Lower Degree Of Structural Order Research Articles

Effect of horizontal insertion of metal wire mesh into the flame on the formation and suppression of soot in acetylene diffusion flame

A simple and efficient strategy to suppress soot from acetylene diffusion flames is reported for the first time. Horizontally insertion of metal wire mesh into the acetylene diffusion flame is found to greatly suppress the soot emission. The effects of experimental parameters such as acetylene flow rate, wire mesh height above nozzle (WHAN), material of wire mesh, mesh number, and inner diameter of the burner nozzle on soot suppression in acetylene diffusion flames are investigated. In addition, the collected soot samples are characterized by TEM, HRTEM, XRD, BET and Raman. The soot suppression efficiency can reach 100 % by horizontal insertion of the metal wire mesh in the acetylene diffusion flame. The WHAN has a great influence on the effect of soot suppression. In the first 210 s of horizontally inserting the metal wire mesh into the flame, the total mass of collected soot first decreases and then increases with the increase of WHAN. The minimum total mass of soot is achieved when the normalized WHAN (obtained by dividing the wire mesh height above nozzle by flame height without insertion of the wire mesh) is at 0.1. This position corresponds to the soot particle inception zone of the acetylene diffusion flame. The flame is divided into two parts when the metal wire mesh is horizontally inserted into the flame. The temperature of the flame below the metal wire mesh decreases from 1770 K to 1480 K. The temperature of the flame above the metal wire mesh increases from 1590 K to 1780 K. The soot collected on the metal wire mesh grows into a volcano-shaped carbon (VSC) structure. The results of the schlieren imaging experiments show that this structure can promote the mixing of air and fuel in the lower region of the flame thereby suppressing the formation of soot particles. The soot analysis shows that the horizontal insertion of metal wire mesh into the flame leads to high amorphous feature and low degree of structural order of the soot, which means that the oxidation reactivity of the soot increases.

Optical parameters and microstructural properties of Solid Bitumens of high reflectance (Impsonites). Reflections on their use as an indicator of organic maturity

Six solid bitumen samples from Paja Formation (Cretaceous of Colombia) were optically, chemically and structurally characterized using bulk chemistry, reflectance indicating surface (RIS), micro-Raman and X-ray diffraction (XRD) parameters. The volatile matter and carbon contents and high random reflectance (Ro%) placed these solid bitumens in the category of cata-impsonites according to Jacob's classification. RIS axes (RMAX, RINT and RMIN) form almost a sphere, and consequently, the anisotropy (Ram or bireflectance values) of these materials is very weak, comparatively to other carbonaceous materials (coals) of similar degree of evolution. The weak anisotropy character of the solid bitumen is related to the absence of pressure in the system, which did not promote the orientation of the basic structural units (BSUs) in a three-dimensional arrangement. The degree of ordering evaluated by Raman parameters, such as full width at half maximum (FWHM) of the D1 and G bands, and XRD parameters, including d002 and crystallite sizes Lc and La, showed that the solid bitumens of the Paja Formation have a low structural order equivalent to high-rank coals, specifically anthracites B (3.0% ≤ Ro < 4.0%), although their reflectance values placed them in a higher rank (Ro > 4.0%). The discrepancy between high reflectance and low degree of structural order can explain why some of the equations used to estimate equivalent vitrinite reflectance (Ro eq. Vite) from solid bitumens do not work universally. Taking in consideration several equations available in the literature, Jacob's equation (Jacob, 1989) was the one that fitted the Ro eq. Vite values in the range of 3.0% to 4.0%, which parallels with the degree of structural order obtained for the solid bitumens. Consequently, Jacob's equation can now be extended to solid bitumen in the range of cata-impsonites.

Blue or green? turquoise–planerite species from Carico Lake Valley in Nevada, the United States: Evidence from Raman spectroscopy

