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Production and purification of zircon opacifier from zircon found in the coastal area of Bangladesh
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 5 ( 2 0 0 8 ) 203–206
journal homepage: www.elsevier.com/locate/jmatprotec
Production and purification of zircon opacifier from zircon found in the coastal area of Bangladesh S. Naher ∗ , A.S.M.A. Haseeb Materials and Metallurgical Engineering Department, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh
a r t i c l e
i n f o
a b s t r a c t
Article history:
In this study the potentiality of Bangladesh zircon as a raw material for opacifier was exam-
Received 1 March 2006
ined. Preparation of zircon flour was done by both wet and dry ball milling. Wet milling
Received in revised form
of zircon was found to be much efficient than dry milling. Zircon flour of peak size 8 m
1 April 2007
obtained by wet milling was purified by leaching in concentrated H2 SO4 acid. Leaching time
Accepted 1 May 2007
was varied from 2 to 20 h and sulphuric acid concentration ranged from 10 to 80 ml/l. Both un-purified and purified Bangladesh zircon flour were tested for their performance as opacifier in a couple of local ceramic factories. The whiteness and glossiness of glazes made
Keywords:
with Bangladesh zircon were compared with that made with imported zircon. It has been
Zircon
demonstrated that Bangladesh zircon is quite satisfactory for the production of zircon flour
Zircon flour
in the ceramic industries. Zircon flour made from Bangladesh zircon can effectively replace
Opacifier
imported zircon flour in ceramic glaze, if adequate size reduction and purification is carried
Acid leaching
out. © 2007 Elsevier B.V. All rights reserved.
1.
Introduction
Opaque glazes are those sufficiently low in light transparancy as to effectively hide the body from the view. They usually are white, but this is not a requirement. Zircon is classified in that type of inert opacifiers which remain in the glaze essentially in the same form in which they are added. The performance of an opacifier of this type depends on the amount present, its particle size and on the difference between the index of refraction of the opacifier and that of the glassy matrix in which it is present (Booth and Peel, 1959). Zirconium compounds have found increasing use in the development of opaque glazes. Formerly they were used in glazes mainly in the form of ZrO2 . The main disadvantage of using ZrO2 as an opacifier is the high cost of its production by process of removing silica from zircon in electric furnaces. Therefore at present zircon, i.e. zirconium silicate (ZrSiO4 ) is
∗
Corresponding author. Tel.: +353 1 700 5712; fax: +353 1 700 7148. E-mail address: [email protected] (S. Naher). 0924-0136/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2007.05.063
being used for this purpose, primarily, for its low cost and wide availability (Bhushan and Sen, 1965). Zircon sand occurs in the beach in the coastal area of Bangladesh along with other heavy mineral sands. Characterization of Bangladesh zircon concentrate has been done in the past (Naher and Haseeb, 1997, 2000, 2006). Chemical analysis revealed that Bangladesh zircon has a purity of 95.88%. The main impurity in Bangladesh zircon was oxides of titanium (3.01%). This is followed by iron oxide (0.42) and traces amounts of other oxides. Petrological investigations also revealed that discrete oxides of titanium, both rutile and ilmenite were the main impurities in Bangladesh zircon. Iron oxide was found to present as both discrete particles and as coating on zircon grain. The state of occurrence of the main impurities of Bangladesh zircon, e.g., titanium oxides and iron oxide renders it amenable to simple purification. Chemically, zircon is a very stable substance, especially at
204
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 5 ( 2 0 0 8 ) 203–206
Table 1 – Grain size distribution of Bangladesh zircon U.S. sieve no. 70 100 140 200 270 Pan
Weight (g) 0 11.34 76.76 11.58 0.082 0.234
lower temperatures. With respect to acids, zircon is one of the most resistant substances (Harley and Kelly, 2007; Eitel, 1951). Most contaminants of zircon or zirconium silicate are soluble in hot concentrated sulphuric acid (Ryshkewitch, 1960). In Bangladesh different ceramic industries consume about 200–300 tonnes of zircon flour per year all of which is currently imported. If Bangladesh zircon can be processed, lots of money could be saved. Therefore attempt has been made to produce zircon flours from Bangladesh zircon and purify them by hot concentrated sulphuric acid in order to test their performance as an opacifier in ceramic glaze. The performance of Bangladesh zircon flour was compared with that of imported zircon flour.
