包头磁尾矿稀土浸出和制备冰晶石的研究

包头白云鄂博矿床产生大量磁尾矿,会产生很大的环境问题。采用纯碱焙烧法对其进行了稀土浸出实验和氟的资源化利用研究。实验结果表明,包头磁尾矿与纯碱混合物于700℃焙烧1.0 h,经稀盐酸洗涤后,以3.0 mol.L-1稀硫酸于65℃下浸出4.0 h,氟的洗脱和稀土浸出效果较好,其中稀土浸出率为97.97%,氟浸出率为99.54%,氟洗脱率为77.32%。以该条件下产生的含氟废水为原料,于90℃下制备了冰晶石,溶液中氟回收率为85.63%,并推算出磁尾矿中氟的总利用率为66.21%。该法使磁尾矿由废弃物变为二次资源成为可能。     

焙烧除硒-火试金法测定银硒渣中金、银含量

建立了银硒渣中金、银含量的测定方法。通过高温焙烧除去银硒渣中的硒,然后用火试金法测定金、银含量。硒在750℃下焙烧30min能够完全除去,不会对火试金中金、银造成损失,在焙烧时铺垫二氧化硅避免样品黏附在试金坩埚壁上,并且配料时易于搅拌均匀。通过加标回收实验,测得金回收率为98.9%~101%,银的回收率为96.3%~98.6%。金相对标准偏差(RSD)小于2.5%,银相对标准偏差(RSD)小于1.1%。方法不仅简单、快速,而且准确度高、精密度好。     

Leaching Studies of Inorganic and Organic Compounds from Fly Ash

Fly ash is produced in massive quantities by fossil fuel based power plants and waste incinerators, and contains high levels of potentially toxic chemicals. Various leaching tests exist to determine the available fractions, but the outcome is strongly dependent on the experimental conditions, and these have not yet been harmonised at the international level. In order to test existing protocols for heavy metals, several intercomparisons were organised within the framework of an EU-INCO project "ANALEACH", in which seven institutes from five countries participated. Two existing reference materials were made available for the project and test batches of two new fly ash reference materials were produced. Availability tests, leaching tests and pH-stat tests were studied and critical steps in the procedures were identified. Fly ashes can also contain large amounts of inorganic sulphur and nitrogen compounds, and the determination and leaching behaviour of these compounds were also studied. In one intercomparison for metals, inorganic S and N-compounds were also included. A five-step leaching test was optimised for fly ash in order to link metal fractions to different types of binding. Column leaching experiments were carried out to investigate leaching from fly ash into soil, mimicking the effects of (acid) rain on fly ash deposited on topsoil after atmospheric transport. The major fraction of the leached metal ions was retained by the soil. Also large numbers of organic compounds (including many toxic ones) were identified in fly ash extracts, especially in city waste incinerator ash. Leaching procedures based on ultrasonic extraction were developed for organic compounds and an intercomparison exercise was organised. In a field study at the river Nitra(Slovakia) numerous organic pollutants were found at elevated levels downstream from a major fly ash dump site.     

Kinetics of Ni,V and Fe Leaching from a Spent Catalyst in Microwave-Assisted Acid Activation Process

Ni, V and Fe are the main contaminant metals that lead to the deactivation of the spent fluid catalytic cracking (SFCC) catalyst. In this work, the properties and distribution of Ni, V and Fe in the SFCC catalyst are investigated by employing EPMA-EDX, SEM and XPS techniques. The kinetics of Ni, V, Fe and Al leaching in organic and inorganic acids are studied under microwave heating. The EPMA-EDX results show that Fe and Ni mainly accumulate near the particle surface, while V eventually distributes throughout the catalyst particle. The XPS result suggests that the phase speciations of Ni in the SFCC catalyst are Ni, Ni₂SiO₄ and NiAl₂O₄, while Fe is present in a mixture of Fe₃O₄, Fe₂O₃ and Fe₂SiO₄. V is in the forms of V₂O₅ and VO₂. Compared with oxalic acid, sulfuric acid has a better removal effect of contaminant metals, especially for Ni. The leaching kinetics results indicate that using either sulfuric acid or oxalic acid, the apparent activation energy of V is obviously lower than that of Fe and Ni, and the priority of the three contaminant metals in the removal effect is V > Fe > Ni. In addition, the leaching kinetics of contaminant metals in the microwave-assisted acid activation process are controlled by the surface chemical reaction control model.     

