Composition Of Solid Phase Research Articles

Magnetoresponsive polymer networks as adsorbents for the removal of U(VI) ions from aqueous media

Magnetoresponsive, methacrylate-based 3D polymer networks containing hydrophilic/thermoresponsive, hydrophilic/pH-responsive and hydrophobic/metal chelating functionalities and oleic acid-coated magnetite nanoparticles, have been synthesized by conventional crosslinking radical polymerization and further evaluated as adsorbents for the removal of U(VI) ions from aqueous media. The adsorption properties of the networks prior and after magnetization regarding U(VI) ion removal from aqueous solutions of varying acidity and initial U(VI) concentration have been investigated. The effect of pH on the interaction of the adsorbents with U(VI) ions was shown to differ dramatically depending on solid phase composition, due to the fact that in the magnetite-loaded network, the Fe3O4 nanoparticles act as buffers by binding solution protons. Nevertheless, U(VI) adsorption on both types of adsorbents follows the Langmuir adsorption isotherm and the value of theirmaximum adsorption capacity is qmax=∼0.02molkg−1 showing no statistically significant differences. The magnetic properties of these materials make their removal and adsorbed uranium separation from the aqueous phase quite simple by using an external magnetic field.

Phase diagrams and physicochemical properties of Li+,K+(Rb+)//borate–H2O systems at 323 K

The phase and physicochemical properties diagrams of Li+,K+(Rb+)//borate–H2O systems at 323 K were constructed using the experimentally measured solubilities, densities, and refractive indices. The Schreinemakers’ wet residue method and the X-ray diffraction were used for the determination of the compositions of solid phase. Results show that these two systems belong to the hydrate I type, with no solid solution or double salt formation. The borate phases formed in our experiments are RbB5O6(OH)4 · 2H2O, Li2B4O5(OH)4 · H2O, and K2B4O5(OH)4 · 2H2O. Comparison between the stable phase diagrams of the studied system at 288, 323, and 348 K show that in this temperature range, the crystallization form of salts do not changed. With the increase in temperature, the crystallization field of Li2B4O5(OH)4 · H2O salt at 348 K is obviously larger than that at 288 K. In the Li+,K+(Rb+)//borate–H2O systems, the densities and refractive indices of the solutions (at equilibrium) increase along with the mass fraction of K2B4O7 (Rb2B4O7), and reach the maximum values at invariant point E.

Peculiarities of the composition of solid phases formed in aqueous calcium–silicate systems with a medium of variable acidity

The effect of a medium’s acidity on the composition of the solid phase formed in aqueous calcium-silicate systems is investigated. Solutions of Са(NO3)2 and Na2SiO3 are used for the synthesis; the pH values were varied in the range 7.00–12.00. Freshly precipitated solid phases and products of their annealing at 1000°C were studied by the methods of Fourier IR spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM).

Phase assemblage in ettringite-forming cement pastes: A X-ray diffraction and thermal analysis characterization

The study attempts to describe the evolution of the solid phase composition with ongoing hydration in three different calcium aluminate rich cement paste mixtures by means of XRD and thermal analysis. The phase assemblage was followed quantitatively at discrete ages of 1, 7, 28, 56 and 90 days. Ettringite was the main crystalline hydration product. Quantification of amorphous fractions using the external standard method was performed and relatively high amounts of amorphous fractions were reported in all the cases.Thermal analysis revealed that the X-ray amorphous hydrate fraction was mainly composed of monosulphate, AH3 and C-S-H. The presence of strätlingite, was not clearly manifested in any of the DTG curves. A mass balance calculation based on stoichiometric reactions was performed in order to estimate the amounts of monosulphate, AH3, and C-S-H. The quantities of the amorphous portions obtained from QXRD were observed to be higher as those estimated from mass balance calculations. Additional calculations from oxide balance suggested that besides AH3 monosulphate and C-S-H, an X-ray amorphous AFm or/and C-S-H type like phase might form in the early age of hydration.During Rietveld refinement, the impact of the number of Chebyshev background polynomials in the determination of amorphous content was investigated.