AbstractBlue and green turquoise–planerite species from Carico Lake Valley in Nevada have the formulae □0.69(Na0.01K0.01Cu0.20Ca0.06Mg0.02Ba0.01 Zn0.01)(Al5.97V0.04 Fe0.03)[PO4]4 (OH)8·4H2O and □0.66(K0.01Cu0.24Ca0.05Mg0.02Ba0.01Zn0.01)(Al5.87Fe0.13)[PO4]4(OH)8·4H2O, respectively. The content of Al3+ and Fe3+ at the B‐site together with slight differences in Cu amount at the A‐site is the main factors that differentiate these two species. Green planerite shows higher crystallinity and contains less water in its structure. The blue species is more porous with a lower degree of structural order and higher water enrichment. The Cu/Fe ratio together with local symmetry around chromophore ions in the structure seem to be responsible for the specific colouration of both phosphates. The species are inhomogeneous and contain a wealth of mineral (goethite, barite, quartz, kaolinite, chloritoid, destinezite, and some vanadate) and organic inclusions (bituminous matter and aliphatic hydrocarbons). Raman microspectroscopy with the application of different exciting radiation, that is, laser lines of 514.5 nm (green) and 442 nm (blue) for blue and green turquoise–planerite species revealed further differences between these two coloured species: (a) various positions of the most intensive band attributed to ν3 (PO4)3‐, (b) shift of ν3 four component bands, (c) various intensity ratios and integral intensity ratios of ν3 component bands, and (d) some diagnostic bands coming from Fe‐O (green species) and Cu‐O vibrations (blue species) obtained with principal component analysis (PCA).

Synthesis of sodalite from Brazilian kaolin wastes

AbstractKaolin wastes from the Capim and Jari regions (Brazil) were used to produce sodalite under the same conditions used in the Bayer process, in order to control its formation when necessary. Of the two kaolin source materials, the kaolinite from the Jari region was more reactive in the synthesis of sodalite, which is attributed to the low degree of structural order of this clay mineral which increased its reactivity. At a temperature of 150°C and with a Na/Al ratio of 2, although the kaolinite did not react completely, sodalitewas the primary reaction product. An increase in the temperature to 200°C provoked the complete reaction of the kaolinite only for the products in which carbonate and sulfate were used. With a Na/Al ratio &gt;2 and for both of the temperatures, the kaolinite reacted completely to form sodalite.

Kinetic behavior of partially dehydroxylated kaolinite

The multi-cycle heating and cooling thermogravimetric (TG) method was used to study the kinetic behavior of three kaolinite samples: defect-free Keokuk kaolinite, KGa-2 with a very low degree of structural order, and KGa-1 having intermediate structural order. In each cycle, the maximum cycle temperature (MCT) was set to 25 °C higher than the preceding cycle. The TG patterns consist of a set of subsequent DTG maxima representing the portions of OH groups that did not dehydroxylate in previous cycles. Each stage of partial dehydroxylation consists of two kinetic mechanisms and for each of them the experimental dα/d t values that characterize the reaction rate of the dehydroxylated fraction, α, within a period of the reaction time, t , were computed. One mechanism corresponds to a zero-order reaction that occurs in each cycle and indicates that the reaction is homogeneous and each non-dehydoxylated layer is transformed into metakaolinite layer without formation of intermediate derivatives. For this step of the cycles activation energy, E a , was calculated from the linear relationship between ln(dα/d t ) and reciprocal temperature, T ; for KGa-2 kaolinite, the E a varies from 32.0 to 38.1 kcal/mol; in KGa-1, E a varies from 37.1 to 40.4 kcal/mol, whereas in Keokuk, E a varies from 42.7 to 47.5 kcal/mol. The particular variation of the E a is discussed in terms of structural and morphological features of the samples. The kinetic mechanism of the second step of reaction corresponds to the temperature range higher than the first step of the same heating cycle. The second step starts from the point where α = α P that was found to vary between 0.25 and 0.45. The acceleration of the reaction rate of dehydroxylation within this interval decreases with increasing α and T , and the mechanism observed for each of the studied samples is independent of its stacking order, average particle size, and particle size distribution. The f (α) is a function of the reaction mechanism in the second step and has the form ![Formula][1] where n is an empirical parameter and its value was found from <0.01 to 0.06–0.08 among cycles and samples. The value of n controls the reaction rate slowing or the deviation from the zero-order reaction and increases with increasing metakaolinite content. Using parameters n , α, and T determined for the second step, E a values were calculated for the second step of reaction in each heating cycle. For the Keokuk kaolinite, E a value varies from 31.6 to 37.5 kcal/mol, in KGa-1 E a is 27.0–35.6 kcal/mol, and in KGa-2 the E a value varies from 26.3 to 34.9 kcal/mol. A structural model explaining the acceleration rate slowing is discussed. [1]: /embed/mml-math-1.gif

Use of 29Si and 27Al MAS NMR to study thermal activation of kaolinites from Brazilian Amazon kaolin wastes

The study of thermal activation of kaolinite at various temperatures to produce highly reactive metakaolinite from Brazilian Amazon kaolin wastes was studied using 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR). The wastes used in the current study came from the Capim and Jari regions in northern Brazil. The mineralogical and chemical characterizations of Jari kaolin (KJ) waste were performed by XRD, FTIR, DTA–TGA, SEM and chemical analyses. The results indicate that the Jari and Capim kaolins (KC) wastes are composed primarily of kaolinite and that KJ is composed of a typical kaolinite with a low degree of structural order. The ideal temperature to produce highly reactive metakaolinite is 600°C for KJ and 700°C for KC, suggesting that the degree of structural order of kaolinite has a definite influence on its dehydroxylation temperature. These results were confirmed when zeolite NaA was synthesized from metakaolins produced at temperatures used in this work.

