Arieh Singer

Cation exchange properties of hydrothermally treated coal fly ash.

Two samples of fly ash were treated for 2-48 h in 3.5 M NaOH at 100 °C. Powder XRD patterns of resulting products were obtained, and their CEC was determined. Zeolite P and/or hydroxysodalite formed during the treatment from the glassy part of fly ash, while quartz gradually dissolved and mullite remained stable. Approximately 50% of fly ash could be converted to zeolites with the CEC of resulting products reaching 2.5-3 mequiv/g. Concentrations of extractable B, Mo, and Se in fly ash considerably decreased upon treatment. Adsorption isotherms of lead on treated fly ash suggested that at low initial lead concentrations and at pH lower than 6 precipitation of lead compounds is not likely. A desorption experiment indicated incomplete reversibility at higher concentrations, suggesting that part of the adsorption may not have been cation exchange related. Treated fly ash displayed high selectivity for Pb 2+ > Sr 2+ > Cu 2+ > Cd 2+ > Zn 2+ > Cs + in competition with Na + , especially at low concentrations of these cations, and was effective in removing Pb and Zn from industrial wastewaters. It was not selective for Ni 2+ and UO 2 2+ . In a column test, 160 bed vols of NH 4 + -contaminated fish-pond water was filtered through treated fly ash until NH 4 + breakthrough occurred.

High capacity cation exchanger by hydrothermal zeolitization of coal fly ash

During; hydrothermal treatment in NaOH medium coal fly ash partially transformed to zeolite P and/or hydroxysodalite, while quartz slowly dissolved and mullite remained stable. Residual coal favored the formation of zeolite P. The relative proportion of the two zeolites could be changed by seeding. During fusion of fly ash with NaOH an endothermic reaction at 170–180°C occurred, resulting in formation of an unreported Na aluminosilicate with approximate composition Na15Si4Al3020 and major XIRD reflections at 4.793, 3.828, 3.000, 2.854, 2.578, and 2.524 A. The product of fusion interacted with water giving aluminosilicate gel, which yielded zeolite P upon hydrothermal treatment at 100°C without aging and zeolite X after aging in water for 12 hours at room temperature. Cation exchange capacity was 420 and 400 meq/ 100 g for zeolite P and zeolite X respectively.

Pedogenic Palygorskite in the Arid Environment

Abstract Pedogenic palygorskite occurrences are reviewed. Pedogenic palygorskite is commonly associated with either: a. modern soils that are at present or have in the past been affected by rising ground water; b. soil formations that include distinct and sharp textural transitions, such as many paleosols; c. pedogenic features, such as calcretes, crusts and caliches. Each one of these specific pedological or geomorphological settings, in association with an arid environment, can apparently satisfy the threshold concentration requirements for palygorskite stability. The pedogenesis of palygorskite in these formations appears therefore to be altogether feasible, as far as requirements of the solution chemistry are concerned.

A digital camera as a tool to measure colour indices and related properties of sandy soils in semi-arid environments

Soil colour carries important information regarding the soils chemical and physical properties. However, common practices for measuring soil colour, either by Munsell charts or by field/laboratory spectrometers, are insufficient, due to the subjective and nonquantitative character of the Munsell charts, and to the high cost and inconvenience of field spectrometers. We present herein, a method to characterize the colour of soil samples, and related chemical and physical properties of the soil, using a digital camera, and an array of coloured plastic chips, that are used for calibration purposes. Using 370 samples of sandy soils, we have demonstrated that both RGB values from digital images and their derived soil indices, correlate highly with similar measurements performed by a field spectrometer. When checked against free iron oxide content and against the percentage of fine particles in a sub‐sample set of 42 soils, the redness index as measured by the digital camera gave similar or better correlations than those obtained from a field spectrometer, against both free iron oxides and fine particle contents (R 2 of 89% for the iron oxides, and of 81% for the fine particles). We propose the use of a digital camera as a field analytical tool to determine precisely: soil colour, iron oxide and fine particle content. Further study in this direction, with other soil population and more soil properties, is strongly advised in order to launch this as a vastly applicable and generic method.

