Development of Nickel- and Magnetite-Promoted Carbonized Cellulose Bead-Supported Bimetallic Pd-Pt Catalysts for Hydrogenation of Chlorate Ions in Aqueous Solution.

Cellulose grains were carbonized and applied as catalyst supports for nickel- and magnetite-promoted bimetallic palladium- and platinum-containing catalysts. The bimetallic spherical aggregates of Pd and Pt particles were created to enhance the synergistic effect among the precious metals during catalytic processes. As a first step, the cellulose bead-based supports were impregnated by nitrate salts of nickel and iron and carbonized at 973 K. After this step, the nickel was in an elemental state, while the iron was in a magnetite form in the corresponding supports. Then, Pd and Pt particles were deposited onto the supports and the catalyst surface; precious metal nanoparticles (10-20 nm) were clustered inside spherical aggregated particles 500-600 nm in size. The final bimetallic catalysts (i.e., Pd-Pt/CCB, Pd-Pt/Ni-CCB, and Pd-Pt/Fe3O4-CCB) were tested in hydrogenation of chlorate ions in the aqueous phase. For the nickel-promoted Pd-Pt catalyst, a >99% chlorate conversion was reached after 45 min at 80 °C. In contrast, the magnetite-promoted sample reached an 84.6% chlorate conversion after 3 h. Reuse tests were also carried out with the catalysts, and in the case of Pd-Pt/Ni-CCB after five cycles, the catalytic activity only decreased by ~7% which proves the stability of the system.

Preparation of 6-carboxyl chitin and its effects on cell proliferation in vitro.

This study concerns the performance evaluation of 6-carboxyl chitin for its wound healing application. 6-Carboxyl chitins were prepared by the oxidation of chitin at C-6 with NaClO/TEMPO/NaBr after α-chitin was pretreated in NaOH/urea solution. The products with different molecular weights were obtained by changing reaction conditions. They all were completely oxidized at C-6 and N-acetylated at C-2 according to FT-IR and NMR results. 6-Carboxyl chitins could stimulate significantly the proliferation of human skin fibroblasts (HSF) and human keratinocytes (HaCaT), and the bioactivities were concentration and Mws dependent. Within the scope of the study, 10-40 kDa of Mws and 10-100 µg/mL of concentrations were most suitable for the HSF proliferation, but the proliferation of HaCaT increased with decreasing the concentration and Mw. In addition, 6-carboxyl chitins could also induce macrophages and fibroblasts to secrete growth factors. Therefore, 6-carboxyl chitins could be expected to be an active ingredient for wound healing.

Growth and survival characteristics of Paucilactobacillus wasatchensis WDCO4.

Understanding characteristics that permit survival and growth of Paucilactobacillus wasatchensis as part of the nonstarter microbiota of cheese is important for minimizing unwanted gas formation in cheese that can cause downgrading because of slits and cracks. The ability of Plb. wasatchensis WDC04 to survive pasteurization was studied by inoculating raw milk with 108 cfu/mL and measuring survival after processing through a high-temperature, short-time pasteurizer. Extent and rate of growth of Plb. wasatchensis WDC04 as a function of pH, salt concentration, and presence of various organic acids were studied using 48-well microplates in an automated spectrophotometer measuring optical density at 600 nm. Better growth in the 1-mL wells was obtained when a micro-anaerobic environment (similar to that which occurs in cheese) was created by enzymically removing the oxygen. Faster growth occurred around neutral pH (pH 6 to 8) than at pH 5 (cheese pH), whereas only marginal growth occurred at pH 4. Adding sodium chloride retarded growth of Plb. wasatchensis WDC04, but slow growth occurred even at salt concentrations up to 6%. At salt-in-moisture (S/M) concentrations found in cheese, the rate of growth at 3.5% S/M >4.5% S/M >5.5% S/M. Thus, low salt level in cheese is a risk factor for Plb. wasatchensis growth during cheese storage and unwanted slits and cracks. Some of the organic acids tested (propionic, formic, and citric) tended to suppress growth of Plb. wasatchensis WDC04 more than would be expected from their effect on pH. No survival of Plb. wasatchensis WDC04 after pasteurization was observed with the reduction in numbers being 8 logs or more. Even subpasteurization heating at 69°C for 15 s was sufficient to inactivate Plb. wasatchensis WDC04, so its presence as part of the nonstarter microbiota of cheese should be considered as a postpasteurization environmental contamination.