Characteristics of Chars from Low-Temperature Pyrolysis of Lignite

Low-temperature pyrolysis offers a potential way of upgrading lignite and producing chars to replace thermal or pulverized coal injection (PCI) coals in combustion or being used as inert components in a blend for coking. In this study, the characteristics of chars from low-temperature pyrolysis of two lignite coals have been investigated. The changes in char morphology and chemical structures were investigated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The combustion reactivity of chars was analyzed in a thermogravimetric analyer (TGA) using non-isothermal techniques. The results show that chars from low-temperature pyrolysis of lignite coal below 450 °C were more reactive than higher temperature chars. Higher reactivity of low-temperature chars was attributed to the higher concentration of active sites and lower degree of structural order compared to that of high-temperature chars. Indonesian (YN) lignite showed a higher weight loss rate compared to Hulunbeier (HL) coal, which was attributed to a higher concentration of liptinite and vitrinite in YN coal. FTIR analysis indicated that the aliphatic structures and oxygen-containing functional groups decreased with an increasing pyrolysis temperature. The intensity of tightly bound cyclic OH tetramers and OH–ether O hydrogen bonds were higher than other hydrogen bonds in the 3700–3600 cm–1 region of infrared (IR) spectra. The density of alkyl chains and cross-linking reactions affected the yield of tar. The aromaticity of char increased with an increasing pyrolysis temperature. The abundance of C═O and COOH structures decreased drastically with increasing temperature. A lower concentration of active sites on high-temperature chars resulted in lower combustion reactivity compared to low-temperature chars. The C–O and C═C groups decreased as the temperature increased possibly because of the aromatic condensation. The extent of aromatic substitution decreased up to 650 °C. At temperatures above 650 °C, the degree of aromaticity was strengthened and larger condensed aromatic nuclei were formed. Brunauer–Emmett–Teller (BET) surface area analysis revealed that high-temperature chars have significantly higher surface area compared to chars produced at low temperatures. However, the concentration of active sites was lower in high-temperature chars. Therefore, it can be concluded that diffusion was the main reaction mechanism in high-temperature chars.

Characterization of β-Sheet Structure in Ure2p1-89 Yeast Prion Fibrils by Solid-State Nuclear Magnetic Resonance

Residues 1-89 constitute the Asn- and Gln-rich segment of the Ure2p protein and produce the [URE3] prion of Saccharomyces cerevisiae by forming the core of intracellular Ure2p amyloid. We report the results of solid-state nuclear magnetic resonance (NMR) measurements that probe the molecular structure of amyloid fibrils formed by Ure2p1-89 in vitro. Data include measurements of intermolecular magnetic dipole-dipole couplings in samples that are 13C-labeled at specific sites and two-dimensional 15N-13C and 13C-13C NMR spectra of samples that are uniformly 15N- and 13C-labeled. Intermolecular dipole-dipole couplings indicate that the beta-sheets in Ure2p1-89 fibrils have an in-register parallel structure. An in-register parallel beta-sheet structure permits polar zipper interactions among side chains of Gln and Asn residues and explains the tolerance of [URE3] to scrambling of the sequence in residues 1-89. Two-dimensional NMR spectra of uniformly labeled Ure2p1-89 fibrils, even when fully hydrated, show NMR linewidths that exceed those in solid-state NMR spectra of fibrils formed by residues 218-289 of the HET-s prion protein of Podospora anserina [as originally reported in Siemer, A. B., Ritter, C., Ernst, M., Riek, R., and Meier, B. H. (2005) Angew. Chem., Int. Ed. 44, 2441-2444 and confirmed by measurements reported here] by factors of three or more, indicating a lower degree of structural order at the molecular level in Ure2p1-89 fibrils. The very high degree of structural order in HET-s fibrils indicated by solid-state NMR data is therefore not a universal characteristic of prion proteins, and is likely to be a consequence of the evolved biological function of HET-s in heterokaryon incompatibility. Analysis of cross peak intensities in two-dimensional NMR spectra of uniformly labeled Ure2p1-89 fibrils suggests that certain portions of the amino acid sequence may not participate in a rigid beta-sheet structure, possibly including portions of the Asn-rich segment between residues 44 and 76.

