Organosulphur-modified biochar: An effective green adsorbent for removing metal species in aquatic systems

Knowledge of the function and structure of small metal clusters is one goal of research in catalysis. One important experimental parameter is cluster size. Ideally, one would like to produce metal clusters of regulated size in order to characterize size-dependent cluster properties.A source has been developed which is capable of producing microscopic metal clusters of controllable size (in the range 5-500 atoms) This source, the Multiple Expansion Cluster Source, with a Free Jet Deceleration Filter (MECS/FJDF) operates as follows. The bulk metal is heated in an oven to give controlled concentrations of monomer and dimer which were expanded sonically. These metal species were quenched and condensed in He and filtered to produce areosol particles of a controlled size as verified by mass spectrometer measurements. The clusters were caught on pre-mounted, clean carbon films. The grids were then transferred in air for microscopic examination. MECS/FJDF was used to produce two different sizes of silver clusters for this study: nominally Ag6 and Ag50.

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Fate of Colloidal-Particulate Elemental Selenium in Aquatic Systems

Journal of Environmental Quality ◽

10.2134/jeq2004.0559 ◽

2004 ◽

Vol 33 (2) ◽

pp. 559 ◽

Cited By ~ 7

Author(s):

Yiqiang Zhang ◽

Zahir A. Zahir ◽

William T. Frankenberger

Keyword(s):

Aquatic Systems ◽

Elemental Selenium

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Effects of NTA on the Fate of Heavy Metals in Sediments

Water Science & Technology ◽

10.2166/wst.1993.0617 ◽

1993 ◽

Vol 28 (8-9) ◽

pp. 191-194 ◽

Cited By ~ 3

Author(s):

S. L. Lo ◽

L. J. Huang

Keyword(s):

Heavy Metals ◽

Sodium Tripolyphosphate ◽

Equilibrium Concentration ◽

Chelating Agent ◽

Metal Species ◽

Pollution Problem ◽

Trisodium Salt ◽

Major Factors ◽

Apparent Equilibrium ◽

Degradation Time

Sodium tripolyphosphate (STPP), which is widely used as a builder in synthetic detergents, was found as one of the major factors of eutrophication in rivers and lakes. Many countries have used nitrilotriacetate (NTA) in detergents to replace STPP, but it induced another pollution problem. Because NTA is an effective chelating agent, it will dissolve heavy metals from the sediments and affect the fate of metal species in rivers. The purpose of this study is to investigate the effect of the mobilization of heavy metals from sediments by NTA. The experimental results indicated that NTA increases the mobilization of heavy metals as the shaking time increases and reaches an apparent equilibrium concentration after 24–48 hours. Typical results show that using 20mg/l of NTA and shaking time of 6 days, the fraction mobilized is about 8 to 15% for Cu, 1 to 7% for Zn, 7 to 10% for Pb, and 7 to 30% for Cd. Hardness of the water affects the formation of heavy metal-NTA complexes significantly. Biodegradation of the trisodium salt of NTA starts after 6–9 days with degradation time of the metal-NTA complexes decreasing in the order of Cu > Cd > Zn > Pb > Ca.

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Metal and phosphate speciation during anaerobic digestion of phosphorus rich sludge

Water Science & Technology ◽

10.2166/wst.1997.0591 ◽

1997 ◽

Vol 36 (6-7) ◽

pp. 191-200 ◽

Cited By ~ 5

Author(s):

C. M. Carliell ◽

A. D. Wheatley

Keyword(s):

Anaerobic Digestion ◽

Metal Speciation ◽

Extraction Methods ◽

Phosphate Removal ◽

Metal Species ◽

Chemical Extraction ◽

Inorganic P ◽

Similar Work ◽

Extractable P ◽

Phosphate Speciation

Chemical extraction methods are used to investigate metal and phosphate speciation during anaerobic digestion of phosphorus-rich sludge. Tests were performed using model compounds to evaluate the efficacy of the reagents in the extraction sequences and these results compared with similar work by other researchers. The metal speciation method was found to be suitable for identifying shifts in metal distribution but was unrepresentative of actual metal species. The phosphate speciation method did give adequate separation of the phosphate compounds tested. Full-scale digesters treating chemical and biological phosphate removal (CPR and BPR) sludge were analysed according to the methods developed. Results show that digestion of CPR sludge did not increase the soluble P concentration in the digester and that most of the precipitated phosphorus appeared to be retained in the sludge as inorganic P. The digester treating BPR sludge showed increased soluble and water-extractable P, in comparison to the control digester. Trace metal speciation profiles were found to be affected by addition of CPR sludge.