Constraining the sources and cycling of dissolved organic carbon in a large oligotrophic lake using radiocarbon analyses

We measured the concentrations and isotopic compositions of solid phase extracted (SPE) dissolved organic carbon (DOC) and high molecular weight (HMW) DOC and their constituent organic components in order to better constrain the sources and cycling of DOC in a large oligotrophic lacustrine system (Lake Superior, North America). SPE DOC constituted a significant proportion (41–71%) of the lake DOC relative to HMW DOC (10–13%). Substantial contribution of 14C-depleted components to both SPE DOC (Δ14C=25–43‰) and HMW DOC (Δ14C=22–32‰) was evident during spring mixing, and depressed their radiocarbon values relative to the lake dissolved inorganic carbon (DIC; Δ14C∼59‰). There was preferential removal of 14C-depleted (older) and thermally recalcitrant components from HMW DOC and SPE DOC in the summer. Contemporary photoautotrophic addition to HMW DOC was observed during summer stratification in contrast to SPE DOC, which decreased in concentration during stratification. Serial thermal oxidation radiocarbon analysis revealed a diversity of sources (both contemporary and older) within the SPE DOC, and also showed distinct components within the HMW DOC. The thermally labile components of HMW DOC were 14C-enriched and are attributed to heteropolysaccharides (HPS), peptides/amide and amino sugars (AMS) relative to the thermally recalcitrant components reflecting the presence of older material, perhaps carboxylic-rich alicyclic molecules (CRAM). The solvent extractable lipid-like fraction of HMW DOC was very 14C-depleted (as old as 1270–2320 14C years) relative to the carbohydrate-like and protein-like substances isolated by acid hydrolysis of HMW DOC. Our data constrain relative influences of contemporary DOC and old DOC, and DOC cycling in a modern freshwater ecosystem.

Modeling the impact of melt on seismic properties during mountain building

AbstractInitiation of partial melting in the mid/lower crust causes a decrease in P wave and S wave velocities; recent studies imply that the relationship between these velocities and melt is not simple. We have developed a modeling approach to assess the combined impact of various melt and solid phase properties on seismic velocities and anisotropy. The modeling is based on crystallographic preferred orientation (CPO) data measured from migmatite samples, allowing quantification of the variation of seismic velocities with varying melt volumes, shapes, orientations, and matrix anisotropy. The results show nonlinear behavior of seismic properties as a result of the interaction of all of these physical properties, which in turn depend on lithology, stress regime, strain rate, preexisting rock fabrics, and pressure‐temperature conditions. This nonlinear behavior is evident when applied to a suite of samples from a traverse across a migmatitic shear zone in the Seiland Igneous Province, Northern Norway. Critically, changes in solid phase composition and CPO, and melt shape and orientation with respect to the wave propagation direction can result in huge variations in the same seismic property even if the melt fraction remains the same. A comparison with surface wave interpretations from tectonically active regions highlights the issues in current models used to predict melt percentages or partially molten regions. Interpretation of seismic data to infer melt percentages or extent of melting should, therefore, always be underpinned by robust modeling of the underlying geological parameters combined with examination of multiple seismic properties in order to reduce uncertainty of the interpretation.

A further discussion on solid-liquid equilibrium in complex synthetic paraffinic systems with the effects of solid-solid transition

A predictive thermodynamic model for the prediction of wax precipitation in paraffinic mixtures is developed, on the basis of the wax prediction model (RSFV-IRSW) established by Yang et al. (2016), where the liquid phase is described by the combination of regular solution model and Flory free-volume equation, and the solid phase is modelled by the combination of improved regular solution model and Wilson equation. Advancements are adopted in the present work: 1. The influence of transition enthalpy between disorder and order solid phases on liquid-solid fugacity ratio of pure component is considered; 2. A method for the precise calculation of fusion enthalpy and transition enthalpy is suggested; 3. The boundary condition to decide whether one component would precipitate out to form the solid phase is added. The predictive model, RSFV-IRSW, predictive Wilson and regular solution model are tested against the experimental data of complex synthetic paraffinic systems. Results show that the predictive model behaves the best with high prediction accuracy in terms of the characteristics of wax precipitation curve and the composition of solid phase.

