Dechlorination of contaminated sediments of Ionian Sea

Natural dredged sediments contaminated by PCBs from the heavy industrialized harbor of Taranto (S. Italy) on the Ionian Sea, previously dechlorinated by mechanical activation in different ball mills (SPEX and AGO-2), together with synthetic mixtures emulating the contaminated sediments, were submitted to thermogravimetric and calorimetric measurements as well as to X-ray powder diffraction in order to clarify the dechlorination reaction mechanism. Both major sediment components, i.e., carbonates and clay minerals, were found to be affected by the mechanical activation. As trace pollutants like PCBs are concentrated in clays, the mechanical activation of sediments increases the release of pollutants yielding a more active decontamination. DSC results were less informative as calorimetric peaks from different thermal events were found to overlap.     

240Pu/239Pu atom ratios in the bottom sediments of the NW Pacific Ocean

^239+240Pu concentrations and ²⁴⁰Pu/²³⁹Pu atom ratios in bottom sediments of the Yellow Sea, Korea Strait, East Sea (Sea of Japan), Sea of Okhotsk, and Northwest Pacific Ocean were determined. In coastal sediments near the Korean Peninsula, ^239+240Pu concentrations varied from 0.02 to 1.72 Bq^.kg^-1, and their ²⁴⁰Pu/²³⁹Pu atom ratios from 0.15 to 0.24, with an average of 0.20±0.03. ²⁴⁰Pu/²³⁹Pu atom ratios of bottom sediments in the deep NW Pacific Ocean and its marginal seas (East, Okhotsk seas) were in the range of 0.15-0.23. A little elevated ²⁴⁰Pu/²³⁹Pu atom ratios in the bottom layer sediment may be due to Pu released into the environment during the pre-moratorium period, having high ²⁴⁰Pu/²³⁹Pu atom ratios and low ²³⁸Pu/^239+240Pu activity ratios.     

EPXMA survey of shelf sediments (Southern Bight, North Sea): A glance beyond the XRD-invisible

Shelf sediments of the southern North Sea, were studied with a microanalytical [electron probe X-ray microanalysis (EPXMA)] and two bulk [X-ray diffraction (XRD) and X-ray fluorescence (XRF)] techniques. The investigation proved that the promptness of the microanalytical method is combined with a reasonable analytical reliability. XRD studies of such a type of sediments with monotonous mineral composition are not able to provide mineralogical information beyond the main well-crystalline minerals and the mineralogical quantitative characteristic of the sediment based on XRD estimations are incorrect. The EPXMA mineralogical interpretations are based on the statistical evaluation of a huge data set (thousands of mineral particles) and provide a rather correct quantitative determination of the main minerals. The comparative EPXMA-XRF study revealed that the Al, Si, K, Ca, Fe and to some extent Ti contents estimated by EPXMA are fairly reliable. In this respect the accuracy of the EPXMA-based mineral identification of the pure silicates, pure aluminosilicates, and Al-, Ca-, Fe- and Ti-containing minerals with simple composition is very high. Mg-calcite, augite and apatite determinations are assessed to be correct. The supposed accuracy of the clay mineral determinations is slightly lower (70-80%) than that of the other main minerals due to the complex and varying composition of the clays. The identification of XRD-invisible accessory minerals and quantification of their presence in the sediments is an essential advantage of the EPXMA, which makes it a useful approach in tracing the origin of the sediments, the pathways of their transport and the geochemical processes they have undergone.However, the EPXMA has several flaws, which need to be solved in the future sediment investigations: (1) calibration with natural standards is needed in order to provide a higher accuracy of the mineral determinations; (2) any EPXMA study of sediments needs to be secured with XRF examinations of selected samples since EPXMA gives only semi-quantitative information about the abundance of the elements; (3) ultra-thin window EPXMA of low-Z elements has to be used since some of them (O, C) are always present in the main sediment components: silicates, aluminosilicates, carbonates and metal oxyhydroxides; (4) the interpretations of the clay fraction have to be supported with detailed XRD investigations of selected samples, while the mineralogy of the silt and sand fractions needs to be backed up with optical microscopy studies. The information from different analytical techniques (EPXMA with XRF-XRD-optical microscopy of selected samples) combined with the knowledge about the most possible minerals in a given environment, would give the most reliable results in studying mineralogical composition of shelf sediments.     

