Sedimentary zeolites

Analogous mechanistic studies of the formation of zeolite minerals have been reported. Kossowskaya (51), in this volume, considers the genetic associations of sedimentary zeolites and the dominant factors controlling their process of formation. An especially lucid and concise presentation of the mechanism of formation of sedimentary zeolites under low temperature conditions is given by Mariner and Surdam (52). In studies on the formation of zeolites in saline alkaline lakes, they show differential... 

Genetic Associations of Sedimentary Zeolites in the Soviet Union... 

Data enabling comparisons of the compositional differences of sedimentary zeolites of different origin are scarce. Such comparisons have been mostly between zeolites from magmatic rocks and those from sedimentary rocks, independent of the genetic type of the latter (1). The studies of Coombs and Whetton (2), which compared the specific features of analcime in metamorphic and unaltered sedimentary rocks, are evidence of the capabilities of this approach. Clinoptilolites belonging to different groups—alkaline basins of the United States (la), true sedimentary rocks... 

Dr. E.M. Flanigen is a world expert on zeolite synthesis. In the early years she was first to synthesize high silica Y with silica/alumina rations above 4.0, first to remove aluminum from zeolite lattices without loss of structure, and was responsible for identification and evaluation of the myriad of samples from Union Carbide s investigation of sedimentary zeolite deposits in Western United States. Additionally, I would like to acknowledge her assistance in... 

The survey teams subsequently identified many large-scale sedimentary zeolite deposits and today these are known to occur worldwide in vast quantities. The occurrences vary from those of high zeolite purity (>90%), such as those located in California, to tuffaceous materials of around 50-60% zeolite content (as in Italy). Commercial mining operations are known in USA, Japan, Cuba, Italy, Hungary, Bulgaria, Czechoslovakia, Indonesia, Korea, Russia, and South Africa. Workable deposits also exist in Mexico, Greece, and other Balkan states. 

Sedimentary formations that contain significant amounts of zeolites are deposited in a number of relatively restricted geologic environments. The most important sedimentary zeolite minerals are analcime, clinoptilolite, heulandite, laumontite and phillipsite, and the dominant reaction is the alteration of volcanic tuff by alkaline solutions, whether in deep-sea deposits, saline, alkaline lake deposits and soils, or thicker, volcanic-rich sedimentary piles (Hay, 1966, 1978 Ikjima and Utada, 1966). Meteoric water moving downward through the last-named units typically forms smectite as an alteration mineral until solution salinity and pH have increased to the point where alteration is principally to zeolites. 

The early discovered sedimentary zeolite deposits, during the 1950s, were the Green tuff formation of Yokolemachi, Akira Prefecture, Japan, [18], the low-grade metamorphic rocks of Southland, New Zealand [19], and the Neapolitan yellow tuff, around Naples, Italy [20], Many zeolite occurrences were made known a few years later in the western USA, as a result of a capillary five-year exploration campaign promoted by Union Carbide and other chemical companies [21]. After these, hundreds of zeolite formations were and are being discovered in many countries around the world. 

Apart from clinoptilolite, other frequent, technologically relevant, sedimentary zeolite occurrences are those of mordenite, phillipsite and chabazite. Mordenite is present in several deposits in eastern Europe (Bulgaria, Hungary, Slovakia, Yugoslavia), in Japan, Russia, the United States and New Zealand [43,44]. Monomineralic deposits of phillipsite and chabazite are infrequent [21,43,44]. On the contrary these two zeolites are rather common in joint occurrences, especially in Italy and in a few other locations, in central Europe (Germany) and in Canary Islands (Spain) [40]. 

Apart from the described types, it is difficult to establish with certainty which sedimentary zeolites, among those discovered [33,41], may have a potential economic interest, because exploitation and utilisations have in some instances a merely local value. Table 2 (first column) lists some zeolite types which, due to relative abundance and/or technical interest, are being exploited or may have chances for future exploitations. 

