Mineralogy,Mössbauer spectra and electrical conductivity of triphylite Li(Fe<Superscript>2+</Superscript>,Mn<Superscript>2+</Superscript>) PO<Subscript>4</Subscript>

The electrical conductivity of monocrystalline triphylite, Li(Fe²⁺,Mn²⁺)PO₄, with the orthorhombic olivine-type structure was measured parallel (∥) to the [010] direction and ∥ [001] (space group Pnma), between ～400 and ～700 K. Electrical measurements on triphylite are of technological interest because LiFePO₄ is a promising electrode material for rechargeable Li batteries. Triphylite was examined by electron microprobe, ICP atomic emission spectroscopy, X-ray diffraction, Mössbauer spectroscopy and microscopic analysis. The DC conductivity σ_DC was determined from AC impedance data (20 Hz–1 MHz) extrapolating to zero frequency. Triphylite shows σ_DC with activated behavior measured ∥ [010] between ～500 and ～700 K during the first heating up, with activation energy of E _A = 1.52 eV; on cooling E _A = 0.61 eV was found down to ～400 K and extrapolated σ_DC (295 K) ～10^?9 Ω^?1cm^?1; ∥ [001] E _A = 0.65 eV and extrapolated σ_DC(295 K) ～10^?9 to 10^?10 Ω^?1cm^?1, measured during the second heating cycle. The enhanced AC conductivity relative to σ_DC at lower temperatures indicates a hopping-type charge transport between localized levels. Conduction during the first heating up is ascribed to ionic Li⁺ hopping. DC polarization experiments showed conduction after the first heating up to be electronic related to lowered activation energy. Electronic conduction appears to be coupled with the presence of Li⁺ vacancies and Fe³⁺, formed by triphylite alteration. For comparison, σ_DC was measured on the synthetic compound LiMgPO₄ with olivine-type structure, where also an activated behavior of σ_DC with E _A ～1.45 eV was observed during heating and cooling due to ionic Li⁺ conduction; here no oxidation can occur associated with formation of trivalent cations.     

Mineralogy, Mössbauer spectroscopy and electrical conductivity of heterosite (Fe3+, Mn3+)PO4

Mineralogical analysis, electrical conductivity and thermopower are reported for monocrystalline heterosite (Fe³⁺, Mn³⁺)PO₄ with the orthorhombic olivine-type structure. The ⁵⁷Fe Mössbauer spectrum could be adequately described using two Fe³⁺ doublets. By impedance spectroscopy (20 Hz–1 MHz) the electrical DC conductivity σ_DC and AC conductivity σ_AC were determined parallel (∥) and perpendicular to the [001] direction (space group Pnma) in the range ～160–440 K. The graph log σ_DC?1/T shows a slightly bent curve in both directions with activation energies of E _A ～0.30 and ～0.15 eV in the high and low temperature ranges, respectively. The reduced E _A is associated with electronic conduction; σ_DC ∥ [001] follows Mott’s T ^1/4 variable range hopping law at lower temperatures with hopping between localized levels. The values of σ_AC are increased relative to σ_DC at high frequencies and low temperatures, obeying Jonscher’s universal dynamic response law; for σ_AC ∥ [001], the variation with temperature of the frequency exponent is in fair agreement with the model of small polaron hopping. The absolute thermopower Θ is negative and low between ～295 and ～440 K, Θ does hardly vary with temperatures in both directions; the temperature independency of Θ ∥ [001] is consistent with the small polaron hopping model.     

Paleoclimatic implications of hydrogen and oxygen isotopic compositions of Cretaceous–Tertiary kaolins in the Douala Sub-Basin,Cameroon

