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Principles of Groundwater Contamination
Published in David H.F. Liu, Béla G. Lipták, Paul A. Bouts, Groundwater and Surface Water Pollution, 2019
David H.F. Liu, Béla G. Lipták, Paul A. Bouts
Halides are the stable anions of the highly reactive halogens: fluoride (F), chloride (C1), bromine (Br), and iodine (I). Halides occur naturally in soils and are also present in many industrial waste streams.
General Princlpes
Published in Martin B., S.Z., of Industrial Hygiene, 2018
Organohalide compounds have halogen-substituted hydrocarbon molecules. This means that each compound has fluorine, chloride, bromine, or iodine atoms in its structure. Alkyl halides in this group include dichlo-romethane (found in paint strippers), carbon tetrachloride (refrigerants), and 1,2-dibromoethane (an insecticide). The alkenyl or olefinic organohalides include: vinyl chloride (used to produce polyvinyl chloride, PVC), a known carcinogen, trichlorethylene (used for degreasing and as a drycleaning solvent), tetrachloroethylene, and hexachlorobutadiene (used as a hydraulic fluid). Aryl halides are used in chemical synthesis and as pesticides and solvents. They are derivatives of benzene and toluene. Polychlorinated bi-phenyls (PCBs), highly toxic materials, are an example of a halogenated biphenyl. Chlorofluorocarbons (CFCs), halons, and hydrogen-containing chlorofluorocarbons are of significant importance to the environment. CFCs, once used primarily as refrigerants and aerosol propellents, are believed to have caused the breakdown of the ozone layer and have been banned from production. Halogens used in fire extinguishers as halon have also been implicated in the depletion of the ozone layer and are being phased out. Hydrogen containing chlorofluorocarbons (HFCs) are being touted as the substitute for CFCs as refrigerants and plastic foam blowing agents. Chlorinated phenyls such as pentachlorophenol, are used to treat wood against fungi and insect infestation. The byproduct of that process causes hazardous waste, which has been known to cause liver damage and dermatitis.
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Published in Luis Liz-Marzán, Colloidal Synthesis of Plasmonic Nanometals, 2020
Samuel E. Lohse, Nathan D. Burrows, Leonardo Scarabelli, Luis M. Liz-Marzán, Catherine J. Murphy
However, despite the huge volume of literature related to synthesis, characterization, and applications of colloidal anisotropic metal nanoparticles,1–4,7–12 the mechanisms behind their formation are still under lively debate.3,8,11–13 Even if the seeded growth method (described in detail below) is accepted as the most efficient one for the synthesis of monodisperse gold nanorods (and other morphologies), it is unclear why growth proceeds along one preferential direction.38 The growth of preformed isotropic nanoparticle seeds into anisotropic nanorods (NRs) requires a symmetry-breaking event, which has not yet been undisputedly disclosed.3 Since the seeded growth process takes place in a rather complex mixture of salts and surfactants, a variety of mechanisms have been proposed to explain symmetry breaking and anisotropic growth.8 From a template effect from micellar arrangements of surfactant molecules8,14 through the selective adsorption of surfactants on certain crystallographic facets,3 even to the effects of exciting LSPR modes during growth,15 chemical researchers have invoked a number of parameters as the main reason behind anisotropic growth. Materials scientists favor crystallographic strain as a mechanism to promote anisotropic growth, although how strain arises in colloidal nanoparticles at the atomic level may involve adsorbates, soft structures, etc. It is possible that all of these parameters are somehow involved in the process. It is also clear that the different shapes are characterized by different crystallographic facets, suggesting that these solvent-exposed faces have the lowest surface energy and thereby provide the energetically most favorable morphology.3,12 However, surface energies are affected not only by the atomic arrangement within the corresponding crystalline lattice (face-centered cubic for these metals) but also by the adsorption of other chemical moieties.12 In most metal nanoparticle (NP) synthesis methods performed in water or polar solvents, other ions (apart from surfactants and/or polymers) are present. Typically, these ions include halides (mainly chloride, bromide, or iodide).q-46-qq Halide ions have a strong tendency to adsorb on metallic surfaces, and thus, they are likely to affect the corresponding surface energies.3,8,12,15 A number of reports have been recently published, regarding the specific use of halides to direct the formation of a certain nanocrystal shape.12,16–20 For example, bromide is often claimed to be indispensable to obtain well-defined gold nanorods (AuNRs), while iodide has been reported to poison NR formation and induce the formation of nanoplates, as well as various platonic shapes.12,16–20
A review of technologies for bromide and iodide removal from water
Published in Environmental Technology Reviews, 2023
So far, a few relative reviews on technologies for bromide and iodide removal from water have been reported. Phanthuwongpakdee et al. [16] reviewed the natural adsorbents for the removal of different iodine species from an aqueous environment. Theiss et al. [17] reviewed the removal of anions and oxyanions of the halogen from aqueous by layered double hydroxides. Watson et al. [18] and Rivera-Utrilla et al. [19] reviewed the strategies for halide removal from water, and they classified them into three types: membrane, electrochemical and adsorptive techniques. However, a comprehensive review of technologies for bromide and iodide removal from water is still lacking. In this work, we reviewed the techniques for bromide and iodide removal from water and unprecedently classified the techniques into four types: membrane techniques, adsorption techniques, electrochemical techniques and chemical oxidation techniques. It is worth mentioning that chemical oxidation is not covered in other reviews before. The unique characteristics and applications of each method were discussed and compared, and the future direction was proposed. It is hoped that this review will provide theoretical support and guidance for the development of new halide removal technologies and decision-making of environmental management.
