A Sequential Extraction Method Measures the Toxic Metal Content in Fly Ash from a Municipal Solid Waste Incinerator

The purpose of this research was to develop an optimized pretreatment procedure for toxic metals (Pb, Cd, Zn and Cu) content in fly ash from a municipal waste incinerator. In addition, modified sequential extraction procedures were used to characterize the chemical composition of the fly ash samples. The sequential extraction resolved the fly ash elements into the following chemical forms: soluble, exchangeable, carbonate, oxide, organic, and silicate compounds. Certified reference city waste incineration ash (BCR.176) was used as target ash samples. A H₂O₂+HNO₃+HF mixed acid digestion solution with a low temperature evaporation procedure was selected as optimal for the fly ash digestion. The digested solution was analyzed by inductively coupled plasma mass spectrometry (ICP‐MS), which effectively determined the concentrations of the toxic metal elements in BCR.176. Except for Cd, the recovery of Pb, Zn, and Cu under H₂O₂+HNO₃+HF digestion and their sequential extraction procedures were higher than 95%. The relative standard deviations (RSD) for recoveries of the four elements were within 10%. Furthermore, the sequential extraction procedure's results provided information on the potential mobility of the studied elements. Most of the Cd was bound to water‐soluble and carbonate material in the fly ash samples. Most of the Pb, Zn, and Cu was released to carbonates and bound to organic matter in the fly ash samples.     

A method for rapid determination of arsenic species in vegetables using microwave‐assisted extraction followed by detection with HPLC hyphenated to inductively coupled plasma‐mass spectrometry

Driven by the significant need for characterization of the chemical speciation of arsenic in food, this work developed a method for rapid determination of four common arsenic species, namely, arsenite, arsenate, monomethyl arsenic acid, and dimethyl arsenic acid, in vegetables using microwave‐assisted extraction, followed by detection with high‐performance liquid chromatography hyphenated to inductively coupled plasma‐mass spectrometry. Initial screening results showed that microwave‐assisted extraction using 1% HNO₃ exhibited the highest overall efficiencies for all arsenic species without causing significant degradation of the organic ones. With the aid of response surface methodology, the optimum conditions established for extraction of arsenic species from vegetables were: 500 mg of freeze‐dried vegetable sample, extracted by closed vessel microwave‐assisted extraction using 10 mL of 2% v/v HNO₃ at 90°C for 17 min. Application of the method in the analysis of 24 market vegetable samples indicates that the extraction efficiencies for total arsenic species were in the range of 91.4–106%. Arsenite and arsenate were found to be the predominant arsenic species in the vegetables, which suggests that vegetable consumption could be an important route of inorganic arsenic exposure for the population with a heavy vegetable diet in arsenic polluted regions.     

Comparative study of bulk and partial digestion methods for airborne PM10-bound elements in a high mineral dust urban site in Constantine,Algeria

When high mineral loads in atmospheric particulate matter (PM) are present, particular attention should be paid to the selection of appropriate acidic digestion protocols for wet chemical analysis. We report on a comparative study of elemental recovery yields from five different pre-analytical acid digestion procedures for mineral-rich urban background PM₁₀ samples collected in the city of Constantine (Northeastern Algeria). Five reference materials (NIST 1633b, UPM 1648, NAT-7, SO-2 and SO-4) were also digested according to the same protocols. The selected acidic digestion/extraction procedures are widely used for PM chemical analysis and comprise P1 (HNO₃/HF/HCl), P2 (HCl/HNO₃), P3 (HCl/H₂O₂/HNO₃), P4 (HNO₃/HF/HClO₄) and P5 (HNO₃/H₂O₂); the latter assisted with microwave digestion. Elemental recovery yields were compared for major and trace elements typically determined in PM for source apportionment analysis and the results evidenced large differences. For most elements, the bulk extraction procedures (requiring the use of HF) allowed a full elemental recovery, particularly for elements that are associated with aluminium silicate species and oxides that are resistant to mild acid attack. In contrast, in the extraction protocols without HF low recovery yields were obtained for elements such as Al, Ti, Zr, Sc and other aluminium silicate-related elements in PM₁₀ samples with high mineral dust load. We highlight that the European standard digestion method EN-14902:2005 should be applied specifically for the metals for which this method was developed, but caution should be taken when the analysis of other elements in PM is required, especially in urban areas where road and vehicle wear dust is likely to be a major component of ambient PM. When using wet chemistry analysis for PM source apportionment studies, we strongly recommend HF bulk dissolution of samples to ensure the reliability of the geochemical information when coupled with an appropriate analytical tool.     

