The Effect of pH and Biogenic Ligands on the Weathering of Chrysotile Asbestos: The Pivotal Role of Tetrahedral Fe in Dissolution Kinetics and Radical Formation

Chrysotile asbestos is a soil pollutant in many countries. It is a carcinogenic mineral, partly due to its surface chemistry. In chrysotile, Fe^II and Fe^III substitute Mg octahedra (Fe[6]), and Fe^III substitutes Si tetrahedra (Fe[4]). Fe on fiber surfaces can generate hydroxyl radicals (HO^.) in Fenton reactions, which damage biomolecules. To better understand chrysotile weathering in soils, net Mg and Si dissolution rates over the pH range 3.0–11.5 were determined in the presence and absence of biogenic ligands. Also, HO^. generation and Fe bulk speciation of pristine and weathered fibers were examined by EPR and Mössbauer spectroscopy. Dissolution rates were increased by ligands and inversely related to pH with complete inhibition at cement pH (11.5). Surface-exposed Mg layers readily dissolved at low pH, but only after days at neutral pH. On longer timescales, the slow dissolution of Si layers became rate-determining. In the absence of ligands, Fe[6] precipitated as Fenton-inactive Fe phases, whereas Fe[4] (7 % of bulk Fe) remained redox-active throughout two-week experiments and at pH 7.5 generated 50±10 % of the HO^. yield of Fe[6] at pristine fiber surfaces. Ligand-promoted dissolution of Fe[4] (and potentially Al[4]) labilized exposed Si layers. This increased Si and Mg dissolution rates and lowered HO^. generation to near-background level. It is concluded that Fe[4] surface species control long-term HO^. generation and dissolution rates of chrysotile at natural soil pH.     

Comparison of secondary-ion mass spectrometry and compleximetric titration for the determination of leaching of magnesium from chrysotile asbestos

The dissolution of chrysotile asbestos in 0.05 M oxalic acid is evaluated by secondary-ion mass spectrometry and by titration of magnesium with EDTA. The results of the two methods agree closely; thus matrix effects in the utilization of sputtering depth profiles of the mass spectrometric determination do not influence the final results.     

Heavy metal sorption in the lichen cationactive layer

Results of copper ion sorption in lichens owing to the ion exchange between the surroundings (aqueous solution) and the lichen cationactive layer have been presented. It indicates that the course of sorption of these ions, similarly as in the case of cations of other heavy metals, depends on the concentration and type of cations naturally found in lichen surroundings: H+, Na+, K+, Mg2+ and Ca2+. A determination method of heavy metal concentration in lichen surroundings has been proposed. It consists in exposure of transplanted lichens in the presence of salts that provide precisely determined, artificial salinity of precipitation with which the lichens are in contact. The studies were conducted on Hypogymnia physodes lichens.     

Laser microprobe mass analysis of o-phenylenediamine on asbestos fibres

The adsorption behaviour of o-phenylenediamine and its catalytically formed oxidation products such as 2,3,-diaminophenazine and higher-molecular-weight compounds on different varieties of asbestos is studied by using laser desorption mass spectrometry. The results prove that amosite adsorbs the product more easily than do crocidolite and anthophyllite, whereas U.I.C.C. chrysotile A does not give rise to detectable adsorption, and the adsorption observed for U.I.C.C. chrysotile B is only fair. The method shows potential for the investigation of the surface reactivity of pure and industrially transformed asbestos and other fibrous materials.     

Nucleation and Growth of Chrysotile Nanotubes in H2SiO3/MgCl2/NaOH Medium at 90 to 300 °C

