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Volume 1974 (1974)
- Issue 133 Pages 216-
- Issue 132 Pages 177-
- Issue 131 Pages 143-
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Volume 1974, Issue 133
Displaying 1-4 of 4 articles from this issue
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Lime Addition and Effect of Aluminum IonJumpei ANDO, Masasi MORI, Yasuo OHNO1974 Volume 1974 Issue 133 Pages 216-221
Published: November 01, 1974
Released on J-STAGE: March 07, 2011
JOURNAL FREE ACCESSWastewaters from phosphoric acid and phosphate plants were treated with lime. Fine crystals of calcium fluoride smaller than 200Å and gel-like fluorapatite precipitated. The filtrate usually contained more than 20 ppm fluorine, while solubility tests showed that fluorine content of saturated solutions of calcium fluoride and fluorapatite was 8 ppm and less than 1 ppm respectively. The high concentration of fluorine in the filtrates is mainly due to the small size of the fluorine compounds a portion of which pass through filter papers. Coagulation of the particles is important and is affected by the concentration, impurities, etc. of wastewaters (Figs. 2 and 3).
Fluorine was considerably reduced by adding aluminum salts (Table 3) but the effect was less with wastewaters containing phosphoric acid (Figs. 4 to 7). A two-stage filtration-addition of lime to pH 4 to 7, filtration, addition of aluminum salt and lime and filtration-reduced fluorine to less than 10 ppm (A-1 and B-2 of Fig. 7) although the process may be expensive.View full abstractDownload PDF (798K) -
Retarding Effect of Sodium Citrate under Strong AlkalinityChikayuki SANO, Natsuji TADOKORO, Kunihiko MIURA, Junichi KASAI1974 Volume 1974 Issue 133 Pages 222-228
Published: November 01, 1974
Released on J-STAGE: March 07, 2011
JOURNAL FREE ACCESSSetting of calcined gypsum is retarded by the addition of citric acid and sodium citrate respectively And setting of prepared gypsum plaster, which is calcined gypsum contained 5% of Ca (OH) 2, is also retarded by the addition of above-mentioned retarders.
For the mechanism of these retarding effect, many investigators support the view 1) or 2) as follows : 1) Slightly soluble calcium citrate is adsorbed on the surface of calcined gypsum CaSO4·1/2H2O, and. then deposit of CaSO4·1/2H2O is prevented.
2) Slightly soluble calcium citrate is adsorbed on the surface of deposited CaSO4·1/2H2, and growth of its crystal is prevented.
Authors never deny the phenomenon of adsorption. But authors think that the complex formation is also one of important factors for retarding effect, and make as following experiments. In addition, authors. experimented about Ca (OH) 2-Citrate system in order to study on retarding effect of sodium citrate under strong alkalinity.
1) Measurement of setting time of calcined gypsum and prepared gypsum plaster.
2) Reaction between Ca (OH) 2 and sodium citrate in liquid phase.
3) Conductivity of Ca (OH) 2-Citrate system.
From 2) and 3), authors confirmed complex formation between Ca2+ ion and citrate ion, and concluded as follows : Retarding effect of sodium citrate to prepared gypsum plaster-under strong alkalinity, is based on the formation of calcium-citrate complex.View full abstractDownload PDF (855K) -
Osao SAKAEDA, Masamichi FUJIHARA, Kiyokata IMAI1974 Volume 1974 Issue 133 Pages 229-234
Published: November 01, 1974
Released on J-STAGE: March 07, 2011
JOURNAL FREE ACCESSDownload PDF (1167K) -
[in Japanese]1974 Volume 1974 Issue 133 Pages 235-240
Published: November 01, 1974
Released on J-STAGE: March 07, 2011
JOURNAL FREE ACCESSDownload PDF (772K)
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