52,5 2.14 100 added as KCN it 360 " Na3C6H5°7 360

»

« (NH4 )2HP04

318

#

« Al8 (S04)g

20

«

" Na-S

Table XX D aterm iaatloa o f Metals In Synthetic Waste Sample Following Evaporation and D igestion w ith HCIO^

Ion

Adàeà

from Sewage^

F,p,m, T otal

found

tirro r

Cu*A

0.10

0,02

0.12

0.13

+ 0.01

Cr >3

0,17

0,02

0.19

0.24

+0.05

Fe+3

0,25

0,80

1.05

0.98

-0.07

Mu**

0,55

0.09

0.64

0.64

+0.00

h i* 3

0,54

0.00

0.54

0.55

+ 0.01

Fb 4,3

0,35

0.02

0.37

0.38

+ 0.01

Zn*3

0,20

0.14

0.34

0.41

♦ 0.07

*Ions were added to 500 ml* sewage (Sample B), th en so lu tio n was d ilu te d to 1 l i t e r w ith d i s t i l l e d w ater. The follow ing concentrations o f diverse ions were a lso added:

90

R esults were corrected fo r tra c e s o f th e m etals p resen t in th e sewage added, a s determined in a sep arate a n a ly s is . A ll samples were c a rrie d through th e p e rch lo ric acid p rellm inary trea tm en t, but comparable r e s u lts were also ob­ ta in ed on samples tre a te d with s u lfu ric acid* Analyses fo r manganese and n ic k e l were c a rrie d out by methods rep o rted elsewhere (37)*

91

Q u a lita tiv e Testa fo r M etals I t I s Im portant to have a v a ila b le a simple q u a lita ­ tiv e t e s t fo r d e te c tin g th e presence o f th e various m etals fo r which q u a n tita tiv e methods have been developed* Spot t e s t s o f the kind described by P elg l are id e a l fo r th is purpose* Those given below have been selec ted as being s a tis f a c to r y from a standpoint of s im p lic ity , s p e c if ic ity and s e n s itiv ity * They may be applied to the raw water sample as receiv ed , but

i t is p re fe ra b le to t e s t the more

concentrated so lu tio n obtained from th e prelim inary tr e a t* of th e sample in order to take advantage o f th e increased s e n s itiv ity * 1* Iro n

The t e s t procedure was adopted from the

2 ,2 1-bypyridine t e s t o f F elg l (16), but 1 ,10-phenanth ro lin e was s u b stitu te d as the color forming reagent* Experiment showed th a t 1 p*p*m* o f iro n could be de­ te c te d in a so lu tio n containing 10© p*p*m* of Cd,Cr, Cu, Mn, N i, Pu, and Zn* Procedure: Place one drop of sample on a spot p la te , add one drop o f 10# hydroxy lamine hydrochloride f o l­ lowed by one drop o f 2# ethanolie 1 ,10-phenanthroline and one drop of 20# sodium acetate* Development o f a pink color before or a f te r a d d itio n of sodium a c e ta te c o n s titu te s a p o sitiv e te st* The procedure o f F e ig l (19) i s given* About 0*8 p,p*m* o f chromium may be detected in a so lu tio n containing 100 p*p*m* of Cd, Cu, Fe, Mn, Ni,Pb and Zn*

92

Procedure: To one drop o f sample on a spot p la te ,a d d one drop o f 20# ammonium p e ro x id is u lfa te (ammonium p e rs u lfa te ) and one drop o f 2# s ilv e r n itra te * Let stand 2-3 m inutes, then destroy any permanganate co lo r th a t may have developed by adding one or two drops of 1# sodium asid e so lu tio n and s tir rin g * F in a lly , add a drop o f 1# eth an o lie diphenylcarba z i de * A purple color which u su a lly fades ra p id ly c o n s titu te s a p o s itiv e t e s t fo r chromium, while a c o lo rle ss o r yellow-brown so lu tio n i s negative* 3* Lead

Use o f d ithizone for th is t e s t was suggested by

F e ig l (17) but th e procedure given by him does not describe th e means o f elim in atin g in te rfe re n c e s in s u f f ic ie n t d e t a il. The procedure given was worked ou t on th e b a s is o f experience with the q u a n tita tiv e d ith izo n e method* Approximately 0*8 p,p,m , o f lead can be detected in th e presence of 100 p.p.m* of Cd, Or, Ou, Fe, N i, Mn, or Zn. Procedure: Tea drops o f sample so lu tio n , one drop of 10# hydroxy lamine hydrochloride, fiv e drops o f 10# sodium c i t r a t e , one drop ÔM ammonium hydroxide, and th re e drops o f 5# potassium cyanide a re added in t h a t order to a semi-micro t e s t tube (8x70 m.m. )♦ Then 0.25 ml* o f 0.005# dithizone in CCl^ i s added and th e tube i s stoppered and shaken vigorously fo r 10 seconds. An orange o r pink color in the CCl^ i s a p o s itiv e t e s t , w hile a c o lo rle s s or pale green i s negative.