Table 2 (second to fourth columns) summarizes some chemical features of the main sedimentary zeolites. It is evident that the mentioned zeolites are medium- to high-silica types. Phillipsite and chabazite belong to the first category, especially if we consider that the values of 7 Sl in the most common joint occurrences [see, e.g., 40] are in the ranges of 0.71-0.73 and 0.69-0.72, respectively. Instead, clinoptilolite, ferrieritc and mordenite are to be considered siliceous zeolites. This chemical character results naturally in different cation exchange capabilities, as it can be seen in the fourth column of Table 2 (CEC values). It is worth to observe that these values are merely indicative, as they refer to pure zeolite species, not to zeolite-rich rocks. On the basis of the theoretical CEC values (Table 2) and zeolite contents in tuff occurrences (see Sub-sec. 5.1), more realistic CEC values for the most common types of zeolitic luffs may be worked out, as follows ...

Comprehensive review papers on the sorption properties of natural zeolites can be found in literature [72,73]. Referring in particular to the main sedimentary zeolites, the last two columns in Table 2 show some structural features of interest for sorption applications. Chabazite, clinoptilolite, faujasite and mordenite, which couple reasonably large to large window sizes with wide inner volumes (except mordenite), appear the most suitable materials for adsorption processes. 

Uses of sedimentary zeolites based on adsorption are limited for the reasons reported at the beginning of See. 6. They regard essentially the more open phases among those listed in Tabic 2, i.e., chabazitc, clinoptilolite and mordenite (faujasitc would be ideal for adsorption, but its presence in sedimentary deposits is limited to the only Arytain Jordanian occurrence). 

Stability and Ion-Exchange Capacity of Natural Sedimentary Zeolites in Acidic Solutions... 

The stability of four natural sedimentary zeolites in acidic solutions (pH 0.75-5) was found to be... 

Large quantities of sedimentary zeolites are known in the western United States (1). One of the more attractive of their potential uses is as an inexpensive, cation-exchange material for metals in environmental improvement. This use includes the removal of heavy metal ions from acid mine-drainage waters and the treatment of industrial waste solutions. Inasmuch as solutions containing unprecipitated heavy metal ions are typically acidic, the stability of zeolites in an acidic environment is an important consideration in evaluating their potential as a cation exchanger in such systems. 

The most common of the natural sedimentary zeolites found in the United States in mineable quantities are chabazite, clinoptilolite, erionite, and mordenite (2). Many crystalline zeolites decompose in acids, although mordenite and, to a lesser extent, erionite have been reported to be stable in acid solutions (2). The goal of this research was to evaluate the stability and cation-exchange capabilities of these common, natural, sedimentary zeolites in acidic solutions. The basic concepts of zeolite ion-exchange, usually emphasizing synthetic zeolites, may be found elsewhere... 

A study of the stability of four natural sedimentary zeolites indicated the order of stability in an acidic environment was found to be Trinity Basin, NV mordenite > Hector, CA clinoptilo-lite > Eastgate, NV erionite > Bowie, AZ chabazite. 

F. A. Mumpton (State University College at Brockport, N. Y.) I would like to compliment our Japanese colleagues on the fine nature and amount of research which they have carried out in recent years on sedimentary zeolites, especially in the area of utilization for which they are well known. I hope that our industrial friends in Union Carbide, W. R. Grace, Mobil, and Norton Companies take note of the size and scale of the zeolite mining operations which you showed in your slide. 

Table 2 reports the chemical composition and the formula of pure phillipsite and chabazite, obtained by microprobe analysis. Phillipsite appears to be rich in K, followed by Na and Ca, with minor amounts of Mg, chabazite is rich K and Ca with minor contents of Na and Mg, which is typical for the Italian sedimentary zeolites [6,7]. 

Sea water, bentonite zeolitisation Secondary synthesis, mesoporous silica Sedimentary zeolites, properties Sedimentary zeolites, volcano-Seeding 02-P-08 02-P-19 02-P-20 02... 

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