Herein, we report new insights into the nucleation and growth processes of chrysotile nanotubes by using batch and semi‐continuous experiments. For the synthesis of this highly carcinogenic material, the influences of temperature (90, 200, and 300 °C), Si/Mg molar ratio, and reaction time were investigated. From the semi‐continuous experiments (i.e., sampling of the reacting suspension over time) and solid‐state characterization of the collected samples by XRPD, TGA, FTIR spectroscopy, and FESEM, three main reaction steps were identified for chrysotile nucleation and growth at 300 °C: 1) formation of the proto‐serpentine precursor within the first 2 h of the reaction, accompanied by the formation of brucite and residual silica gel; 2) spontaneous nucleation and growth of chrysotile between about 3 and 8 h reaction time, through a progressive dissolution of the proto‐serpentine, brucite, and residual silica gel; and 3) Ostwald ripening growth of chrysotile from 8 to 30 h reaction time, as attested to by BET and FESEM measurements. Complementary results from batch experiments confirmed a significant influence of the reaction temperature on the kinetics of chrysotile formation. However, FESEM observations revealed some formation of chrysotile nanotubes at low temperatures (90 °C) after 14 days of reaction. Finally, doubling the Si/Mg molar ratio promoted the precipitation of pure smectite (stevensite‐type) under the same P (8.2 MPa)/T (300 °C)/pH (13.5) conditions.     

真菌毒素的液相色谱分离和检测

本文研究了一项分离棒曲霉素,青霉酸,赭曲霉素A和B,桔青霉素,玉米赤霉烯酮及柄曲霉素七种真菌毒素的高效液相色谱分离和检测方法。为实现分离,选择了反相方式。流动相为乙腈-水(55:45v/V),并添加了2.5mm草酸,pH为5.5。流量1.0ml/min。文中讨论了流动相中乙腈%、添加草酸的浓度对七种真菌毒素k’值的影响,对柱效N的影响,并从原理上讨论了保留机理。本文也综合地讨论了检测条件。也讨论了有关定量分析的参数,建立了一种较好的分析七真菌毒素的痕量定量方法。     

Fe(II)(EDTA)螯合物/UV催化臭氧工艺降解PAM溶液研究

研究采用Fe(II)(EDTA)螯合物/UV催化臭氧降解聚丙烯酰胺(PAM)溶液。考察Fe(II)(EDTA)螯合物/UV催化臭氧法对PAM溶液粘度、PAM去除率和可生化性的影响。研究表面活性剂对Fe(II)(EDTA)螯合物/UV催化臭氧工艺降低PAM粘度的影响,并探讨草酸对该工艺降解PAM溶液影响规律。研究结果表明,Fe(II)(EDTA)螯合物/UV催化臭氧法对PAM溶液降解效能良好,在15min内,PAM溶液粘度的可以降低57%,在120min后,PAM去除率可达75%,B/C从0.121提升到0.423。表面活性剂对Fe(II)(EDTA)螯合物/UV催化臭氧工艺降低PAM溶液粘度影响较小。草酸不利于Fe(II)(EDTA)/UV催化臭氧工艺去除PAM和降低PAM溶液粘度,这是因为草酸造成的酸性环境抑制了臭氧在水中的分解作用,从而导致草酸/Fe(II)(EDTA)/O3体系中PAM溶液的降粘效果和去除率低于Fe(II)(EDTA)/O3体系。     

The iron-related molecular toxicity mechanism of synthetic asbestos nanofibres: a model study for high-aspect-ratio nanoparticles

Asbestos shares with carbon nanotubes some morphological and physico-chemical features. An asbestos-like behaviour has been recently reported by some authors, though the mechanism of toxicity may be very different. To identify at the atomic level the source of toxicity in asbestos, the effect of progressive iron loading on a synthetic iron-free model nanofibre previously found non-toxic in cellular tests was studied. A set of five synthetic chrysotile nanofibres [(Mg,Fe)3(Si2O5)(OH)4] has been prepared with Fe ranging from 0 to 1.78?wt?%. The relationship between fibre-induced free-radical generation and the physico-chemical characteristics of iron active sites was investigated with spin-trapping techniques on an aqueous suspension of the fibres and M?ssbauer and EPR spectroscopies on the solids, respectively. The fully iron-free fibre was inert, whereas radical activity arose with even the smallest amount of iron. Surprisingly, such activity decreased upon increasing iron loading. M?ssbauer and EPR revealed isolated iron ions in octahedral sites that undergo both axial and rhombic distortion and the occurrence of aggregated iron ions and/or extra-framework clustering. The isolated ions largely prevailed at the lowest loadings. Upon increasing the loading, the amount of isolated iron was reduced and the aggregation increased. A linear relationship between the formation of carbon-centred radicals and the amount of rhombic-distorted isolated iron sites was found. Even the smallest iron contamination imparts radical reactivity, hence toxicity, to any chrysotile outcrop, thereby discouraging the search for non-toxic chrysotile. The use of model solids that only differ in one property at a time appears to be the most successful approach for a molecular understanding of the physico-chemical determinants of toxicity. Such findings could also be useful in the design of safer nanofibres.     