93

4» Zinc

No t e a t could be located in th e li te r a t u r e which

was s u f f ic ie n tly s p e c ific fo r z in c . The CKHg(CHS)4 t e s t suggested by F eig l appeared to be in s e n s itiv e in th e presence of larg e amounts o f o th er m etals. The t e s t given below was devised by th e w rite r; i t makes use o f a p r e c ip ita tio n w ith sodium hydroxide to remove most o f th e in te rfe r in g metals# About 0,8 p,p,m , of zinc can be d etected . Procedure: To 5 ml, o f sample in a t e s t tube* add 1 drop o f phenoIphthalein in d ic a to r and make a lk a lin e w ith 4M NaOH, then add 0 .5 ml. in excess. C entrifuge th e p r e c ip ita te , or allow to s e t t l e . Place 1 drop of th e supernatant liq u id in an 8x70 sum, semi-micro t e s t tube and add 1 drop o f a methanol so lu tio n containing 3.5$ carbon d is u lfid e and 18$ diethanolamine by weight ( th is i s th e so lu tio n used in th e q u a n tita tiv e zinc method).

Then f i l l th e t e s t tube 1/3 f u l l of d i s t i l l e d

w ater, add 1 drop o f g la c ia l a c e tic acid and shake fo r 30 seconds w ith 0.85 o f 0.005 dithizone in CC14 . A purple o r red color in th e C014 c o n s titu te s a p o s itiv e t e s t fo r zin c. 5, Copper

The dithiooxamide t e s t recommended by West (90)

i s given.

The lim it of id e n tif ic a tio n i s said to be

0 .3 mi programs a t a lim itin g concentration o f 10 p.p.m. Procedure: Place a drop of a 20$ malonio acid so lu tio n on S and S No. 601 t e s t paper. Add one drop of a n early

94

n e u tra l so lu tio n of th e sample, one drop of 10# ethylene diamine, and one drop o f 1# ethanolie dithiooxamide# À green c o lo ra tio n in d ic a te s th e presence of copper*

95

PAHT I I POIAROGHAFHIC DETERMINATION OF METALS IN INDUSTRIAL WASTES INTRODUCTION In d e fin in g th e o b je ctiv e s o f th i s re se a rc h , i t was s ta te d th a t methods must be developed which do not re q u ire th e use o f expensive instrum ents, since these w ill g e n e ra lly no t be a v a ila b le in small la b o ra to rie s .

This co n d itio n , a s

w ell a s o th e r c o n sid e ra tio n s, led i n i t i a l l y to th e in v e s ti­ g a tio n of co lo rim etric methods. On th e other hand, polarography i s a ls o a very u se fu l a n a ly tic a l to o l fo r th e d e te r­ m ination of sm all amounts of m etals, and due to th e f a c t th a t a number of inexpensive and dependable instrum ents are commercially a v a ila b le , many la b o ra to rie s a re now equipped w ith polarographic apparatus# Accordingly, I t was f e l t th a t polarographlc methods fo r th e determ ination of m etals in in d u s tr ia l w astes should be investigated# Comparison o f C olorim etric and Polarographic Techniques The c h ie f advantage to be expected from polarographic measurements I s th a t th e time of a n a ly sis may be m a te ria lly shortened when a number of m etals a re to be determined in a s in g le sample# M ulti component a n a ly s is , 1. e. th e simul­ taneous determ ination of sev eral c o n s t!tu te n ts by measure­ ments on a sin g le chemical system, i s r a r e ly p o ssib le in colorim etry but i s a ro u tin e operation in polarographic work#

