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Thermal Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
Why are Europium (III) chelates preferred in this application? Europium (III) chelates display highly temperature-dependent emissions, large Stokes’ shift (the difference between excitation wavelength and emission wavelength), and long lifetime (the average time the molecule stays in its excited state before emitting a photon), which make them strong candidates for fluorescent temperature sensing. A chelate is a chemical compound composed of a metal ion and a chelating agent. A chelating agent is a substance whose molecules can form several bonds to a single metal ion. In other words, a chelating agent is a multidentate ligand, i.e., a ligand capable of donating two or more pairs of electrons in a complexation reaction to form coordinate bonds. The ligand is a molecule, ion, or atom bonded to the central metal atom of a coordination compound.
An At-Source Treatment for Organomercury-Containing Hazardous Liquid Waste
Published in John W. Bell, Proceedings of the 45th Industrial Waste Conference May 8, 9, 10, 1990, 1991
Ralph J. Magliette, D. McKinney, E. S. Venkataramani, S. Bacher, B. Brian
This technology is used to remove strongly chelated and complexed metal compounds. Precipitation by complex organo-sulfur reagents is similar to conventional sulfide precipitation. Both rely upon the insolubility of mercuric sulfide or mercuri-mercapto compounds to achieve removal of mercury from aqueous waste streams. The organo-sulfur precipitation technology does successfully remove thimerosal from solution. Removal efficiencies were found to be approximately 92%. The filter cake from the filtration contains mercury salts up to 10% by weight. This cake, being hazardous and unacceptable for reclamation, would require additional treatment or disposal. Land disposal of mercury is restricted and is not a desired disposal option. The only alternative for the disposal of mercury salts formed from the precipitation reaction would be incineration. Incineration of mercury compounds is normally not an environmentally sound disposal option as most of it exits in the stack gas as mercury oxides with a small fraction exiting with the incinerator ash.22-23
Contrast enhancement agents and radiopharmaceuticals
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
The first gadolinium-based contrast agent (Magnevist®; Gd-DTPA, Bayer Healthcare) was introduced to clinical imaging in 1988 and at the time was seen as the gold standard in MRI contrast agents. Since then other manufacturers have created other compounds, which has now created an open market for gadolinium use. Gadolinium agents can be differentiated on the basis of their stability, viscosity and osmolality, all of which are determined by the chelate that has been added to reduce the toxicity of the product. A chelate is a compound containing a ligand bonded to an atom at one or more points.
Chelate assisted phytoextraction for effective rehabilitation of heavy metal(loid)s contaminated lands
Published in International Journal of Phytoremediation, 2023
Akshaya Prakash Chengatt, Nair G. Sarath, Delse Parekkattil Sebastian, N. Shibin Mohanan, E. S. Sindhu, Satheesh George, Jos T. Puthur
Citric acid-assisted phytoextraction of Cd was studied by Arsenov et al. (2017). The application of 20 mM citric acid/kg of soil increased the phytoremediation potential and activities of the antioxidant defense system of Salix viminalis, S. alba, and S. matsudana. It could reduce the negative effect of Cd on photosynthesis and other physiological processes. Chen et al. (2019) examined the effect of EDDS, citric acid, and oxalic acid on the phytoextraction of Cd by Zebrina pendula. It was found that 5 mM citric acid applied per kilogram of soil resulted in the maximum accumulation of Cd in the plant. Liang et al. (2019) carried out a pot experiment to find out the effects of citric acid, EDDS, and oxalic acid on the growth and phytoremediation potential of P. vittata L. toward cadmium and soil microbial responses in multimetal (loid) (Cd, Pb, and As) contaminated soil. An increased shoot and rhizoid biomass were observed in oxalic acid treatment. Moreover, the Cd extraction efficiency of the plants was increased in EDDS treatment. The chelants like oxalic acid augmented the microbial diversity and soil enzyme activities even under heavy metal stress. So, chelate-assisted remediation increases/preserve the soil microflora and is a means for in-situ reclamation of heavy metal contaminated areas.
Remediation of a metal-contaminated soil by chemical washing and repeated phytoextraction: a field experiment
Published in International Journal of Phytoremediation, 2021
Xian’an Yu, Tong Zhou, Jie Zhao, Changxun Dong, Longhua Wu, Yongming Luo, Peter Christie
Soil washing with chemical agents can give rapid and efficient removal of metals in a relatively short time (Meng et al. 2017; Yoo et al. 2018). Chelating agents such as ethylenediaminetetra-acetic acid (EDTA), ethylenediaminedisuccinic acid (EDDS) and their derivatives have been frequently proposed because of their ability to chelate metals (Koopmans et al. 2008). However, the residual chelate-metal complexes remaining in the soil after washing are often harmful to soil biota and crops (Wu et al. 2004). Recent studies have proposed some alternative chemical washing agents such as citric acid (Schwab et al. 2008) and FeCl3 (Makino et al. 2006; Yoo et al. 2016). The citric acid and FeCl3 not only have high extraction efficiency of metals but also show high biodegradability, readily availability, cost-effectiveness, and less detrimental effects on soils and crops. Compared with the FeCl3 alone, the combining utilization of FeCl3 with citric acid significantly increased the removal efficiencies of Cd, Cu, Zn, and Pb from a neutral soil (Gao et al. 2018). However, chemical washing agents usually lead to some degradation of soil quality such as low pH, poor texture, and nutrient loss and may then negatively influence plant growth (Jelusic and Lestan 2014; Fedje and Stromvall 2016). After washing, a portion of residual metals may be also destabilized and shift to exchangeable fractions in the remediated soil (Tsang and Hartley 2014).
A Review on the Application of Quaternary Ammonium-Based Ionic Liquids in Mineral Flotation
Published in Mineral Processing and Extractive Metallurgy Review, 2020
Hrushikesh Sahoo, Swagat S. Rath, Bisweswar Das
A wide range of both inorganic and organic reagents are used in industries for flotation to recover the fine particles from the ores. The reagents used in flotation study can be classified as collector, frother, activator, depressant, dispersant, modifier, etc. Among all these parameters, the collector has the highest impact on the flotation process. Thiols, alkyl carboxylates, sulfates, sulfonates, phosphates, amines, alkylphosphonic acid, and different chelating agents are used in mineral flotation. For the interaction of collector with the mineral surface, forces like electrostatic, Van der Walls, chemical bonding, and salvation at crystal lattice are collectively responsible. The sulfide ores are most widely treated in the flotation process. The collectors can be classified as anionic, amphoteric, or cationic. Generally, the anionic collectors such as carboxylates, sulfates, sulfonates, phosphates, phosphonates, and hydroxamates are used for the flotation of oxide minerals. These reagents are dissociable, ionizable, and hydrolysable. Cationic collectors having long hydrocarbon chain with amine head are most common reagents in the separation of silicates and quartz minerals in the flotation process. The chelating reagents can be used in flotation as they have selectivity to capture the metal ion-forming chelates. Chelates are a special class of metal complex-forming compounds which may be organic or inorganic with bidentate, tridentate, or tetradentate coordination sphere containing N, O, and S as the donor atoms.