2.
Fig. 1 – Experimental setup for the purification of zircon.
Experimental work
2.1. Preparation and purification of zircon flour from Bangladesh zircon Zircon flour was prepared from Bangladesh zircon obtained as zircon sand concentrate from the Beach Sand Exploitation Centre, Bangladesh Atomic Energy Commission, Cox’s Bazar. The grain size distribution of Bangladesh zircon was determined earlier (Naher and Haseeb, 1997) and is reproduced in Table 1. Both dry and wet ball milling were done in alumina lined ball mill using alumina as the grinding media. The volume of the pot was 1100 cm3 and that of the grinding ball was 270 cm3 . Each charge to the mill consisted of 300 g of zircon sand. For wet milling 400 cm3 of water was added to the pot. Milling was carried out at 78 rpm for 240 h. After milling, the mill was discharged and zircon flour separated which (was subsequently dried in a water bath in the case of wet milling) and stored in bottles. The particle size and distribution of the zircon flour were determined by Micrometrix Sedigraph 5100. Part of the zircon flour produced was purified by leaching in a custom made leaching apparatus. Fig. 1 shows the leaching set up which essentially consists of a conical leaching flask (1000 cm3 ) two condensers in series and a magnetic stirrer hot plate. The flask was also fitted with a thermometer to monitor the temperature which was controlled by the thermostatic controller of the hot plate. During leaching 100 g of zircon flour and 500 cm3 of sulphuric acid was used in each batch. Leaching temperature was maintained at 180 ◦ C. Leaching time was varied from 2 to 20 h and sulphuric acid concentration ranged from 10 to 80 ml/l. A constant stirring speed of 100 rpm was used during the entire leaching period. At the end of the treatment, the flask was taken out and allowed to cool, and the zircon flour allowed to settle. It was
then washed thoroughly in distilled water and dried first in a water bath and finally in an oven at 110 ◦ C.
2.2.
Test of Bangladesh zircon as an opacifier
The suitability of Bangladesh zircon as an opacifier was investigated in a couple of local ceramic industries which includes table ware and sanitary ware manufacturers. For this purpose, both un-purified and purified zircon flours were used. Proprietary transparent glaze of each factory was used as the base. Zircon flour was added to the base glaze in an amount ranging from 8 to 12%. For every sample, 400 g of glaze was prepared by milling for 15 h. The prepared glaze was passed through 200 mesh sieve and its properties recorded. Glaze was then applied onto ceramic bodies of proprietary compositions, which were then fired at 150 ◦ C temperature. The appearance, colour and relevant properties of the glaze were then studied.
3.
Results and discussion
3.1. Preparation and purification of zircon flour from Bangladesh zircon Comparative results on the sieve analysis of zircon flour obtained by 24 h of wet and dry grinding can be found in Table 2. It is seen in the table that wet milling is more efficient than dry milling for zircon sand as wet grinding results in much finer grain sizes. That is why wet milling was used in all subsequent experiments. Milling time used was 240 h at 78 rpm rotational speed and the resulting grain size was 8 m. The effects of sulphuric acid concentration and leaching time on the purity of zircon flour were studied in order to find out an optimum leaching condition. It was found that lower
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 5 ( 2 0 0 8 ) 203–206
Table 2 – Comparison of wet and dry grinding result for Bangladesh zircon after 24 h grinding U.S. sieve no.
