Chemicals used for treatment of water intended for human consumption. Chlorine dioxide generated in situ

2016 ◽  
Keyword(s):  
Chlorine Dioxide ◽  
Human Consumption

Reduction of adsorbable organically bound halogens (AOX) formation at near-neutral pH chlorine dioxide bleaching of softwood kraft pulp

Holzforschung ◽  
2020 ◽  
Vol 74 (6) ◽  
pp. 597-604
Author(s):  
Sara Starrsjö ◽  
Olena Sevastyanova ◽  
Peter Sandström ◽  
Juha Fiskari ◽  
Maria Boman ◽  
...  
Keyword(s):  
Chlorine Dioxide ◽  
High Selectivity ◽  
Bicarbonate Buffer ◽  
Neutral Ph ◽  
Elemental Chlorine ◽  
Pulp Viscosity ◽  
Softwood Kraft Pulp ◽  
New Type ◽  
Adsorbable Organically Bound Halogens

AbstractRecently, a new type of bleaching sequence, Elemental Chlorine Free (ECF) light with one D stage, has been developed. It combines the efficiency and high selectivity of chlorine dioxide (ClO2) bleaching with more environmental friendly oxygen based bleaching chemicals. This work examines the effect of pH on the formation of adsorbable organically bound halogens (AOX) in an intermediate D stage – a single ClO2 stage at the middle of an ECF light bleaching sequence. Carbon dioxide (CO2) is used to generate a bicarbonate buffer in situ, stabilizing the pH during the bleaching. Near-neutral pH is hypothesized to decrease the formation of strongly chlorinating species, so that the AOX formation is reduced. The results indicate that a near-neutral pH D stage can reduce the AOX content in the effluents with up to 30%. The ISO brightness was unchanged to a lower ClO2 consumption. The pulp viscosity was slightly higher after near-neutral pH D stage, but to its disadvantage a lesser delignification and removal of HexA was obtained. The degradation of HexA correlated well with the AOX, affirming earlier theories that HexA has a major impact on the AOX formation. The higher amounts of residual HexA and lignin resulted in more thermal yellowing of the pulps bleached with a near-neutral pH D stage.

scholarly journals Tertiary amine-catalyzed generation of chlorine dioxide from hypochlorous acid and chlorite ions

2020 ◽  
Author(s):  
Estefania Isaza Ferro ◽  
Jordan Perrin ◽  
Owain George John Dawson ◽  
Tapani Vuorinen
Keyword(s):  
Chlorine Dioxide ◽  
Tertiary Amine ◽  
Hypochlorous Acid ◽  
Suitable Candidate ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Chlorite Ions ◽  
The Stability ◽  
Rate Limiting

AbstractThe reaction between hypochlorous acid and chlorite ions is the rate limiting step for in situ chlorine dioxide regeneration. The possibility of increasing the speed of this reaction was analyzed by the addition of tertiary amine catalysts in the system at pH 5. Two amines were tested, DABCO (1,4-diazabicyclo[2.2.2]octane) and its derivative CEM-DABCO (1-carboethoxymethyl-1-azonia-4-aza-bicyclo[2.2.2]octane chloride). The stability of the catalysts in the presence of both reagents and chlorine dioxide was measured, with CEM-DABCO showing to be highly stable with the mentioned chlorine species, whereas DABCO was rapidly degraded by chlorine dioxide. Hence, CEM-DABCO was chosen as a suitable candidate to catalyze the reaction of hypochlorous acid with chlorite ions and it significantly increased the speed of this reaction even at low catalyst dosages. This research opens the door to a faster regeneration of chlorine dioxide and an improved efficiency in chlorine dioxide treatments.

scholarly journals British Museum Natural Radiocarbon Measurements XXII

Radiocarbon ◽  
1991 ◽  
Vol 33 (1) ◽  
pp. 51-68 ◽  
Author(s):  
Janet Ambers ◽  
Keith Matthews ◽  
Sheridan Bowman
Keyword(s):  
Humic Acid ◽  
Humic Acids ◽  
Chlorine Dioxide ◽  
Liquid Scintillation Counting ◽  
Liquid Scintillation ◽  
British Museum ◽  
Scintillation Counting ◽  
Dilute Acid ◽  
Organic Fraction

The following list consists of dates, obtained by liquid scintillation counting of benzene, for archaeologic samples mostly measured between June 1987 and October 1989.Charcoal and grain samples were pretreated with 1M HCl followed by washing in water and, where considered necessary, with dilute alkali for the removal of humic acids. Wood samples were treated either in the same way, or, where large enough, were reduced to cellulose by the action of chlorine dioxide produced in situ. All antler and bone samples were treated with cold dilute acid. The term ‘collagen’ is used throughout to mean the acid insoluble organic fraction produced by this treatment. Peat samples were treated with dilute acid and alkali to separate the humin and humic acid fractions, which were dated individually.

scholarly journals British Museum Natural Radiocarbon Measurements XXIII

Radiocarbon ◽  
1994 ◽  
Vol 36 (1) ◽  
pp. 95-111 ◽  
Author(s):  
Janet Ambers ◽  
Sheridan Bowman
Keyword(s):  
Humic Acids ◽  
Chlorine Dioxide ◽  
British Museum ◽  
Dilute Acid ◽  
Organic Fraction

The following list consists of dates for archaeological samples measured mostly between October 1989 and November 1990. Charcoal and grain samples were pretreated with 1M HC1 followed by washing in water and, in the majority of cases, with dilute alkali for the removal of humic acids. Wood samples were treated in the same way, or, if large enough, reduced to cellulose with chlorine dioxide produced in situ. Antler and bone samples were treated with cold dilute acid. We use the term “collagen” to mean the acid-insoluble organic fraction produced by this treatment rather than the true biochemical definition.