Indirect ultraviolet spectrophotometric detection in the ion chromatography of common mono- and divalent cations on an aluminium adsorbing silica gel column with tyramine-containing crown ethers as eluent

The application of laboratory-made aluminium-adsorbing silica gel (Al-Silica) as a cation-exchange stationary phase to ion chromatography-indirect photometric detection (IC-IPD) for common mono- and divalent cations (Li+, Na+, NH+, K+, Mg2+ and Ca2+) was carried out by using protonated tyramine (4-aminoethylphenol) as eluent ion. When using 1.2 mM tyramine-0.2 mM oxalic acid at pH 4.5 as eluent, incomplete separation of the monovalent cations and complete separation of the divalent cations were achieved in 17 min. Then, the addition of crown ethers in the eluent was carried out for the complete separation of the mono- and divalent cations. As a result, when using 1.2 mM tyramine--0.2 mM oxalic acid at pH 4.5 containing either 5 mM 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane) or 0.5 mM and 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) as eluent, excellently simultaneous separation of these cations was achieved in 21 min. The proposed IC-IPD was successfully applied to the determination of major cations in natural water samples.     

Investigation of mechanical properties of anodized aluminum using dilatometric measurements

Mechanical properties of anodized aluminum were studied using the results of dilatometric measurements of thermal expansion of anodized Al (the symmetric structure Al(2)O(3)-Al-Al(2)O(3)). The 100-microm-thick Al(2)O(3 )oxide layer was formed in 4% aqueous solution of oxalic acid in the galvanostatic regime at a current density of 20 mA cm(-2). Measurements of thermal expansion of anodized Al (Al and Mg alloy of 2.7-3.2%, and 0.3-0.6% Mn, and 0.5-0.8% Si) with the thickness of initial Al from 0.6 to 3.7 mm and ceramic from Al(2)O(3) in the temperature range of 20-500 degrees C were conducted using an automatic quartz dilatometer. Intrinsic stress in the Al layer, the values of the modulus of elasticity, and the porosity of Al oxide formed on Al of different thickness are calculated.     

Analysis of cement and cement raw meal by atomic absorption spectrophotometry using a new fusion agent

A new fusion agent is proposed for the analysis of cement and cement raw meal using AAS. In the described method, 0.8 g of the fusion agent, consisting of equal portions of oxalic acid, lithium carbonate and lithium tetraborate, was mixed with 0.2 g of the sample, and the mixture was fused for 10 min at 925 degrees C in a platinum crucilbe. The fusion cake was dissolved with dilute hydrochloric acid (1 + 10) and diluted to 500 ml for the determination of Si, Al, Fe, Ti, Na and K expressed as SiO(2), Al(2)O(3), Fe(2)O(3), TiO(2), Na(2)O, and K(2)O respectively. For the determination of Ca and Mg (expressed as CaO and MgO respectively), 10 ml of the previous sample solution were mixed with 4 ml of 6% (m/v) lanthanum nitrate solution and the solution was diluted to 100 ml. The method was found to have good accuracy and precision. The time required to determine the eight elements was around 80 min for each sample.     

Dopant incorporation into garnet solid solutions--a breakdown of Goldschmidt's first rule

Atomistic simulations suggest trace elements are more soluble in a 50:50 pyrope (Mg3Al2Si3O12)-grossular (Ca3Al2Si3O12) garnet mixture than in either end-member; consistent with partitioning experiments, and, contrary to Goldschmidt's first rule, large trace element cations may substitute for Mg2+, small trace elements for Ca2+.     

