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[en] In X-ray florescence (XRF) spectrometry, the weight of a sample can be partially lost during the high temperature fusion necessary for the casting of borate glass disks. This weight loss is due to the decomposition of compounds such as carbonates and nitrates, and the subsequent loss of loss-on-fusion (LOF) compounds such as CO2, NO2 and O2, etc. Without a prior experimental determination of LOF, its effects on XRF analysis can be eliminated using special matrix correction coefficients called loss-eliminated alphas (LEAs) or αije. Using this method, samples are usually analyzed 'as-received' and the difference between 100% and the measured sum of elemental oxides gives the LOF. The LEAs are dependent on the nominal weights of sample and flux specified for the calculation of LEAs. The effect of the use of catch-weights (CWs; weights other than the nominal weights) on the analysis is generally corrected using a simple proportional correction factor. In contrary to the popular belief that CWs can be satisfactorily used for all sample matrices, the results presented here indicate that the error can be significant (>typical precision) and systematic as in the analysis of limestone where the LOF is approximately 40-45%. However, CWs could be used with a modified LEA value to eliminate the error on the analysis of major elements associated with the lost compounds. The results for the analysis of Standard Reference Material, 1C Argillaceous Limestone, are in good agreement with the certified values
[en] Highlights: • Current iron recovery techniques using red mud are depicted. • Advantages and disadvantages exist in different recovering processes. • Economic and environmental friendly integrated usage of red mud is promising. - Abstract: Bauxite residue (red mud) is a hazardous waste generated from alumina refining industries. Unless managed properly, red mud poses significant risks to the local environment due to its extreme alkalinity and its potential impacts on surface and ground water quality. The ever-increasing generation of red mud poses significant challenges to the aluminium industries from management perspectives given the low proportion that are currently being utilized beneficially. Red mud, in most cases, contains elevated concentrations of iron in addition to aluminium, titanium, sodium and valuable rare earth elements. Given the scarcity of iron supply globally, the iron content of red mud has attracted increasing research interest. This paper presents a critical overview of the current techniques employed for iron recovery from red mud. Information on the recovery of other valuable metals is also reviewed to provide an insight into the full potential usage of red mud as an economic resource rather than a waste. Traditional hydrometallurgy and pyrometallurgy are being investigated continuously. However, in this review several new techniques are introduced that consider the process of iron recovery from red mud. An integrated process which can achieve multiple additional values from red mud is much preferred over the single process methods. The information provided here should help to improve the future management and utilization of red mud
[en] This paper reports the detailed composition and morphology of one-step green synthesized bimetallic Fe/Pd nanoparticles (NPs) using grape leaf aqueous extract and identification of active biomolecules involved in the synthesis employing various techniques. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) revealed that Fe/Pd NPs were polydispersed and quasi-spherical with a diameter ranging from 2 to 20 nm. X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray Spectroscopy (EDS) provided evidence for the composition of Fe and Pd and for their species existing on the surface of Fe/Pd NPs. In addition, biomolecules in the grape leaf aqueous extract were identified but their functions are still unclear. Biomolecules in the aqueous extract such as methoxy-phenyl-oxime, N-benzoyl-2-cyano-histamine, 2-ethyl-phenol, 1,2-benzenediol, β-hydroxyquebracamine, hydroquinone, 2-methoxy-4-vinylphenol, 5-methyl-2-furancarboxaldehyde, 4-(3-hydroxybutyl)-3,5,5-trimethyl-2-cyclohexen and some polyphenolic compounds were identified as reducing and capping agents, which were studied by Chromatography-Mass Spectroscopy (GC–MS), XPS and Fourier Transform Infrared Spectroscopy (FTIR). Our finding suggests a new insight into cost-effective, simple, and environmentally benign production of bimetallic Fe/Pd NPs. - Graphical abstract: TEM image for the Fe/Pd NPs synthesized by grape leaf aqueous extract. - Highlights: • The one-step green synthesis of Fe/Pd nanoparticles has been systematically characterized. • TEM showed that the Fe/Pd NPs were polydispersed with a diameter ranging from 2 to 20 nm. • Active biomolecules in the grape extract were identified.