Occurrence of perchlorate, chlorate and polar herbicides in different baby food commodities.

The incidence of endocrine disruptors, both possible (glyphosate and glufosinate), and demonstrated (perchlorate and chlorate), was estimated in baby food commodities (meat, fish, cheese, vegetable and fruit). Ion-chromatography coupled to high resolution mass spectrometry analysis of the 105 samples did not show traces of glyphosate, glufosinate or their metabolites, while in 10.5% of the samples a quantifiable amount of perchlorate was found. Some samples based on fruit and vegetables revealed a substantial amount of chlorate, especially the preparations that contained carrots and potatoes: five samples were in a concentration range of 40-120 µg kg-1, while one homogenized pear sample reached 372.2 µg kg-1. The pure meat samples revealed occasional chlorate appearance, with less than 10 µg kg-1. This is the first report of chlorate evaluated in various types of baby food and may serve as symptomatic data regarding its occurrence in infant/toddler diets. Therefore, effective monitoring programs and subsequent strict regulations are strongly required.

Reduction of bromate and chlorate contaminants in water using aqueous phase corona discharge.

This work demonstrates the ability of aqueous phase corona discharge to chemically reduce bromate and chlorate ions, common disinfection byproducts, to bromide and chloride ions, respectively. A high voltage pulse was applied to a needle electrode, submerged in the target solution, to generate highly reactive oxidative and reductive species in a temperature-controlled reactor. Optimal water matrix conditions were sought through changing the solution pH, temperature, and dissolved oxygen concentration. Additionally, several oxidative species scavengers were investigated, including methanol, ethanol, sucrose, and D-sorbitol. Chemical reduction rates were improved at low pH (3.5). The presence of dissolved oxygen significantly reduced the chemical reduction rate, and thus high solution temperature (50 °C) also achieved better chemical reduction. All oxidative species scavengers improved the chemical reduction rate; however, methanol and ethanol were superior as these compounds generate hydrogen bubbles in the presence of plasma, which deoxygenates the solution further improving the chemical reduction rate. The application of this technology to 30 µM bromate and chlorate solutions, under optimal water matrix conditions and with the addition of 72 g/L-COD methanol, achieved greater than 95% removal of the target compounds within 60 min. Increasing the initial concentration of the target compounds to 300 µM required 90 and 150 min to achieve similar chemical reductions for bromate and chlorate, respectively.

Ultra-sonication for controlling the formation of disinfection by-products in the ClO2 pre-oxidation of water containing high concentrations of algae.

Eutrophication has become great concern in recent years due to the fact that rivers, lakes, and reservoirs are the main drinking water source. Studies have been performed to enhance the removal of algae with ClO2 pre-oxidation, but there was high potential in the formation of chlorite and chlorate. In this study, ultra-sonication was employed to assist algae removal and control disinfection by-products formation in ClO2 pre-oxidation processes. It was found that solo ultra-sonication for 10 min (algae removal 86.11 ± 2.16%) could achieve similar algae removal efficiency as that with solo ClO2 (0.5 mg/L) pre-oxidation for 10 min (algae removal 87.10 ± 3.50%). In addition, no formations of chlorite and chlorate were detected in solo ultra-sonication process. Five-minutes ultra-sonication followed by 5-min 0.5 mg/L ClO2 treatment (total treatment time 10 min; algae removal 93.55 ± 3.22%) provided a better performance on algae removal compared to the solo ClO2 (0.5 mg/L) pre-oxidation for 10 min. Moreover, chlorite was undetectable. It suggests that the utilization of ultra-sonication in ClO2 pretreatment for algae removal has highly prevented the formations of chlorite and chlorate.

