Journal o f Radioanalytical Chemistry, Vol. 10 (1972) 27--33

REMOVAL OF CYANIDE AND PHOSPHATE TRACES FROM

BRINES AND SEA-WATER ON METAL ION DERIVATIVES

OF CHITOSAN

R. A. A. MUZZARELLI, B. SPALLA

'G. Ciamician' Chemical Institute, University o f Bologna, Bologna (Italy)

(Received May 25, 1971)

Chitosan polymolybdate and silver-pretreated chitosan are proposed for collection of phosphate and cyanide traces, respectively, from ammonium salt brines and from sea-water. Small columns of 1 • 7 cm can be used to treat samples of a few liters of water, or brine samples of several hundred milliliters.

Introduction

It was recently demonstrated that substituted celluloses previously treated with metal ions can collect amines from organic solvents, a'' Chitosan, a chelating poly- mer obtained from naturally occurring chitin, is able to collect metal ions not only from organic solvents, but also from aqueous solutions, brines and sea- water; 2-1~ therefore one can expect that chitosan previously treated with a suit- able metal ion would be able to collect anions or complexing agents such as cyanide, phosphate and amino acids from waters and brines without any metal ion leakage.

Traces of cyanide in concentrated ammonium sulfate solutions are discharged from acrylonitrile plants, this being a major point of concern about water pollu- tion and brine recovery. Traces of phosphate should also be concentrated from many kinds of solutions or waters for analytical or technological purposes.

The present research was undertaken in order to demonstrate that metal ion-treated chitosan is a good chromatographic support for collecting phosphate and cyanide from waters of current interest to industry and pollution researchers.

Experimental Columns

For their preparation, about 2 g of 100-200 mesh chitosan powder was shaken in 50 ml of 0.44M ammonium sulfate, containing 0.4 g of silver nitrate, or cad- mium chloride, or zinc sulfate for 15 min. The polymer was then washed with 300 ml distilled water to eliminate unfixed ions and then conditioned by washing with 300 ml ammonium sulfate.

J. Radioanal. Chem. 10 (1972)

28 R . A . A . MUZZARELLI , B. SPALLA: REMOVAL OF CYANIDE

The molybdate derivative, which is called chitosan polymolybdate, was pre- pared according to the technique based on the dissolution of chitosan in 1 : 10 acetic acid. The chromatographic supports were used to fill 1 cm diameter What- man columns fed with a peristaltic pump via teflon diffusors.

Solutions

Ammonium sulfate solution was 0.44M. Radioactive potassium cyanide was supplied by the Radiochemical Centre, Amersham. One ml water containing 0.68 #mole C N - corresponding to 40 #Ci was used for each experiment. Radio- active phosphoric acid was supplied by Sorin, Saluggia; 1 ml containing 16 ng of P initially corresponding to 100 #Ci was used for each experiment.

Instruments

A Desaga- Berthold chromatogram scanner equipped with an a rgon-methane gas-flow counter was used to locate the radiotracers in the columns, which were mounted on the moving plate 1 mm below the detector window. For the figures reported here the window was 1.2 x 0.3 cm, the time-constant 1 sec, the pen excur- sion 30 cps, and the integral readings were coupled from the pulse counter to the automatic Metrawatt integrator. This arrangement permitted the determination of all radioisotopes except 14C because of the column glass shielding. Cyanide was determined by extruding equal amounts of polymer from the glass tube into 14 mm diameter plastic plates, which were measured under the same window with a standard deviation of __ 11 ~ . A Laben 512-channel 7-ray spectrometer was also used.

Results and discussion

Large amounts of ammonium sulfate allow trace metal ions present in solution to be collected at the top of the chitosan column. Further washing with ammonium sulfate solution does not appreciably displace the chromatographic band in the case of silver, presented in Fig. 1, copper and cadmium, while the zinc band, after 200 ml brine appears a little lowered as in Fig. 2.

In view of the need to fix cyanide traces, one can take advantage of the above data in order to be sure that no leakage of metal ions takes place when passing a sulfate solution containing trace cyanide through a silver-treated chitosan column. In fact cyanide ion at the ppm level in concentrated ammonium sulfate solutions at pH = 8.0 with NaOH is collected on the pretreated chitosan columns as seen from Table 1. The most satisfactory results are those obtained with silver; a good cyanide retention is also achieved with zinc but there is some risk of leakage. An amount of cyanide exceeding the ratio CN/Ag 1 : 1 would elute silver, in agreement with previous data on the elution of silver from chitosan with 0.1M K C N ?