Heavy Metals in Wastewater: The Effect of Electrolyte Composition on the Precipitation of Cadmium(II) Using Lime and Magnesia

The effect of effluent composition on the efficiency of hydroxide precipitation of Cd(II), using both lime and magnesia as precipitants, has been modelled by the solubility domain approach in order to provide wastewater effluent treatment limits, and has been experimentally validated. Common anionic species such as Cl−, SO42− and CO32− have been treated. Solubility domain calculations were based on those phases that were found to determine metal solubility for systems representing the upper and lower limits of potential effluent chemical compositions. The isolated phases were found to resemble their mineralized counterparts, although in several cases exhibited a lower degree of structural order. Experimentally determined Cd(II) solubilities were generally encompassed within the calculated solubility domains, indicating that solubility domain predictions provide effluent treatment quality assurance ranges for the hydroxide precipitation process. The formation of gypsum (CaSO4.2H2O) and calcite (CaCO3) at higher SO42− and CO32− concentrations as secondary precipitates using lime as the precipitant, and the hydroxy-sulfate Mg2(OH)2SO4.xH2O, nesquehonite (MgCO3.4H2O), hydromagnesite [Mg5(OH)2(CO3)4.4H2O] and brucite [Mg(OH)2] when employing magnesia was shown to have little effect on the observed residual Cd(II) solubility, although Mg(OH)2 did promote β-Cd(OH)2 formation in the Mg2+-containing Cd(II)/Cl− and Cd(II)/SO42− systems.

Determination of structural disorder degree using an XRD profile fitting procedure. Application to Czech kaolins

Diffractions of (02, 11) band are very sensitive to the structural defects in kaolinite structure. Therefore, the empirical relation based on weighting peak intensity ratio of 0 2 0, 1 1̄ 0, and 1 1 1̄ (1 1̄ 1̄) reflections was used to estimate the degree of disorder in kaolinite samples collected from different Czech Republic kaolin deposits. X-ray diffraction (XRD) profiles taken from <5 μm fraction of kaolinite samples were used for determination of peak intensities I(1 1̄ 0), I(1 1 1̄), I(1 1̄ 1̄), I(0 2 0) and full width at half maximum (FWHM) values using profile fitting and decomposition procedure. The weighting intensity ratio index (WIRI) WIRI=1− exp{−[w 1I(1 1 ̄ 0)+w 2I(1 1 1 ̄ )+w 3I(1 1 ̄ 1 ̄ )]/[w 4I(0 2 0)]} was calculated. The w 1, w 2, w 3, and w 4 weight values are the reciprocal values of FWHM for 1 1̄ 0, 1 1 1̄, 1 1̄ 1̄, and 0 2 0 reflections, respectively. According the WIRI values (theoretically ranging from 0 to 1), three groups of kaolinite samples can be recognized: (I) one sample with high degree of structural order (0.70<WIRI<1.00), (II) two samples with medium degree of structural order (0.40<WIRI≤0.70), and (III) five samples with low degree of structural order (0.00<WIRI≤0.40). The WIRI values obtained were compared with Hinckley (HI) and Aparicio–Galán–Ferrell (AGFI) indices and very good relations were found between them.

Mg-Rich Light Alloys Synthesised by Mechanical Alloying

In this work, MgxTi1-x (x = 18, 50 and 95 at.%) and Mg88Ti4Si7 alloys were synthesised by mechanical alloying. Phase transformations occurring in the samples as a function of milling time and during subsequent heating were studied by means of x-ray diffraction, scanning electron microscopy, differential scanning calorimetry and electron probe microanalysis. Concerning the TiMg binary system, super-saturated Ti(Mg) solid solutions with low degree of structural order were obtained after milling. The Mg88Ti4Si7 mechanical alloyed sample was formed by a Mg2Si intermetallic phase in a Mg matrix. During heating up to 600oC, there was the formation of further Mg2Si at 380oC, followed by the formation of Ti5Si3 at 540oC. No decomposition of either Mg2Si or Ti5Si3 phases was detected during cooling. The final structure of mechanically alloyed and heat treated Mg88Ti4Si7 sample consist of a fine precipitation of these two intermetallics in a Mg matrix.