Increased interest in paleoenvironmental studies is a result of climatic changes occurring at present and predicted for the future. Such studies could be done using the stable isotope compositions (δ²H and δ¹⁸O) of kaolins, which provide knowledge on the paleoenvironmental conditions prevailing during the time of kaolinisation. In this study, the stable isotopic compositions of clay-size fraction of kaolins occurring in Cretaceous and Tertiary Formations of the Douala Sub-Basin in Cameroon are presented, with the aim of reconstructing the paleoenvironmental conditions of the Sub-Basin. To achieve this, the clay-size fraction (< 2 μm fraction) of 8 kaolinite-rich samples were analysed for their δ²H and δ¹⁸O compositions, and results were reported as part per mil (‰) relative to the SMOW standard. The δ¹⁸O values of kaolins found in the Cretaceous–Tertiary Formations of the Douala Sub-Basin varied between +18.2 and +21.0‰, whereas the δ²H values varied between –69 and –53‰. Nine of the eleven samples plotted on the right of the supergene–hypogene line. Five of these nine samples plotted very close to the kaolinite line, which represents the composition of kaolinite in equilibrium with meteoric water at 20 °C; suggesting a supergene weathering origin of these kaolins. The determination of the temperature of kaolinisation yielded mean formation temperatures of 22 ± 2 °C and 27 ± 6 °C for Cretaceous and Tertiary kaolins, respectively. Excluding the two samples falling in the hypogene field, averages of kaolinisation temperatures were 20 and 25 °C during the Cretaceous and Tertiary periods, respectively. These temperatures are slightly below the present mean annual temperature in Douala (27 °C), thereby suggesting that the climate was becoming warmer from the Cretaceous to the Present. Therefore, Douala had a cooler and rainy climate during the Cretaceous, and the climate is gradually becoming hotter and more humid, favouring the refinement of existing kaolins and the kaolinisation of kaolin-forming minerals in the Sub-Basin.     

Mineralogy, geochemistry and genesis of kaolins from the Amazon region

The kaolin deposits of the Amazon region of Brazil are of lateritic origin, modified by subsequent reduced lacustrine and/or swamp environment. They are contemporaneous with lateritic bauxites found in the same region, all formed from aluminium silicate rocks. These are principally sedimentary rocks from the Cretaceous period (Itapecuru and Alter do Chão), but also include metamorphic and felsic volcanic rocks. After erosion of the upper part of these profiles they became locally a substratum for swampy and/or lacustrine environments mostly developed over the clayey saprolitic horizon where kaolin occurs. The saprolitic horizon is made up mainly of iron-mottled kaolinite which has been subject to an intense deferrification, which has increased the kaolin brightness and thickness. The kaolins are basically made up of well-crystallized kaolinite, quartz, sometimes illite-muscovite, anatase and hematite. In certain locations, crandallite-goyazite is also present. The deposits studied differ from each other in the mineral content levels, concentration of principal elements and in trace element distribution. The greatest quantity of quartz and, consequently SiO₂, is intrinsically related to the type of parent rock. Small sedimentary deposits occur in alluvial flood plains located not very far from the lateritic source.     

Modified water treatment residual as flocculant for <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> removal and water purification

Based on previous research, muriatic modification parameters (including the volume of hydrochloric acid, modification temperature and reaction time) were optimized by L₉ (3³) orthogonal design using the removal efficiency of unicellular M. aeruginosa as an index. The results showed that the optimized modification conditions consisted of a hydrochloric acid volume of 4 mL, a modification temperature of 200 °C and a reaction time of 3 h. Under the above conditions, the removal rate for unicellular and colonial M. aeruginosa was 89.26 and 75.53%, respectively. In addition, the flocculation process caused no cell damage, and the cells remained intact after use of the modified water treatment residuals (WTRs) flocculant. TP and TN in water were reduced by 63.37 and 19.03%, respectively. Therefore, the modified WTR flocculant was a technically viable method to remove unicellular and colonial M. aeruginosa.     

Application of Cracked Triangular Specimen Subjected to Three-Point Bending for Investigating Fracture Behavior of Rock Materials

Numerical and experimental studies were performed on a new fracture test configuration called the edge cracked triangular (ECT) specimen. Using several finite-element analyses, the fracture parameters (i.e., K _I, K _II, and T-stress) were obtained for different combinations of modes I and II. The finite-element results show that the ECT specimen is able to provide pure mode I, pure mode II, and any mixed-mode loading conditions in between. Also, a series of mixed-mode fracture experiments were conducted on Neiriz marble rock using the proposed specimen. Furthermore, the generalized maximum tangential stress (GMTS) criterion was used to predict the experimental results. The GMTS criterion makes use of a three-parameter model (based on K _I, K _II, and T) for describing the crack tip stresses. Due to the significant positive T-stresses that exist in the ECT specimen, typical minimum fracture toughness values were expected to be obtained when the ECT specimen is used. The direction of fracture initiation and the path of fracture growth were also obtained theoretically using the GMTS criterion, and good agreement was observed between the experimental fracture path and theoretical simulations. The fracture study of this specimen reveals that the ECT specimen can be also used in mixed-mode fracture studies of rock materials in addition to the conventional circular or rectangular beam test samples.     