Evaluation of the thermal degradation of PC/ABS/montmorillonite nanocomposites

Polycarbonate (PC)/acrylonitrile‐butadiene‐styrene (ABS) polymer alloy/montmorillonite (MMT) nanocomposites were prepared using a direct melt intercalation technique. The pyrolytic degradation and the thermo‐oxidative degradation of the polymer alloy and the nanocomposites were studied by thermogravimetric analysis (TGA). The kinetic evaluations were performed by the model‐free kinetic analysis and the multivariate non‐linear regression. Apparent kinetic parameters for the overall degradation were calculated. The results show that PC/ABS/MMT nanocomposites have high thermal stability and low flammability. Their pyrolytic degradation and the thermo‐oxidative degradation model are different. The pyrolytic degradation reaction of the polymer is a two‐step parallel reaction model: nth‐order reaction model, and ath‐degree autocatalytic reaction with an nth‐order reaction autocatalytic reaction, whereas the thermal oxidative degradation reaction of the polymer is a two‐step following reaction model: A → B → C of nth‐order reaction model, and autocatalytic reaction model. Copyright © 2005 John Wiley & Sons, Ltd.     

Polyisobutylene containing organic/inorganic hybrid block copolymers and their crystalline behavior

Block copolymer comprising of polyisobutylene (PIB) soft segment and poly(3‐(3,5,7,9,11,13,15‐heptaisobutyl‐pentacyclo[9.5.1.1^3,9.1^5,15.1^7,13]‐octasiloxane‐1‐yl)propyl methacrylate) (PMAPOSS) hard segment was synthesized by combination of living carbocationic and reversible addition‐fragmentation chain transfer (RAFT) polymerizations. Block copolymers were characterized by ¹H and ²⁹Si NMR spectroscopy, FT‐IR study, energy dispersive X‐ray spectroscopy (EDX), and gel permeation chromatography (GPC). The EDX, combined with scanning electron microscopy (SEM) was employed for determination of elemental composition. Thermal transition and degradation behaviors were confirmed by differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA), respectively. Although both the PIB and MAPOSS homopolymers are amorphous in nature, in their block copolymers the PMAPOSS domain showed crystalline behavior, as confirmed from wide‐angle X‐ray scattering (WAXS) technique, DSC studies and polarized optical microscopy (POM). Interestingly, crystalline melting temperatures (T_m) can be tuned by changing the PIB to PMAPOSS block length ratios. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1125–1133     

Structural and conformational changes during thermally‐induced crystallization of poly(trimethylene terephthalate) by infrared spectroscopy

Conformational changes occurring during thermally‐induced crystallization of poly(trimethylene terephthalate) (PTT) by annealing have been studied using density measurement, differential scanning calorimetry (DSC), and mid‐infrared spectroscopy (MIR). Infrared spectra of amorphous and semicrystalline PTT were obtained, and digital subtraction of the amorphous contribution from the semicrystalline PTT spectra provided characteristic MIR spectra of amorphous and crystalline PTT. The normalized absorbance of 1577, 1173, and 976 cm^?1 were plotted against the crystallinity showing that these bands can be used unambiguously to represent the trans conformation while the band at 1358 cm^?1 can be used to represent gauche conformation of methylene segment. The presence of a weak band at 1358 cm^?1 in the amorphous spectrum suggested that a small amount of gauche conformation is present in the amorphous phase. Infrared spectroscopy has been used for the first time as a means to estimate the trans and gauche conformations of methylene segments in PTT as a function of T_a. The amount of gauche conformation was plotted against the crystalline fraction and the extrapolation of this plot to zero crystalline fraction provided a value of 0.07, suggested that the pure amorphous phase consist of ～ 7% gauche conformation. It was found that the amorphous and crystalline gauche conformation increases at the expense of amorphous trans conformation during thermally induced crystallization of PTT. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1497–1504, 2008     

