ions which are abundant in waste water. Since zeolites are

Transcription

1 b QUARTERLY PROGRESS REPORT (1/1/953/31/95) Contract No. DEFG2294PC94215 Project Title: Conversion of Coal Wastes into WasteCleaning Materials Principal nvestigator: WeiHeng Shih Graduate Student: HsiaoLan Chang. NTRODUCTON As indicated in the last quarterly report, the objective of our research in this quarter is studying the ionexchange properties of the zeolites converted from fly ash. t is well known that zeolites Y and A have good ionexchange capabilities with ions such as Cs and Co which are abundant in nuclear wastes,l**and ions which are abundant in waste water. Since zeolites are formed within the fly ash, and it is not a simple task to separate them from the fly ash, the ionexchange study was done on the treated fly ash without separating the zeolites from the fly ash. 11. EXPERMENTAL PROCEDURE The raw materials for the experiments were class F fly ash from Eddystone power plant of PECO. Fly ash was mixed with 2.8 M sodium hydroxide solution and the weight ratio of sodium hydroxide solution to that of fly ash was 2.5. The mixture was kept at room temprature and ambient atmosphere for 2 days. After aging, the mixture was curried at 38 4 C for several days.3 To control the SVAl ratio in the mixtures some aluminum hydroxide powders was added before aging. For comparison, synthesis of pure zeolites4 was also studied. For the preparation of synthetic zeolites, aluminum hydroxide powder was dissolved into 5 ml of 6 M sodium hydroxide solution and then diluted to 12 ml solution, into which 3 ml Du Pont Ludox HS3 solution (density = l.2lg/cm3, silica = 3 wt%) was added. The amount of aluminum hydroxide was 14.2 gm and 7.1 gm for the formation of zeolite A and faujasite. All mixtures were aged 1 day at room temperature and ambient atmosphere followed by curing at 8 "Cfor 1 day. The ion exchange capacities were tested for ammonium ions and cesium ions at two concentrations. For high concentrationsof Nl&+ and Cs+, 1.8 gm pure zeolites or treated fly ash were dissolved in 8 ml distilled water, stirred completely and the ph value of each solution was measured. Because of residual sodium hydroxide in samples of converted fly ash and synthetic zeolites, a high ph value would be an indication of higher sodium hydroxide content in the sample solution. Washing the sample before the ion exchange experiment was necessary and the value of ph should be lower than 11. After washing, the samples were centrifuged and dried at 6 8 O C for 1 day. The ion exchange behavior was studied with two concentrations of NT&+ and Cs+ ions. For high concentration of ions, 8N of Nl&+ or Cs+ solutions were added in small quantity to the treated fly ash solution and the Na+ concentration in the solution was measured using a sodium ion probe. As the or Cs+ ions exchanges with the Na+ in the zeolites, the Na+ concentration in the solution would increase. As the ionexchange capability of the treated fly ash saturates, the sodium concentration in the solution would saturate. For low concentration of ions, the ion exchange capacity was tested in a.1n cesium chloride solution. Each 4 ml sample solution consisting of.7 gm synthetic zeolites or treated fly ash was stirred before testing. When cesium chloride solution was gradually added into the sample solutions, the sodium concentratjons$erelmeasured until saturation occurred. The ion exchange capacity of treated fly ash was compae3 with those of two kinds of pure zeolites: one source of zeolites was provided by UOP k% (& Aigonquin, Des Plaines, L ), the other was made by mixing aluminum hy&oxi& Tri F powders, Ludox silica and sodium hydroxide solution, as described above. m+ T 1% u 1 CLEARED BY... c NT COUNSEL l

2 DSCLAMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

3 DSCLAMER Portions of this document may be illegible in electronic image products. mages are produced from the best available original document.

4 111. RESULTS The concentration of Na+ in solutionsof treated fly ash is plotted as a function of the amount of ions added is shown in Fig. 1.Also shown in Fig. 1are the results for pure syntheticzeolites and fly ash respectively. t can be seen that without converted zeolites, no ion exchange was observed in fly ash. However, when there were zeolites in the fly ash, ion exchange behavior was observed. From the data in Fig. 1, the exchange capacity per gram of treated fly ash A is.86 milliequivalents,which is 3%of exchange capacity of syntheticpure zeolite A. The ion exchange capacity of treated fly ash with faujasite was found to be higher than that of treated fly ash with A. The higher ionexchange capacity of fly ash faujasite is in conformity with the higher Xray diffraction peak intensity of treated fly ash faujasite. m+ 25 n E 8c 9 cu 1 f 5 8 Zeolite A converted from fly ash Faujasis converted from fly ash 15 8 Synthesized zeolite A 2 A A A A A A A A A A A A o o o o o o o o o o o o o Amount (ml) of 8N ammonium hydroxide Figure 1. Concentration of sodium ion of 8 ml of 1.8 gm zeolites or fly ash as a function of added amount of 8 N ammonium hydroxide Fig.2 shows the ion exchange behavior of treated fly ash with Cs ion. t was found that the concentration of sodium in the solution of treated fly ash faujasite and A increases with increasing amount of 8N cesium chloride solution added. Similar to the ion exchange with the exchange capacity of faujasiteconverted from fly ash is higher than the capacity of zeolite A converted from fly ash. n addition, both the treated fly ash A and faujasite have a preference of exchange for ammonium ion than cesium ion at the same concentration. The number of exchanged ammonium ions is 2.5 times the number of exchanged cesium ions for fly ash A and 1.37 for treated fly ash faujasite. m+, 2