Dry grinding (g)
Wet grinding (g)
100 200 325 400 Pan
24.51 99.26 93.68 60.22 22.30
0.5 0.5 63 61 164
concentration of sulphuric acid was not effective in removing the impurities. Sulphuric acid with a concentration of 80% was found suitable in removing the impurities within a reasonably short time period of time. It was found that a leaching time of 10 h was suitable to yield zircon flour of white colour. Therefore 80% H2 SO4 and a leaching time of 10 h were used for producing purified zircon for subsequent use in the opacifier tests.
3.2.
Test of Bangladesh zircon as an opacifier
As has been mentioned, the opacifier tests were carried out in local ceramic factories. For proprietary reasons, these fac-
205
tories did not disclose the composition of the base glaze and bodies used. Fig. 2 shows three glazed samples prepared in an insulator and sanitary ware factory. The base glaze and the body composition are the same as those used in their production line. The usual glaze of the factory with the addition of imported zircon flour is shown in Fig. 2a. Fig. 2b shows the transparent glaze without the addition of any opacifier. Fig. 2c shows the glaze prepared by replacing the imported zircon flour with that produced from Bangladesh zircon. In each case 10% of zircon was used. The zircon flour was produced from as-received Bangladesh zircon without any purification. It was found that the glaze prepared using as-received Bangladesh zircon posses white color with a grayish tint. It appears that the as-received zircon flour produced from Bangladesh zircon does not provide a completely white color. Its color was slightly darker than that of the glaze with imported zircon. It was found however that the glossiness of the glaze containing Bangladesh zircon was similar to that of the sample containing imported zircon. The former sample did not show any tendency to craze. The irregular line in Fig. 2c was the result of incomplete spreading of the glaze caused by inadequate viscosity. The grayish tint of the glaze containing Bangladesh zircon is believed to be due to presence of impu-
Fig. 2 – Glazed sample prepared in an insulator factory (a) the usual glaze of the factory (b) transparent glaze without addition opacifier, and (c) glaze prepared with Bangladesh zircon. In each cases 10% of zircon were used.
Fig. 3 – Samples prepared in a tableware factory. (a) Glaze prepared by purified Bangladesh zircon and (b) the usual glaze of the factory. In both cases 10% of zircon were used.
206
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 5 ( 2 0 0 8 ) 203–206
rities, particularly oxides of titanium (Cherniak and Watson, 2007). Glazes prepared using purified Bangladesh zircon in a local tableware factory are shown in Fig. 3a. With the removal of impurities from Bangladesh zircon, the whiteness of the glaze improved. Fig. 3b shows the usual glaze of the factory contains imported zircon. In these glazes the zircon content in 8 wt.%. It was seen that the color of the glaze containing purified Bangladesh zircon flour (Fig. 3a) was comparable to that of the usual glaze of the factory containing imported zircon Fig. 3b. Glaze containing purified Bangladesh zircon was found to have the same gloss as the usual glaze used by the tableware factory. Further, the former did not show any crazing tendency in an oven test. Although Bangladesh zircon flour produced adequate glossiness, it was found to yield a slightly rough surface. This is thought to be linked to the particle size of zircon flour. In the present study, flour produced from Bangladesh zircon has peak particle size at 8 m. Particle size could not be reduced due to experimental limitations. It is well established that finer zircon particles, with peak size at around 2 m, are for optimum for glaze applications. It can be concluded based on the results described above that zircon flour made from Bangladesh zircon can effectively replace imported zircon flour, if adequate size reduction and purification is carried out.
4.
Conclusion
Wet milling of zircon was found to be much effective than dry milling. 80% H2 SO4 and a leaching time of 10 h were found to be best parameters for producing purified zircon flour. Practical ceramic experiments have demonstrated that Bangladesh zircon is quite satisfactory for preparing zircon flour in ceramic industries. The glossiness of the glaze containing Bangladesh zircon was similar to that of the sample containing imported zircon. Zircon flour made from Bangladesh zircon can effectively replace imported zircon flour.