A RAMAN-SPECTROSCOPIC STUDY OF PHASE STRUCTURE OF DRAWN POLYETHYLENE

A drawn high density polyethylene(HDPE)has been measured by Raman spectroscopy and differential scanning calorimetry (DSC). The crystalline structure of drawn HDPE is analysed by the Raman internal modes in terms of mass fractions of the crystalline orthorhombic phase, the liquid- like amorphous phase and the disordered anisotropic phase. The mass fractions depend on draw temperature T_d and draw ratio R_d . The fraction of disordered anisotropic amorphous phase changes very little with, the T_d and increases with increasing R_d. Sum of the mass fractions of crystalline orthorhombic phase and the disordered anisotropic phase increases linearly as the same slope as the crystallinity W_c determined from DSC measurements with increasing T_d or R_d and it is higher than the W_c for all the samples. The results show that the mass fraction of disordered anisotropic phase is partially devoted by the taut tie molecules (TTM s) in the amorphous state. The dependence of the disordered anisotropic phase on T_d and R_d supports the mechanism of plastic deformation of fibre structure.     

Effects of the reduction of PAni-coated oxidized multiwall carbon nanotubes on the positive temperature coefficient behaviors of their carbon black/high density polyethylene composites

Polyaniline (PAni)-coated reduced multiwall carbon nanotubes (PRMWNTs) and carbon black (CB)-filled high-density polyethylene (HDPE) composites (PRMWNTs/CB/HDPE) were prepared through a melt mixing method. Oxidized MWNTs (OMWNTs) were prepared by treating pristine multiwall carbon nanotubes (MWNTs) with an acid mixture (HNO₃:H₂SO₄), and PAni-coated OMWNTs (POMWNTs) were synthesized via in-situ polymerization of aniline monomer in the presence of OMWNTs. POMWNTs were further reduced using hydrazine monohydrate to obtain the PRMWNTs. Fourier transform infrared (FT-IR) spectra and thermogravimetric analysis (TGA) confirmed the formation of PRMWNTs. PRMWNTs showed significantly improved thermal stability and electrical conductivity comparing to POMWNTs. The positive temperature coefficient (PTC) behavior of PRMWNTs/CB/HDPE composites revealed enhanced PTC intensity and electrical conductivity at room temperature compared to POMWNTs/CB/HDPE composites. The PRMWNTs-10/CB/HDPE composite showed high peak resistivity (301.99 MΩ-cm) and low room temperature resistivity compared to the POMWNTs/CB/HDPE composite, and thus showed the highest PTC intensity value of 6.693 as well as very excellent cyclic stability.     

Synthesis of ethylene/vinyl ester copolymers with pendent linear branches via ring‐opening metathesis polymerization of fatty acid‐derived cyclooctenes

Fatty acid‐derived cyclooctenes, including n‐hexanoic acid ( M1 ), n‐octanoic acid ( M2 ), lauric acid ( M3 ), and palmitic acid ( M4 ), were prepared as monomers and polymerized by ring‐opening metathesis polymerization (ROMP) using Grubbs second‐generation catalyst ( G2 ). In all the cases, the regio‐irregular unsaturated polymers with pendent linear branches were obtained, which could be saturated by chemical hydrogenation with TSH/TPA in high conversion, yielding ethylene/vinyl ester copolymers with pendent linear branches on precisely every eighth backbone carbon. Both unsaturated and saturated polymers were amorphous, and their structures were characterized by FTIR, ¹H and ¹³C NMR spectra, and elemental analysis. Differential scanning calorimetry (DSC) and thermo‐gravimetric analysis (TGA) were used to study their thermal properties. The chain length of branches greatly affected the thermal properties of polymers. After hydrogenation, the thermal degradation stability of polymers was relatively improved. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2211–2220     