Nontronite in a deep-sea core from the South Pacific

Smectite close to the pure Fe end member of the nontronite-beidellite series was found in the fine clay separated from a 354-cm deep sediment core in the southwestern Pacific Basin. The mineral has a è-axis of 9.09 Å and an unusually low dehydroxylation temperature of 454°C and is composed of sheaves of fibers less than 50 Å wide. Its charge density is 5.09 × 10~4 esu/cm2. The charge originates mainly from the presence of 18% of the total Fe in tetrahedral positions, as determined by Mössbauer analysis. Slight deviations of the infrared spectra from those reported for nontronites are probably due to the presence of more octahedral Mg. The presence of authigenic quartz in the same sample permits some speculation on the concentration of dissolved silicon during nontronite genesis. A δ18O value of 26 ± 0.3‰ indicates a temperature of formation of about 22°C. The Sr isotope ratio suggests that the nontronite formed at least 12 million years ago.РезюмеСмектит, близкий чистому Ре конечному члену серии нонтронит-бейделлит, обнаруживался в мелкой глине, отделенной из 354 цм глубокой колонки осадка в юго-западном районе Тихого Океана. Минерал имеет ось b равную 9,09 Å и необыкновенно низкую температуру дегидроксилирования и состоит из связок волокон менее, чем 50 Å широких. Плотность заряда равна 5,09 х 10−4 эсе/цм2. Заряд возникает, главным образом, в следствие присутствия 18% всех атомов Ре в тетраэдрических местах, как это было определено при помощи анализа Мессбауера. Небольшие отклонения инфракрасного спектра этого минерала от спектра нонронита являются результатом присутствия большого количества октаэдрического Mg. Присутствие аутигенного вкарца в этом же самом образце дает возможность какого-либо предположения концентрации растворенного кремния во время генезиса нонтронита. Значение δ18O, равное 26 ± 0,3‰, указывает на температуру формирования около 22°С. Sr изотопный состав показывает, что нонтронит образовался по крайней мере 12 миллионов лет тому назад. [Е.G.]ResümeeEin Smektit, der in der Zusammensetzung dem reinen Fe-Endglied der Nontronit-Beidellit-Mischungsreihe sehr nahekommt, wurde in der feinen Tonfraktion, die von einem 354 cm tiefen Sedimentbohrkern von südwestlichen Pazifik Becken abgetrennt wurde, gefunden. Das Mineral hat eine kleine è-Achse von 9,09 Å und eine ungewöhnlich niedrige Dehydroxilierungstemperatur von 454°C und ist aus Faserbündeln zusammengesetzt, die eine Dicke unter 50 Å haben. Seine Ladungsdichte beträgt 5,09 × 10−4 esu/cm2. Die Ladung rührt hauptsächlich von der Anwesenheit von 18% Gesamteisen in tetraedri-scher Koordination her, wie aus der Mössbauerbestimmung hervorgeht. Geringe Abweichungen der Infrarotspektren von denen, die für Nontronit angegeben werden, kommen wahrscheinlich durch die Anwesenheit von mehr oktaedrischem Mg. Die Anwesenheit von autigenem Quarz in der gleichen Probe erlaubt einige Spekulationen über die Konzentration des gelösten Siliziums während der Nontronitent-stehung. Ein δ18O-Wert von 26 ± 0,3‰ deutet auf eine Bildungstemperatur von etwa 22°C hin. Das Sr-isotopen Verhältnis läßt daraufschließen, daß der Nontronit vor mindestens 12 Millionen Jahren gebildet wurde. [U.W.]RésuméDe la smectite proche du membre terminal Fe pur de la série nontronite-beidellite a été trouvée dans l’argile fine séparée d’une carotte sédimentaire de 354 cm de profondeur dans la Basin Pacifique du sud-ouest. Le minéral a un axe-b de 9,09 Å et une température de déshydroxylation inhabituellement basse de 454°C et est composé d’un ensemble de fibres d’une longueur de moins de 50 Å. Sa densité de charge est 5,09 × 10~” esu/cm2. L’origine de la charge est principalement due à la présence de 18% du Fe total en positions tétraèdrales, comme l’a déterminé l’analyse de Mössbauer. De légères déviations des spectres infrarouges par rapport à ceux déterminés pour des nontronites sont probablement dues à la présence de plus de Mg octaèdral. La présence de quartz authigénique dans le même échantillon permet quelque speculation quant à la concentration de silice dissoute pendant la genèse nontronite. Une valeur δ18O de 26 ± 0,3‰ indique une température de formation d’environ 22°C. La proportion d’isotope Sr suggère que la nontronite s’est formée il y a au moins 12 million d’années. [D.J.]