Kinetics of chlorate formation during ozonation of aqueous chloride solutions.

Chlorate ion ClO3- is formed as a result of the complex chemical interaction of ozone with chloride ion in aqueous solution. In neutral and basic solutions, chlorate is the main product. In acid solutions, the main product is molecular chlorine Cl2, and the yield of chlorate is 50-100 times lower. Dependencies have been studied of chlorate formation rate on significant experimental factors: concentrations of initial substances, ozone and chloride ion, acidity (pH), ionic strength and temperature of the reaction solution. The kinetic laws of chlorate generation have been established, and the expressions are given for rate constants of chlorate formation as functions of temperature and ionic strength. When tert-butanol is added to the reaction system, the formation of chlorate ceases, which is an evidence of the crucial role of free radical reactions in this process.

Formation, distribution, and speciation of DBPs (THMs, HAAs, ClO2-,andClO3-) during treatment of different source water with chlorine and chlorine dioxide.

Formation potential and speciation characteristics of two important groups of disinfection byproducts (DBPs), namely, trihalomethanes (THMs) and haloacetic acids (HAAS), during Cl2 and ClO2 treatment of water samples collected from three different sources, namely, sea, river, and reservoir, were investigated with reference to key controlling parameters. Formation of inorganic DBPs such as chlorate and chlorite was evaluated. Dissolved organic carbon (DOC) and UV absorbance (UV254) of the sea, river, and reservoir samples were 3.35 ±â€¯0.05, 3.12 ±â€¯0.05, and 3.23 ±â€¯0.05 mg/L and 0.062 ±â€¯0.01, 0.074 ±â€¯0.01, and 0.055 ±â€¯0.01 cm-1, respectively. For Cl2 and ClO2 treatments, the respective formation potential of THMs and HAAs from the three water sources studied exhibited unidentical trend suggesting that higher THM formation was not necessarily associated with higher HAA formation. On chlorination, the concentrations of total HAAs formed were 9.8 µg/L (sea), 12.8 µg/L (river), and 20.6 µg/L (reservoir) and total THM yields were 38.3 µg/L (sea), 18.8 µg/L (river), and 21.5 µg/L (reservoir) for a Cl2 dose of 1 mg/L and 30 min reaction time. The trend of formation of THMs and HAAs for Cl2 treatment was similar to that for ClO2 treatment. However, the amount of HAAs (3.5 µg/L (sea), 1.8 µg/L (river), and 1.9 µg/L (reservoir)) and THMs (not detected) formed was much lower than that formed during chlorination. Regardless of source water type, di-HAAs were the most favored HAAs, followed by tri-HAAs with a small amount of mono-HAAs formed for both Cl2 and ClO2 treatment. Chlorination yielded more THMs than HAAs, whereas it was reverse for chlorine dioxide treatment. Irrespective of treatment with ClO2 or Cl2, seawater samples showed the highest bromine incorporation percentage (BIP) in both THMs and HAAs followed by that for river and reservoir water samples. HAAs were found to be always associated with lower amount of BIP than THMs.

Effect of Potassium Chlorate on the Treatment of Domestic Sewage by Achieving Shortcut Nitrification in a Constructed Rapid Infiltration System.