Degradation of dimethyl sulfoxide through fluidized-bed Fenton process: kinetic analysis

In this study, fluidized-bed Fenton process (FBF) was used to degrade dimethyl sulfoxide (DMSO), one of the most widely used solvents. Oxidation by Fenton’s reagent, Fe⁺² and H₂O₂, is one of the cheapest advanced oxidation processes due to the high availability of the reagents. FBF is a modified approach that reduces the large amount of iron oxide sludge formed in conventional Fenton process. The optimal treatment efficiencies by FBF with 2 h of reaction were 95.22 % of DMSO degradation and 34.38 % of COD removal at the conditions of 5 mM DMSO, 68.97 g/L SiO₂ carrier, pH_initial 3.0, 5 mM Fe²⁺, and 32.5 mM H₂O₂. The kinetic study was also done to investigate the two stages involved in the oxidation. The first stage fitted the zero reaction order with overall initial rate’s apparent rate constant, k ₁, of ?0.099. The second stage fitted the first order of DMSO degradation, with rate constant, k ₂, of ?0.0005.     

关于高岭村高岭土矿物的新认识

江西省景德镇市高岭村是世界闻名的高岭土产地,高岭石矿物的定名即渊源于此。搞清该区高岭土的成因和矿物组成,对我国粘土矿物学的研究具有一定意义。1978年我们对高岭村地区的高岭土矿物作了进一步的分析研究,获得了一些新认识,报导出来供有关方面讨论。     

Sorption of surfactants and personal care products in Indian soils

Sorption of three surfactants and personal care products in four types of commonly occurring Indian soils was extensively studied. The soils used in the study were red soil, clay soil, compost soil and sandy soil as classified by American Society for Testing and Materials (ASTM). The three surfactants used in the study were representative of cationic, non-ionic and anionic surfactant groups. The sorption of surfactants followed the descending order: sodium dodecyl sulphate (SDS) > trimethyl amine (TMA) > propylene glycol (PG). The maximum adsorption capacity (Q_max) was obtained in compost soil (28.6 mg/g for SDS; 9.4 mg/g for TMA and 4 mg/g for PG). The rate of adsorption was the maximum in compost soil followed by clay and red soils, and minimum for sandy soils. It is found that the Freundlich model fits the isotherm data better than the Langmuir model. Freundlich coefficient (K _f) increased as the organic content of soils increased. Desorption of target pollutants in tap water was 20–50% whereas acid desorbs 40–90% of target pollutants from soil matrix. It was also found that the adsorption and desorption were significantly affected by the presence of clay and organic matter. The results also indicate that surfactants and personal care products, especially TMA and PG, are highly mobile in sandy soil followed by red soil. Therefore, immobilization of target pollutants is most economical and effective in compost and clayey soils whereas for other type of soils the combination of physiochemical and biological process will be effective option for remediation.     

Structural-morphological features of kaolinite from clayey rocks subjected to different stages of lithogenesis: Evidence from the Voronezh anteclise

This paper reports the results of precision structural-morphological study of kaolinite from clayey rocks taken in various areas of the Voronezh anteclise subjected to different stages of lithogenesis: primary kaolins of the weathering crust, proluvial-talus and lacustrine secondary kaolins, as well as lacustrine-swampy fireproof and deltaic-lagoonal refractory clays. The clayey material was transported over more than 300 km. The formation of the fireproof and refractory kaolin deposits in the Voronezh anteclise was related to the Devonian and Early Cretaceous stages of the geological evolution of the region. In terms of spatiotemporal and facies features, the studied genetic series of the kaolin clay deposits is unique. It was established that the sequential structural-morphological evolution o kaolinite in the considered deposits was caused by its mechanical disintegration during transport and redeposition. Interrelation between organic and mineral matters in the fireproof clays was revealed for the first time. Experimental studies of the behavior of kaolinite during sequential grinding and heating confirmed the main reasons for its natural degradation. The formation of virtually monomineral kaolin clays was provoked by the “flow-through” diagenesis, which is similar to weathering in trend. Evolution of mineral matter of the considered genetic series in kaolinite clay deposits was accompanied by the increase of δ¹⁸O values and their dispersion. Peculiarities identified in the behavior of kaolinite and related oxygen isotope characteristics of different-aged denudation and redeposition products of the Devonian weathering crust can play an indicator role in studying different stages of the lithogenesis of clayey rocks.     