Fibrous clay minerals in the soils of Namaqualand, South Africa: characteristics and formation

Abstract Palygorskite- or sepiolite-containing soils occur at elevations up to 1000 m, in gently sloping landscapes formed by aeolian sands or by strongly eroded pedisediments overlying the Namaqualand Metamorphic Complex. The unconsolidated sands are in various stages of calcretization. Most of the soils are sandy, shallow, non-saline, with a pH ranging between 7.2 and 8.2. Carbonate contents are low, but increase towards the calcretized horizons. Most of the carbonates appear in the form of nodules. In the clay fractions, palygorskite or sepiolite dominate and are accompanied by illite and non-expanding 14 A minerals, or mixed-layer minerals. DTA, TGA and chemical analysis indicate that the sepiolite is Fe-rich and contains organic material trapped within its channels. The highest concentrations of the fibrous clay minerals commonly occur in the bottom horizons. It is postulated that they formed pedogenically from silica released by silicates and Mg derived from Mg-rich carbonates introduced by aeolian accretion. This hypothesis is supported by a decrease in Mg Ca of the carbonates with soil depth. Another possible Mg source considered is sea-spray. Soil-water extract compositions are not compatible with fibrous clay mineral stability. Electron micrographs of sepiolite clays suggest alteration into sheet clay minerals.

Illite in aridic soils, desert dusts and desert loess

Abstract In some desert loess deposits, notably those of Central Asia, illite dominates the clay fraction, in others, such as in the Near East and North Africa, illite is a minor component. The interaction between desert loess deposits and aridic (desert) soils, via desert dusts, is used to explain the difference in illite contents. Vertical profile distribution of illite, as well as vertical distributions of soluble and exchangeable potassium, are taken to indicate that illite forms pedogenetically in the surface horizon of aridic soils. Once formed, it is stable and accumulates. It is postulated that the potassium required for the illitazation process is introduced by aeolian dusts. The process is facilitated by wetting and drying cycles. Dusts originating in deserts where they are presently produced by desert weathering of various rocks are defined as primary or “juvenile” dusts. They have low illite contents. Such are the dusts that are carried from the eastern Sahara and Sinai peninsula northeast towards the Middle East, where they form local loess deposits. The Central Asian dusts, on the other hand, have been subjected to numerous cycles of deflation and deposition resulting in relatively long residence times in the pedogenic environment of aridic soils. This results in the enrichment of these dusts with illite. The Central Asian desert loess deposits that interact with these dusts are consequently enriched with illite. Similar processes of illite enrichment may have operated in other areas, such as Australia.

Effects of humic acid on the crystallization of aluminum hydroxides

The effects of humic acid (HA) on the crystallization of precipitation products of Al under mildly acidic to alkaline conditions were investigated. The extent of Al precipitation substantially decreased with increasing HA concentration (0 to 75 µg/ml) in the pH range 6 to 10 during the 80-day aging period. The X-ray powder diffraction (XRD) data show that, at pH 6.0, the amount of pseudoboehmite formed in the systems decreased with the increasing concentration of HA present. The proportion of Al hydroxide polymorphs (gibbsite and bayerite) was greatly influenced by the amounts of HA present in the systems. At pH 6.0 and HA concentration of 37.5 µg/ml, all the precipitation products of Al were noncrystalline. At pH 8.0 and a HA concentration of 12.5 µg/ml, the formation of gibbsite and bayerite was completely inhibited and only pseudoboehmite was evident in the XRD patterns. Further increase in HA concentration (25–75 µg/ml HA) at pH 8.0 resulted in no precipitation of Al, and only a broad peak at ≈3.3 Å, characteristic of HA, was observed. The XRD patterns of the precipitates of Al formed in the absence of HA at pH 10.0 showed the characteristic peaks of bayerite. At pH 10.0, the precipitation products of Al formed even at the HA concentration of 2.5 µg/ml yielded no XRD peaks. Infrared absorption spectra and transmission electron micrographs of the precipitation products of Al formed in the systems studied substantiate the findings obtained by XRD. The data obtained in this study indicate that HA affects the formation of Al hydroxide polymorphs, pseudoboehmites and short-range ordered mineral colloids.