On‐line process monitoring of coffee roasting by resonant laser ionisation time‐of‐flight mass spectrometry: bridging the gap from industrial batch roasting to flavour formation inside an individual coffee bean

Resonance‐enhanced multiphoton ionisation time‐of‐flight mass spectrometry (REMPI‐TOFMS) enables the fast and sensitive on‐line monitoring of volatile organic compounds (VOC) formed during coffee roasting. On the one hand, REMPI‐TOFMS was applied to monitor roasting gases of an industrial roaster (1500 kg/h capacity), with the aim of determining the roast degree in real‐time from the transient chemical signature of VOCs. On the other hand, a previously developed μ‐probe sampling device was used to analyse roasting gases from individual coffee beans. The aim was to explore fundamental processes at the individual bean level and link these to phenomena at the batch level. The pioneering single‐bean experiments were conducted in two configurations: (1) VOCs formed inside a bean were sampled in situ, i.e. via a drilled μ‐hole, from the interior, using a μ‐probe (inside). (2) VOCs were sampled on‐line in close vicinity of a single coffee bean's surface (outside). The focus was on VOCs originating from hydrolysis and pyrolytic degradation of chlorogenic acids, like feruloyl quinic acid and caffeoyl quinic acid. The single bean experiments revealed interesting phenomena. First, differences in time–intensity profiles between inside versus outside (time shift of maximum) were observed and tentatively linked to the permeability of the bean's cell walls material. Second, sharp bursts of some VOCs were observed, while others did exhibit smooth release curves. It is believed that these reflect a direct observation of bean popping during roasting. Finally, discrimination between Coffea arabica and Coffea canephora was demonstrated based on high‐mass volatile markers, exclusively present in spectra of Coffea arabica. Copyright © 2013 John Wiley & Sons, Ltd.     

Leaching of zinc and germanium from zinc oxide dust in sulfuric acid-ozone media

A new process of leaching zinc oxide dust by ozone oxidation in a sulfuric acid system was studied. The main factors affecting the leaching rate, such as ozone time, leaching temperature, initial acidity, leaching time, and liquid/solid mass ratio, were comprehensively investigated. The results show that leaching efficiency depends on all the above factors. The optimum conditions for leaching Zn and Ge from zinc oxide dust are as follows: ozone time 10 min, leaching temperature 90 ℃, initial acidity 160 g/L, leaching time 60 min, and liquid/solid mass ratio 7:1. Under the optimum conditions, the leaching rates of Zn and Ge are 95.79% and 93.65%, respectively. The leaching rates of zinc and germanium in the ozone leaching are 4.05% and 10.49% higher than those of the atmospheric leaching, respectively. Therefore, it is determined that ozone in solution plays a key role in rapidly oxidizing sulfide and releasing encapsulated germanium. Sulfuric acid-ozone media can efficiently extract Zn and Ge from zinc oxide dust.     

Sulfamethoxazole Leaching from Manure-Amended Sandy Loam Soil as Affected by the Application of Jujube Wood Waste-Derived Biochar

Vertical translocation/leaching of sulfamethoxazole (SMZ) through manure-amended sandy loam soil and significance of biochar application on SMZ retention were investigated in this study. Soil was filled in columns and amended with manure spiked with 13.75 mg kg⁻¹ (S1), 27.5 mg kg⁻¹ (S2), and 55 mg kg⁻¹ (S3) of SMZ. Jujube (Ziziphus jujube L.) wood waste was transformed into biochar and mixed with S3 at 0.5% (S3-B1), 1.0% (S3-B2), and 2.0% (S3-B3) ratio. Cumulative SMZ leaching was lowest at pH 3.0, which increased by 16% and 34% at pH 5.0 and 7.0, respectively. A quicker release and translocation of SMZ from manure occurred during the initial 40 h, which gradually reduced over time. Intraparticle diffusion and Elovich kinetic models were the best fitted to leaching data. S3 exhibited the highest release and vertical translocation of SMZ, followed by S2, and S1; however, SMZ leaching was reduced by more than twofold in S3-B3. At pH 3.0, 2.0% biochar resulted in 99% reduction in SMZ leaching within 72 h, while 1.0% and 0.5% biochar applications reduced SMZ leaching to 99% within 120 and 144 h, respectively, in S3. The higher SMZ retention onto biochar could be due to electrostatic interactions, H-bonding, and π-π electron donor acceptor interactions.     

Spectroscopic investigations of nanohydroxyapatite powders synthesized by conventional and ultrasonic coupled sol-gel routes

In the present work, the synthesis and characterization of nano-HAP powders by a novel ultrasonic coupled sol-gel synthesis is reported. The obtained powders were sintered by conventional means at different temperatures. In addition to this, HAP powders prepared through the sol-gel method without the aid of the ultrasonic waves is also studied. The obtained nano-HAP powders were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopic (SEM) techniques. The results have proved that the nano-HAP powders synthesized by ultrasonic coupled sol-gel synthesis showed remarkable reduction in the particle size when compared with the conventional sol-gel method and hence these powders could be used as a coating material in biomedical applications.     

