Alkali activation

Active alkali Active chlorine Active dry yeast Active dry yeasts Active oxygen (AO)... 

Jiang, W Wu, X. Roy, D. M. 1993. Alkali activated fly ash - slag cement based nuclear waste forms. Materials Research Society Symposium Proceedings, 294, 255-260. 

Mg(II) forms a complex with 8-hydroxyquinoline-5-sulfonic acid (37) at pH 9.0 with Tris-HCl buffer, which can be determined by ELD (X x = 388 nm, ka = 495 nm) with micellar enhancement by cetyltrimethylammonium chloride (38). Masking of Ca(II) is achieved by EGTA (19). The method was applied in a SIA system for analysis of natural waters . After elution of the Mg(II) ions adsorbed on an alkali-activated PTFE tube with 0.1 M HCl and addition of A,A -bis(salicylidene)-2,3-diaminobenzofuran (39), the end analysis was by fluorometric determination of the Mg(II) complex (kex =475 nm, kfl = 545 nm). Possible interference of Ca(II) is masked on addition of the chelating agent... 

Now we might consider what is in fact the common clay mineralogy of sandstones. Shelton (1964), Bucke and Mankin (1971) find it to be most often dominated by kaolinite. This mineral although hydrous, is conspicuous by its lack of alkalis. Thus one could suspect that alkali activity in pore solutions of sandstones is, or was, frequently low, lower at any rate than adjacent mica-bearing shales. Laboratory studies by Hanshaw and Coplen (1973) and Khareka and Berry (1973) would give a plausible explanation for such a phenomenon. If solutions are forced hydrostatically across the argillaceous membrane, ionic species in solution are selectively... 

The identification of a specific zeolite species with a particular genesis or environment of formation is very difficult if natural mineral occurrence is used as the sole criteria. Most alkali zeolites are found at one place or another in most low temperature geological situations. Various authors have cited various physical and chemical factors which would control the sequence or particular species of alkali zeolite found in nature. Silica and alkali activities in solution are of great importance in surface and buried deposits (Sheppard and Gude, 1971 Honda and Muffler, 1970 Hay, 1964 Coombs, t al.. 1959 Read and Eisbacher, 1974). 

If we assume that alkali activity varies independently of the masses in the silicate system, the activities (more precisely, the chemical potentials) become internal variables of the system where the activity is controlled by potentials or reservoirs outside of the rock observed. 

Next, when the content of dissolved ionic species due to weathering increases in the fluid, the alkali activity in solution will dictate the formation of an expanding phase then at high activity of K+ the stability of mica. Finally, the feldspar-quartz assemblage is stable. This would happen where the solutions migrate slowly enough so that the original minerals are not dissolved and remain stable in the chemical system. 

In the presence of alkali metal the solubility of aluminum in the reaction mixture increases considerably, and it is undoubtedly the dissolved part of the metal which catalyzes the esterification in a homogeneous reaction. When the residue is filtered off, this time after a reaction period of 45 minutes, the esterification proceeds at the same speed as without filtration. The filtered residue can be used effectively again and again so that, in the case of the alkali-activated catalysis, it may be denied that only specific active regions of the solid catalyze the reaction. 

Fern ndez-Jimenez, A., Palomo, A., Macphee, D.E. and Lachowski, E.E. (2005) Fixing arsenic in alkali-activated cementitious matrices. Journal of the American Ceramic Society, 88(5), 1122-26. 

Smith and Lieber (36) reported that, although the use of alkali activated Raney nickel for the hydrogenation of carbonyl groups, it had a deterring effect on the reduction of aromatic nitro compounds. In particular, alkali retarded the reduction of nitrobenzene and the three isomeric sodium nitrobenzoates, whereas it increased the velocity of reduction of the methyl and ethyl esters of nitrobenzoic acid. 

Total alkali Titratable alkali Active alkali Effective alkali... 

Tlte synthesis of liquid hydrocarbons was first reported in patents from BASF in 1913. Alkali activated Co/Os catalysts were used at pressures over 100 bar and temperatures exceeding 300 C. The products obtained consisted of paraffins, olefins, and oxygenated products (I ). Tlte continuation of these studies led to the development of the methanol synthesis. The first commercial plant went on stream in 1923. 

For more basic systems a decreased alkali activity is possible. 

We believe that a similar water vapor solubility enhancement of alkali vapor transport is possible in soda-lime-silica glass systems, and work is in progress to verify this. Some of the disparities between various glass vaporization studies may well result from variations in water content and, hence, alkali activities. The common explanation for water vapor enhanced alkali vapor transport over silicates has revolved around formation of volatile NaOH (77) and KOH (53) species. However, no direct test for the presence of these species has been made, and the possibility of water vapor enhancement of atomic Na and K transport exists in these systems. 

Me than alio n (CO + 3H2 — CH +H20) Ni/AI203 Alkalis Activity/ lifetime... 

In 1913, the Badische Anilin und Soda-Fabrik (1) disclosed that hydrogen and carbon monoxide would react at 100-200 atmospheres pressure in the presence of alkali-activated cobalt or osmium oxide supported on asbestos to form a liquid product containing alcohols, aldehydes,... 

A Fernandez-Jimenez. and F.Puertas, Alkali-activated slag cements Kinetic studies Cement and Concrete Research, Vol. 27, N°3 (1997) p. 359... 

Fig. 6.54 Shrinkage of the samples from alkali activated slag cement paste without Portland eement elinker, with Na SiO addition in concentrated MgClj solution. (After [246])...

Fig. 6.56 Pores size distribution in the alkali activated slag cement paste after 2 years of curing in the magnesium chloride solution of high concentration. (According to [245])...

Concentration of these ions in pore solution of concrete plays a decisive role in the formation of efflorescence. Pore solution, in the case of ordinary cements, is always satinated with calcium hydroxide— the basic somce of efflorescence. The concentration of potassium and sodium is important too the potassium content is always several times higher. These both components occm in pore solution in the form of hydroxides, as a result of reaction with calcimn ions. Particularly sodium is a very mobile ion and in the case of concrete produced from alkali activated slag cement, with sodimn compound addition and without Portland cement clinker, Na+ ions migrate to the smface and the white sodimn carbonate effloreseenee is formed. 

Also in other countries alkali activated slag cements, with Na2Si03 and gypsum [101], as well as cement F with 5-8% sodiiun activator and Ugnosulphonate as a plasticizer [102] are produced. 

The structure of C-S-H phase formed in alkali activated slag cements was studied by Deja [98], He found the elongation of sihcate chains, that is the ordering of the stmcture with its transformation closer to tobermorite, as a function of lydration time. [98]. The aluminate ions occur in the paste of this cement primarily in C-S-H (even about 7 % AI2O3), however, they can form also hydrogamet phase rich in silicon [98]. 

---