Development of Effective Cobalt Catalysts for Hydrogen-Generating Solid Phase Compositions Based on Sodium Borane

Hydrogen-generating solid phase compositions based on sodium boran are promising systems for storage and transportation of hydrogen to be used for low-temperature fuel cells with proton-exchange membranes. Catalysts are added to the compositions in order to generate hydrogen at ambient temperature. The studies were focused on the influence of conditions of the cobalt catalysts preparation on the rate of gasgeneration. The efficiency of hydrogen evolution depended on the nature of the cobalt salt and pH of its aqueous solution where the active component precursor was reduced under the action of the hydride; these factors determined the composition, dispersion and magnetic behavior of the cobalt systems. The maximal rate of gas generation (505 cm 3 /min per 1 g of the composition containing 8.4 wt % of hydrogen) was observed in the presence of the sample reduced by sodium borane in a cobalt chloride solution with pH 1.3. The results obtained can be used to develop effective and inexpensive cobalt catalysts for generation of hydrogen from solid compositions based on sodium borane.

Quantification of carbon dioxide sourced by mineral reactions in ultradeep sedimentary basins

The accumulation of CO2 in some natural gas fields represents a risk for exploration, and calls for a way of integrating its occurrence in basin modelling. Among several possible sources we investigate mineral reactions able to take place within bottom sediments of particularly deep and hot sedimentary basins, i.e. at conditions of low-grade metamorphism (up to 500 °C and 2500 bar). These reactions involve lithologies where carbonate and alumino-silicate minerals are combined to form a « mixed composition ». For appraising decarbonation quantitatively we propose a method founded on thermodynamic calculations, that follows a modelling approach commonly used in metamorphic petrology. At given bulk composition and temperature-pressure (T-P) conditions, the composition and proportions of solid and fluid phases that coexist at equilibrium are computed using a Gibbs Energy Minimization (GEM) algorithm. On the basis of R.G. Berman's database we incorporate thermodynamic parameters for a variety of solid solutions including clay minerals, and for a CH4–CO2–H2O fluid mixture represented by the CPA-Electrolyte equation of state. A large range of decarbonation reactions is explored through a systematics involving 85 model compositions, and a unique T-P path typical of the targeted basins. We confirm that pure carbonate lithologies do not behave as CO2 source in the conditions explored. In contrast, we demonstrate that mixed compositions are likely to yield CO2 from successive mineral reactions, in which clay minerals play a prominent role. We also show that the temperature of incipient decarbonation, staggered over 325–425 °C, depends on the Ca/Mg/Fe composition ratio of the bulk sediment. CO2-prone reactions occurring from a selection of natural sediments are then presented. The CO2-prolific character of particular facies associated to the rift phase of a basin evolution is illustrated, notably in the case of lacustrine oil shales. Finally, we indicate a protocol that integrates the decarbonation scheme derived from thermodynamics into a CO2-generation formalism compatible with the usual formalism of a basin model.

Effect of Li doping on the superconducting properties of single domain GdBCO bulks fabricated by the top-seeded infiltration and growth process

Single domain GdBCO bulk superconductors have been fabricated by the top-seeded infiltration and growth process (Gd+011 TSIG) with solid phase compositions of (1-x)(Gd2O3+1.2BaCuO2)+xLi2CO3, (x=0, 0.04, 0.08, 0.10, 0.12, 0.16wt%). The effect of Li2CO3 doping on the growth morphology, microstructure, levitation force, trapped field and critical temperature (Tc) of single domain GdBCO bulks have also been investigated based on these samples. The results show that the single-domain GdBCO bulks can be fabricated when x is in the range of 0–0.16wt%. The size and distribution of Gd211 particles are not influenced by the Li2CO3 doping in the samples. The Tc of the samples decrease from 92.5K (x=0wt%) to 89.5K (x=0.16wt%) when x increases. The decreasing trend of Tc was caused by the substitution of Li+ on Cu2+ site in the GdBCO crystal. Both of the levitation forces and trapped fields of the samples increase first and then decrease with the increase of x; both of the largest levitation force of 38.5N（77K，0.5T） and the largest trapped field of 0.31T（77K，0.5T） are obtained in the sample when x=0.10wt%. These results show that appropriate Li doping is an effective way to enhance the flux pinning force and the other physical properties of GdBCO bulk superconductors fabricated by the Gd+011 TSIG method.