Adsorption of nitrobenzene andn-pentanol from aqueous solution on hydrophilic and hydrophobic clay minerals

The sorption of nitrobenzene andn-pentanol from dilute aqueous solution on swelling clay minerals and their organophilized derivatives (organo clays) was studied. Adsorption excess isotherms were obtained by the immersion method. The basal spacings of the clay minerals were determined by X-ray diffraction measurements. By combining these two independent methods, composition and structure of the interlamellar space could be calculated. On the hydrophilic surface of montmorillonite negative adsorption of the organic component was observed at low molar fractions of nitrobenzene or pentanol, i.e., water was preferentially adsorbed. On organophilized montmorillonite and vermiculite adsorption of nitrobenzene and pentanol was positive over the whole range of liquid composition. The amount of interlamellar alkyl chains which is determined by the surface charge of clay mineral inversely affected the adsorption of both solutes.     

Mineral and chemical compositions and structure-sorption properties of bottom sediments as the basic components of enterosorbents and application materials

The mineral and chemical compositions, as well as some structure-sorption characteristics were determined for clay minerals selected for examination. The integrated coefficients of contamination of bottom sediments with each of the toxicant metals (Fe, Ni, Co, Cu, Zn, Pb, Mn) were calculated. The minerals examined presumably can be used in medicine as efficient application materials, cosmetic agents, and sorbents (enterosorbents).     

Analysis of major and trace elements by INAA to predict the thousands year old sediment deposition environment in the Meghna river delta

Major, trace and rare earth elements have been measured in sediments of different layers to determine the controls of constituent minerals on the distribution of elements and sediment deposition environment in the Meghna river delta. The geochemical composition of sediments was enriched in SiO₂, Ca, Mg and Ba and depleted in Al, Fe, Ti, Mn, and Sr relative to PAAS (Post-Archaen Average Shale) value. The X-ray diffraction and elemental analyses demonstrate the dominant presence of quartz, micas, feldspar, chlorite, amphibole and clay minerals in sediments. The very low contents of trace elements suggest that the oxic condition was more prevalent during sediment deposition of Pleistocene-Holocene period and reflect the massive chemical weathering by biogeochemical reactions. The enrichment of light rare earth elements and La/Yb ratio reflect the intense silicate weathering of crustal materials and the high sediment depositional rate in the Meghna river delta.     

Pu and Am sorption to the Baltic Sea bottom sediments

Sorption of Am and Pu isotopes to bottom sediments of the Baltic Sea has been studied under natural and laboratory conditions. Data obtained from sequential extraction, sorption of Am(III), Pu(IV) and Pu(V) as well as oxidation state distribution experiments have shown that Pu(V) sorption mechanism includes a very fast Pu(V) reduction (reaction rate ≤ 2.33 × 10^?3 s^?1) to Pu(IV) by humic substances and/or by Fe(II) to Pu(IV) and partly to Pu(III). Following reduction Pu isotopes were bound to various components of bottom sediments via ion exchange and surface complexation reactions and a slow incorporation into the crystalline structure of Fe minerals. Kinetics experiments showed that the sorption of Pu(V), Pu(IV) and Am(III) to bottom sediments from natural seawater was controlled by the inert layer diffusion process.     

CLAY MINERALS IN THE CHINA SEA AND ADJACENT SEAS

The clay minerals in the surface sediments from 354 stations have been analyzed qualita-tively and semiquantitatively. The obtained data are dealt mathematically. According to thecalculated results, the distribution laws and the trends of content changes of clay mineralsare discussed. The studied area is divided into four main provinces of sediments with differ-ent sources. Finally the author approached the laws of the migration and dispersal of thefine-grained matter carried into the seas by the Huanghe River, the Changjiang River, theZhujiang River and the Philippine Archipelagoes, and set up the transport model of the fine-grained matter in the China Sea and adjacent seas.     

Some Remarks on the Methodology of Thermal Analysis of Clay Minerals

The influence of certain experimental conditions on the courses of the thermal curves (DTA and DTG) of selected clay minerals was studied. The thickness of the sample layer, the sample mass, the type of sample holder and the parameters of the air atmosphere were varied in thermal analyses of 13 samples of clay minerals. Comparison of the results obtained on different clay samples analysed under different experimental conditions may serve as the basis for the improvement of the thermal analysis methodology applied for the study of clay minerals. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Adsorption of Herbicides and Pesticides on Clay Minerals and Soils. Part 2. Atrazine

The adsorption of atrazine and two model compounds,2-chloropyrimidine and 3-chloropyridine on clay minerals(bentonite, montmorillonite and kaolinite), organic matter (humic acid) and soil (with and without organic matter) has beenstudied using FT-infrared spectroscopy (IR), thermogravimetric analysis (TGA), high pressureliquid chromatography (HPLC) and X-ray diffraction (XRD).3-Chloropyridine, 2-chloropyrimidine and atrazine were adsorbedthrough hydrogen bonding on bentonite, montmorillonite, humic acid and soil. In addition tohydrogen bonding, protonation of 3-chloropyridine and atrazine was also observed.In the adsorption of 2-chloropyrimidine on bentonite and montmorillonitean ion exchange mechanism also occurred. No adsorption of 3-chloropyridine or 2-chloropyrimidine wasobserved on the kaolinite clay mineral.Both the clay minerals and organic matter of soil contribute tothe adsorption of organic compounds on soil but the clay minerals bentonite and montmorilloniteplay a major role in their adsorption on soil.     

