Kinetic study of time-dependent fixation of UVI on biochar

Biochar, a by-product from the production of biofuel and syngas by gasification, was tested as a material for adsorption and fixation of UVI from aqueous solutions. A batch experiment was conducted to study the factors that influence the adsorption and time-dependent fixation on biochar at 20oC, including pH, initial concentration of UVI and contact time. Uranium (UVI) adsorption was highly dependent on pH but adsorption on biochar was high over a wide range of pH values, from 4.5 to 9.0, and adsorption strength was time-dependent over several days. The experimental data for pH > 7 were most effectively modelled using a Freundlich adsorption isotherm coupled to a reversible first order kinetic equation to describe the time-dependent fixation of UVI within the biochar structure. Desorption experiments showed that UVI was only sparingly desorbable from the biochar with time and isotopic dilution with 233UVI confirmed the low, or time-dependent, lability of adsorbed 238UVI. Below pH 7 the adsorption isotherm trend suggested precipitation, rather than true adsorption, may occur. However, across all pH values (4.5–9) measured saturation indices suggested precipitation was possible: autunite below pH 6.5 and either swartzite, liebigite or bayleyite above pH 6.5

Soluble polyacetylenes derived from the ring-opening metathesis polymerization of substituted cyclooctatetraenes: electrochemical characterization and Schottky barrier devices

Recent developments in ring-opening metathesis polymerization (ROMP) have enabled the synthesis of poly-cyclooctatetraene (poly-COT), a material which is isostructural to polyacetylene. This liquid-phase polymerization method allows facile construction of interfaces, films, and devices with polyacetylene-like materials. The ROMP method also allows the preparation of soluble, yet highly conjugated polyacetylene analogs from substituted cyclooctatetraenes (R-COT). The redox characteristics of R-COT polymers were investigated at electrodes modified with thin polymer films. Voltammetric methods were used to characterize the redox response, band gap, electrochemical doping, and cis-trans isomerization properties of these polyenes. We have applied poly-COT technology to the fabrication of Schottky diodes and photoelectrochemical cells, by forming poly-COT films on semiconductor surfaces. The resultant semiconductor/organic-metal interfaces behave more ideally than semiconductor contacts with conventional metals, in that changes in the work function of the conducting polymer exert a large and predictable effect on the electrical properties of the resulting Schottky diodes. Transparent films of the solution-processible polymer poly- trimethylsilyl-cyclooctatetraene (poly-TMS-COT) have been cast onto n-silicon substrates and doped with iodine to form surface barrier solar cells. These devices produce photovoltages that are much larger than can be obtained from n-silicon contacts with conventional metals

The Otterbein Miscellany - December 1980

https://digitalcommons.otterbein.edu/miscellany/1014/thumbnail.jp

Living together in student accommodation: Performances, boundaries and homemaking

Recent discussions of the geographies of students have drawn attention to the trajectories of UK students electing to leave home for university. While such debates recognise these important mobilities, little has been discussed as to how students interact within their term-time accommodation. Through a qualitative study of the living arrangements of UK students, this paper will demonstrate that much can be drawn from focusing on the micro-geographies of non-local students within their term-time homes. Student accommodation is more than simply somewhere to live. Student homes are intensely dynamic places, perhaps more so than family homes as they contain multiple, disconnected identities. This research contributes to research on the geographies of the home by unpacking how house-sharers in transition interact with each other, how they transfer their identities from one home to another, how they delineate their territory and whether they integrate or withdraw within their term-time accommodation. This paper addresses this by exploring (1) how students negotiate their habitualised behaviours in shared spaces and (2) how these behaviours become spatialised through the configuration and maintenance of boundaries

Sediment tracing from the catchment to reef 2016 to 2018: Flood plume, marine sediment trap and logger data time series

The sediment dynamics at marine sites in the inshore GBRL region likely fall into three separate categories including sites where: 1. input of new terrigenous sediments have by far the greatest influence on sediment exposure and subsequent resuspension (e.g. Dunk Island, Orpheus Island, Havannah Island, Cleveland Bay?); 2. input of new terrigenous sediments are at least equivalent to resuspension events which likely increases upon larger river discharge events (e.g. Cleveland Bay?, Orchard Rocks). 3. input of new terrigenous sediments are less than or equal to common resuspension events (e.g. Middle Reef, Geoffrey Bay). This provides some of the first empirical data to support the findings of the satellite photic depth modelling of Fabricius et al. (2014, 2016) where the delivery of new terrigenous sediment considerably influences water clarity on the inshore Great Barrier Reef

Bacterial dissolution of fluorapatite as a possible source of elevated dissolved phosphate in the environment

In order to understand the contribution of geogenic phosphorus to lake eutrophication, we have investigated the rate and extent of fluorapatite dissolution in the presence of two common soil bacteria (Pantoea agglomerans and Bacillus megaterium) at T = 25 °C for 26 days. The release of calcium (Ca), phosphorus (P), and rare earth elements (REE) under biotic and abiotic conditions was compared to investigate the effect of microorganism on apatite dissolution. The release of Ca and P was enhanced under the influence of bacteria. Apatite dissolution rates obtained from solution Ca concentration in the biotic reactors increased above error compared with abiotic controls. Chemical analysis of biomass showed that bacteria scavenged Ca, P, and REE during their growth, which lowered their fluid concentrations, leading to apparent lower release rates. The temporal evolution of pH in the reactors reflected the balance of apatite weathering, solution reactions, bacterial metabolism, and potentially secondary precipitation, which was implied in the variety of REE patterns in the biotic and abiotic reactors. Light rare earth elements (LREE) were preferentially adsorbed to cell surfaces, whereas heavy rare earth elements (HREE) were retained in the fluid phase. Decoupling of LREE and HREE could possibly be due to preferential release of HREE from apatite or selective secondary precipitation of LREE enriched phosphates, especially in the presence of bacteria. When corrected for intracellular concentrations, both biotic reactors showed high P and REE release compared with the abiotic control. We speculate that lack of this correction explains the conflicting findings about the role of bacteria in mineral weathering rates. The observation that bacteria enhance the release rate of P and REE from apatite could account for some of the phosphorus burden and metal pollution in aquatic environments

Ectopic expression of chloramphenicol acetyltransferase (CAT) in the cerebellum in mice transgenic for a carbonic anhydrase II promoter-CAT construct that is without apparent phenotypic effect

We have developed six transgenic lines of mice with constructs containing presumptive 5′ regulatory regions of carbonic anhydrase II (CA II). Four of the lines contained 1,100 bases of the 5′ flanking region of the human CA II gene, and two transgenic lines resulted from a construct containing 500 bases of the 5′ flanking region of the mouse CA II gene. Tissue-specific expression of the chloramphenicol acetyltransferase (CAT) gene was not obtained in any of the transgenic lines. One of the transgenic lines was found to have high levels of expression of CAT in cerebellum. This expression persisted through multiple generations and was independent of the parental origin of the transgene. On the assumption that the expression was due to the insertion of the transgene in or near a gene expressed normally in cerebellum, homozygous mice were bred for the transgenic insert to see if a mutation might have been induced. Homozygous mice were found and seemed to be normal in all aspects of their phenotype studied. Thus, in this case, neither the insertion of the gene nor the ectopic expression of CAT seemed to be harmful to the animals.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50416/1/1080270204_ftp.pd