Phase equilibria in the Mg(NO3)2–Ln(NO3)3 (Ln = La, Ce, Pr)–HNO3 (∼21%)–H2O systems at 298.15 K and thermodynamic properties of 3Mg(NO3)2·2Ln(NO3)3·24H2O

The solid-liquid equilibria of the Mg(NO3)2–Ln(NO3)3 (Ln=La, Ce, Pr)–HNO3–H2O systems in the (∼21%) HNO3 regions at T=298.15K were studied by using the method of isothermal solubility, the phase diagrams were obtained based on the measured data. The Schreinemaker’s wet residues method was used to determine the compositions of solid-phases. The three quaternary systems are all composed of three equilibrium solid-phases Mg(NO3)2·6H2O, 3Mg(NO3)2·2Ln(NO3)3·24H2O, Ln(NO3)3·6H2O. The new solid-phase compounds 3Mg(NO3)2·2La(NO3)3·24H2O, 3Mg(NO3)2·2Ce(NO3)3·24H2O and 3Mg(NO3)2·2Pr(NO3)3·24H2O are congruently soluble in an average medium of ∼21mass% HNO3, and they were characterized by chemical analysis, X-ray diffraction (XRD), X-ray diffraction single crystal structure analysis, and thermogravimetric/differential thermogravimetric (TG–DTG) techniques. The XRD graphs of 3Mg(NO3)2·2La(NO3)3·24H2O, 3Mg(NO3)2·2Ce(NO3)3·24H2O and 3Mg(NO3)2·2Pr(NO3)3·24H2O are identical due to their isomorphic structure. The X-ray diffraction single crystal structure analysis show that 3Mg(NO3)2·2Ln(NO3)3·24H2O (Ln=La, Ce, Pr) all belong to hexagonal systems, with space group R3, for 3Mg(NO3)2·2La(NO3)3·24H2O, a=b=1.1082±0.0009nm, c=1.7422±0.0013nm, V=1.853±0.002nm3, Dc=3.976g·cm−3, Z=3, for 3Mg(NO3)2·2Ce(NO3)3·24H2O, a=b=1.1056±0.0003nm, c=1.7438±0.0009nm, V=1.8462±0.0008nm3, Dc=3.997g·cm−3, Z=3, for 3Mg(NO3)2·2Pr(NO3)3·24H2O, a=b=1.0992±0.0009nm, c=1.7211±0.0007nm, V=1.8012±0.0013nm3, Dc=4.101g·cm−3, Z=3. The ΔsolHθm (standard molar enthalpies of solution) of the compounds 3Mg(NO3)2·2La(NO3)3·24H2O, 3Mg(NO3)2·2Ce(NO3)3·24H2O and 3Mg(NO3)2·2Pr(NO3)3·24H2O in water (aq) were measured to be (107.96±0.74)kJ·mol−1, (110.18±0.54)kJ·mol−1 and (102.96±0.55)kJ·mol−1, respectively, and their ΔfHθm (standard molar enthalpies of formation) were calculated to be −(12242.6±2.5)kJ·mol−1, −(12223.1±2.4)kJ·mol−1 and −(12232.6±2.5)kJ·mol−1, respectively.

Carbonation Reaction and Microstructural Changes of Metro-Tunnel Segment Concrete Coupled with Static and Fatigue Load

AbstractCarbonation problems relating to concrete durability cannot correspond to the real engineering service environment, because the degradation of concrete properties is actually affected by load and multiple environment factors for a coupling effect. This paper studies the chemical reaction mechanism, carbonation depth, pH values, and pore-structure changes under a load and carbonation coupling effect. The authors study the time-dependent evolution of carbonation depth under different levels of tensile and compressive loads. The authors then further study the time-dependent evolution of concrete carbonation depth under fatigue bending loads at different stresses levels and cycles. While taking advantage of the microstructure characterization methods, X-ray diffraction (XRD), mercury intrusion porosimetry (MIP) and a pH-value meter were used to analyze the chemical reaction mechanism of the concrete carbonation process, undertake a quantitative analysis of the solid phase composition, and examine the ...