Organic geochemistry of artificially matured conodonts

Organic geochemical methods for conodont analysis have been developed. Coniform elements of the conodont genus Drepanodus from the Ordovician Emanuel Formation and pectiniform elements of the conodont genus Polygnathus from the Devonian Napier Formation both from the Canning Basin, Australia have been shown to contain different organic matter. Both conodont samples have been artificially matured and the structure of organic matter present related to the conodont alteration index (CAI) and maturation temperature (TM). The carbon 1s X-ray photoelectron spectra (XPS) acquired from both sample sets contain six peaks. These peaks are assigned to highly ordered graphitic like carbon (282.9 eV), sp 3 hybridised carbon bonded to only carbon or hydrogen (284.7 eV), ether (286.1 eV), alcohol (287.0 eV), carbonyl (287.6 eV) and carboxyl (289.0 eV) functional groups. Alkene and aromatic carbon is also probably present but is difficult to delineate. During artificial maturation, XPS analysis monitors the main chemical modifications expressed by the carbon–oxygen functional groups. The first stage of maturation begins with the removal of carboxyl and alcohol groups before a CAI of 2 (TM 450 °C). Between a CAI of 3–6 (TM 450–800 °C) an increase of sp 3 hybridised carbon bonded to only carbon or hydrogen is found, which is accompanied by a decrease in ether and carbonyl functional groups. From a CAI of 6–7 (TM 800–950 °C), sp 3 hybridised carbon bonded to hydrogen or carbon and carbonyl decreases while the development of highly ordered graphitic like carbon is observed. The first order laser Raman spectra recorded for both sample sets show a low degree of structural order from a CAI of 2–3, and from CAI 4–6 show a progressive increase in structural disorder of conodont organic matter. The D/G band (band at approximately 1345–1365/band at 1610 cm −1) line width ratio correlates with CAI. Conodont colour during artificial maturation occurs by migration of compounds to the surface. As the nitrogen compounds are volatilised from the surface, colour disappears.

Deposition of hydrogenated amorphous carbon films from CH4/Ar plasmas: Ar dilution effects

Hydrogenated amorphous carbon (a-C:H) films were deposited, at room temperature, from a CH4/Ar plasma produced by a radio frequency (r.f.) glow discharge system at 13.56 MHz, and different power values. Two different characterisation techniques, Raman and FTIR spectroscopies, have been used to investigate correlations between deposition conditions and properties of hydrogenated amorphous carbon films. The composition of the initial gaseous mixture and the r.f. power input are shown to affect significantly both mechanical and microstructural properties of deposited films. As the fraction of argon in the feed gas is increased, the deposition rate increases and the deposited film shows a higher friction coefficient, thus suggesting the production of a softer material. On the other hand, Raman measurements suggest the occurrence of a lower degree of structural order in the sp2 lattice. Experimental findings are discussed in terms of the different chemical composition of the plasma.

Effect of electrolyte composition, and of added iron(III) in the presence of selected organic complexing agents, on nickel(II) precipitation by lime

The effect of effluent composition involving the common anionic species Cl −, SO 4 2− and CO 3 2− on the efficiency of nickel(II) precipitation, modelling lime (CaO) as the precipitant, has been investigated using the solubility domain approach. Solubility domains were based on the phases that were found to limit metal solubility for systems representing potential effluent composition limits. These phases were found to resemble their mineralized counterparts, but with a lower degree of structural order. At higher SO 4 2− and CO 3 2− concentrations both gypsum (CaSO 4·2H 2O) and calcite (CaCO 3) were formed, but these had little effect on the observed residual nickel solubility. The calculated solubility domains were found to generally encompass the experimentally determined solubilities, thereby providing quality assurance ranges for hydroxide precipitation. The effect of the complexing anions tartrate and EDTA 4− on residual Ni(II) in solution as well as the effects of the addition of Fe(III) on the removal of Ni(II) complexed by these species are described.

Effect of electrolyte composition on zinc hydroxide precipitation by lime

The effect of effluent composition on the efficiency of the hydroxide precipitation of Zn 2+ modelling lime (CaO) as a precipitant has been predicted using the solubility domain approach and experimentally validated. Solubility domains were based on the phases that were found to be solubility limiting for systems representing potential effluent chemical composition limits. All such phases were found to resemble their mineralized counterparts with a lower degree of structural order. The generated solubility domains generally encompassed the experimentally observed solubilities, thus providing effluent treatment quality assurance ranges for the hydroxide precipitation process. The presence of calcite (CaCO 3) and gypsum (CaSO 4.2H 2O) as secondary precipitates had little effect on the observed residual zinc solubilities. Validation of the solubility domain approach using real industrial wastewater was accomplished.