A constructed rapid infiltration (CRI) system is a new type of sewage biofilm treatment technology, but due to its anaerobic zone it lacks the carbon sources and the conditions for nitrate retention, and its nitrogen removal performance is very poor. However, a shortcut nitrification–denitrification process presents distinctive advantages, as it saves oxygen, requires less organic matter, and requires less time for denitrification compared to conventional nitrogen removal methods. Thus, if the shortcut nitrification–denitrification process could be applied to the CRI system properly, a simpler, more economic, and efficient nitrogen removal method will be obtained. However, as its reaction process shows that the first and the most important step of achieving shortcut nitrification–denitrification is to achieve shortcut nitrification, in this study we explored the feasibility to achieve shortcut nitrification, which produces nitrite as the dominant nitrogen species in effluent, by the addition of potassium chlorate (KClO3) to the influent. In an experimental CRI test system, the effects on nitrogen removal, nitrate inhibition, and nitrite accumulation were studied, and the advantages of achieving a shortcut nitrification–denitrification process were also analysed. The results showed that shortcut nitrification was successfully achieved and maintained in a CRI system by adding 5 mM KClO3 to the influent at a constant pH of 8.4. Under these conditions, the nitrite accumulation percentage was increased, while a lower concentration of 3 mM KClO3 had no obvious effect. The addition of 5mM KClO3 in influent presumably inhibited the activity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), but inhibition of nitrite-oxidizing bacteria (NOB) was so strong that it resulted in a maximum nitrite accumulation percentage of up to over 80%. As a result, nitrite became the dominant nitrogen product in the effluent. Moreover, if the shortcut denitrification process will be achieved in the subsequent research, it could save 60.27 mg CH3OH per litre of sewage in the CRI system compared with the full denitrification process.

Genome-resolved metagenomics identifies genetic mobility, metabolic interactions, and unexpected diversity in perchlorate-reducing communities.

Dissimilatory perchlorate reduction is an anaerobic respiratory pathway that in communities might be influenced by metabolic interactions. Because the genes for perchlorate reduction are horizontally transferred, previous studies have been unable to identify uncultivated perchlorate-reducing populations. Here we recovered metagenome-assembled genomes from perchlorate-reducing sediment enrichments and employed a manual scaffolding approach to reconstruct gene clusters for perchlorate reduction found within mobile genetic elements. De novo assembly and binning of four enriched communities yielded 48 total draft genomes. In addition to canonical perchlorate reduction gene clusters and taxa, a new type of gene cluster with an alternative perchlorate reductase was identified. Phylogenetic analysis indicated past exchange between these gene clusters, and the presence of plasmids with either gene cluster shows that the potential for gene transfer via plasmid persisted throughout enrichment. However, a majority of genomes in each community lacked perchlorate reduction genes. Putative chlorate-reducing or sulfur-reducing populations were dominant in most communities, supporting the hypothesis that metabolic interactions might result from perchlorate reduction intermediates and byproducts. Other populations included a novel phylum-level lineage (Ca. Muirbacteria) and epibiotic prokaryotes with no known role in perchlorate reduction. These results reveal unexpected genetic diversity, suggest that perchlorate-reducing communities involve substantial metabolic interactions, and encourage expanded strategies to further understand the evolution and ecology of this metabolism.

Ion aggregation in high salt solutions. VII. The effect of cations on the structures of ion aggregates and water hydrogen-bonding network.

Ions in high salt solutions have a strong propensity to form polydisperse ion aggregates with broad size and shape distributions. In a series of previous comparative investigations using femtosecond IR pump-probe spectroscopy, molecular dynamics simulation, and graph theoretical analysis, we have shown that there exists a morphological difference in the structures of ion aggregates formed in various salt solutions. As salt concentration increases, the ions in high salt solutions form either cluster-like structures excluding water molecules or network-like structures entwined with water hydrogen-bonding networks. Interestingly, such morphological characteristics of the ion aggregates have been found to be in correlation with the solubility limits of salts. An important question that still remains unexplored is why certain salts with different cations have notably different solubility limits in water. Here, carrying out a series of molecular dynamics simulations of aqueous salt solutions and analyzing the distributions and connectivity patterns of ion aggregates with a spectral graph analysis method, we establish the relationship between the salt solubility and the ion aggregate morphology with a special emphasis on the cationic effects on water structures and ion aggregation. We anticipate that the understanding of large scale ion aggregate structures revealed in this study will be critical for elucidating the specific ion effects on the solubility and conformational stability of co-solute molecules such as proteins in water.