Extraction of antioxidants from plants using ultrasonic methods and their antioxidant capacity

The analytical method based on the HPLC coupled with UV detection (HPLC‐UV) for the determination of selected antioxidants (i.e. esculetin, scopoletin, 7‐hydroxycoumarine, rutin, xanthotoxin, 5‐methoxypsoralen and quercetin) in plant material was developed. Two ultrasonic extraction methods for the isolation of these compounds from the plants such as Mentha longifolia L., Mentha spicata L., Ruta graveolens L., Achyllea millefolium L., Plantago lanceolata L. and Coriandrum sativum L. were used. Both of these methods, i.e. ultrasonic probe and ultrasonic bath, were optimised and compared to each other. For the proposed HPLC‐UV method LOQ values in the range from 22.7 (xanthotoxin) up to 97.2 ng/mL (rutin) were obtained. For all extracts the antioxidant capacity based on the reduction of free 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical was also determined. Obtained results ranged from 10.11 up to 73.50% of DPPH radical inhibition.     

Cold ultrasonic acid extraction of copper, lead and zinc from soil samples

A cold ultrasonic acid method for extracting Pb, Cu and Zn from soil samples has been studied. This work focused on studying the experimental condition for extrating trace metals from soil samples at ambient temperature (≈25 °C) using Syrian soil samples; the same conditions were applied to reference soil samples(SL-1, Soil-7, SDM, and BCR-32). A short exposure time (4 h), and 2 ml of concentrated hydrochloric acid were found to be best. Under the applied conditions Pb, Cu and Zn were quantitavely extracted, while Sr, Mn, Fe, Al, Cr, Co, and Ni were partialy extracted. The advantages of the cold ultrasonic extraction method are as follows: it is selective, it is matrix free, the extraction time is short, the amounts of consumed chemicals are small, the by-products of the process are negligible and it is environmentally clean, since no fume emissions are emitted. The only disadvantage is that it is not a real total digestion method. Comparable results for the proposed ultrasound method and the hot-plate acid digestion method for Cu, Pb and Zn in certified refrence soil samples(SL-1, SDM, Soil-7, BCR-32, Soil-6) and some Syrian soil samples are obtained.     

Determination of vitexin and isovitexin in pigeonpea using ultrasonic extraction followed by LC-MS

A method based on ultrasonic extraction (USE) followed by LC-MS is presented for the determination of vitexin and isovitexin in pigeonpea extracts in this study. The influential parameters of the USE procedure were optimized, and the optimal conditions were as follows: extraction solvent, 60% ethanol solution; liquid/solid ratio 10:1 (mL/g), extraction power, 250 W; temperature, 40-50 degrees C; and three extraction cycles, each cycle 15 min. Validation of the USE method was performed in terms of repeatability and reproducibility. RSDs for extraction yields were lower than 5.85 and 8.09%, respectively. The LOD and LOQ of chromatographic determination were 0.96 and 3.2 ng/mL for vitexin and 0.84 and 2.8 ng/mL for isovitexin. The method was also successfully applied for the determination of vitexin and isovitexin in stems, leaves, and root extracts of pigeonpea. From all these results, we may conclude that the developed method is appropriate for the quality control of pigeonpea and other plant extract products developed from pigeonpea.     

The Reductive Leaching of Chalcopyrite by Chromium(II) Chloride for the Rapid and Complete Extraction of Copper

A hydrometallurgical process is developed to lower the costs of copper production and thereby sustain the use of copper throughout the global transition to renewable energy technologies. The unique feature of the hydrometallurgical process is the reductive treatment of chalcopyrite, which is in contrast to the oxidative treatment more commonly pursued in the literature. Chalcopyrite reduction by chromium(II) ion is described for the first time and superior kinetics are shown. At high concentrate loadings of 39, 78, and 117 g L⁻¹, chalcopyrite reacted completely within minutes at room temperature and pressure. The XRD, SEM-EDS, and XPS measurements indicate that chalcopyrite reacts to form copper(I) chloride (CuCl). After the reductive treatment, the mineral products are leached by iron(III) sulfate to demonstrate the complete extraction of copper. The chromium(II) ion may be regenerated by an electrolysis unit inspired by an iron chromium flow battery in a practical industrial process.     

