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Multiwalled carbon nanotubes (MWCNTs) were used as the active elements for the first time for affinity-based elimination of ionic dyes. MWCNTs were encapsulated it cross-linked alginate (ALG) microvesicles using Ba2+ as the bridging ion. The Ba2+-alginate matrix constitutes a cage which holds the physically trapped MWCNTs. The cage carries negative charges on its surface. The cage restricts the access of anions of large molecular weight. such as humic acids, because of electrostatic repulsion. U cage also restricts the access of colloids of large size, because of size exclusion. Ionic dyes partition into the cage and then are captured by MWCNTs probably on the basis of van der Waals interactions occurring between the hexagonally arrayed carbon atoms in the graphite sheet of MWCNTs and the aromatic backbones of the dyes. As a result of these interactions the target species, namely, the ionic dyes, are eliminated efficiently by the MWCNTs of Ba2+ -ALG/MWCNT composite adsorbents. The adsorptive capacities for elimination of acridine orange, ethidium bromide, eosin bluish, and orange B (the model species used for this study) were found as high as 0.44, 0.43, 0.33, and 0.31 μmol, respectively, for 1.0 mg of the caged MWCNTs. Adsorptive experiments with carbon nanofibers and activated carbons as the adsorbents were also performed. The MWCNT-based adsorbents provided the best capability for the affinity-based elimination of these targeted species. Biocompatibility experiments performed in vitro and in vivo provided promising results, suggesting potential applications of the caged MWCNTs in in situ environmental remediation. [ABSTRACT FROM AUTHOR]

The mechanism of the spontaneous decomposition of 3-bromo-2,2-bis(bromomethyl)propanol (TBNPA) and the kinetics of the reaction of the parent compound and two subsequent products were determined in aqueous solution at temperatures from 30 to 70 °C and pH from 7.0 to 9.5. TBNPA is decomposed by a sequence of reactions that form 33-bis(bromomethyl)oxetane (B B MO), 3-bromomethyl-3- hydroxymethyloxetane (B MHMO), and 2,6-dioxaspiro[3.3]- heptane (DOH), releasing one bromide ion at each stage. The pseudo-first-order rate constant of the decomposition of TBNPA increases linearly with the pH. The apparent activation energy of this transformation (98 ± 2 KJ/mol) was calculated from the change of the effective second-order rate constant with temperature. The pseudoactivation energies of BBMO and BMHMO were estimated to be 109 and 151 KJ/mol, respectively. Good agreement was found between the rate coefficients derived from changes in the organic molecules concentrations and those determined from the changes in the Br- concentrations. TBNPA is the most abundant semivolatile organic pollutant in the aquitard studied, and together with its byproducts they posess an environmental hazard. TBNPA half-life is estimated to be about 100 years. This implies that high concentrations of TBNPA will persist in the aquifer long after the elimination of all its sources. [ABSTRACT FROM AUTHOR]

The application of photoactivated periodate (UV/I04-) to the degradation of 4-chlorophenol (4-CP) was explored in this study. Under low irradiation intensities (23 μW/ cm2), wavelength of 266 nm, and pH 3, 4-CR was observed to degrade by pseudo-first-order reaction kinetics. The small reduction in 4-CP degradation in the presence of tert-butyl alcohol (t-BuOH) suggests that degradation of 4-CP by UV/lO4- was not dominated by an OH pathway. 03 production was suppressed in the presence of t-BuOH under O2-limited environments and in the presence of 4-CP. Faster degradation of 4-CP in the presence of an OW scavenger under nitrogen purging as compared to air- saturated conditions indicates that O(3P) is an important reactive species with 4-CR in this system. When 4-CP is added to the system, 103 production is enhanced. On the basis of the elimination of potential reaction pathways, O(3P) and lO3- are suspected reactive species with 4-CP in this system. [ABSTRACT FROM AUTHOR]