Unsaturated hyperbranched polyester as a surface modifier of CaCO3 and enhanced effect on mechanical properties of HDPE/CaCO3 composites

The unsaturated hyperbranched polyester (UH20) based on Boltorn™ H20 (H20) end‐capped with methacrylate groups and carboxylic acid groups was introduced to treat calcium carbonate (CaCO₃) as a new type of surface modifier by a wet‐coating technique. The interaction between CaCO₃ and modifier was proven to be due to the ionic character by FT‐IR after the extraction with acetone. The maximum amount of tightly bonded UH20 modifier was determined to be around 9% by thermogravimetric analysis (TGA). The incorporation of CaCO₃ coated with UH20 into high‐density polyethylene (HDPE) decreased the mechanical performance of HDPE/CaCO₃ composite in comparison with CaCO₃ coated with stearic acid. In the presence of a small amount of dicumyl peroxide (DCP), a greatly improvement of the notched impact strength as well the tensile strength of HDPE/CaCO₃ coated with UH20 composite was obtained. An enhanced effect in the mechanical performance of the composite between CaCO₃ coated with UH20 and HDPE matrix in the existence of DCP was suggested. Moreover, the morphological structures of impact fracture surface of the HDPE/CaCO₃ composites were studied by scanning electron microscopy (SEM) to confirm the possible mechanism for explaining the improvement of mechanical properties of the composite. Copyright © 2005 John Wiley & Sons, Ltd.     

Crystallization and chain conformation of semicrystalline and amorphous polymer blends studied by wide‐angle and small‐angle scattering

We examine the crystallization and chain conformation behavior of semicrystalline poly(ethylene oxide) (PEO) and amorphous poly(vinyl acetate) (PVAc) mixtures with wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS), and small‐angle neutron scattering (SANS) experiments. For blends with PEO weight fractions (wt_PEO) greater than or equal to 0.3, below the melting point of PEO, the WAXD patterns reveal that crystalline PEO belongs to the monoclinic system. The unit‐cell parameters are independent of wt_PEO. However, the bulk crystallinity determined from WAXD decreases as wt_PEO decreases. The scattered intensities from SAXS experiments show that the systems form an ordered crystalline/amorphous lamellar structure. In a combination of WAXD and SAXS analysis, the related morphological parameters are assigned correctly. With the addition of amorphous PVAc, both the average amorphous layer thickness and long spacing increase, whereas the average crystalline layer thickness decreases. We find that a two‐phase analysis of the correlation function from SAXS, in which the scattering invariant is linearly proportional to the volume fraction of lamellar stacks, describes quantitatively the crystallization behavior of PEO in the presence of PVAc. When wt_PEO is close to 1, the samples are fully spaced‐filled with lamellar stacks. As wt_PEO decreases from 1.0 to 0.3, more PVAc chains are excluded from the interlamellar region into the interfibrillar region. The fraction outside the lamellar stacks, which is completely occupied with PVAc chains, increases from 0 to 58%. Because the radius of gyration of PVAc with a random‐coil configuration determined from SANS is smaller than the average amorphous layer thickness from SAXS, we believe that the amorphous PVAc chains still persist with a random‐coil configuration even when the blends form an ordered structure. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2705–2715, 2001     

Multielement characterization of soil samples with ICP-MS for environmental studies

The recovery of trace elements of ecotoxic importance has been studied on certified soil and sediment reference samples after pressurized digestions with HNO₃, HNO₃+HF and HNO₃+HCl+HF mixtures, respectively. The acid digests have been analyzed by ICP-MS. The results indicate that digestion with nitric acid alone is satisfactory for the recovery of As, Cd, Co, Cu and Zn. Cr and Pb showed lower recoveries with HNO₃ alone but addition of HF improved their extraction. With appropriate corrections, ICP-MS can be used for the routine analysis of soils and sediments. These digestion procedures, evaluated based on reference samples, have been used for the trace element characterization of soil samples from the German Environmental Specimen Bank.     