.1.. RadioanaL Chem. 10 (1972)

R . A , A . M U Z Z A R E L L I , B . S P A L L A : R E M O V A L O F C Y A N I D E 29

c m

0 , . , , m , J l H o l

H i , , g , i , o * , . l w u

i w J | , . * , , . m ,

I I H H H , . m l

5 : : : :

4 6 9 7

. . . o

�9 i . # _ _

, . , , _ _

w,,, = mJm* - -

l l * l - -

i i ~ i - -

a)

{ : i n

0 : : : :

, , H

H H

H H

4 5 3 0

5 w , o ,

, , H - -

w,,, -- ,,,o H H - - . . H H =

HH =_-

Fig. 1. n~ radioactivity profile on a 100-200 mesh chitosan powder chroma- tographic column: a - - before passing am- monium sulfate, b - -a f te r passing ammonium

sulfate, 200 ml

c m

0 o o , , . u . . . , o 1 , u , , ~ , m . ,

i m l | I J J J H , I m V H

w | , l I , , I

I , , g H , ,

H , , , , , U U , , I m l l , , m o * , , *

1 6 3 0 0

a)

c r n

0 ,,o, ,oo, o,., i,i,

l,i, ,,o, .i~

: I : I m , , o , a , I H , , i i , , , , . i

5 1 : : : H H . l l m , m l l

m l m |

, , l *

14400

Fig. 2. 65Zn radioactivity profile on a

b)

100-200 mesh chitosan powder chromato- graphic column: a -- before passing ammo- nium sulfate, b -- after passing ammonium

sulfate, 200 ml

Table 1

Percent collection of cyanide at the 0.4 ppm level from 50 m[ of 0.44M ammonium salt solutions, p H = 8.0, on metal ion-pretreated chitosan

columns 1• 7 cm. Values are averages of six measurements

N H 4 s a l t

Sulfate Nitrate Chloride

A g

88

M e t a l i o n s o n c h i t o s a n

Z n I C d C u

100 73 30 100 i

7 6 1 6 6

Mo

J. Radioanal, Chem. 10 (1972)

30 R . A . A . M U Z Z A R E L L I , B. S P A L L A : R E M O V A L O F C Y A N I D E

As for mo lybda te - t r ea t ed chi tosan, it is stressed here tha t this derivat ive is o f a different na ture than those l isted in Table 1. In fact, derivatives of chi tosan with me tavanada te , m o l y b d a t e or p a r a m o l y b d a t e , and tungs ta te m a y conta in m o r e meta l by weight than o ther derivatives, to the po in t tha t the inorganic po r t i on exceeds the organic one, as can be seen in Fig. 3.

Therefore , chi tosan p o l y m o l y b d a t e can be expected to be a quite stable chro- ma tog raph i c suppo r t in sal t solut ions and in acid solut ions, and to be a selective agent for the col lect ion o f phospha te because of the wel l -known reac t ion of phos- pha te with molybda te .

�9 Mo

" . W

~ 200

o

~' v

Q t00

0 D,- 5O

0xyanion solution of 0.011 added h m[

Fig. 3. Amounts of chitosan derivatives obtained when adding measured amounts of oxy- anion to a 100 mg chitosan solution in acetic acid. The precipitates were lyophilized before

weighing

Several water samples were spiked with label led phospha t e and passed t h rough chi tosan p o l y m o l y b d a t e columns. The results are shown in Table 2.

Table 2

Percent collection of 16 ng phosphate on polymolybdate 1 x 7 cm columns, from various amounts of brine or water

Solut ion Volume, ml . Collection,

Distilled water Potable water Sodium nitrate, 0.5 g/l Sea-water

1000 500

1000 2000

100 100 100" 100"

* See Figs 4 and 5.

.1. Radioanal. Chem. 10 (1972)

R . A . A . M U Z Z A R E L L I , B . S P A L L A : R E M O V A L O F C Y A N I D E 31

In all cases the radioactive phosphorus was completely collected, and could not be removed by brines like sodium nitrate solution, as seen from Fig. 4. To judge from the most evident yellow band formed at the top of the column when passing 2 1 sea-water samples (Fig. 5), one would expect that most if not all the phosphorus naturally present in sea-water was collected. The bands are in fact very sharp in Fig. 5, and they still remain sharp when collecting phosphate from 5 1 distilled water.