Synthesis and characterization of novel segmented polyurethane/clay nanocomposite via poly(ε-caprolactone)/clay

A novel segmented polyurethane/clay (PU/clay) nanocomposite based on poly(caprolactone), diphenylmethane diisocyanate, butanediol, and poly(caprolactone)/clay prepolymer was synthesized as evidenced by FTIR and X-ray diffraction studies. Poly(caprolactone)/clay (PCL/clay) prepolymer was first synthesized in a nanocomposite form as confirmed by X-ray diffraction. X-ray diffraction study showed that PU/clay contained crystalline structure due to the presence of PCL/clay. In mechanical properties, about 1.4% PCL/clay in PU/clay resulted in a large increase in the elongation of PU/clay. However, when the amount of PCL/clay was 4.2%, the elongation of PU/clay was reduced drastically. This behavior indicated that PU/clay can be transformed from an elastomer to a thermoplastic material as the amount of PCL/clay in PU/clay increased. Additionally, the lap shear stress of PU/clay was at least three times that of neat PU as a result of the PCL/clay component. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2225–2233, 1999     

Interlamellar adsorption of organic pollutants in hydrophobic montmorillonite

The adsorption of nitrobenzene, 2-chlorophenol, and 4-chlorophenol from water on organophilized derivatives of n-hexadecylpyridinium-montmorillonite (HDP-montmorillonite) was studied. Adsorption excess isotherms were obtained by the immersion method and were analyzed to determine the adsorption capacity of organic pollutants on the hydrophobized surface. The basal spacings of the clay minerals were determined by X-ray diffraction. The results of X-ray diffraction measurements are in good agreement with excess isotherms: whenever a region of the isotherm indicates an increase for the adsorption of organic component, an increase in basal spacing (interlamellar swelling) is also observed. By combining these two independent methods, composition and structure of the interlamellar space between the silicate layers could be accurately calculated. The free enthalpy of adsorption, the adsorption capacity, and the separation factor for adsorption are calculated by analyzing the adsorption isotherm on the basis of the Gibbs equation and Everett-Schay method. The results are utilizable for planning environmental procedures and systems (water clarification and soil remediation). Received: 17 July 2000   Accepted: 5 October 2000     

Natural and synthetic manganese minerals

The mineral and microelement composition and structures have been studied and a comparative analysis has been carried out for manganese minerals with the general formula [Mn(O,OH)₂]⁺[R_0.5–1(OH)_21.5] · nH₂O (R = Mn, Na, K, Ni, Co, Ca, and others) that built iron-manganese concretions raised from different areas of the Sea of Okhotsk and the Bering Sea, and their synthetic analogues. The structures of synthetic manganese species were found to better withstand temperature impacts than those of the native minerals studied under the same conditions.     

Metal nanoparticle formation on layer silicate lamellae

Nanoparticles (Ag, Pd) were prepared by heterogeneous nucleation on the interlayer space of layered montmorillonite and kaolinite minerals in aquatic dispersion. Interlamellar incorporation of nanoparticles was monitored by X-ray diffraction and verified by transmission electron microscopy (TEM). After the reduction of adsorbed metal ions, a new Bragg reflection appeared, proving the formation of nanoparticles in the interlamellar space of clay mineral. Lamellar structure of layered silicates is partly destroyed by the particle formation. TEM images showed that larger nanoparticles were formed by UV irradiation and hydrazine hydrate than in the case of reduction by NaBH₄. Aqueous solutions of polyvinyl pyrrolidone and clay minerals were used for the stabilization of Pd° nanoparticles. The size of particles generated on the surface of clay minerals by heterogeneous nucleation increased with increasing metal concentration. When polymer is added to this system, particle size can be decreased by increasing polymer concentration. In this case, the particles are stabilized by the concerted action of the support and the macromolecule. The polymers promoted intercalation of nanoparticles into the clay mineral. In the absence of nanoparticles, the intercalation of polymers was significantly less extensive.     