Comment on “In Situ and Ex Situ Infrared Studies of Nature and Structure of Thiol Monolayers Adsorbed on Cuprous Sulfide at Controlled Potential. Simulation and Experimental Results”

In situ and ex situ infrared reflection spectroscopy combined with spectral simulation were applied to the study of monolayers of ethyl xanthate (C 2 H 5 OCS 2 - ) formed at controlled potential on cuprous sulfide. Because cuprous sulfide is a semiconductor and shows low absorption in the infrared region, the reflection spectra were recorded at different incident angles and polarizations allowing full spectral characterization ofthe molecules in the adsorption layer. Detailed compositional and structural characterization is presented on the basis of the comparison of simulated and experimental spectroscopic results. Quantitative evaluation of the orientation of particular molecular groups in the adsorbed xanthate molecules and the thickness of the surface layers produced under different adsorption conditions are discussed in detail. The in situ cell configuration used in this study was tailored specifcally for the investigated system. Two major factors were considered in designing the in situ cell : the optimum of experimental sensitivity and, equally as important, the maximum confidence in the interpretation of experimental results. Spectral simulation of different in situ cell configurations enabled the determination of experimental conditions under which optical effects are less dependent on certain parameters which are difficult to precisely control in real experimental systems (uncollimated incident beam, surface roughness, real thickness of solution layer). Also, the verification of the quantitative results obtained from the in situ experiments is discussed. Three adsorption products were identified (i) cuprous ethyl xanthate complex, (ii) product(s) of surface-induced decomposition of the first adsorbed xanthate molecules, and (iii) xanthate oxidation product, dixanthogen ((C 2 H 5 OCS 2 ) 2 ), formed at very high potentials. The xanthate decomposition product is formed only at submonolayer coverage and its presence results in a low degree of structural order of the adsorbed cuprous ethyl xanthate molecules. Under conditions which favor slow adsorption kinetics (low concentration, open circuit potential) the decomposition product can be removed from the surface structure. During this process the surface diffusion and reorientation of the adsorbed xanthate molecules take place. This results in the formation of a well-ordered structure of the cuprous ethyl xanthate surface complex with the methyl group oriented toward the aqueous solution. Removal of the decomposition product and changes in the structural order of the adsorbed xanthate molecules on cuprous sulfide were observed when the sample was immersed in a low-concentration xanthate solution or into water. Under fast kinetic conditions, i.e., xanthate concentration above 1 x 10 -4 M and at potentiostatic control, the decomposition product is trapped at the interface within a multilayer structure of cuprous xanthate and cannot be easily removed. This surface structure shows a very low degree of structural order. Formation of close to monolayer coverage by cuprous xanthate complex is observed at a potential close to 0 mV, which agrees with the thermodynamic data. At lower potentials, between -60 and 0 mV (underpotential adsorption) only submonolayer coverage was produced.

Use of the Solubility Domain Approach for the Modeling of the Hydroxide Precipitation of Heavy Metals from Wastewater

The use of the solubility domain approach for providing representative effluent treatment quality assurance standards for the hydroxide precipitation of Zn2+, Pb2+, and Fe3+ from various wastewater composition types has been modeled and experimentally validated. Solubility domain calculations were based on the precipitated phases isolated from systems representing the upper and lower limits of potential effluent chemical compositions. All such phases resembled their mineralized counterparts with a lower degree of structural order. For all systems modeled, the experimentally observed solubilities were generally encompassed within the predicted solubility domains. Validation of the approach using real treatment data demonstrated the effectiveness of the solubility domain method in predicting optimum operating condition ranges for wastewater treatment. Prediction accuracy was largely dependent on the nature of the solubility-limiting phase. With the exception of carbonate-rich systems, changes to the aqueous-phase complexation had a minimal impact on solubility in comparison to selection of the solubility-limiting phases.

Imogolite from New Guinea

Imogolite is a hydrous aluminium silicate mineral (Cradwick et al., 1973) with a fibrous morphology and low degree of structural order, which, since first described by Y oshinaga and Aomine (1962), has been reported to occur as a weathering product of pyroclastic materials in many localities. However, Wada et al. (1972) have recently drawn attention to the fact that imogolite occurs in gels derived from massive, though jointed, basalt in Hawaii. The purpose of the present note is to describe the identification of imogolite in some very young volcanic ash soils from New Guinea-a finding that has important genetic implications.