Sediment Denitrification in Two Contrasting Tropical Shallow Lagoons

Sediment denitrification was monthly evaluated in two tropical coastal lagoons with different trophic states using the ¹⁵N isotope pairing technique. Denitrification rates were very low in both environments, always <5.0 μmol N₂ m^?2 h^?1 and were not significantly different between them. Oxygen consumption varied from 426 to 4248 μmol O₂ m^?2 h^?1 and was generally three times higher in the meso-eutrophic than the oligotrophic lagoon. The low denitrification activity was ascribed to both low water NO₃ ^? concentrations (<2.0 μM) and little nitrate supply from nitrification. There was no correlation of denitrification with nitrate or ammonium fluxes. Sediments in temperate environments with similar oxygen consumption rates usually presented a higher proportion of nitrification–denitrification rates. Sediment oxygen consumption was a good predictor of sediment denitrification in both studied lagoons.     

Textural characterization, major and volatile element quantification and Ar–Ar systematics of spherulites in the Rocche Rosse obsidian flow, Lipari, Aeolian Islands: a temperature continuum growth model

Spherulitic textures in the Rocche Rosse obsidian flow (Lipari, Aeolian Islands, Italy) have been characterized through petrographic, crystal size distribution (CSD) and in situ major and volatile elemental analyses to assess the mode, temperature and timescales of spherulite formation. Bulk glass chemistry and spherulite chemistry analyzed along transects across the spherulite growth front/glass boundary reveal major-oxide and volatile (H₂O, CO₂, F, Cl and S) chemical variations and heterogeneities at a ≤5 μm scale. Numerous bulk volatile data in non-vesicular glass (spatially removed from spherulitic textures) reveal homogenous distributions of volatile concentrations: H₂O (0.089 ± 0.012 wt%), F (950 ± 40 ppm) and Cl (4,100 ± 330 ppm), with CO₂ and S consistently below detection limits suggesting either complete degassing of these volatiles or an originally volatile-poor melt. Volatile concentrations across the spherulite boundary and within the spherulitic textures are highly variable. These observations are consistent with diffusive expulsion of volatiles into melt, leaving a volatile-poor rim advancing ahead of anhydrous crystallite growth, which is envisaged to have had a pronounced effect on spherulite crystallization dynamics. Argon concentrations dissolved in the glass and spherulites differ by a factor of ~20, with Ar sequestered preferentially in the glass phase. Petrographic observation, CSD analysis, volatile and Ar data as well as diffusion modeling support continuous spherulite nucleation and growth starting at magmatic (emplacement) temperatures of ~790–825 °C and progressing through the glass transition temperature range (T _g ~ 750–620 °C), being further modified in the solid state. We propose that nucleation and growth rate are isothermally constant, but vary between differing stages of spherulite growth with continued cooling from magmatic temperatures, such that there is an evolution from a high to a low rate of crystallization and low to high crystal nucleation. Based on the diffusion of H₂O across these temperature ranges (~800–300 °C), timescales of spherulite crystallization occur on a timescale of ~4 days with further modification up to ~400 years (growth is prohibitively slow <400 °C and would become diffusion reliant). Selective deformation of spherulites supports a down-temperature continuum of spherulite formation in the Rocche Rosse obsidian; indeed, petrographic evidence suggests that high-strain zones may have catalyzed progressive nucleation and growth of further generations of spherulites during syn- and post-emplacement cooling.     