Chemical and spectroscopic properties of leaf litter and decomposed organic matter in the Carmel Range, Israel

Abstract The characteristics of litter and soil organic matter (SOM) from the Carmel Range woodland, Israel, were investigated. Pinus Halepensis (‘pine’) is the dominant tree species with Quercus calliprinos (‘oak’) as the dominant understory species. In situ leachates were collected and aqueous extracts and humic acids (HA) were obtained from litter and sub-surface horizons under both tree species. Salts of atmospheric origin, mainly CaSO 4 , accumulate on pine needles, facilitating enhanced breakdown of the needles as compared to oak leaves, apparently causing less litter to accumulate under pine trees compared to oaks. Pine litter exhibited a greater degree of oxidation. 13 C-nuclear magnetic resonance (NMR) results, supported by Fourier-transform infrared spectroscopy (FTIR) and chemical analyses, indicated that pine litter HA has more aliphatic-C (60.5% of total C) and less aromatic-C (28.1%) compared to oak HA (52.3 and 31.1%, respectively). FTIR also suggested that under both species polysaccharides decreased and oxidation increased with increasing soil depth. Concentrations of N and organic C were higher under oak. C:N ratios were higher for pine litter compared to oak litter (51.3 and 44.0, respectively), although ratios for A 1 horizons were equal (20.6). Concentrations of S, Na, Mg, K and Ca in the leachates were significantly higher under pine. The pH values (7.1–7.9) were buffered by high CaCO 3 content in the soil with the exception of the thick litter layer under oak (pH 5.8). Evidence of metal transport as a result of OM leaching was not detected. Correlations between Na, Mg, Ca concentrations and S concentration in leachates ( r 2 =0.88; 0.89; and 0.84, respectively) suggest these elements originate from salt deposited on the litter. The high content of pine needles (51%) in the oak litter of the mixed woodland mitigates the extent of the differences below the two species.

Soil evolution on basalt and basic pyroclastic materials in the Golan Heights

Abstract The soils of the Golan basaltic plateau were surveyed and analyzed. Soils on uneroded plateaus range from montmorillonitic calcareous Reddish Brown Grumusols in the semi-arid areas through noncalcareous Brown Grumusols in the sub-humid areas to Brown and Red Mediterranean Soils with typical argillic horizons and dominance of kaolinitic clay in the humid parts of this region. Protogrumusols and basaltic Lithosols are found in eroded places. Volcanic cone soils in the humid Golan parts range from tuffic Regosols on the youngest cones and most eroded areas through tuffic Red Mediterrranean silty clay loam and silty loam on less eroded areas to tuffic Red Mediterranean clays on the older volcanic eruption sites and comparatively stable slopes. The weathering of the basalt is comparatively very slow, especially in the drier upland areas of the southern Golan. The weathering of the pyroclastic materials, on the other hand is fast, due to the great internal surface of this parent material. The various soils exhibit different leaching stages. A gradual disappearance of lime, decrease in pH values, increase in exchangeable H+ and a shift from montmorillonite clay dominance to kaolinite and similar clay types expresses the increase in the leaching degree from the dry areas to the moist ones. The textural profile of Golan soils depend on clay content and type. A soil sequence commencing with self-mulching Grumusols through various intermediate types to typical ABC Red and Brown Mediterranean Soils may be distinguished along climatic, time and drainage gradients.