Synthesis and characterization of sulfamic acid supported on Fe3O4 nanoparticles: A green,versatile and magnetically separable acidic catalyst for oxidation reactions and Knoevenagel condensation

Sulfamic acid immobilized on diethylenetriamine functionalized Fe₃O₄ nanoparticles (SA‐DETA‐Fe₃O₄) was successfully prepared and characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), vibrating sample magnetometer (VSM), thermo gravimetric analysis (TGA), X‐Ray diffraction (XRD) and scanning electron microscopy (SEM). The sulfamic acid was found as a magnetically separable and highly active catalyst for the oxidative coupling thiols, oxidation of sulfides. Furthermore, the SA‐DETA‐Fe₃O₄ showed the high catalytic activity in Knoevenagel condensation of aromatic aldehydes with active methylene compounds (malononitrile and ethyl cynoacetate). The nanosolid catalyst could be easily recovered by a simple magnetic separation and reused for many cycles without deterioration in catalytic activity.     

Post-irradiation oxidation of different polyethylenes

The radiation-induced oxidative degradation of polyethylenes (PEs) with different degrees of crystallinity was characterized after electron-beam irradiation and during storage at room temperature.UHMWPE, HDPE, LDPE, LLDPE and an ethylene-octene copolymer (Engage) were e-beam irradiated to 30 or 60 kGy in vacuum or in air and stored at room temperature in air. EPR spectroscopy was used to investigate macro-radicals produced during irradiation and their post-irradiation changes. FTIR spectroscopy was used to monitor changes in the polymer structure, induced by irradiation, and to follow post-irradiation oxidation.We found that the crystallinity and the size of the crystalline lamellae, in particular, play a major role on the post-irradiation effects. The low-crystallinity polyethylenes showed no oxidation or oxidation only to a small extent, even when irradiated and stored in air. On the contrary, development of post-irradiation oxidation was observed in HDPE and UHMWPE. We attribute these results to a different reactivity of the macro-alkyl radicals formed upon irradiation in the amorphous or in the crystalline phase. While the radicals formed in the amorphous phase decay in short time, the migration time of the radicals trapped in the crystalline phase to the amorphous one is a key factor, governing the oxidation process.     

Characterization of polymer soil burial degradation by thermal analysis and mechanical spectroscopy

Polypropylene (PP) and High density polyethylene (HDPE) / Polypropylene (PP) blend with different biodegradable additives (Granular starch/iron oxide mixture, Bioefect 72000 and Mater-Bi AF05H) were selected for degradation experiments. All the samples, processed by injection as seedboxes, have been subjected to an outdoor soil burial test and removed at different periods of time between 0 and 21 months. Their chemical structure and morphology have been analysed. Studies of dynamic-mechanical relaxation spectra of the samples before and after each exposure time have been carried out. The three characteristic relaxation zones α, β and γ, in order of decreasing temperature, have been obtained. It has been observed that due to the degradation process both, the HDPE/PP blend and the PP matrix, become more brittle than the undegraded ones regardless of the additive used. Degradation seems to start from the molecular chains of the amorphous phase or interfacial region. However the analysis of the mechanical behaviour manifested that the crystalline zone is also been affected by the exposure time.     

Insights into the Mechanism of Extraction of Uranium (VI) from Nitric Acid Solution into an Ionic Liquid by using Tri‐n‐butyl phosphate

We present new results on the liquid–liquid extraction of uranium (VI) from a nitric acid aqueous phase into a tri‐n‐butyl phosphate/1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (TBP/[C₄mim][Tf₂N]) phase. The individual solubilities of the ionic‐liquid ions in the upper part of the biphasic system are measured over the whole acidic range and as a function of the TBP concentration. New insights into the extraction mechanism are obtained through the in situ characterization of the extracted uranyl complexes by coupling UV/Vis and extended X‐ray absorption fine structure (EXAFS) spectroscopy. We propose a chemical model to explain uranium (VI) extraction that describes the data through a fit of the uranyl distribution ratio D_U. In this model, at low acid concentrations uranium (VI) is extracted as the cationic complex [UO₂(TBP)₂]²⁺, by an exchange with one proton and one C₄mim⁺. At high acid concentrations, the extraction proceeds through a cationic exchange between [UO₂(NO₃)(HNO₃)(TBP)₂]⁺ and one C₄mim⁺. As a consequence of this mechanism, the variation of D_U as a function of TBP concentration depends on the C₄mim⁺ concentration in the aqueous phase. This explains why noninteger values are often derived by analysis of D_U versus [TBP] plots to determine the number of TBP molecules involved in the extraction of uranyl in an ionic‐liquid phase.     