Stability of Sodium Chlorate Residues in Frozen Tomato and Cantaloupe Homogenates.

The objective of this study was to determine the stability of sodium chlorate in frozen (-24 °C) tomato or cantaloupe homogenates for up to 17 weeks (119 days). Chlorate stability was assessed by ultraperformance liquid chromatography-mass spectrometry (UPLC-MS/MS) at two fortification levels (80 or 600 ng/g for tomato and 200 or 3000 ng/g for cantaloupe, n = 3 each) for each fruit after storage for 0, 1, 7, 14, 28, 56, or 119 d. Within matrix type, chlorate recovery was determined by fortifying duplicate blank homogenate samples on the day of analysis with the same concentrations used for the stability samples. Chlorate limits of quantitation for cantaloupe and tomato matrices were 30 and 60 ng/g, respectively. Sodium chlorate residues were stable (P > 0.05) in frozen tomato and cantaloupe homogenates during storage for 119 days at -24 °C.

Chlorate adsorption from chlor-alkali plant brine stream.

Chlorates are present in the brine stream purged from chlor-alkali plants. Tests were conducted using activated carbon from coconut shell, coal or palm kernel shell to adsorb chlorate. The results show varying levels of adsorption with reduction ranging between 1.3 g/L and 1.8 g/L. This was higher than the chlorate generation rate of that plant, recorded at 1.22 g/L, indicating that chlorate can be adequately removed by adsorption using activated carbon. Coconut based activated carbon exhibited the best adsorption of chlorate of the three types of activated carbon tested. Introducing an adsorption step prior to purging of the brine will be able to reduce chlorate content in the brine stream. The best location for introducing the adsorption step was identified to be after dechlorination of the brine and before resaturation. Introduction of such an adsorption step will enable complete recovery of the brine and prevent brine purging, which in turn will result in less release of chlorides and chlorates to the environment.

Challenges in using allylthiourea and chlorate as specific nitrification inhibitors.

Allylthiourea (ATU) and chlorate (ClO3-) are often used to selectively inhibit nitritation and nitratation. In this work we identified challenges with use of these compounds in inhibitory assays with filter material from a biological rapid sand filter for groundwater treatment. Inhibition was investigated in continuous-flow lab-scale columns, packed with filter material from a full-scale filter and supplied with NH4+ or NO2-. ATU concentrations of 0.1-0.5 mM interfered with the indophenol blue method for NH4+ quantification leading to underestimation of the measured NH4+ concentration. Interference was stronger at higher ATU levels and resulted in no NH4+ detection at 0.5 mM ATU. ClO3- at typical concentrations for inhibition assays (1-10 mM) inhibited nitratation by less than 6%, while nitritation was instead inhibited by 91% when NH4+ was supplied. On the other hand, nitratation was inhibited by 67-71% at 10-20 mM ClO3- when NO2- was supplied, suggesting significant nitratation inhibition at higher NO2- concentrations. No chlorite (ClO2-) was detected in the effluent, and thus we could not confirm that nitritation inhibition was caused by ClO3- reduction to ClO2-. In conclusion, ATU and ClO3- should be used with caution in inhibition assays, because analytical interference and poor selectivity for the targeted process may affect the experimental outcome and compromise result interpretation.

Radiation-Driven Formation of Reactive Oxygen Species in Oxychlorine-Containing Mars Surface Analogues.