The composition of natrophosphate (sodium fluoride phosphate hydrate)

Natrophosphate is a common trace mineral in alkaline rocks and a major salt in alkaline nuclear waste that complicates waste processing. Natrophosphate has historically been assigned the composition Na7F(PO4)2·19H2O, but this conflicts with a more recent solubility study that claimed natrophosphate is a solid solution of NaF and Na3PO4. It is not possible to model the solubility of natrophosphate in nuclear waste until this controversy is resolved. The present study mixed stock solutions of 0.9 M NaF and Na3PO4 at different ratios at 8 °C. The compositions of the liquid phase and wet natrophosphate sample were measured by ion chromatography. Plotting the tie-lines between the solid and liquid phase composition showed convergence on a single composition, indicating that natrophosphate is not a solid solution. The resulting composition is approximately the same as the composition first reported more than 140 years ago. Thus, this study resolves the long-standing controversy in the literature concerning the composition of natrophosphate.

First assessment of the pore water composition of Rupel Clay in the Netherlands and the characterisation of its reactive solids

AbstractThe Rupel Clay member in the Netherlands largely corresponds to the Boom Formation in Belgium, and this marine, clay-rich deposit is a potential candidate to host radioactive waste disposal facilities. Prediction of the speciation of radionuclides in Rupel Clay pore water and their retardation by interactions with Rupel Clay components requires knowledge about the composition of Rupel Clay pore water, the inventory of reactive solids and understanding of interactions between Rupel Clay and pore water. Here, we studied Rupel Clay material which was obtained from cores collected in the province of Zeeland, the Netherlands, and from drilling cuttings retrieved from a drilling in the province of Limburg, the Netherlands. Pore water was obtained by mechanical squeezing of Rupel Clay material from Zeeland. Additionally, anaerobic dilution experiments were performed in which the clay material was suspended with demineralised water or a 0.1M NaHCO3solution. Solid-phase characterisation included determination of carbon, nitrogen and sulphur contents, measurement of cation exchange capacity (CEC) and sequential extraction of iron phases.In contrast to the pore water in Belgian Boom Clay, pore water collected from the location in Zeeland has a higher salinity, with chloride concentrations corresponding to 70–96% of those in seawater. The high chloride concentrations most likely result from the intrusion of ions from saline waters above the Rupel Clay in Zeeland. Cation exchange during salinisation might account for the observed deficit of marine cations (Na, K, Mg) and excess of Ca concentrations, in comparison with seawater. The measured CEC values at both locations in the Netherlands vary between 7 and 35 meq(100g)−1and are, for most samples, in the range reported for Boom Clay in Belgium (7–30meq(100g)−1).Pore water and solid-phase composition indicate that Rupel Clay from Zeeland has been affected by oxidation of pyrite or other Fe(II)-containing solids. When coupled to the dissolution of calcium carbonates, oxidation of pyrite can account for the elevated sulphate and calcium concentrations measured in some of the pore waters. The relatively low concentrations of pyrite, organic carbon and calcite in the Rupel Clay in Zeeland, in comparison to Limburg, might be an indicator for an oxidation event. Higher contents of dithionite-extractable Fe in Rupel Clay in Zeeland (0.7–2.6mg Fe / g clay) than in Limburg (0.4–0.5mg Fe / g clay) might also be a consequence of the oxidation of Fe(II) minerals. Oxidation in the past could have accompanied partial erosion of Rupel Clay in Zeeland before deposition of the Breda Formation. However, indications are given that oxidation occurred in some of the pore waters after sampling and that partial oxidation of the cores during storage cannot be excluded. Results from dilution experiments substantiate the influence of equilibration with calcium carbonates on pore water composition. Furthermore, removal of dissolved sulphate upon interaction with Rupel Clay has been observed in some dilution experiments, possibly involving microbial sulphate reduction.

