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Contaminant Characteristics
Published in Stephen S. Olin, Exposure to Contaminants in Drinking Water, 2020
David A. Reckhow, Stephen S. Olin
Of the 1-, 2-, and 3-carbon chlorinated compounds, several are solvents (methylene chloride, carbon tetrachloride, trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, 1,2-dichloropropane), some are intermediates (vinyl chloride, 1,1-dichloroethylene, 1,2-dichloroethane, 1,1,2-trichloroethane), and others are mainly byproducts of industrial processes (cis- and trans-1,2-dichloroethylene). The chlorobenzenes (chlorobenzene, o- and p-dichlorobenzene, 1,2,4-trichlorobenzene, hexachlorobenzene) have found use as solvents, intermediates, and pesticides. Hexachlorocyclopentadiene has been used principally as an intermediate in the manufacture of a number of chlorinated pesticides. The aromatic hydrocarbons include four of the most common aromatic solvents (benzene, toluene, ethylbenzene, xylenes) and styrene, an important monomer.
Nanomaterials for sustainable remediation of chemical contaminants in water and soil
Published in Critical Reviews in Environmental Science and Technology, 2022
Raj Mukhopadhyay, Binoy Sarkar, Eakalak Khan, Daniel S. Alessi, Jayanta Kumar Biswas, K. M. Manjaiah, Miharu Eguchi, Kevin C. W. Wu, Yusuke Yamauchi, Yong Sik Ok
The prevalence of surface charges and different functional groups on EGO, GO, and rGO play important roles in the adsorption of polar contaminants such as phenolics and naphthol, charged heavy metals (Ahmad et al., 2020; Ersan et al., 2017), antibiotics such as sulfamethoxazole, sulfapyridine, and sulfathiazole (Çalışkan Salihi et al., 2020), and volatile organic compounds (Kumar et al., 2020b). The adsorption of phenolic compounds generally increases with increasing reduction degree in GO, whereas the adsorption of heavy metal ions shows the reverse trend (Wang & Chen, 2015). Likewise, Cd(II) and organic pollutants were co-adsorbed onto graphene via surface-bridging mechanisms (Wang & Chen, 2015). The adsorption affinity of four aromatics on GO increased in the following order: naphthalene (NAPH) < 1,2,4-trichlorobenzene (TCB) < 2,4,6-trichlorophenol (TCP) < 2-naphthol (Pei et al., 2013). The π–π interaction was the main mechanism involved during TCB, TCP and 2-naphthol adsorption onto graphene (Zhou et al., 2015), whereas H-bonding and O-containing surface functional groups were responsible for the adsorption of TCP and 2-naphthol onto GO (Pei et al., 2013). However, graphene-based NMs often suffer from low densities of reactive sites, including less oxygen-containing functional groups, while graphene-based nanocomposites show variable colloidal stability depending on modification type (Perreault et al., 2015). Future research should focus on the development of functionalized and stable graphene-based NMs for bulk removal of contaminants from aqueous solutions.
The needle trap extraction capability of a zinc-based metal organic framework with a nitrogen rich ligand
Published in Journal of Coordination Chemistry, 2021
Zinc(II) nitrate tetrahydrate (Zn(NO3)2·4H2O), diaminomaleonitrile (DAMN) (98%), hydrochloric acid (37% w/w), sodium nitrite, diethyl ether, zinc chloride, sodium azide (99%), dimethyl formamide (DMF), sodium hydroxide, methanol and sodium chloride were obtained from Merck (Darmstadt, Germany). All chemicals were used without purification. Chlorobenzenes (including monochlorobenzene (MCB), 1,4-dichlorobenzene (14-DCB), 1,2-dichlorobenzene (12-DCB), 1,2,4-trichlorobenzene (124-TCB) and 1,2,3,4-tetrachlorobenzene (1234-TeCB)), polycyclic aromatic hydrocarbons (including naphthalene, anthracene, fluorene, acenaphthylene and acenaphthene) and benzene homologs (including benzene, toluene, ethylbenzene, m-xylene and o-xylene) were purchased from Merck. Stock solutions of CBs (1000 mg L−1), PAHs (2000 mg L−1) and BTEX (1000 mg L−1) were prepared in methanol and stored at 4 °C. The working standard solutions were prepared weekly by diluting the stock solution with methanol, and more diluted working solutions were prepared daily by diluting these solutions with double distilled water (DDW).
Ring inversion in cyclohexane: a textbook example
Published in Liquid Crystals, 2020
E. Elliott Burnell, Cornelis A. de Lange, Ronald Y. Dong
Cyclohexane was studied [20] as a solute in the nematic liquid crystal Merck ZLI-1132 (1132 for short), a nematic phase composed of 24% trans-4--propyl-(4-cyanophenyl)-cyclohexane, 36% trans-4--pentyl-(4-cyanophenyl)-cyclohexane, 25% trans-4--heptyl-(4-cyanophenyl)-cyclohexane, and 15% trans-4--pentyl-(4-cyanobiphenyl-4)-cyclohexane. A sample of approximately 6.8 mol per cent cyclohexane was made up in 1132 and some 1,3,5-trichlorobenzene (tcb, 0.2 mol percent) was added as an orientational reference. The sample tube was placed into the magnet of a Bruker 400 MHz spectrometer with an inverse probe. H spectra were obtained by adding 256 scans for a range of temperatures between 238.5 and 332.4 K (see Figure 2). A spectral width of about 8 kHz was measured and solute line widths varied strongly as a function of temperature, indicating interconversion dynamics. Results of a preliminary investigation of these spectra has been reported elsewhere [20]. Here we extend the temperature range that was amenable to investigation in the earlier study, and report a more complete analysis of the spectra. We now compare our results with those from H NMR as reported by Luz. [21,22]