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Modelling heavy metal mobilisation in solid waste deposits - a predictive tool for environmental risk assessment

Water Science & Technology ◽

10.2166/wst.1999.0654 ◽

1999 ◽

Vol 39 (10-11) ◽

pp. 193-196

Author(s):

J. Petersen ◽

J. G. Petrie

Keyword(s):

Heavy Metal ◽

Solid Waste ◽

Environmental Risk ◽

Mechanistic Model ◽

Small Sample ◽

Waste Material ◽

Metal Species ◽

Model Parameters ◽

Assessment Methodology ◽

Predictive Tool

The release of heavy metal species from deposits of solid waste materials originating from minerals processing operations poses a serious environmental risk should such species migrate beyond the boundaries of the deposit into the surrounding environment. Legislation increasingly places the liability for wastes with the operators of the process that generates them. The costs for long-term monitoring and clean-up following a potential critical leakage have to be factored in the overall project plan from the outset. Thus assessment of the potential for a particular waste material to generate a harmful leachate is directly relevant for estimating the environmental risk associated with the planned disposal operation. A rigorous mechanistic model is proposed, which allows prediction of the time-dependent generation of a leachate from a solid mineral waste deposit. Model parameters are obtained from a suitably designed laboratory waste assessment methodology on a relatively small sample of the prospective waste material. The parameters are not specific to the laboratory environment in which they were obtained but are valid also for full-scale heap modelling. In this way the model, combined with the assessment methodology, becomes a powerful tool for meaningful assessment of the risks associated with solid waste disposal strategies.

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Piperazine as an Inexpensive and Efficient Ligand for Pd-Catalyzed Homocoupling Reactions to Synthesize Bipyridines and Their Analogues

Current Organic Synthesis ◽

10.2174/1570179415666180913131905 ◽

2019 ◽

Vol 16 (1) ◽

pp. 173-180

Author(s):

Mingwei Chen ◽

Jinyu Hu ◽

Xiaoli Tang ◽

Qiming Zhu

Keyword(s):

Transition Metal ◽

Oxidation State ◽

Coupling Reaction ◽

Aryl Halides ◽

Metal Species ◽

Good Substrate ◽

Active Metal ◽

Homocoupling Reaction ◽

Catalytic Cycles ◽

Reductive Homocoupling

Aim and Objective: The synthesis of bipyridines, especially 2, 2’-bipyridines, remains challenging because the catalytic cycle can be inhibited due to coordination of bipyridine to transition metal. Thus, the development of efficient methods for the synthesis of bipyridines is highly desirable. In the present work, we presented a promising approach for preparation of bipyridines via a Pd-catalyzed reductive homocoupling reaction with simple piperazine as a ligand. Materials and Methods: Simple and inexpensive piperazine was used as a ligand for Pd-catalyzed homocoupling reaction. The combination of Pd(OAc)2 and piperazine in dimethylformamide (DMF) was observed to form an excellent catalyst and efficiently catalyzed the homocoupling of azaarenyl halides, in which DMF was used as the solvent without excess reductants although stoichiometric reductant was generally required to generate the low-oxidation-state active metal species in the catalytic cycles. </P><P> Results: In this case, good to excellent yields of bipyridines and their (hetero) aromatic analogues were obtained in the presence of 2.5 mol% of Pd(OAc)2 and 5 mol% of piperazine, using K3PO4 as a base in DMF at 140°C. Conclusion: According to the results, piperazine as an inexpensive and efficient ligand was used in the Pd(OAc)2-catalyzed homocoupling reaction of heteroaryl and aryl halides. The coupling reaction was operationally simple and displayed good substrate compatibility.

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Green synthesis of silver nanoparticles using sustainable resources and their use as antibacterial agents: A review

Current Materials Science ◽

10.2174/2666145413666201207204617 ◽

2020 ◽

Vol 13 ◽

Author(s):

Kumari Jyoti ◽

Punyasloka Pattnaik ◽

Tej Singh

Keyword(s):

Silver Nanoparticles ◽

Plant Extracts ◽

Metallic Nanoparticles ◽

Cost Effective ◽

Biological Properties ◽

Metal Species ◽

Sustainable Resources ◽

Research Areas ◽

Low Toxicity

Background:: Synthesis of metallic nanoparticles has attracted extensive vitality in numerous research areas such as drug delivery, biomedicine, catalysis etc. where continuous efforts are being made by scientists and engineers to investigate new dimensions for both technological and industrial advancements. Amongst numerous metallic nanoparticles, silver nanoparticle (AgNPs) is a novel metal species with low toxicity, higher stability and significant chemical, physical and biological properties. Methods:: In this, various methods for the fabrication of AgNPs are summarized. Importantly, we concentrated on the role of reducing agents of different plants parts, various working conditions such as AgNO3 concentration; ratio of AgNO3/extract; incubation time; centrifugal conditions, size and shapes. Results:: This study suggested that eco-friendly and non toxic biomolecules present in the extracts (e.g. leaf, stem and root) of plants are used as reducing and capping agents for silver nanoparticles fabrication. This method of fabrication of silver nanoparticles using plants extracts is comparatively cost-effective and simple. A silver salt is simply reduced by biomolecules present in the extracts of these plants. In this review, we have emphasized the synthesis and antibacterial potential of silver nanoparticles using various plant extracts. Conclusion:: Fabrication of silver nanoparticles using plant extracts have advantage over the other physical methods, as it is safe, eco-friendly and simple to use. Plants have huge potential for the fabrication of silver nanoparticles of wide potential of applications with desired shape and size.

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