Leaching Behaviour and Solid Phase Fractionation of Selected Metals as Affected by Thermal Treatment of a Polluted Sediment

Abstract

A contaminated dredged sediment was subjected to a thermal treatment at temperatures ranging from 120 to 450°C. The leaching behaviour of selected metals (Cd, Cu, Pb, Zn, Fe, Mn) was studied using NH₄OAc-EDTA extraction. In addition, solid phase fractionation was carried out by means of a sequential extraction procedure.

The NH₄OAc-EDTA extraction showed a sharp increase in metal leachability from sediments treated at intermediate temperatures (120–350°C). The metal fractionation of the solid phases at the different temperatures did not reveal relevant shifts except for Cu. The decrease of the oxidizable Cu fraction was highly correlated (P < 0.001) with the disappearance of organic matter at higher treatment temperatures. It is suggested that binding energy changes within the fractions rather than shifts between chemical forms account for the observed leaching behaviour.     

Effects of ultrasonic extraction on the physical and chemical properties of polysaccharides from longan fruit pericarp

An ultrasonic technique was employed to extract polysaccharides from longan fruit pericarp (PLFP). Effects of ultrasonic power, time and temperature on the extraction of PLFP were examined. Different effects of ultrasonic time were observed at two different ultrasonic power of 120 and 300 W. A higher recovery rate of PLFP at an ultrasonic power of 300 W was obtained as compared with 120 W. The recovery rate of PLFP was slightly increased by elevating the ultrasonic temperature up to 60 °C. The highest recovery rate of PLFP was achieved at 120 W and 70 °C for 20 min. Furthermore, PLFP I and PLFP II-IV were prepared by hot-water extraction and ultrasonic extraction, respectively, and then used for the analyses of physical and chemical properties. Analysis by differential scanning calorimetry showed that the onset temperature, peak temperature, conclusion temperature and melting enthalpy (ΔH) of PLFP by hot-water extraction were lower than those by ultrasonic extraction. These results suggested that rearrangement of PLFP microstructure could occur and development of a higher proportion of crystalline regions might be induced by the ultrasonic treatments. The highest ΔH (8.02 J/g) and two endothermic peaks were observed in the thermogram of PLFP II. Scanning electron micrographs revealed more aggregated particles in PLFP III and IV compared with PLFP I and II. However, no apparent differences were found from the spectra of these four PLFP samples at a range of 195-550 nm, which indicated that ultrasonic treatment might not cause significant chemical modification of groups in the PLFP chain.     

Improving the catalytic activity of magnetic Fe3O4/ZnO-CdO/reduced graphene oxide for ultrasonic degradation of the organic pollutants and the green oxidation of olefins

Magnetic Fe₃O₄/ZnO-CdO/reduced graphene oxide (MFZC/RGO) has been synthesized by simple hydrothermal method. The structure and morphology were investigated by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), Diffuse reflectance spectroscopy (DRS), Vibrating sample magnetometer (VSM), Raman and Fourier-transform infrared spectroscopy (FTIR). MFZC/RGO was applied as catalyst in degradation of methylene blue (MB), rhodamin B (RhB) and methylorange (MO) under ultrasonic irradiation. Based on the results, excellent degradation efficiencies of MB, RhB and MO (>99%) were achieved within 10, 20 and 20 min, respectively under oxygen flow. Moreover the catalytic property of MFZC/RGO was investigated in oxidation of styrene, α-methyl styrene, cyclohexene and cyclooctene under oxygen flow. In addition, MFZC/RGO can be easily collected and separated by an external magnet. The catalyst displayed negligible loss in activity and selectivity within several successive runs due to super paramagnetism.     

Gel permeation chromatographic characterization of sodium hyaluronate and its fractions prepared by ultrasonic degradation

Summary High-molecular-weight sodium hyaluronate isolated from rooster combs was degraded by ultrasonication. The molecular weight of hyaluronate and its polydispersity was determined by gel-permeation chromatography. During 75-min treatment the molecular weight value decreased from 1.39×10⁶ Da to 2.25×10⁵ Da while the polydispersity of the molecular weight increased from 1.29 to 2.36. The reciprocal value of the square of the hyaluronate's molecular weight was linearly proportional to the time of ultrasonication.     

Synthesis and electrochemical performance of LiCr x Mn2-xO4(x=0,0.02,0.05,0.08,0.10) powders by ultrasonic coprecipitation

LiCr _x Mn_2-x O₄(x=0, 0.02, 0.05, 0.08, 0.10) compounds with a spinel crystal structure have been prepared by a novel ultrasonic co-precipitation method. The effects of the calcination temperature and the citric acid-to-metal ion molar ratio (R) on powder characteristics and electrochemical performance are evaluated. It is found that the optimum R and sintering temperature for LiCr _x Mn_2-x O₄ materials by the ultrasonic co-precipitation method are R= 5/6 and 800°C, respectively. The calcined powders are loosely bound agglomerates of abnormally coarsened particles with a narrow range of particle sizes. The effect of Cr doping was also explored. Electrochemical studies show that optimum materials synthesized by the ultrasonic co-precipitation method demonstrate good cycling performance.     