[en] Pollution of shooting range soils by lead from bullets represents a widespread and potentially significant concern for impact on the environment. High concentrations of lead in particular are reported in bullet impact berms and shot fall zones. The other components of bullets used in shooting including antimony, copper and zinc may also be present at elevated concentrations. Antimony is a concern due to its mobility in the environment. It has been recognised that the status of contamination is important for the risk presented by shooting ranges. Lead bullets are subject to weathering in the soil, forming secondary minerals, which may be solubilised and may release lead and co-contaminants into the soil. The mobility and availability of contaminants in the soil affect their potential for spreading in the environment and for uptake and toxicity in organisms. Soil physicochemical properties affect bullet weathering and availability of contaminants in the soil. A number of strategies have been researched for management of shooting range pollution such as chemical stabilisation, phytoremediation and soil washing. This review considers the current state of knowledge and research of contamination and management of shooting ranges from recent literature (2014–2017) reflecting on new knowledge and novel management strategies for shooting range soil management. Ultimately, management of pollution in shooting range soils should seek to remove bullets from soil, reduce the weathering of bullets and reduce the mobility and bioavailability of contaminants. Adopted management practices should be based an understanding of site-specific condition, to achieve the most optimal outcome.
[en] This study aimed to investigate the potential of Rhodopseudomonas palustris C1 and Rubrivivax benzoatilyticus C31 to ameliorate As toxicity and to reduce As uptake in rice. Strain C1 was superior to strain C31 for siderophore production. The mixed culture (1: 1) was most effective in reducing the toxicity of As species [As(III) and/or As(V), each 30 mg/l] by yielding maximal germination index that related to α- and β-amylase activities in two Thai rice cultivars (HomNil: HN and PathumThani 1: PT). Arsenic toxicity to the seed germination followed the order: mixed As species > As(III) > As(V); and the toxicity was reduced in inoculated sets, particularly with a mixed culture. The mixed culture significantly enhanced rice growth under As stress in both rice cultivars as indicated by an increase in the production of chlorophyll a and b, and also supporting the non-enzymatic (carotenoids, lipid oxidation, and nitric oxide) and enzymatic (superoxide dismutase, ascorbate peroxidase, catalase, and glutathione reductase) activities. These were concomitant with productions of 5-aminolevulinic acid, indole-3-acetic acid, exopolymeric substances, and siderophores which significantly reduced As accumulation in treated rice. It can be concluded that the mixed culture has great potential to ameliorate rice from As toxicity by preventing As species entry into rice for enhancing rice growth and also for reducing As accumulation to produce safe rice from rice grown in contaminated paddy fields.
[en] The Basel Convention on the Control of Transboundary Movement of Hazardous Wastes and their Disposal was adopted on March 22, 1989 and enforced on May 5, 1992. Since then, the USA, one of the world's largest e-waste producers, has not ratified this Convention or the Basel Ban Amendment. Communities are still debating the legal loophole, which permits the export of whole products to other countries provided it is not for recycling. In January 2011, China's WEEE Directive was implemented, providing stricter control over e-waste imports to China, including Hong Kong, while emphasizing that e-waste recycling is the producers' responsibility. China is expected to supersede the USA as the principal e-waste producer, by 2020, according to the UNEP. Uncontrolled e-waste recycling activities generate and release heavy metals and POPs into the environment, which may be re-distributed, bioaccumulated and biomagnified, with potentially adverse human health effects. Greater efforts and scientific approaches are needed for future e-product designs of minimal toxic metal and compound use, reaping greater benefits than debating the definition and handling responsibilities of e-waste recycling. - Highlights: ► We recommended to ban uses of deca-BDE in addition to penta- and octa-BDEs. ► We suggested to replace PVC in electronic products with non-chlorinated polymers. ► Spend less time on debating responsibilities and definition of e-waste and recycling. ► Proposed to work more on eliminating sources and potentials of toxic substances
[en] Highlights: • Uranium contamination of soil has been a major concern. • Remediation of uranium-contaminated soils investigated by various techniques. • Challenges faced and complexities in remediation discussed. • Significance of the integrated role of various factors in uranium decontamination process. - Abstract: Uranium contamination of soil has been a major concern with respect to its toxicity, accumulation in the food chain and persistence in the environment. Owing to these problems, remediation of uranium-contaminated soils has been investigated by various techniques. This review focuses on the challenges and complexities associated with the remediation of uranium-contaminated soil at field level. Therefore, laboratory studies have been excluded from this review. Challenges faced during remediation of uranium-contaminated soil using various techniques such as microbial/phyto/chemical/material based strategies have been discussed with suitable examples. Various factors that have a major influence on uranium decontamination process in soil such as soil type, uranium speciation, the presence of coexisting ions and organics, etc., have been highlighted. This review brings out the significance of the integrated role of various factors which determine the efficiency of the uranium decontamination process.