X-ray diffraction study of zirconia pillared clays

X-ray powder diffraction (XRPD) and X-ray radial electronic distribution density (RED) of initial and zirconia-pillared interlayered clays (Zr-PILC) were studied. After pillaring, the basal (001) spacing was found to increase from 11 Å in the initial clay kept under air to 17.7 Å in Zr-PILC. The structure of zirconium nanopillars was characterized. The interatomic distances with corresponding coordination numbers obtained from the RED curves were close to those in zirconium tetramers.This revised version was published online in December 2005 with corrections to the Cover Date.     

Magnetic normalization of particle size effects in a heavy metal pollution study of intertidal sediments from the Yangzte Estuary

Magnetic, granulometric and geochemical analyses were conducted on an intertidal sediment core from the Yangtze Estuary to evaluate the possibility of normalizing samples for particle size effects in a heavy metal pollution study by means of magnetic proxies. It has been found that the magnetic parameter XARM, indicating fine grained ferrimagnetic minerals, correlates well with the clay content and organic matter concentration of the sediments. XARM also shows significant relationship with heavy metals. Therefore XARM is proposed as a proxy for clay content in the sediments, and can be used to compensate for the particle size effect in sedimentary heavy metal records, where magnetic minerals are not subject to significant post-depositional alteration.     

Comparison studies adsorption of thorium and uranium on pure clay minerals and local Malaysian soil sediments

Adsorption studies of thorium and uranium radionuclides on 9 different pure clay minerals and 4 local Malaysian soil sediments were conducted. Solution containing dissolved thorium and uranium at pH 4.90 was prepared from concentrate sludges from a long term storage facility at a local mineral processing plant. The sludges are considered as low level radioactive wastes. The results indicated that the 9 clay minerals adsorbed more uranium than thorium at pH ranges from 3.74 to 5.74. Two local Malaysian soils were observed to adsorb relatively high concentration of both radionuclides at pH 3.79 to 3.91. The adsorption value 23.27 to 27.04 ppm for uranium and 33.1 to 50.18 ppm for thorium indicated that both soil sediments can be considered as potential enhanced barrier material for sites disposing conditioned wastes containing uranium and thorium.     

Surface Modification of Smectite Clay Induced by Non-thermal Gliding Arc Plasma at Atmospheric Pressure

Smectite clay from Sabga (west-Cameroon) was treated in aqueous suspension by gliding arc plasma to modify its surface properties. The evolution of the modifications was followed with the exposure time and post-discharge duration using Fourier transformed infra red spectroscopy and scanning electron microscopy. X-ray diffraction and nitrogen physisorption analyses were also performed to evaluate if both crystalline and textural properties of the material are affected by the treatment. The results obtained show that the plasma treatment causes the breakdown of structural bounds at the clay surface and induces the formation of new hydroxyl groups (Si–OH and Al–OH) on the clay edges. Crystallinity, sheet structure and textural properties are not significantly affected by the plasma treatment. However, it should be noted that an intensive treatment of the clay lowers the pH of the suspension, which subsequently induces an acid attack of the clay. In such case, the specific surface area of the clay increases. This study demonstrates that gliding arc plasma treatments can be used to activate clay minerals for environmental application.     

Spectroscopic study of phase transitions in natural calcite mineral

The process and the formation of new minerals upon heating the carbonate rocks containing clay minerals, together with calcite are determined with thermal analysis, X-ray diffraction, infrared and Raman spectroscopy. The calcite-calcium oxide phase transition sequence was followed up to 947 degrees C in naturally occurring limestone samples. The spectral variations of the internal modes of the carbonate trigonal (nu(1), nu(2), nu(3) and nu(4)) were used to probe the structural phase transitions. The calcium oxide phase (which on reaction with atmospheric water forms portlandite) with an onset temperature of around 950 degrees C was also characterized by the appearance of the infrared mode around 450 cm(-1). The minerals, which were formed upon heating the calcite, were calcium oxide and wollastonite.     

Physico-chemical behaviour of hydrated aluminium oxides and associated clay minerals occurring around Pipra,district Sidhi,India

DTA techniques were employed to study the thermal and structural characteristics of hydrated aluminium oxides and aluminous clays of the Pipra pelitic rocks from district Sidhi, India. Detailed microscopic investigations, X-ray and chemical analyses reveal that these clays were derived by the localized weathering of arkosic metasediments. The chemical and normative behaviours have confirmed their formation by the isochemical metamorphism of arkose, aided by a little granitization and followed by minor retrogression. A tentative correlation between the thermal and structural changes of these oxides and clay minerals at various transition temperatures has nicely displayed the presence of kaolinite, diaspore and gibbsite. The exothermic curves of kaolinite confirm the recrystallization. The presence of kaolinite in the clay fractions indicates the detrital origin.