Acknowledgements The authors would like to thank Bangladesh Atomic Energy Commission for supplying the zircon concentrate used in this study. The authors also acknowledge with thanks some experimental facilities provided by Bangladesh Insulator and Sanitary ware Factory, Bangladesh Council for Scientific and Industrial Research, and a local tableware factory.
references
Bhushan, B., Sen, S., 1965. Zircon glazes, central glass and ceramic research institute, calcatta-32. Trans. Indian Ceram. Soc. 12 (2.). Booth, F.T., Peel, G.N., 1959. The principles of glaze opacification with zirconium silicate. Trans. Br. Ceram. Soc. 58 (9), 532–564. Cherniak, D.J., Watson, E.B., 2007. Ti diffusion in zircon. Chem. Geol. 242, 473–486. Eitel, W., 1951. Silicate Mett Equilibria. Rutgrs University Press, New Brunswick, NJ, p. 17. Harley, S.L., Kelly, N.M., 2007. The impact of zircon–garnet REE distribution data on the interpretation of zircon U–Pb ages in complex high-grade terrains: an example from the Rauer Islands, East Antarctica. Chem. Geol. 241, 62–87. Naher, S., Haseeb, A.S.M.A., 1997. Characterization of Bangladesh zircon and its application in steel foundries. In: Proceedings of the International Conference on Structure Processing and Properties of Materials, Dhaka, Bangladesh, pp. C129–C134. Naher, S., Haseeb, A.S.M.A., 2000. Physical chemical mineralogical characteristics of Bangladesh zircon. In: Proceedings of the MINPREX 2000 Conference, Carlton, South VIC 3053, Australia, pp. 391–396. Naher, S., Haseeb, A.S.M.A., 2006. A technical note on the production of zirconia and zircon brick from locally available zircon in Bangladesh. J. Mater. Process. Technol., 388–393. Ryshkewitch, E., 1960. Oxide Ceramics Physical Chemistry and Technology. Eugene Ryshkewitch National Beryllia Corporation, Haskell, NJ.
journal homepage: www.elsevier.com/locate/jmatprotec
Production and purification of zircon opacifier from zircon found in the coastal area of Bangladesh S. Naher ∗ , A.S.M.A. Haseeb Materials and Metallurgical Engineering Department, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh
a r t i c l e
i n f o
a b s t r a c t
Article history:
In this study the potentiality of Bangladesh zircon as a raw material for opacifier was exam-
Received 1 March 2006
ined. Preparation of zircon flour was done by both wet and dry ball milling. Wet milling
Received in revised form
of zircon was found to be much efficient than dry milling. Zircon flour of peak size 8 m
1 April 2007
obtained by wet milling was purified by leaching in concentrated H2 SO4 acid. Leaching time
Accepted 1 May 2007
was varied from 2 to 20 h and sulphuric acid concentration ranged from 10 to 80 ml/l. Both un-purified and purified Bangladesh zircon flour were tested for their performance as opacifier in a couple of local ceramic factories. The whiteness and glossiness of glazes made
Keywords:
with Bangladesh zircon were compared with that made with imported zircon. It has been
Zircon
demonstrated that Bangladesh zircon is quite satisfactory for the production of zircon flour
Zircon flour
in the ceramic industries. Zircon flour made from Bangladesh zircon can effectively replace
Opacifier
imported zircon flour in ceramic glaze, if adequate size reduction and purification is carried
Acid leaching
out. © 2007 Elsevier B.V. All rights reserved.
1.