The present study demonstrates that γ-radiolyzed perchlorate-containing Mars soil salt analogues (in a CO2 atmosphere) generate upon H2O wetting the reactive oxygen species (ROS) superoxide radical (O2•-), hydrogen peroxide (H2O2), and hydroxyl radicals (•OH). This study also validates that analogue radiolysis forms oxychlorine species that, in turn, can UV-photolyze to •OH upon UV photolysis. This investigation was made possible by the development of a new assay for inorganic-origin O2•- and H2O2 determination and by the modification of a previous assay for soil •OH. Results show that radiolyzed Mg(ClO4)2 generates H2O2 and •OH; and when included as part of a mixture analogous to the salt composition of samples analyzed at the Mars Phoenix site, the analogue generated O2•-, H2O2, and •OH, with •OH levels 150-fold higher than in the radiolyzed Mg(ClO4)2 samples. Radiolyzed Mars Phoenix site salt analogue that did not contain Mg(ClO4)2 generated only •OH also at 150-fold higher concentration than Mg(ClO4)2 alone. Additionally, UV photolysis of the perchlorate γ radiolysis product chlorite (ClO2-) generated the oxychlorine products trihalide (Cl3-), chlorine dioxide (ClO2•), and hypochlorite (ClO-), with the formation of •OH by UV photolysis of ClO-. While the generation of ROS may have contributed in part to 14CO2 production in the Viking Labeled Release (LR) experiment and O2 (g) release in the Viking Gas Exchange (GEx) experiment, our results indicate that they are not likely to be the major contributor to the LR and GEx results. However, due to their highly reactive nature, they are expected to play a significant role in the alteration of organics on Mars. Additionally, experiments with hypochlorite show that the thermal stability of NaClO is in the range of the thermal stability observed for thermally liable oxidant responsible for the Viking LR results. Key Words: Mars-Oxygen-Salts-Radiation-Habitability. Astrobiology 17, 319-336.

Assessing the Impact of Lithium Chloride on the Expression of P-Glycoprotein at the Blood-Brain Barrier.

In addition to extruding drugs from the brain, P-glycoprotein (P-gp) at the blood-brain barrier (BBB) facilitates the brain-to-blood clearance of beta-amyloid (Aß) and is down-regulated in Alzheimer's disease. Studies suggest that the mood-stabilizing drug lithium exerts a protective effect against Alzheimer's disease. Although the mechanisms underlying this effect are not fully understood, evidence suggests that lithium chloride (LiCl) increases P-gp expression in vitro, albeit at concentrations substantially outside the therapeutic window. Therefore, we investigated the effects of pharmacologically-relevant concentrations of LiCl on P-gp expression using in vitro and in vivo approaches. Swiss outbred mice administered LiCl (300 mg/kg/day, 21 days) showed no change in brain microvascular P-gp protein expression. Furthermore, P-gp transcript and protein levels were unaltered by LiCl (1.25-5 mM, 24 h) in human immortalized brain endothelial cells, while both gene and protein expression were significantly enhanced by the P-gp up-regulator, SR12813 by 1.5-fold and 2.0-fold, respectively. P-gp efflux function was also unaffected by LiCl in vitro, by measuring accumulation of the fluorescent P-gp substrate rhodamine-123. This suggests therefore that LiCl is unlikely to affect the BBB efflux of Aß or other P-gp substrates at pharmacologically-relevant concentrations, suggesting that the Aß-lowering effects of LiCl are unrelated to elevated BBB P-gp expression.

Contact Electrification of Regolith Particles and Chloride Electrolysis: Synthesis of Perchlorates on Mars.

Contact electrification of chloride-impregnated martian regolith particles due to eolian agitation and moisture condensation on coalesced oppositely charged grains may lead to spontaneous electrolysis that generates hypochlorite, chlorite, chlorate, and perchlorate with a concomitant reduction of water to hydrogen. This process is not curtailed even if moisture condenses as ice because chloride ionizes on the surface of ice. Limitations dictated by potentials needed for electrolysis and breakdown electric fields enable estimation of the required regolith grain size. The estimated dimension turns out to be of the same order of magnitude as the expected median size of martian regolith, and a simple calculation yields the optimum rate of perchlorate production. Key Words: Mars oxidants-Perchlorate-Dust electrification-Electrolysis. Astrobiology 16, 811-816.