水热法合成掺杂铁离子纤蛇纹石纳米管

本工作研究了在水热条件下纤蛇纹石纳米管的人工合成，通过掺杂Fe³⁺离子替代了纤蛇纹石晶格中的Mg²⁺离子。采用X-射线衍射、扫描电镜、透射电镜、红外光谱和电子自旋共振谱等手段研究了掺杂离子对纤蛇纹石晶体生长和晶体结构的影响。X-射线衍射分析表明随着掺杂Fe³⁺离子量的增加所得到的纤蛇纹石样品其晶胞参数b值逐渐减小。电子自旋共振谱、红外光谱分析表明Fe³⁺离子部分替代了Mg²⁺离子和Si⁴⁺离子进入纤蛇纹石的八面体和四面体结构单元。透射电镜研究表明掺杂前后所得到的纤蛇纹石内径分别为6～8 nm和8～15 nm。     

Application of pure silica gel as cation-exchange stationary phase in lon chromatography with indirect photometric detection for common mono-and divalent cations using aromatic monoamines as eluents

Summary A pure silica gel (Pia Seed 5S-60-SIL), synthesized by the hydrolysis of pure tetraethoxysilane [Si(OCH₂CH₃)₄], was applied as a cation-exchange stationary phase in ion chromatography with indirect photometric detection for common mono-and divalent cations (Li⁺, Na⁺, NH₄ ⁺, K⁺, Mg²⁺, and Ca²⁺) using various protonated aromatic monoamines (tyramine [4-(2-aminethyl) phenol], benzylamine, phenylethylamine, 2-methylpyridine and 2,6-dimethylpyridine) as eluet ions. When using 0.75 mM tyramine-0.25 mM oxalic acid-1.5 mM 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) at pH 5.0 as the eluent, excellent simultaneous separation and highly sensitive detection at 275 nm for these mono-and divalent cations were achieved on the Pia Seed 5S-60-SIL column (150×4.6 mm I.D.) in 20 min.     

Interaction of bovine serum albumin with chrysotile: spectroscopic and morphological studies

The biodurability of chrysotile fibers, which is related to their cytotoxicity and mutagenic responses, is strongly affected by the surface chemical adsorption of biological molecules. Natural chrysotile is a heterogeneous material in both structure and composition. The availability of synthetic stoichiometric chrysotile of constant structure and uniform morphology has allowed us to investigate its interaction with bovine serum albumin (BSA). By using transmission electron microscopy (TEM) and atomic force microscopy (AFM), we have obtained the first morphological evidence of albumin adsorption onto chrysotile nanocrystals. FTIR spectroscopy was used to quantify modifications of BSA secondary structure that were induced by the surface interaction. The protein transition to beta-turns allows a stronger interaction between the protein hydrophilic side-chains and the charged asbestos surface, which is consistent with hydrogen bonds involving the superficial OH groups. Synthetic stoichiometric chrysotile nanocrystals were shown to be an ideal reference standard with which to study the interaction of asbestos fibers with biological systems, in order to elucidate the chemical mechanisms of asbestos toxicity.     

Electro-fenton and photoelectro-fenton degradation of sulfanilic acid using a boron-doped diamond anode and an air diffusion cathode

The mineralization of sulfanilic acid has been studied by electro-Fenton (EF) and photoelectro-Fenton (PEF) reaction with UVA light using an undivided electrochemical cell with a boron-doped diamond (BDD) anode and an air diffusion cathode able to generate H(2)O(2). Organics were then oxidized by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between generated H(2)O(2) and added Fe(2+). The UVA irradiation in PEF enhanced the production of hydroxyl radicals in the bulk, accelerating the removal of organics and photodecomposed intermediates like Fe(III)-carboxylate complexes. Partial decontamination of 1.39 mM sulfanilic acid solutions was achieved by EF until 100 mA cm(-2) at optimum conditions of 0.4 mM Fe(2+) and pH 3.0. The increase in current density and substrate content led to an almost total mineralization. In contrast, the PEF process was more powerful, yielding almost complete mineralization in less electrolysis time under comparable conditions. The kinetics for sulfanilic acid decay always followed a pseudo-first-order reaction. Hydroquinone and p-benzoquinone were detected as aromatic intermediates, whereas acetic, maleic, formic, oxalic, and oxamic acids were identified as generated carboxylic acids. NH(4)(+) ion was preferentially released in both treatments, along with NO(3)(-) ion in smaller proportion.     