红外光谱法在淀粉/聚乙烯低温热氧降解研究中的应用

共聚物;聚乙烯/淀粉共聚物;红外光谱法在淀粉/聚乙烯低温热氧降解研究中的应用     

Polyisobutylene‐based polyurethanes: VII. structure/property investigations for medical applications

The outstanding hydrolytic and oxidative stabilities of polyisobutylene‐based polyurethanes (PIB‐based PUs) were reported earlier. Herein, we summarize recent investigations aimed at further enhancing hydrolytic‐oxidative stabilities (in terms of resistance to aqueous buffer, nitric acid and CoCl₂/H₂O₂) together with excellent mechanical properties. The purity and dryness of ingredients together with precise NCO/OH stoichiometry (～1.05) are essential to obtain PIB‐based PUs with improved properties. Static and dynamic mechanical properties were optimized by analyzing stress–strain traces, thermal (TGA, DSC) responses, self‐organization (XRD) profiles, and rheological (DMA, creep) information. According to microstructure and surface analyses (AFM, contact angle) annealing increases the segregation of individual segments and increases surface hydrophobicity, which in turn enhances the shielding of hydrolytically oxidatively vulnerable carbamate bonds by inert PIB barriers, and thus significantly improves hydrolytic‐oxidative stability. Annealing does not much affect bulk properties, such as static and dynamic mechanical and thermal properties; however, it increases damping over a wide temperature range. Annealed PIB‐based PU containing 72.5% PIB exhibits outstanding hydrolytic‐oxidative stability together with ～26 MPa tensile strength, ～500% elongation, and ～77 Microshore hardness. PIB‐based PUs are significantly more resistant to hydrolytic and oxidative degradation than ElastEon? E2A, a commercially available PDMS‐based PU, widely used for medical applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 532–543     

Assessment of a geochemical extraction procedure to determine the solid phase fractionation and bioaccessibility of potentially harmful elements in soils: A case study using the NIST 2710 reference soil

Three mineral acid sequential extraction regimes (HNO₃ only, HNO₃ followed by HCl and aqua regia) were applied to the NIST 2710 contaminated reference soil. The major and trace element chemical analysis data from the extractions were subjected to a chemometric self-modelling mixture resolution procedure which identified that 12 distinct physico-chemical components were extracted. The fractionation of As, Cd, Ni and Pb between these components were determined. Tentative assignments of the mineralogical sources of the components were made. The human ingestion bioaccessible fraction of As, Cd and Pb were determined using the in vitro BARGE UBM bioaccessibility test and were found to be 51.6%, 68.0% and 68.4% respectively. The relationship between the lability of the physico-chemical components and the bioaccessible fraction of the soils was investigated and the bioaccessible fractions were assigned to specific components. The extraction scheme using aqua regia was found to be the most suitable as it was the only one which extracted the iron sulphide phase in the soil.     

An Ultrastable Matryoshka [Hf13] Nanocluster as a Luminescent Sensor for Concentrated Alkali and Acid

Stable metal clusters that can resist both highly concentrated acid and alkali are unknown. Herein, we present a discrete neutral cluster, Hf₁₃(μ₄‐O)₈(OCH₃)₃₆ ( 1 ), which features extraordinary chemical stability by preserving its crystalline state in concentrated aqueous solutions of both acid (10 m HNO₃) and alkali (20 m boiling NaOH). Importantly, 1 can serve as a luminescent probe for detecting both concentrated alkali (20 m NaOH) and strong acid (1 m HNO₃) with high selectivity and repeatability. DFT studies of the electronic structure and bonding revealed that 1 has an extremely large HOMO–LUMO gap due to strong d π–p π bonding that accounts for the ultrahigh stability.