(Per)chlorate in Biology on Earth and Beyond.

Respiration of perchlorate and chlorate [collectively, (per)chlorate] was only recognized in the last 20 years, yet substantial advances have been made in our understanding of the underlying metabolisms. Although it was once considered solely anthropogenic, pervasive natural sources, both terrestrial and extraterrestrial, indicate an ancient (per)chlorate presence across our solar system. These discoveries stimulated interest in (per)chlorate microbiology, and the application of advanced approaches highlights exciting new facets. Forward and reverse genetics revealed new information regarding underlying molecular biology and associated regulatory mechanisms. Structural and functional analysis characterized core enzymes and identified novel reaction sequences. Comparative genomics elucidated evolutionary aspects, and stress analysis identified novel response mechanisms to reactive chlorine species. Finally, systems biology identified unique metabolic versatility and novel mechanisms of (per)chlorate respiration, including symbiosis and a hybrid enzymatic-abiotic metabolism. While many published studies focus on (per)chlorate and their basic metabolism, this review highlights seminal advances made over the last decade and identifies new directions and potential novel applications.

Secretory locations of SIPC in Amphibalanus amphitrite cyprids and a novel function of SIPC in biomineralization.

Settlement-inducing protein complex (SIPC) is a pheromone that triggers conspecific larval settlement in the barnacle Amphibalanus amphitrite. In the present study, immunostaining and scanning electron microscopy of SIPC revealed signals in the frontal horn pores and the secretions from carapace pores, suggesting that SIPC might be directly secreted from these organs in A. amphitrite cyprids. Further observations showed that the frontal horn pores could contact surfaces while cyprids were "walking". Immunostaining for SIPC on the contacted surfaces displayed SIPC signals. These signals were similar to the frontal horn pores in size and morphology, suggesting that frontal horn pores might deposit SIPC. Besides, full-length SIPC was expressed and subsequent assays indicated that recombinant SIPC was able to bind to chitins and induce the precipitation of CaCO3. Furthermore, recombinant SIPC inhibited the formation of vaterites and regulated the morphology of calcite crystals. The crystals that formed with recombinant SIPC were more stable against water erosion. Overall, these results reported a novel function of recombinant SIPC that regulates crystal formation in barnacle shells.

Formation of Chlorination Byproducts and Their Emission Pathways in Chlorine Mediated Electro-Oxidation of Urine on Active and Nonactive Type Anodes.

Chlorination byproducts (CBPs) are harmful to human health and the environment. Their formation in chlorine mediated electro-oxidation is a concern for electrochemical urine treatment. We investigated the formation of chlorate, perchlorate, and organic chlorination byproducts (OCBPs) during galvanostatic (10, 15, 20 mA · cm(-2)) electro-oxidation of urine on boron-doped diamond (BDD) and thermally decomposed iridium oxide film (TDIROF) anodes. In the beginning of the batch experiments, the production of perchlorate was prevented by competing active chlorine and chlorate formation as well as by direct oxidation of organic substances. Perchlorate was only formed at higher specific charges (>17 Ah · L(-1) on BDD and >29 Ah · L(-1) on TDIROF) resulting in chlorate and perchlorate being the dominant CBPs (>90% of initial chloride). BDD produced mainly short chained OCBPs (dichloromethane, trichloromethane, and tetrachloromethane), whereas longer chained OCBPs (1,2-dichloropropane and 1,2-dichloroethane) were more frequently found on TDIROF. The OCBPs were primarily eliminated by electrochemical stripping: On BDD, this pathway accounted for 40% (dichloromethane) to 100% (tetrachloromethane) and on TDIROF for 90% (1,2-dichloroethane) to 100% (trichloromethane) of what was produced. A post-treatment of the liquid as well as the gas phase should be foreseen if CBP formation cannot be prevented by eliminating chloride or organic substances in a pretreatment.