Assessment of pesticide contamination in soil samples from an intensive horticulture area, using ultrasonic extraction and gas chromatography-mass spectrometry

In order to reduce the amount of sample to be collected and the time consumed in the analytical process, a broad range of analytes should be preferably considered in the same analytical procedure. A suitable methodology for pesticide residue analysis in soil samples was developed based on ultrasonic extraction (USE) and gas chromatography–mass spectrometry (GC–MS). For this study, different classes of pesticides were selected, both recent and old persistent molecules: parent compounds and degradation products, namely organochlorine, organophosphorous and pyrethroid insecticides, triazine and acetanilide herbicides and other miscellaneous pesticides. Pesticide residues could be detected in the low- to sub-ppb range (0.05–7.0 μg kg⁻¹) with good precision (7.5–20.5%, average 13.7% R.S.D.) and extraction efficiency (69–118%, average 88%) for the great majority of analytes. This methodology has been applied in a monitoring program of soil samples from an intensive horticulture area in Póvoa de Varzim, North of Portugal. The pesticides detected in four sampling programs (2001/2002) were the following: lindane, dieldrin, endosulfan, endosulfan sulfate, 4,4′-DDE, 4,4′-DDD, atrazine, desethylatrazine, alachlor, dimethoate, chlorpyrifos, pendimethalin, procymidone and chlorfenvinphos. Pesticide contamination was investigated at three depths and in different soil and crop types to assess the influence of soil characteristics and trends over time.     

Approach for rapid extraction and speciation of mercury using a microtip ultrasonic probe followed by LC-ICP-MS

A fast method for mercury extraction from biological samples based on the use of HCl leaching plus different enzymatic hydrolysis (with and without mercury complexing agents), and the use of focussed ultrasounds (2-mm microtip) is here proposed. Total mercury content in several biological samples was determined by FI-ICP-MS using a carrier solution consisting of 0.1% (v/v) HCl, 0.1% (v/v) 2-mercaptoethanol, to avoid memory effect, and 0.15% (w/v) KCl. For mercury speciation a RP18 chromatographic column coupled to ICP-MS was used. A mobile phase consisting of 0.1% (v/v) formic acid, 0.1% (v/v) HFBA, 2% (v/v) methanol, and 0.02% (w/v) mM l-cysteine at pH 2.1 was used for chromatographic separation of the mercury species in the sample extracts. Extraction procedures were validated by using 50 mg of tuna fish tissue CRM-463 (2.85 ± 0.16 mg kg⁻¹ for methylmercury). The recoveries obtained were 99 ± 3% and 93 ± 1% after acid leaching (HCl 7 M) and enzymatic extraction (15 mg protease type XIV in 2.5% (v/v) 2-mercaptoethanol), respectively. The optimal sonication conditions (5 min of exposure time and 40% of ultrasound amplitude) were applied to 5 mg of CRM-463 (88 ± 5%), 5 mg of mussel tissue (81 ± 11%) and to 2 mg of zebra fish embryos (90 ± 10%) obtaining good recoveries in all cases. Methylmecury was found to be the most abundant Hg specie in all samples. The developed method is simple and rapid (5 min sample treatment); it is suitable for very small samples and does not alter the original form of the mercury species. Thus, it is of special interest in those cases in which validation of the results may often be hampered by lack of sample availability.     

Determination of trace and major elemental profiles in street dust samples by fast miniaturized ultrasonic probe extraction and ICP-MS

A simple, fast and miniaturized ultrasonic probe assisted protocol for acid extraction of trace and major elements from street dust samples, prior to final determination by ICP-MS, has been optimized and validated by standard reference materials and applied during an urban air quality monitoring campaign. 15 mg samples were treated for 3 min with 1 mL concentrated HNO₃-HCl (1:3, v/v) extracting solution, by a 1 mm diameter titanium sonotrode connected to a 200 W and 24 kHz ultrasonic device at 80% amplitude. After centrifugation, the extracts were assayed by ICP-MS with good recoveries for the certified elements. Statistical analysis of real sample results by cluster analysis allowed the correct grouping of the samples according to the influence of traffic and construction/demolition activities. Correlation of street dust and PM10 elemental profiles showed the potential applicability of the proposed analytical protocol as a simple and effective way for urban air quality monitoring.