Introduction
Opaque glazes are those sufficiently low in light transparancy as to effectively hide the body from the view. They usually are white, but this is not a requirement. Zircon is classified in that type of inert opacifiers which remain in the glaze essentially in the same form in which they are added. The performance of an opacifier of this type depends on the amount present, its particle size and on the difference between the index of refraction of the opacifier and that of the glassy matrix in which it is present (Booth and Peel, 1959). Zirconium compounds have found increasing use in the development of opaque glazes. Formerly they were used in glazes mainly in the form of ZrO2 . The main disadvantage of using ZrO2 as an opacifier is the high cost of its production by process of removing silica from zircon in electric furnaces. Therefore at present zircon, i.e. zirconium silicate (ZrSiO4 ) is
∗
Corresponding author. Tel.: +353 1 700 5712; fax: +353 1 700 7148. E-mail address: [email protected] (S. Naher). 0924-0136/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2007.05.063
being used for this purpose, primarily, for its low cost and wide availability (Bhushan and Sen, 1965). Zircon sand occurs in the beach in the coastal area of Bangladesh along with other heavy mineral sands. Characterization of Bangladesh zircon concentrate has been done in the past (Naher and Haseeb, 1997, 2000, 2006). Chemical analysis revealed that Bangladesh zircon has a purity of 95.88%. The main impurity in Bangladesh zircon was oxides of titanium (3.01%). This is followed by iron oxide (0.42) and traces amounts of other oxides. Petrological investigations also revealed that discrete oxides of titanium, both rutile and ilmenite were the main impurities in Bangladesh zircon. Iron oxide was found to present as both discrete particles and as coating on zircon grain. The state of occurrence of the main impurities of Bangladesh zircon, e.g., titanium oxides and iron oxide renders it amenable to simple purification. Chemically, zircon is a very stable substance, especially at
204
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 5 ( 2 0 0 8 ) 203–206
Table 1 – Grain size distribution of Bangladesh zircon U.S. sieve no. 70 100 140 200 270 Pan
Weight (g) 0 11.34 76.76 11.58 0.082 0.234
lower temperatures. With respect to acids, zircon is one of the most resistant substances (Harley and Kelly, 2007; Eitel, 1951). Most contaminants of zircon or zirconium silicate are soluble in hot concentrated sulphuric acid (Ryshkewitch, 1960). In Bangladesh different ceramic industries consume about 200–300 tonnes of zircon flour per year all of which is currently imported. If Bangladesh zircon can be processed, lots of money could be saved. Therefore attempt has been made to produce zircon flours from Bangladesh zircon and purify them by hot concentrated sulphuric acid in order to test their performance as an opacifier in ceramic glaze. The performance of Bangladesh zircon flour was compared with that of imported zircon flour.
2.
Fig. 1 – Experimental setup for the purification of zircon.
Experimental work
2.1. Preparation and purification of zircon flour from Bangladesh zircon Zircon flour was prepared from Bangladesh zircon obtained as zircon sand concentrate from the Beach Sand Exploitation Centre, Bangladesh Atomic Energy Commission, Cox’s Bazar. The grain size distribution of Bangladesh zircon was determined earlier (Naher and Haseeb, 1997) and is reproduced in Table 1. Both dry and wet ball milling were done in alumina lined ball mill using alumina as the grinding media. The volume of the pot was 1100 cm3 and that of the grinding ball was 270 cm3 . Each charge to the mill consisted of 300 g of zircon sand. For wet milling 400 cm3 of water was added to the pot. Milling was carried out at 78 rpm for 240 h. After milling, the mill was discharged and zircon flour separated which (was subsequently dried in a water bath in the case of wet milling) and stored in bottles. The particle size and distribution of the zircon flour were determined by Micrometrix Sedigraph 5100. Part of the zircon flour produced was purified by leaching in a custom made leaching apparatus. Fig. 1 shows the leaching set up which essentially consists of a conical leaching flask (1000 cm3 ) two condensers in series and a magnetic stirrer hot plate. The flask was also fitted with a thermometer to monitor the temperature which was controlled by the thermostatic controller of the hot plate. During leaching 100 g of zircon flour and 500 cm3 of sulphuric acid was used in each batch. Leaching temperature was maintained at 180 ◦ C. Leaching time was varied from 2 to 20 h and sulphuric acid concentration ranged from 10 to 80 ml/l. A constant stirring speed of 100 rpm was used during the entire leaching period. At the end of the treatment, the flask was taken out and allowed to cool, and the zircon flour allowed to settle. It was
then washed thoroughly in distilled water and dried first in a water bath and finally in an oven at 110 ◦ C.