Polyvinyl alcohol (PVA) as a biodegradable polymeric anticorrosive material: A review on present advancements and future directions
Published in Corrosion Engineering, Science and Technology, 2022
Chandrabhan Verma, M. A. Quraishi
Sabirneeza and Rajalakshmi [79] developed a PVA and leucine, an amino acid, based composites (PVAL) and tested for MS/1M HCl system consuming many methods. Outcomes of weight loss investigation showed that PVAL manifests the best %IE of 87.83% at 0.60% concentration and at the same concentration its %IE was increased to 98.18% in the presence of 10−2 M KI. The mixed nature of PVAL with and without halide ions was determined by the Tafel polarisation study. The effectiveness of halide ions followed the sequence: I > Br > Cl. In the same year, another group of authors demonstrated the %IE of PVA for the MS/1M H2SO4 system and showed the synergistic effect of two surfactants, namely sodium dodecyl sulphate (SDS) and cetylpyridinium chloride (CPC) [80]. It was assessed that PVA showed the best potential of 79.43% (30°C) at 500 ppm concentration and in the presence of 5 ppm of SDS and CPC, its efficiency increased to 84.83% and 87.53%, respectively. The adsorption of PVA follows Langmuir isotherm and with and without SDS and CPC it behaves as a mixed-type inhibitor. Karthikaiselvi and Subhashini developed a poly (vinyl alcohol-o-methoxy aniline) composite (PVAMOA; Figure 6) and tested it as an inhibitor for the MS/1M HCl system [81]. PVAMOA exhibits the %IE of 72.99% at 2000ppm concentration. The mixed-type behaviour was addressed by PDP analysis and its adsorption mode of inhibition efficiency was studied using SEM study. It was observed that the presence of the PVAMOA improves the surface morphology significantly, establishing that its molecules build a protective film through their adsorption. EIS investigation reveals that PVAMOA forms corrosion protective film. This group of authors investigated similar results with Polyvinyl alcohol–sulphanilic acid composite (PVASA) for the same metal and electrolyte [82].
Degradation mechanism of tributyl phosphate by UV/H2O2 treatment and parameters optimization towards the design of a pilot reactor
Published in Environmental Technology, 2021
Thibault D’halluin, Célia Lepeytre, Antoine Leydier, Carine Julcour
Advanced Oxidation Processes (AOPs) are attractive in this context as their efficiency for the removal of refractory organic compounds is proven. The highly reactive and non-selective oxygen species such as hydroxyl radicals (•OH) generated in AOPs decompose the target compounds into non-toxic intermediates, such as short carboxylic acids, yielding CO2, H2O and mineral acids as final compounds. This contrasts with other powerful treatments such as chlorination, which produce toxic halides. Applying AOPs to industrial effluent treatment seems therefore to be a promising solution [6]. For TBP and similar molecules in particular, Cristale et al. [3] have shown for instance that an initial ozone concentration of 25 mg.L−1 can reduce the total OPFR content of industrial effluent treatment plant effluents by 25% to 50%. Similarly, using ultraviolet (UV)-C photocatalyzed β-Ga2O3, Seshadri and Sinha [7] were able to degrade 95% of the TBP in a 400 mg.L−1 solution in 30 min. Effective but slower removal was also achieved with a classical catalyst (TiO2), with an equivalent degradation yield reached in 70 min [7,8], while Drinks et al. [8] degraded 87.5% of the TBP in a 100 mg.L−1 solution in 80 min using 0.5 g.L−1 TiO2 and UV-A irradiation. The combination of UV light and H2O2 is a particularly interesting method of generating radicals because of its low cost and the easy availability of hydrogen peroxide. According to the review of Miklos et al. [9] UV/H2O2 appears among the most energy-efficient AOPs with EEO (electrical energy per order) values in the order of 1 kWh/m3 (compared to 100 kWh/m3 or more for UV-based photocatalysis or ultrasound). Their study also revealed that this figure was influenced to some extent by water quality (median EEO values ranging from 0.63 kWh/m3 for drinking water to 2.2 kWh/m3 for wastewater and 2.7 kWh/m3 for ground water) and was reduced with an increase in scale (from 2.2 kWh/m3 at lab-scale to 0.68 kWh/m3 for pilot-scale and 0.5 kWh/m3 for full-scale applications) [9]. Furthermore, the process is simple to manage, adaptable to changes in the influent [6,9] and industrial scale systems are available (Calgon Carbon’s Peroxpure™ and Rayox® systems for drinking water treatment for instance).