96

A lso, the in te rfe re n c e problem i s le s s serio u s in polarography* Separations can o ften be avoided by ad d itio n of a s u ita b le com pleting agent to the supporting e le c tro ­ ly te ; i f t h i s i s not p o s sib le , many separations can be accomplished by the a d d itio n o f a s e le c tiv e p re c ip ita n t w ithout th e n e c e s s ity of f i l t e r i n g o ff the p re c ip ita te or o f removing the excess of p re c ip ita tin g ag en t• I t i s obvious th a t a p p lic a tio n of these p rin c ip le s can co n trib u te m a te ria lly to sim plifying and shortening the o v e ra ll a n a ly tic a l procedure* On th e o th er hand, co lo rim etric methods are much more s e n s itiv e , and g e n e ra lly more accurate# Although no over­ a l l fig u re can be given, th e optimum working concentration fo r a s e n s itiv e co lo rim etric method is g en erally 10-50 tim es sm aller than th e minimum concentration s u ita b le fo r polarographic measurement# As regards accuracy and pre­ c isio n under highly favorable conditions a p re c isio n of &1# can be obtained in polarographic analysis# This fig u re does not hold, however, in th e determ ination of small con­ c e n tra tio n s , or when several e le c tro re d u c ib le ions are p re se n t in th e same so lu tio n . Thus, th e accurate determ ina­ tio n of a m etal becomes d i f f i c u l t when i t s polarographic wave i s preceded by th e wave of another metal present in higher concentration# Also, when the waves of two ions a re close to g e th e r, th e In fle c tio n point between th e waves i s poorly defined and cannot be discerned w ith a high degree o f accuracy#Consequently in th e polarographic determ ination

97

of combinations o f m etals in low co n cen tratio n s, an accuracy o f 3-10# can be considered normal* G enerally speaking, polarographic measurements should be confined to samples containing a t le a s t 5 p*p*m o f th e desired constituent* I t i s lik e ly , th e re fo re , th a t polarographic procedures w ill prove most u sefu l to a n a ly sts in manufacturing p la n ts confronted with waste d isp o sal problems, due to th e f a c t th a t th e ir samples are taken near the source and are s t i l l r e la tiv e l y concentrated* P rin c ip le s and Technique The th e o re tic a l background of polarographic a n a ly sis i s w ell known (37) and w ill not be reviewed here* However, some p o in ts p e rtin e n t to th e a n a ly sis of m ixtures of m etals re q u ire fu rth e r discussion* When two or more e le c tro re d u c ib le ions are present in th e sample, i t i s p o ssib le to determ ine them sim ultaneously providing th e ir h a lf «wave p o te n tia ls a re s u f f ic ie n tly d is ­ placed th a t the waves do not merge to g e th er; g en erally speaking^ th e half-wave p o te n tia ls should be a t le a s t 0*2 v o lts a p a rt and in some eases 0*3 v o lts or more* When two m etals a re p re se n t whose half-wave p o te n tia ls do not d if f e r s u f f ic ie n tly , i t i s o fte n p o ssib le to e f f e c t a se p aratio n of th e waves by adding an excess of a s u ita b le eomplexlng agent* The half-wave p o te n tia l of a sim ple ion Is s h ifte d to a more negative value by com plexation, the amount of s h i f t being a function of the s t a b i l i t y of th e complex and

98

th e concentration of the eomplexant# As a clo se approxi­ mation the d ifferen c e i s expressed by th e equation:

t E t>. - IE * ), = 2.255. i 0g

p-2t£S5- 11>g „

urtiere th e su b scrip ts c and s r e f e r to th e eomplexed and simple c a tio n s re sp e c tiv e ly , K i s the I n s ta b i lit y constant o f th e complex, p the coordination number o f th e eomplexed m etal, and C the concentration of th e eomplexlng agent (38)* U sually a 0 ,1 M to 1#0 M so lu tio n of the eomplexlng agent i s used as the supporting e le c tro ly te ; th e co n cen tratio n of the eomplexlng agent i s then very la rg e in comparison w ith th a t of th e e le c tro -re d u c ib le ion and may be assumed co n stan t, in which case a d e fin ite value may be assigned to th e half-wave p o te n tia l of a metal in t h i s base solution# In Table XO th e half-wave p o te n tia ls o f a number o f m etals of I n te r e s t in t h i s work have been l i s t e d f o r d if fe re n t supporting e le c tr o ly te s , most of th e values being taken from th e t r e a t i s e by K olthoff and Llngant (45)# A potassium n i t r a te so lu tio n may be considered as a noneomplexlng support­ ing e le c tr o ly te , so th a t the e ffe c ts o f complexation re ­ fe rre d to above may be seen by comparing the half-wave po­ t e n tia l s in o th er so lu tio n s with the value l i s t e d fo r 1 M KNO5. —

I t w ill be noted th a t in some media the wave

of a m etal may be com pletely elim inated, e. g , no wave i s found fo r e ith e r copper or zinc in 1 M KUN* Other means besides complexation may be used to ellm ii

n ate an in te rf e r in g wave# Use o f a supporting e le c tro ly te

Half-Wave Potentials of Metals in Various Supporting E lectro ly tes Sti H § o M

SI

Sbd h| S9

a

8 *

Î

IO

?

§# O

a ig

I M

Q

to

O

•

•

^ g

S

? r4

♦

CV2

fr-

g

HI

O

t

to

$

•

01

01

O

r4

#

ai

K> l*i

O S H

g