2.2.
Test of Bangladesh zircon as an opacifier
The suitability of Bangladesh zircon as an opacifier was investigated in a couple of local ceramic industries which includes table ware and sanitary ware manufacturers. For this purpose, both un-purified and purified zircon flours were used. Proprietary transparent glaze of each factory was used as the base. Zircon flour was added to the base glaze in an amount ranging from 8 to 12%. For every sample, 400 g of glaze was prepared by milling for 15 h. The prepared glaze was passed through 200 mesh sieve and its properties recorded. Glaze was then applied onto ceramic bodies of proprietary compositions, which were then fired at 150 ◦ C temperature. The appearance, colour and relevant properties of the glaze were then studied.
3.
Results and discussion
3.1. Preparation and purification of zircon flour from Bangladesh zircon Comparative results on the sieve analysis of zircon flour obtained by 24 h of wet and dry grinding can be found in Table 2. It is seen in the table that wet milling is more efficient than dry milling for zircon sand as wet grinding results in much finer grain sizes. That is why wet milling was used in all subsequent experiments. Milling time used was 240 h at 78 rpm rotational speed and the resulting grain size was 8 m. The effects of sulphuric acid concentration and leaching time on the purity of zircon flour were studied in order to find out an optimum leaching condition. It was found that lower
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 5 ( 2 0 0 8 ) 203–206
Table 2 – Comparison of wet and dry grinding result for Bangladesh zircon after 24 h grinding U.S. sieve no.
Dry grinding (g)
Wet grinding (g)
100 200 325 400 Pan
24.51 99.26 93.68 60.22 22.30
0.5 0.5 63 61 164
concentration of sulphuric acid was not effective in removing the impurities. Sulphuric acid with a concentration of 80% was found suitable in removing the impurities within a reasonably short time period of time. It was found that a leaching time of 10 h was suitable to yield zircon flour of white colour. Therefore 80% H2 SO4 and a leaching time of 10 h were used for producing purified zircon for subsequent use in the opacifier tests.
3.2.
Test of Bangladesh zircon as an opacifier
As has been mentioned, the opacifier tests were carried out in local ceramic factories. For proprietary reasons, these fac-
205
tories did not disclose the composition of the base glaze and bodies used. Fig. 2 shows three glazed samples prepared in an insulator and sanitary ware factory. The base glaze and the body composition are the same as those used in their production line. The usual glaze of the factory with the addition of imported zircon flour is shown in Fig. 2a. Fig. 2b shows the transparent glaze without the addition of any opacifier. Fig. 2c shows the glaze prepared by replacing the imported zircon flour with that produced from Bangladesh zircon. In each case 10% of zircon was used. The zircon flour was produced from as-received Bangladesh zircon without any purification. It was found that the glaze prepared using as-received Bangladesh zircon posses white color with a grayish tint. It appears that the as-received zircon flour produced from Bangladesh zircon does not provide a completely white color. Its color was slightly darker than that of the glaze with imported zircon. It was found however that the glossiness of the glaze containing Bangladesh zircon was similar to that of the sample containing imported zircon. The former sample did not show any tendency to craze. The irregular line in Fig. 2c was the result of incomplete spreading of the glaze caused by inadequate viscosity. The grayish tint of the glaze containing Bangladesh zircon is believed to be due to presence of impu-
Fig. 2 – Glazed sample prepared in an insulator factory (a) the usual glaze of the factory (b) transparent glaze without addition opacifier, and (c) glaze prepared with Bangladesh zircon. In each cases 10% of zircon were used.