The growth and stress vs. strain characterization of the silver solid solution phase with indium

Silver solid solution phase with indium has been discovered to have great mechanical properties and anti-tarnishing property, as shown in the results of our previous study. It is important to know the stress vs. strain curve before adopting this material in industrial applications. The growth of the homogeneous silver solid solution phase with indium is first described. The X-ray diffraction (XRD) patterns and scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDX) results are reported to verify the chemical composition of silver solid solution phase with indium samples. Based on the results, one could reversely determine the indium element composition in (Ag)–xxIn solid solution by examining the lattice constant value using XRD for unknown compositions. The preparation of ASTM tensile test samples and tensile test experimental setting are explained in details. The intrinsic mechanical material properties of silver solid solution phase with indium, i.e., characteristic stress vs. strain curves, are presented and analyzed, with pure silver stress vs. strain curve in comparison. According to the experimental results, silver solid solution phase with indium exhibits low yield strength, high ultimate tensile strength, and large elongation value before fracture, compared to pure silver. In addition, fractography of the fracture surface of the tested sample has been studied to confirm the superior ductility of silver solid solution phase with indium. These superior mechanical properties may bring silver solid solution phase with indium new applications in various industries such as electronics and brazing.

Application of the buffer theory for evaluating attenuation and natural remediation of ionic pollutants in aquatic ecosystems

The main focus in this review is showing how to use the developed buffer theory for assessing and predicting the long-term phenomena of attenuation and natural remediation of ionic pollutants in contaminated aquatic ecosystems, as well as for analyzing the way by which metals move and transform within the environment, the distribution of metals in ecosystems, their deposition and cycling in the terrestrial environment. The buffer theory is based on the rigorous thermodynamic analysis of complex chemical equilibria under environmental conditions in aquatic ecosystems, as natural waters and soils. It has been established that both homogeneous and heterogeneous systems manifest a buffer action towards all their components. The buffer properties in relation to the solid phase components are amplified with an increase of solubility due to protolytic or complex formation equilibria in saturated solutions. It has been established that the buffer capacities of components are mutually proportional, whereas for heterogeneous systems these relationships depend on the stoichiometric composition of solid phases. The use of the developed buffer approach may yield extended knowledge and a deeper understanding of the processes that control the concentrations of components. A number of the important conclusions concerning the investigated buffer systems have been made. The obtained results are indented to provide researchers with a tool needed to help them to set reliable limits of ion (metal) levels in the environment.

Effect of Isovalent Substitution on the Structure and Properties of the Zintl Phase Solid Solution Eu7Cd4Sb8-xAsx (2 ≤ x ≤ 5).

A novel Zintl phase structure type, Eu7Cd4Sb8-xAsx (x = 2, 3, 4, and 5), with the general formula Eu7Cd4Pn8 (Pn = mixed occupancy Sb and As), was synthesized by molten tin flux reaction. Its structure was determined using single-crystal X-ray diffraction methods. This structure type is only preserved for 2 ≤ x ≤ 5 under our experimental conditions, and efforts to synthesize samples with x < 2 or x > 5 resulted in other structure types. The mixed occupancy Sb and As can be thought of as a pseudoatom whose ideal size, in this range of Sb/As ratios, fits the structure. The title phase crystallizes in the I-centered monoclinic space group I2/m (No. 12, Z = 4) with unit cell parameters ranging as follows: a = 19.7116(17)-19.4546(13) Å, b = 4.6751(4)-4.6149(3) Å, c = 24.157(2)-23.871(15) Å, and β = 95.8798(1)-96.016(5)°, depending on the Sb/As ratio. The structure can be described as parallel double pentagonal tubes resulting from Cd-Pn and Pn-Pn bonding. These double pentagons are formed through corner sharing of the Cd-centered CdPn4 tetrahedra and a Pn-Pn interaction from two adjacent CdPn4 tetrahedra. This structure type is closely related to the Sr11Cd6Sb12 structure type as both share the same bonding features of Pn-Pn bonding and double pentagonal tubes. Electron microprobe analysis confirms the composition of these new Zintl solid solution phases. The As exhibits preferential substitution on specific sites, and site specificity trends are supported by lowest energy models from theoretical calculations. Theoretical calculations also predict that Sb-rich compounds should be metallic or semimetallic and that they should become more insulating as As content increases. Members of the solid-solution order ferromagnetically between 5 and 6 K and exhibit relatively low electrical resistivity between 50 and 300 K, ranging from ∼0.57 to ∼26 mΩ·cm, increasing with increasing As content.