X射线衍射法测定滑石粉中石棉成分

使用X射线衍射法,通过石棉的2θ特征峰进行判断,分析滑石粉中可能存在的石棉成分。结果表明,样品中不含温石棉、铁石棉和青石棉,并对温石棉和绿泥石进行了有效区分。方法快速,灵敏,可有效用于滑石粉中石棉的测定。     

(Ni,Mg)3Si2O5(OH)4 solid-solution nanotubes supported by sub-0.06 wt % palladium as a robust high-efficiency catalyst for Suzuki-Miyaura cross-coupling reactions

(Ni(1-x),Mg(x))(3)Si(2)O(5)(OH)(4) solid-solution nanotubes (NTs) with tunable compositions were hydrothermally synthesized by altering the molar ratio of Mg(2+) to Ni(2+). The as-synthesized NTs were loaded with sub-0.06 wt % palladium (Pd; ～0.045 wt %) for Suzuki-Miyaura (SM) coupling reactions between iodobenzene or 4-iodotoluene and phenylboronic acid. The (Ni,Mg)(3)Si(2)O(5)(OH)(4) (Mg(2+):Ni(2+) = 1.0:1.0) NTs supported by 0.045 wt % Pd promoted the iodobenzene-participated coupling reaction with a high yield of >99%, an excellent recycling catalytic performance during 10 cycles of catalysis with yields of ～99%, and also an extremely low Pd releasing level of ～0.02 ppm. High-activity Pd and PdO clusters, multitudes of dislocations, and defects and terraces contained within the NTs should contribute to the (Ni,Mg)(3)Si(2)O(5)(OH)(4) (Mg(2+):Ni(2+) = 1.0:1.0) NTs supported by 0.045 wt % Pd as a robust, reusable, and high-efficiency catalyst for SM coupling reactions with an extremely low Pd releasing level. The present hydrothermally stable (Ni,Mg)(3)Si(2)O(5)(OH)(4) (Mg(2+):Ni(2+) = 1.0:1.0) solid-solution silicate NTs provided an ideal alternative tubular-structured support for noble- or transition-metal catalysts with low Pd loading, good recycling, and extremely low ppb levels of Pd release, which could also be extended to some other SM coupling reactions.     

Low-valent vanadium oxide nanostructures with controlled crystal structures and morphologies

Low-valent vanadium oxide nanostructures have been synthesized in large quantities using commercial V2O5 powder as the precursor by a facile reduction method. The crystal structures and morphologies of vanadium oxide nanostructures can be adjusted by altering the concentrations and types of reductants. VO2(B) nanostructures are fabricated using oxalic acid as the reductant. VO2(B) nanobelts with widths of 80-150 nm, thicknesses of 20-30 nm, and lengths up to several micrometers can evolve to olive-like nanostructures composed of nanosheets with thicknesses of several nanometers and lateral dimensions of several micrometers as the concentration of oxalic acid increases. H2V3O8 nanobelts with widths of 200-300 nm, thicknesses of 10-20 nm, and lengths up to several 10s of micrometers are obtained under the reduction of V2O5 powder with ethanol. The belt-shaped morphologies of H2V3O8 are not affected by the concentration of ethanol.     

Correlation of mercury concentrations in tree core and lichen samples in southeastern Louisiana

To determine if a correlation exists between mercury concentrations in lichens and wood from tree cores, tree core and lichen samples were taken from sites under mercury advisories and analyzed for mercury using a Bacharach 50B Mercury Analyzer System employing the Manual Cold Vapor Atomic Absorption EPA method 7471A. Wood from tree cores was dated using tree ring data. Wood samples from the cores were analyzed for various depths in the tree core (periods of time) to determine if variations occur throughout the cores. Preliminary data indicate that a strong correlation exists between mercury concentrations in tree core and lichen samples. Samples were analyzed for the 6-month period of summer 2003–winter 2004. A correlation coefficient of 0.882 was found between the tree core and lichen data sets. The derived correlations were used to estimate concentrations of mercury in tree rings for sites in lichen samples which were previously analyzed. These predicted values compared favorably to recently determined concentrations of Hg in tree cores. The strong correlation between lichen and tree core Hg concentrations suggests similar uptake mechanism for the two types of biota.