[en] We report on a glassy carbon electrode modified with bismuth nanoparticles (NanoBiE) for the simultaneous determination Pb2+ and Cd2+ by anodic stripping voltammetry. Operational parameters such as bismuth nanoparticles labelling amount, deposition potential, deposition time and stripping parameters were optimized with respect to the determination of Pb2+ and Cd2+ in 0.1 M acetate buffer solution (pH 4.5). The NanoBiE gives well-defined, reproducible and sharp stripping peaks. The peak current response increases linearly with the metal concentration in a range of 5.0–60.0 μg L−1, with a detection limit of 0.8 and 0.4 μg L−1 for Pb2+ and Cd2+, respectively. The morphology and composition of the modified electrode before and after voltammetric measurements were analysed by scanning electron microscopy and energy dispersive X-ray analysis. The NanoBiE was successfully applied to analysis of Pb2+ and Cd2+ in real water samples and the method was validated by ICP-MS technique, suggesting that the electrode can be considered as an interesting alternative to the bismuth film electrode for possible use in electrochemical studies and electro analysis. (author)
[en] Highlights: ► Comprehensive and critical literature review on various adsorbents used for defluoridation. ► pH, temperature, kinetics and co-existing anions effects on F adsorption. ► Choice of adsorbents for various circumstances. ► Adsorption thermodynamics and mechanisms. ► Future research on efficient, low cost adsorbents which are easily regenerated. -- Abstract: Excessive intake of fluoride (F), mainly through drinking water, is a serious health hazard affecting humans worldwide. There are several methods used for the defluoridation of drinking water, of which adsorption processes are generally considered attractive because of their effectiveness, convenience, ease of operation, simplicity of design, and for economic and environmental reasons. In this paper, we present a comprehensive and a critical literature review on various adsorbents used for defluoridation, their relative effectiveness, mechanisms and thermodynamics of adsorption, and suggestions are made on choice of adsorbents for various circumstances. Effects of pH, temperature, kinetics and co-existing anions on F adsorption are also reviewed. Because the adsorption is very weak in extremely low or high pHs, depending on the adsorbent, acids or alkalis are used to desorb F and regenerate the adsorbents. However, adsorption capacity generally decreases with repeated use of the regenerated adsorbent. Future research needs to explore highly efficient, low cost adsorbents that can be easily regenerated for reuse over several cycles of operations without significant loss of adsorptive capacity and which have good hydraulic conductivity to prevent filter clogging during the fixed-bed treatment process
[en] A new chemically modified glassy carbon electrode based on bismuth film coated mesoporous silica nanoparticles was developed and evaluated for reliable quantification of trace Pb2+ and Cd2+ by anodic stripping square wave voltammetry in natural water samples. Compared with conventional bismuth film electrodes or bismuth nanoparticles modified electrodes, this electrode exhibited significantly improved sensitivity and stability for Pb2+ and Cd2+ detection. The key experimental parameters related to the fabrication of the electrode and the voltammetric measurements were optimized on the basis of the stripping signals, where the peak currents increased linearly with the metal concentrations in a range of 2-150 μg L−1 with a detect limit of 0.2 μg L−1 for Pb2+, and 0.6 μg L−1 for Cd2+ for 120s deposition. Good reproducibility was achieved on both single and equally prepared electrodes. In addition, scanning electron microscopy reveals that fibril-like bismuth structures were formed on silica nanoparticles, which could be responsible for the improved voltammetric performance due to the enhanced surface area. Finally, the developed electrode was applied to determine Pb2+ and Cd2+ in water samples, indicating that this electrode was sensitive, reliable and effective for the simultaneous determination of Pb2+ and Cd2+