Results The combination of chlorate and acid conditions resulted in extensive oxidative damage to the resin a t 90” C. No oxidation nor chlorate consumption was observed in neutral or alkaline media. However, static exposure of the resins a t room temperature to acid and chlorate for periods up to 30 days resulted in no significant changes. The changes in the resins exposed to the chloric acid at 90’ C . were severe. The volume of rinse water required to wash out excess alkali increased at least 300Yo when compared with samples heated in acid without chlorate. Except for the A-30B, which increased in volume, all of the resins decreased in volume. Capacity losses ranged from 25 to 30%. These static qualitative tests were exploratory and designed to give direction to the more significant column work. Anion exchangers are seldom, if ever, operated at temperatures approaching
90” c.
The column tests show that chloratc can be selectively removed from sodium hydroxide solutions during regeneration and that the sorption of chlorate is reversible (Table I). Salt brine removes it completely, but significantly, sulfuric acid exhaustion removes only part of the oxidant. The four resins differ markedly in their affinity for chlorate and in the amounts eluted by water and acid. Equilibrium is reached with PSA after about 5 cycles with caustic soda and acid, wherein the net chlorate sorbed amounts to 141 mg. for a 50-ml. column (26.5 millimoles per liter). ES-114 and A-30B reached equilibrium in 3 cycles with net sorption of 31 and 32 mg. of chlorate, respectively. A-7 removed 46 mg. chlorate from the regenerant in the first cycle, but most of it was eluted by the rinse water. All of the cyclic tests showed that the polvstvrene weakly basic resins sorb and retain the greatest amount of chlorate. Tests on the resins after 10 cycles showed significant changes only in the rinse requirements (Table 11). A rough parallel was seen between the color changes and increasing rinse volumes. No capacity losses were observed during this short interval and the changes in resin volume were not sufficient to be significant. Other Observations. Columns containing adsorbed chlorate could be eluted with reagent grade sodium hydroxide and thus be completely freed of chlorate. Addition of reducing agents such as sodium sulfite, sodium hydrosulfite, sucrose, and formaldehyde to the “blue liquor” caustic does not result in chlorate reduction a t room temperature; nor d o these agents prevent sorption of the chlorate by the weak base anion exchangers. I n a series of qualitative static tests, it was found that iron catalyzes the oxida-
1044
tive effect of chlorate. As little as 1 mg. of iron per gram of resin causes a significant increase in the reaction rate. Discussion
Although these accelerated laboratory tests can hardly be used to accurately predict field performance, the evidence presented is sufficient to indicate the use of rayon grade or solid form caustic soda for regenerating weakly basic anion exchangers. Similarities were noted between the phenolic and polystyrene resins exposed to hot chloric acid and several deteriorated samples obtained from field installations. In field experience, increased rinse \vater requirement is usually the first indication of oxidation. Such effects are observed very early in the life of the resin. Significantly, the onll-value which changed notably in the cycling tests (Table 11), \vas the rinse volume. Based on preliminary results, prediction of further deterioraiion upon further cycling with chlorate-containing caustic soda is tenable.
No changes occurring after 30 days in chloric acid at room temperature are difficult to explain; however, field operation and laboratory cycling frequently expose deteriorative effects which are not obtained in static tests. All of the present experiments were conducted with weak base anion exchangers. Increases in rinse requirements of strong base resins are generally less severe and frequently have been traced to other causes, such as irreversibly adsorbed weak acids. literature Cited (1) Abrams, I. M., Roberts, M. A., Dickinson, B. N., Proc. A m . Power Conf.XX, 674 (1958).
(2) Frisch, N. W., Kunin, R., IND. Exc. CHEM.49, 1365 (1957). (3) Williams, D., Haines, G. S., IKD.ENG. CHEM., ANAL.ED. 17, 538 (1945). 14) Wirth, L., Jr., Combustion 25, No. 11, 45 (1954). RECEIVED for review October 14, 1958 ACCEPTED May 14, 1959 Division of Industrial and Engineering Chemistry, 134th Meeting, ACS, Chicago, Ill., September 1958.
Correction Chelating Ion Exchange Resins In the article on “Chelating Ion Exchange Resins” [L. D. Pennington, M. B. Williams, IND. EKG. CHEM,51, 759 (1 959) ] the captions were wrongly placed. They should have been as follows: Page 760, lower left. Absorption of resorcinol resin in acid range i s higher than would b e expected from weakly acidic phenolic groups, may involve chelation with free methylol groups. Resacetophenone and @-resorcylic acid resins show similar absorption curves Page 760, lo\ver right. Resorcylic acid resin
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Page 761, upper left, 8-Quinolinol resin shows the greatest selectivity of resins tested Page 761, upper right. o-Aminophenol resin shows good selectivity and capacity Page 762, upper left. Resacetophenone resin Page 762, upper right. Sulfonic acid resin Amberlite IR- 1 20 shows relatively slight effect of pH except as the nature of the ionic species present is affected The following illustration should also have been inclided:
2.5
g
20
. L
[5,
Lc -
Carboxylic resin, Amberlite IRC-50, shows some selectivity toward copper
1.5
E C ‘
.o 4
1.0
P 0 cn
2 0.5 00
2
4
PH
8
10