Distribution of nitrogen forms in surface sediments of lakes from different regions,China

The characteristics of nitrogen fractions in the surface sediments of lakes from Eastern Plain Region, Yunnan-Guizhou Plateau Region, Northeast China Region, Qinghai-Tibet Plateau Region and Mongolia-Xinjiang Plateau Region were investigated and the differences of five lake regions on nitrogen fractionation were discussed. The results indicated that organic nitrogen (N_org) was the major nitrogen fraction accounting for 76.38–92.02 % of N_tot in sediments. The rank order of average N_org and N_tot of sediments in five lake regions was: Yunnan-Guizhou Plateau Region > Northeast China Region > Mongolia-Xinjiang Plateau Region > Qinghai-Tibet Plateau Region > Eastern Plain Region. The exchangeable nitrogen had a similar distribution as organic nitrogen in the studied sediments. NH₄ ⁺–N is the main exchangeable nitrogen of sediments in the studied lakes except in Lake Qinghai and Lake Yamdrok which contained higher nitrate concentrations than ammonium. Fixed ammonium (N_fix) in the sediments of studied lakes was irregularly distributed with the values ranging from 99.45 to 329.02 mg/kg. TOC was significantly and positively correlated with ammonium, nitrate, N_org and N_tot, while N_fix was negatively correlated with nitrate probably due to electrostatic attraction between N_fix and nitrate in layers of sediments.     

Mass-size distribution of PM10 and its characterization of ionic species in fine (PM2.5) and coarse (PM10−2.5) mode, New Delhi, India

Size distribution of PM₁₀ mass aerosols and its ionic characteristics were studied for 2 years from January 2006 to December 2007 at central Delhi by employing an 8-stage Andersen Cascade Impactor sampler. The mass of fine (PM_2.5) and coarse (PM_10?2.5) mode particles were integrated from particle mass determined in different stages. Average concentrations of mass PM₁₀ and PM_2.5 were observed to be 306 ± 182 and 136 ± 84 μg m^?3, respectively, which are far in excess of annual averages stipulated by the Indian National Ambient Air Quality Standards (PM₁₀: 60 μg m^?3 and PM_2.5: 40 μg m^?3). The highest concentrations of PM_10?2.5 (coarse) and PM_2.5 (fine) were observed 505 ± 44 and 368 ± 61 μg m^?3, respectively, during summer (June 2006) period, whereas the lower concentrations of PM_10?2.5 (35 ± 9 μg m^?3) and PM_2.5 (29 ± 13 μg m^?3) were observed during monsoon (September 2007). In summer, because of frequent dust storms, coarse particles are more dominant than fine particles during study period. However, during winter, the PM_2.5 contribution became more pronounced as compared to summer probably due to enhanced emissions from anthropogenic activities, burning of biofuels/biomass and other human activities. A high ratio (0.58) of PM_2.5/PM₁₀ was observed during winter and low (0.24) during monsoon. A strong correlation between PM₁₀ and PM_2.5 (r ² = 0.93) was observed, indicating that variation in PM₁₀ mass is governed by the variation in PM_2.5. Major cations (NH₄ ⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺) and anions (F^?, Cl^?, SO₄ ^2? and NO₃ ^?) were analyzed along with pH. Average concentrations of SO₄ ^2? and NO₃ ^? were observed to be 12.93 ± 0.98 and 10.33 ± 1.10 μg m^?3, respectively. Significant correlation between SO₄ ^2? and NO₃ ^? in PM_1.0 was observed indicating the major sources of secondary aerosol which may be from thermal power plants located in the southeast and incomplete combustion by vehicular exhaust. A good correlation among secondary species (NH⁺, NO₃ ^? and SO₄ ^2?) suggests that most of NH₄ ⁺ is in the form of ammonium sulfate and ammonium nitrate in the atmosphere. During winter, the concentration of Ca²⁺ was also higher; it may be due to entrainment of roadside dust particles, traffic activities and low temperature. The molar ratio (1.39) between Cl^? and Na⁺ was observed to be close to that of seawater (1.16). The presence of higher Cl^? during winter is due to western disturbances and probably local emission of Cl^? due to fabric bleaching activity in a number of export garment factories in the proximity of the sampling site.     

