Michihiro Miyake

TL;DR: In this article, the selectivity of the heavy metal ions for carbonate compounds was determined as follows: rmPb 2+ > Sr 2+> Ba 2+ >> Cd 2+ for calcite; pb 2 + > Cd2+ > Ba 2 + for aragonite; Pb 2+, Cd+ >Pb+ >Ba 2+ + for strontianite; and pb2+>Cd 2 + + for witherite.

Abstract: Abstract. The reactions of wollastonite, CaSi03 and xonotlite, Ca6Si6Oi7(OH)2 with NH 4 H 2 P0 4 and H 3P0 4 have been investigated to determine whether silicophosphates can be synthesized topotactically. Hydroxyapatites were easily obtained from the reaction of the phosphate sources with xonotlite and wollastonite. The crystallinity of the hydroxyapatites increased with a decrease in the concentration of NH 4H 2P0 4 and H3PO4 solution and an increase in temperature. Scanning electron microscopy showed that the morphology of the hydroxyapatite obtained was different from those of wollastonite and xonotlite. The chain structures of the S1O4 tetrahedra in wollastonite and xonotlite, however, were broken down by the attack of the P04~ ions, and products such as hydroxyapatite, brushite and orthophosphate were produced. Hydroxyapatite was found to be the stable product above pH ~ 4.0 when xonotlite and wollastonite reacted with the above phosphate sources. The low-temperature transformation of calcium silicates to hydroxyapatites may find applications in the production of prosthetic implants.

TL;DR: Tobermorite, a hydrous calcium silicate that has a layer-type of structure similar to that of the 2:l clay minerals, exhibits reversible alkali cation exchange and selective cesium uptake upon a coupled substitution of (Al 3 § + Na § for Si 4+. Substituted tobermorites were synthesized using aluminosilicate gels, NaOH, and CaO, in Parr bombs at 175~ for 4 days as mentioned in this paper.