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Algae: Source of Biofuel and Phytoremediation
Published in Jos T. Puthur, Om Parkash Dhankher, Bioenergy Crops, 2022
N.K. Aliya, C.M. Jijeesh, K.C. Jisha
In the case of metallic cation sequestration, complex formation happens between a metal ion and functional groups on the surface or inside the porous structure of the biological material. In this complexation process, the carboxyl groups present in the alginate provide a significant contribution. The adsorption capacity of different algal species may vary. Because of the high levels of alginates and sulfated polysaccharides in their cell walls and on which metals show a strong attraction, the brown algae are more competent accumulators of metals (Davis et al. 2003). The precipitation of lead phosphate in Anabaena cylindrica on the cell wall and inside the cell was recorded by Swift and Forciniti (1997). In their work, it was confirmed that the fast uptake of lead occurred on the cell wall, while the absorption of lead and its subsequent precipitation inside the cell occurred very slowly. The pH can directly affect the metal uptake by algae. When the proton increases or a decrease in pH occurs, the metal ions compete with the protons for the binding site. Therefore, due to lower competition with protons, most cation adsorption occurs at a high pH (Schiewer and Volesky 1995). Due to its rapid sorption rate and its high sorption capacity, Spirulina platensis was found to be well suited for the removal of cadmium from waste water. It can also extract cadmium at a wide range of pH and temperature levels.
Fundamentals of Receptor Assessment
Published in Jack Daugherty, Assessment of Chemical Exposures, 2020
Antagonists are chemicals that lessen the predicted effect when combined. Four types of antagonists are functional, chemical, dispositional, and receptors. Functional antagonists produce opposite effects on the same physiological function. Phosphates reduce lead absorption in the GI tract, by forming insoluble lead phosphate, for instance. Chemical antagonism involves the reaction of the antagonist with the toxic compound to form a less toxic product. Toxic heavy metals, such as lead, arsenic, and mercury, can be bound up with chelating agents. Dispositional antagonists alter absorption, metabolism, distribution, or excretion, such as the way some alcohols use enzymes in their metabolism. Methanol breaks down to formaldehyde, which breaks down to formic acid. Ethanol breaks down to acetaldehyde, which breaks down to acetic acid. The aldehydes cause hangover, and even blindness. Since ethanol is more readily metabolized than methanol, methanol is not metabolized and gets excreted before it breaks down to formaldehyde. When Antabuse is administered to alcoholics, the metabolism of acetaldehyde is inhibited, and the patient gets a severe, prolonged hangover if ethanol is consumed. Receptor antagonists either bind to the same tissue receptor as the toxic chemical or blocks the action of the receptor, reducing the toxic effect. The toxic effects of organophosphate pesticides on receptor cells are blocked by atropine.
Nanoscintillators
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Santosh K. Gupta, Yuanbing Mao
The main interest in the development of scintillating glasses was mainly because it can be easily fabricated compared with other available scintillating materials during that time. The advantage was that a good glass-forming composition could be tailor-made into any kind of thickness and shape and can form an integral part of PMT. However, there was a lack of development in glass scintillators because of its relatively low scintillation effciency than that of crystalline scintillators. The main reason for such performance is their lack of long-range ordering, which inhibits the transfer of energy over long distances compared with crystals. However, Ginther and Schulman discovered scintillating glasses in 1950. Afterward a research perspective in this area has changed [110,111]. In the past, most of the scintillation glasses were developed for neutron detection. Recently extensive research on scintillation glasses is conducted in the direction of X-ray and gamma ray detection [112]. For example, two emission peaks can be seen in a typical radioluminescence emission spectrum of a phosphate glass, one due to the emission from the activation ion and one due to a defect within the glass (Figure 6.15a). Figure 6.15b shows the RL spectra of lead phosphate glass.
Investigating triple superphosphate for lead removal from aqueous solutions
Published in Journal of Environmental Science and Health, Part A, 2022
Mahamane Chapiou Souley Garba, Erol Kaya, Mertol Gökelma, Abdullah Seyrankaya
In this study, the solution chemistry of TSP [monocalcium phosphate monohydrate, Ca(H2PO4)2.H2O] was investigated for the removal of lead from the aqueous solutions using stability diagrams [Eh-pH, Pb-H2O and Pb-PO43--H2O] and laboratory precipitation tests. The results of this study indicate that TSP can precipitate lead from an aqueous solution as metal phosphate compounds [(PbHPO4(c), Pb(H2PO4)2(c), Pb3(PO4)2(c), Pb4O(PO4)2(c)] in both acidic and basic conditions as identified through the stability diagrams. Lead phosphate species formed were insoluble (stable) in a wide range of pH and Eh values. It was observed that TSP could remove up to 99.9% of the Pb from the solution depending upon the solution conditions. The removal rate of lead decreases with low TSP and high Pb concentrations. The removal mechanism of lead by TSP includes the dissolution of TSP and the formation of lead phosphate compounds during the precipitation process. The lead phosphate compounds, identified through the stability area diagrams, were obtained with the batch tests and verified with the x-ray diffraction (XRD) analysis.