In Situ Generation of Chlorine Dioxide for Surface Decontamination of Produce

2017 ◽  
Vol 80 (4) ◽  
pp. 567-572 ◽  
Author(s):  
Cheng-An Hwang ◽  
Lihan Huang ◽  
Vivian Chi-Hua Wu
Keyword(s):  
Chlorine Dioxide ◽  
Foodborne Pathogens ◽  
Fruits And Vegetables ◽  
Sequential Treatment ◽  
Sodium Chlorite ◽  
Plant Tissues ◽  
Foodborne Illnesses ◽  
Surface Decontamination ◽  
Unique Surface

ABSTRACT Fresh fruits and vegetables are frequently contaminated with bacterial pathogens and implicated in foodborne illnesses. The objective of this study was to develop a unique surface decontamination method for produce using sodium chlorite and an acid in a sequential treatment. The surfaces of cantaloupe rinds, peels of cucumbers, stem scars of grape tomatoes, and leaves of baby spinach were inoculated with Salmonella or Listeria monocytogenes at 5 to 6 log CFU/g, submerged in 1.6 to 4% sodium chlorite solutions for 10 or 30 min, dried for 20 min, and then soaked in 6 mM hydrogen chloride (HCl) for 10 or 30 min and dried for 20 min. Control samples were treated with deionized water, sodium chlorite, HCl, or a premixed solution of sodium chlorite and HCl for comparison. The control treatments reduced the levels of both pathogens on the samples by only 0.3 to 2.9 log CFU/g, whereas the sequential treatment caused significantly higher reductions (P < 0.05) of 5.1 to 5.6 log CFU/g, effectively eliminating the inoculated pathogens. The more effective decontamination resulting from the sequential treatment was attributed to the in situ formation of chlorine dioxide within the plant tissues under the surface by the reaction between sodium chlorite absorbed by the produce and HCl. These results suggest that the sequential use of sodium chlorite and acid is a potentially effective treatment for elimination of foodborne pathogens on produce.

scholarly journals Archaeobiogeography of extinct rice rats (Oryzomyini) in the Lesser Antilles during the Ceramic Age (500 BCE–1500 CE)

The Holocene ◽  
2020 ◽  
pp. 095968362097278
Author(s):  
Marine Durocher ◽  
Violaine Nicolas ◽  
Sophia Perdikaris ◽  
Dominique Bonnissent ◽  
Gwenola Robert ◽  
...  
Keyword(s):  
Lesser Antilles ◽  
Archaeological Sites ◽  
Human Consumption ◽  
Human Populations ◽  
Long Distance ◽  
Geometric Morphometric ◽  
The North ◽  
Ceramic Age ◽  
Ecological Importance

During the Ceramic Age (500 BCE–1500 CE), Lesser Antilles rice rats (Tribe Oryzomyini) made up a significant portion of the diet of Caribbean islanders. Archaeological excavations across the archipelago resulted to the discovery of large quantities of remains from to these now extinct taxa. It offers a unique opportunity to investigate the past biogeography of this taxon of high cultural and ecological importance. We have studied 1140 first lower molars originating from 40 archaeological sites across eleven islands of the Lesser Antilles archipelago using two-dimensional geometric morphometric approaches to establish spatiotemporal patterns relying on phenotypic variations. This study identified three morphological groups, present in all chrono-cultural periods, that were geographically restricted and consistent with published ancient mitochondrial DNA clusters. These three geographically-separate groups likely represent three distinct genera of rice rats. The first group includes specimens from the North of the archipelago (Saint-Martin, Saba, Saint-Eustatius, Saint-Kitts, and Nevis) and likely referable to as Pennatomys sp.; the second, occurring in the South (Martinique), is assigned to Megalomys desmarestii; and the third corresponds to specimens from the center of the Lesser Antilles (Antigua, Barbuda, Marie-Galante, and Guadeloupe) and likely corresponds to Antillomys sp. These oryzomyine morphotypes are present during all studied periods and support an older presence of these rodents in the region. Our results are congruent with ancient DNA studies that favor the hypothesis of a natural introduction of the group in the archipelago before settlement of human populations. Moreover, the observed phenotypic homogeneity and stability over the 2000 years of Pre-Columbian occupation suggests that rice rats were not part of long-distance inter-island exchanges by humans. Instead, rice rat human consumption was likely based on in-situ hunting of local populations.

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