5 + Faujasite converted from fly ash [ 1.8gm, 8Oml3 Zeolite A converted from fly ash [ 1.8gm, 8mll Amount (ml) of 8N CsCl Figure 2, Concentration of sodium ion of 8 ml of 1.8 gm zeolites as a function of added amount of 8 N cesium chloride. When cesium concentration was decreased to.1 N, the cesium exchange capacity was shown in Fig.3 for zeolite A and Fig.4 for faujasite. The cesium exchange capacity of commercial zeolite A (UOP) is 5.26 times that of treated fly ash A and the ratio of cesium exchange capacities between treated fly ash A and synthetic zeolite A is 26%. The cesium exchange capacity of faujasite converted from fly ash is.67 milliequivalents per gram while the cesium exchange capacity of zeolite A by treated fly ash is.27 milliequivalents per gram. On the other hand, the cesium exchange capacity of untreated fly ash is very small, less than.3 milliequivalents per gram. Similar trends were found for faujasite. However the cesium exchange capacity for.1n cesium chloride solution of faujasite (UOP) is only 2.5 times larger than that of faujasite converted from fly ash and the ratio of cesium exchange capacity between converted faujasite and synthetic faujasite is.42. These results indicate that the yield of faujasite converted from fly ash might be higher than the yield of zeolite A from fly ash. n addition. as the concentration of cesium chloride was increase from.1 N to 8N, the exchange capacity for each type of zeolites converted from fly ash increases. The summary of ion exchange capacity was listed in Table. 3

6 8 6 4 i, Zeolite A (UOP) Ell Synthestic zeolie A Treated fly ash (Zedire A) 8 B U B n 8 a 2 B B o Amount(m1) of.1n CsCl Figure 3. Concentration of sodium ion of 4 ml of.7 gm zeolite A or fly ash as a function of added amount of.1 N CsCl L 75 A Faujasite(UP) Synthetic Faujasite Faujasite converted fiom fly ash Fly ash Amount(m1) of O.1N CsCl Figure 4. Concentration of sodium ion of 4 ml of.7 gm faujasite or fly ash as a function of added amount of.1 N cesium chloride 4

7 9. J., Sample Table. on Exchange Capacity of S a mles Exchanged on on Exchange Capacity hilliequivalents per m) and concentrahon Synthetic pure Zeolite A, 1.8 gm zeolite A from fly ash, 1.8 gm Faujasite from fly ash, 1.8 gm Fly ash, 1.8 gm 8N NHq+ 8N NHq+ 8N N &+ 8N NHq <.1 Zeolite A from fly ash, 1.8 gm Faujasite from fly ash, 1.8 gm 8N Cs+ 8N Cs N Cs+.1N Cs+.1N Cs+.1N Cs+ O.1N Cs+.1N Cs+.1N Cs <.3 UOP, zeolite A,.7 gm UOP, faujasite,.7 gm Synthetic pure zeolite A,.7 gm Synthetic pure faujasite,.7 gm Zeolite A from fly ash,.7 gm Faujasite from fly ash,.7 gm Fly ash,.7 gm SUMMARY Two useful kinds of zeolites had been converted from fly ash: faujasite and A. The ion exchange property of treated fly ash was quantitatively measured. The faujasite formed by treating fly ash showed a better ion exchange capacity than zeolite A from fly ash. The ion exchange capacity of treated fly ash is 24% of those of synthetic pure zeolites. Our results showed that treated fly ash has great potential in immobilization of radioactive ions in nuclear waste and harmful ions in municipal waste water. V. PLAN FOR NEXT QUARTER The ion concentration effect on the ion exchange behavior will be studied in more detail. The ionexchange isotherms of the converted zeolites A and faujasite with Cs will be studied. n addition, ion exchange with other ions such as Co and Cr is planned. The effect of surfactant on ill also be investigated. the formation of the zeolites and mesoporous materials w V. REFERENCES 1. M. A. Lewis, A. F. Fischer, and L. J. Smith, "SaltOccluded Zeolites as an mmobilization Matrix for Chloride Waste Salt," J. Am. Ceram. SOC.,76,2826 (1993) 2. L. M. Carrera, S. Gomez, P. Bosch, and S. Bulbulian, "Removal of 6oCo by Zeolites and Clays," Zeolites, 13, 62225, (1993). 3 W.H. Shih, H.L.Chang, and Z. Shen, Conversion of class F fly ash to zeolites", Mat. Res. SOC. Symp. Proc. Vol. 371, 3944, (1995). 4. P.K. Dum and J.Bronic, "Mechanism of zeolite formation seedgel interaction", Zeolites, 14, 25, (1994). '