不同表面活性剂修饰TiO2柱撑粘土的制备及其光催化活性研究

本文分别采用阴离子、非离子、阳离子三种不同类型的表面活性剂对河北蒙脱石进行改性修饰,并以酞酸丁酯和盐酸分别为前驱物和酸催化剂,采用溶胶-凝胶法（Sol-gel）制备了不同表面活性剂修饰TiO2柱撑粘土催化剂.用X射线粉末衍射（XRD）和场发射扫描电子显微镜（SEM）等手段表征了催化剂的微观结构,以2,4,6-三氯苯酚（2,4,6-trichlorophenol, TCP）和甲基橙染料的吸附、降解为模型反应,考察了改变溶胶和表面活性剂的不同添加顺序对阳离子表面活性剂所修饰的催化剂性质的影响,以及不同类型的表面活性剂修饰所得的催化剂的光催化活性.实验结果表明,通过添加不同的表面活性剂能够不同程度地改变柱撑粘土的BET比表面积,并使其对不同目标污染物具有不同的吸附能力和光催化活性.阴离子表面活性剂十二烷基苯磺酸钠（DBS）修饰的TiO2柱撑粘土具有较好的光催化活性,其次是非离子表面活性剂聚乙烯醇（PVA）修饰的TiO2柱撑粘土,而阳离子表面活性剂十六烷基三甲基溴化铵（CTMAB）修饰的柱撑粘土光催化活性较差.     

Geochemistry of the kaolin deposits of Swat (Pakistan)

Kaolin deposits of the Swat District in Pakistan are indicated to have derived by hydrothermal alteration of more feldspathic parts of felsic intrusives, which occur enclosed in orthoamphibolites and orthogneisses of the Cretaceous Kohistan Island Arc terrane. These latter “country rocks” formed under epidote–amphibolite conditions that prograde northwards to amphibolite facies, and locally manifest slight metamorphic differentiation. The felsic intrusives exhibit a general decrease in siliceous character from west to east, but are less siliceous than most hosts of world kaolins. They are composed of chemically allied quartz diorite, tonalite, trondhjemite and pegmatoids, which evolved mainly by an orthomagmatic crystal fractionation. These parental rocks are calc-alkaline in nature, and kaolinization has proceeded in Ca-richer environment. This is in variance with the occurrence of most known kaolin deposits over potassic granites or rhyolites. Ca-metasomatism of the “host rocks” is in evidence. Kaolin formation by a supergene process is not displayed.The raw kaolin with contained unaltered plagioclase is characterized by a rather low silica (46.54–50.93%) and potash (<1%), and high alumina (23.54–26.77%), Fe₂O₃ (1.73–5.45%) and lime (8.13–16.93%) content. Kaolinization proceeded with a decrease in SiO₂ and concomitant increase in Al₂O₃. The same trend is followed with fineness of grain size of washed fractions, in resemblance to other known kaolin deposits of primary as well as secondary origin.     

Composition,radioactivity, and possible applications of kaolin deposits of Sinai,Egypt

This work discusses the composition, radioactivity, and possible utilization of the kaolin resources in Sinai which are hosted in thick sandstone sequences belonging to the Carboniferous (Wadi Khaboba) and Early Cretaceous (Wadi Iseila and Abansakar) ages. The characterization of kaolin was done by microscopic and SEM examination, supported by XRD and ICP-MS analyses. The studied kaolin resources consist of kaolinite, as the main constituent, associated with subsidiary dickite and halloysite, and minor contribution of smectite and illite. The most dominant non-clay mineral is quartz, besides minor gypsum, dolomite, and hematite. Ferrugination dominates, in most cases, at the upper boundaries of the kaolin lenses, suggesting possible supergene activity. The high Al₂O₃/SiO₂ ratio for the Cretaceous kaolin (0.54, in average) specifies its better grade relative to the Carboniferous kaolin (0.43, in average). The kaolin of the middle part of lens C in Wadi Iseila contains Si/Al molecular ratio of about unity, suggesting high-grade kaolin. The Carboniferous kaolin has enriched the radionuclides: U, Th, and Ra (at disequilibrium state due to leaching of eU relative to Ra) and the REE, relative to that of the Cretaceous age. The Carboniferous kaolin is characterized by a higher contribution of HREE (zircon signature), whereas LREE seems to be more influential for the Early Cretaceous kaolin (monazite signature). In spite of the very high CIA index (93 to 99), none of the analyzed kaolin deposits displays Ce abnormality. The high radioactivity of some Carboniferous kaolin can be a serious impediment for its utilization or its exportation. The kaolin of Sinai does not satisfy the international standards for paperwork industries and refractory manufacturing, but beneficiation may overcome this challenge. However, some lenses have high-grade kaolin with a low percentage of oxides of iron, magnesium, calcium, sodium, and potassium and a low radioactivity, hence nominated for the local refractory industry. The high-grade kaolin of Sinai fulfills the standards required for ceramics manufacturing in the global market. Grade 3 kaolin (< 30%, Al₂O₃) can be used in the manufacturing of white Portland cement and red glaze manufacturing on both local and global markets.     