Utilization of Some Egyptian Waste Kaolinitic Sand as Grog for Bricks and Concrete

The aim of the present study is to assess the suitability of some waste kaolinitic sand as grog for bricks and concretes. Three samples were selected and their chemical and mineralogical compositions as well as their ceramic and mechanical properties were investigated. The solid phase composition as well as the microstructure of the vitrified samples was also carried out using XRD and SEM methods. Refractoriness under load and thermal shock resistance are also investigated. Chemical and phase composition confirm that two samples (1 and 2) are fireclay with total impurities oxide contents (TIOC) less than 3.0 % while the third is mainly silica with TIOC less than 0.5 %. The microstructure of samples 1 and 2 shows predominant mullite crystals, bonded by silicate phases as confirmed by XRD, whereas silica phases are the main components of the third sample with minor intercalation of mullite phase. It is concluded that samples 1 and 2 fired at 1500 ◦C can be used as grog for brick and concrete manufacture in industrial furnaces up to 1400 °C while sample 3 needs some additives to form denser grains.

Mineralogical and chemical composition analysis of some saudian raw materials

This work aims at studying the solid phase composition and chemical constitution of some mineralogical raw materials widespread in Gholaa and Osfan regions, Khulais Governorate, in the western area of the Kingdom of Saudi Arabia. Ten samples were investigated through their phase composition using X-ray diffraction (XRD). Four of which were selected for further investigations. The quantitative phase compositions of the selected samples were calculated from XRD data. Their chemical constitutions were determined using x-ray fluorescence technique (XRF). The microstructure of one selected sample was depicted using scanning electron microscope attached with EDAX unit to analyze elementary some selected crystals. Most of the investigated samples composed mainly of albite mineral (NaAlSiO3) and they are suitable for glass ceramic industries. One sample contains considerable contents of quartz (SiO2) and kaolinite (Al2O3.2SiO2.2H2O) in addition to albite; it is suitable for the cement, brick and ceramic industry. Some minerals were present in varying amounts in the samples namely; chlorite (Mg6Si4O10(OH)8), chamosite (Fe3Si2O5(OH)4), chabazite (CaSrAl silicate), biotite (H4K2Mg6Al2Si6O2), microcline (KAlSi3O8), montimorillonite (Mg.Al2O3.5SiO2.xH2O), hematite (Fe2O3) tremolite (Na0.11Ca1.69Mg4.6Fe0.48Al0.29Si7.82O22(OH)2), kaolinite (Al2Si2O5(OH)4) and anatase (TiO2). Based on their chemical and mineralogical compositions the raw materials are suitable for various chemical, mineralogical, and engineering applications.

Benthic-pelagic coupling of nutrients and dissolved organic matter composition in an intertidal sandy beach

Subterranean estuaries (STEs) are important biogeochemical land–sea interfaces, where fresh groundwater mixes with seawater in coastal aquifers. However, the sources of dissolved organic matter (DOM) and the connection of its molecular-level processing to pore water chemistry and redox conditions in these ecosystems are still not well understood. We studied the cycling of DOM in the STE of an intertidal sandy beach of the North Sea on spatial and seasonal scales. Ultrahigh-resolution mass spectrometry was used to identify thousands of DOM molecular formulae. These data were interpreted in the context of inorganic pore water chemistry, stable carbon isotope composition of solid-phase extracted (SPE) DOM and chemical tracers for bioavailable (dissolved carbohydrates, DCHOs) as well as biorefractory DOM (dissolved black carbon, DBC). Numerical modelling was used to estimate pore water residence times indicating relatively young pore water in the upper saline plume (USP, <4 years) and decades-old groundwater in the freshwater discharge tube. The detected levels of dissolved Fe and ammonium in the USP at sediment depths exceeding 50cm demonstrated suboxic conditions. Statistical analyses revealed complex biotic and abiotic DOM processing apart from conservative mixing of marine and terrestrial endmembers. We propose that the input of bioavailable marine and terrestrial DOM, such as DCHOs, by percolating seawater and meteoric groundwater and its degradation by microbes caused oxygen depletion favoring Fe oxide/hydroxide reduction. In the freshwater discharge tube, the presence of highly aromatic compounds, DBC, and 13C-depleted SPE-DOM indicated the intrusion of meteoric groundwater containing terrestrial DOM. The discharge of this groundwater appears to be a significant source of nutrients (e.g., ammonium) and biorefractory, e.g. combustion-derived, DOM to the adjacent water column.