0 ::1:

o,n

.~ ~ _ _ - - ~

o,lJ

.... = 2300 , , , ~ - o o ,

, , ~

5 : : : : =--

cm % o ::::

,o,J Ill,

.oo.

.ooo

, * o o

.... ~---- 2 3 0 0 o , , , o . , , o o , , o , , ,

5 Z:: :

b)

Fig. 4. 32p radioactivity profile on a chitosan molybdate column: a -- before passing sodium nitrate, b -- after passing 350 ml sodium nitrate, 0.5 g/1

Conclusions

The choice of a suitable metal ion to be fixed on chitosan permits the use of the resulting product as a chromatographic support for the collection of trace anions or complexing agents. The results obtained with silver-pretreated chitosan for the collection of cyanide, and with chitosan polymolybdate for the collection o f phosphate show that the metal ion which is supported on the polymer acts selec- tively for the collection of anions, even in the presence of exceedingly large amounts of sulfate, nitrate and chloride.

In addition the present results confirm that a trace transition metal ion present in a brine, such as trace silver in ammonium sulfate, can be efficiently collected on a small chitosan column.

While the technique based on silver-pretreated chitosan can be correlated to argentation and to precipitation chromatography, the technique based on the use of chitosan polymolybdate makes use of a substance which has the properties

o r. R a d i o a n a l . C h e m . 10 ( 1 9 7 2 )

32 R . A . A . M U Z Z A R E L L I , B . S P A L L A : R E M O V A L O F C Y A N I D E

= =

( :m

0 , v ,

i , , i i im ,

~ 5 B o o H I n i , * * H l l

I l l , , I , I , , | m , t u * * , , I . , , . , H I . H q , U * , , , ~

511 " I , , , , _ _

pH I

i i i ! - H i m a l l J ~ n H m l , i

a)

m

0 |::| -----__ i o o l l,m, ,,,, , . , ,

: : : 1 - - ' -

. . . . 190000 , , , ,

, , , ,

!ii~ _---

: : : : _-

~ : : : _ - - I I H -

, , , , - , , . . - �9 , , - = i , , l _ Iw , , - - , , , , -

Fig. 5. a2p radioactivity profile on a chitosan molybdate column: phosphorus was collected from 2000 ml sea-water (a), and from 5000 ml sea-water (b) after different decay periods

of both a chelating organic polymer and an inorganic chromatographic support; as far as we know, this is the first example of application in chromatography of such a substance.

ion-pretreated chitosans, copper-pretreated chi tosanwasnot Among other metal quite suited for collection of cyanide, but in view of its stability and absence of leakage, it is possibly very useful for collecting amino acids by ligand exchange chromatography.

The present work was performed under the auspices of the National Research Council of Italy, Rome and of the International Atomic Energy Agency, Vienna.

J. RadioanaL Chem. 10 (1972)

R. A. A. MUZZARELLI, B. SPALLA: REMOVAL OF CYANIDE 33

References

1. R. A. A. MUZZARELLI, G. MARCOTRIGIANO, C. S. LIU, A. FRECHE, Anal. Chem., 39 (1967) 1762.

2. R. A. A. MUZZARELLI, A. MARTELLI, O. TUBERTINI, Analyst, 94 (1969) 616. 3. R. A. A. 4. R. A. A. 5. R. A. A. 6. R. A. A. 7. R. A. A. 8. R. A. A. 9. R. A. A.

10. R. A. A. 11. R. A. A.

MUZZARELLI, O. TUBERTINI, Talanta, 16 (1969) 1571. MUZZARELLI, G. RAITH, O. TtJBERTINI, J. Chromatogr. 47 (1970) 414. MUZZARELLL Rdv. Intl. Oc~anogr. M~dicale, 21 (1971) 93. MUZZARELLI, Water Res., 4 (1970) 495. MUZZARELLI, O. TUBERTINI, Mikrochim. Acta, (1970) 892. MUZZARELLI, Anal. Chim. Acta, 54 (1971) 133. MOZZARELLI, L. SIPOS, Talanta, 18 (1971) 853. MUZZARELLI, R. ROCCHETTI, G. MARANGIO, J. Radioanal. Chem., 10 (1972) 17. MUZZARELLI, A. ISOLATI, Water, Air, Soil Poll., 1 (1971) 65.

3 J. Radioanal. Chem. 10 (1972)