Experimental study of natrolite and scolecite saturation with ammonium, methane, and propane

The incorporation of the molecular species of C-H-N fluid (ammonium, methane, and propane) into the structural cavities of natrolite and scolecite was experimentally studied at t = 200°C, P = 20 MPa, and an experiment duration of 192 h. The zeolites were modified without ion exchange by the exposure of a preliminarily dehydrated mineral to the appropriate gas. The presence of ammonium and light hydrocarbons in the crystal matrix of zeolites was confirmed by IR and Raman spectroscopy and gas chromatography. The data of differential thermogravimetry revealed differences in the behavior of CH₄- and NH₃-zeolites during heating. The X-ray diffraction patterns and IR and Raman spectra of zeolites in the region of framework vibration indicate deformations in the matrix structure after the experiments. The interaction of dehydrated scolecite with “dry” propane resulted in amorphization under the experimental parameters. The maximum methane contents in the freshly synthesized zeolites determined by gas chromatography are 4.12 wt % for CH₄-scolecite and 8.96 wt % for CH₄-natrolite. The synthetic C₃H₈-natrolite contains 4.45 wt % C₃H₈. In the zeolites saturated with respect to dry ammonium, the highest NH₃ contents were observed in the 0.4–0.25 mm scolecite fraction (12.86 wt %), 0.25–0.05 mm scolecite fraction (11.43 wt %), and NH₃-natrolite (9.28 wt %).     

Effects of alkaline earth metals on the surface,structure, and reactivity of α-alumina

A series of strontium- and barium-doped alumina samples were prepared by hydrolysis, in neutral medium, starting from commercial Al₂O₃, SrCO₃, and BaCO₃ materials. The precursors thus obtained were calcined under air at 700 °C; then, the bulk and surface properties of the resulting mixed oxides were characterized by nitrogen physisorption, X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H₂-TPR), thermogravimetry (TGA), and differential thermal analysis (DTA). Contrary to SrCO₃, an addition of BaCO₃ to α-Al₂O₃ increases slightly the specific surface area. XRD patterns essentially reveal the characteristic reflections assigned to α-Al₂O₃. In agreement with TGA and XRD analysis, strontium and barium carbonates remain after calcination at 700 °C, their decomposition starting above 800 °C. Let us note that this decomposition occurs more readily on AlSr-100 than on AlBa-100 with no apparent relationship with the evolution observed on the specific surface areas. H₂-TPR experiments underline a significant bulk reduction of barium and strontium carbonates taking place significantly above 900 °C with similar trend noticed during TGA regarding their thermal decomposition. However, the most relevant observation is related to a sharp enhancement of the reducibility of AlSr-y with the appearance two reduction ranges highlighting the existence of different types of interactions with strontium and the alumina substrate.     

Fate and transport of ethanol-blended dissolved BTEX hydrocarbons: a quantitative tracing study of a sand tank experiment

To estimate the behavior of ethanol-blended dissolved BTEX hydrocarbons in groundwater, a quantitative tracing study instead of qualitative analysis was carried out by using a large sand tank, into which 2-L solution including bromide, ethanol and dissolved BTEX was injected under a controlled hydraulic condition. Mean residence time (MRT), pore volume swept by solute (V _p), retardation coefficient (R) and biodegradation rate constant (k) of injected solutes were estimated. Compared with bromide that was used as a conservative tracer, ethanol and BTEX had shorter MRT and smaller V _p with the sequence of EtOH < T < E < m/p-X < o-X < B < Br. Biodegradation was confirmed as evidenced by the consumptions of dissolved oxygen (DO), nitrate and sulfate, and the production of acetate. The sequence of k as EtOH > T > E > m/p-X > o-X > B was just opposite to the sequences of MRT and V _p. The relationship among above sequences implies that MRT and V _p can be used as indicators to assess in situ biodegradability of a solute. Biodegradation of a reactive solute can make its MRT shortened and V _p shrunk. In addition, the sorption of ethanol could be neglected (R = 1.0), whereas BTEX compounds were adsorbed (R = 1.04–1.15). It should be noted that biodegradation of a solute can affect the estimation of its retardation coefficient. To our knowledge, this paper provides an available route to quantitatively estimate biodegradability of a solute in groundwater.