Fig. 3 – Samples prepared in a tableware factory. (a) Glaze prepared by purified Bangladesh zircon and (b) the usual glaze of the factory. In both cases 10% of zircon were used.
206
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 5 ( 2 0 0 8 ) 203–206
rities, particularly oxides of titanium (Cherniak and Watson, 2007). Glazes prepared using purified Bangladesh zircon in a local tableware factory are shown in Fig. 3a. With the removal of impurities from Bangladesh zircon, the whiteness of the glaze improved. Fig. 3b shows the usual glaze of the factory contains imported zircon. In these glazes the zircon content in 8 wt.%. It was seen that the color of the glaze containing purified Bangladesh zircon flour (Fig. 3a) was comparable to that of the usual glaze of the factory containing imported zircon Fig. 3b. Glaze containing purified Bangladesh zircon was found to have the same gloss as the usual glaze used by the tableware factory. Further, the former did not show any crazing tendency in an oven test. Although Bangladesh zircon flour produced adequate glossiness, it was found to yield a slightly rough surface. This is thought to be linked to the particle size of zircon flour. In the present study, flour produced from Bangladesh zircon has peak particle size at 8 m. Particle size could not be reduced due to experimental limitations. It is well established that finer zircon particles, with peak size at around 2 m, are for optimum for glaze applications. It can be concluded based on the results described above that zircon flour made from Bangladesh zircon can effectively replace imported zircon flour, if adequate size reduction and purification is carried out.
4.
Conclusion
Wet milling of zircon was found to be much effective than dry milling. 80% H2 SO4 and a leaching time of 10 h were found to be best parameters for producing purified zircon flour. Practical ceramic experiments have demonstrated that Bangladesh zircon is quite satisfactory for preparing zircon flour in ceramic industries. The glossiness of the glaze containing Bangladesh zircon was similar to that of the sample containing imported zircon. Zircon flour made from Bangladesh zircon can effectively replace imported zircon flour.
Acknowledgements The authors would like to thank Bangladesh Atomic Energy Commission for supplying the zircon concentrate used in this study. The authors also acknowledge with thanks some experimental facilities provided by Bangladesh Insulator and Sanitary ware Factory, Bangladesh Council for Scientific and Industrial Research, and a local tableware factory.
references
Bhushan, B., Sen, S., 1965. Zircon glazes, central glass and ceramic research institute, calcatta-32. Trans. Indian Ceram. Soc. 12 (2.). Booth, F.T., Peel, G.N., 1959. The principles of glaze opacification with zirconium silicate. Trans. Br. Ceram. Soc. 58 (9), 532–564. Cherniak, D.J., Watson, E.B., 2007. Ti diffusion in zircon. Chem. Geol. 242, 473–486. Eitel, W., 1951. Silicate Mett Equilibria. Rutgrs University Press, New Brunswick, NJ, p. 17. Harley, S.L., Kelly, N.M., 2007. The impact of zircon–garnet REE distribution data on the interpretation of zircon U–Pb ages in complex high-grade terrains: an example from the Rauer Islands, East Antarctica. Chem. Geol. 241, 62–87. Naher, S., Haseeb, A.S.M.A., 1997. Characterization of Bangladesh zircon and its application in steel foundries. In: Proceedings of the International Conference on Structure Processing and Properties of Materials, Dhaka, Bangladesh, pp. C129–C134. Naher, S., Haseeb, A.S.M.A., 2000. Physical chemical mineralogical characteristics of Bangladesh zircon. In: Proceedings of the MINPREX 2000 Conference, Carlton, South VIC 3053, Australia, pp. 391–396. Naher, S., Haseeb, A.S.M.A., 2006. A technical note on the production of zirconia and zircon brick from locally available zircon in Bangladesh. J. Mater. Process. Technol., 388–393. Ryshkewitch, E., 1960. Oxide Ceramics Physical Chemistry and Technology. Eugene Ryshkewitch National Beryllia Corporation, Haskell, NJ.