Study of the Adsorption of Methylene Blue and Tartrazine in Aqueous Solution by Local Materials of Cameroonian Origin
Djakba Raphaël,
Harouna Massaï,
Wangmene Bagamla,
Bouba Talami
Issue:
Volume 9, Issue 3, September 2020
Pages:
45-51
Received:
12 July 2020
Accepted:
27 July 2020
Published:
17 August 2020
Abstract: The present work concerns the study of the adsorption of methylene blue (MB) and tartrazine (TAR) in aqueous solution by the raw clay (AB) and bridged clay (AP) of "Boboyo". Studies show that the adsorption of these two dyes on both adsorbents is very fast. The adsorption equilibrium time is 25 minutes for AB for both adsorbates and 15 and 30 minutes for TAR and BM on AP, respectively. The maximum adsorbed amounts of BM are of the order of 4.49mg/g on AB and 4.39mg/g on AP. They are of the order of 2.43mg/g on AB and 2.64mg/g on AP for TAR. The experiments show that the adsorbed quantity of these two dyes decreases with the increase of the mass of the adsorbents, is maximum at pH = 3 and increases with the increase of the initial concentration of the two dyes. The modeling of the adsorption kinetics reveals a conformity to the pseudo-second order model for the two dyes studied on adsorbent disputes. Experimental results are better described with the Freundlich isothermal model. The thermodynamic parameters showed that the adsorption of the two dyes is favorable and endothermic.
Abstract: The present work concerns the study of the adsorption of methylene blue (MB) and tartrazine (TAR) in aqueous solution by the raw clay (AB) and bridged clay (AP) of "Boboyo". Studies show that the adsorption of these two dyes on both adsorbents is very fast. The adsorption equilibrium time is 25 minutes for AB for both adsorbates and 15 and 30 minut...
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Dynamics of Different Sulfur Forms in Natural Waters and Their Influence on the Redox State
Gheorghe Duca,
Vladislav Blonschi,
Viorica Gladchi,
Sergey Travin
Issue:
Volume 9, Issue 3, September 2020
Pages:
52-61
Received:
16 July 2020
Accepted:
31 July 2020
Published:
19 August 2020
Abstract: Sulfur-containing substances with reducing properties in natural water bodies are partners in the reactions with active oxygen forms (ROS) and so are their specific antipodes. The ratio of counterflows of an oxidizer and a reducing agent sets the redox potential of the aquatic environment, is responsible for its self-purification and ultimately forms the quality of water as a habitat. At the same time, data on the formation and destruction channels of substances with the reduced sulfhydryl groups and correlation dependences of their quantity with regard to the other components’ concentrations in natural aquatic environment are fragmentary and insufficient. During the years 2015-2019, four water bodies, two lotic systems and two lentic ones were monitored. Thiols and sulfates were monitored, and it was found that in all the monitored aquatic systems the thiols content is subject to seasonal variation; therefore, its provenance is predominantly natural. To elucidate the seasonal dynamics of different sulfur forms in natural waters, the Pearson linear correlation coefficient was calculated and a positive summer correlation was attested related to the maximal biological activity. This proves that sulfate ions are used by hydrobionts as a source of sulfur for the synthesis of organic compounds, including thiols. In spring and autumn, the calculated coefficients have negative values, which denotes the dominance of chemical oxidation of the organic compounds with sulfur. These are periods with minimal biological activity. It was shown that out of two studied thiols, cysteine and glutathione, only the first one has shown the toxicity with regard to cyanobacteria.
Abstract: Sulfur-containing substances with reducing properties in natural water bodies are partners in the reactions with active oxygen forms (ROS) and so are their specific antipodes. The ratio of counterflows of an oxidizer and a reducing agent sets the redox potential of the aquatic environment, is responsible for its self-purification and ultimately for...
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The Photochemistry of Gas Molecules in Earth’s Atmosphere Determines the Structure of the Atmosphere and the Average Temperature at Earth’s Surface
Issue:
Volume 9, Issue 3, September 2020
Pages:
62-85
Received:
23 July 2020
Accepted:
3 August 2020
Published:
19 August 2020
Abstract: A molecule of oxygen absorbing solar ultraviolet-C radiation is photo-dissociated into two atoms of oxygen that fly apart at high velocity, converting kinetic energy of oscillation of the molecular bond directly and completely into kinetic energy of linear motion of the oxygen atoms. This increases air temperature. Two oxygen atoms can then collide forming a new oxygen molecule that can then be dissociated again as long as sufficient ultraviolet-C radiation exists. This continual dissociation of oxygen molecules is the primary reason for the stratopause being 30-40 degrees warmer than the tropopause and for all ultraviolet-C radiation being absorbed before reaching the lower stratosphere. Furthermore, an oxygen molecule and an oxygen atom can collide to form a molecule of ozone, which is photo-dissociated by solar ultraviolet-B radiation. Normally, 97-99 percent of ultraviolet-B radiation is absorbed in the ozone layer, warming the lower stratosphere. By 1970, however, humans manufacturing chlorofluorocarbon gases caused up to 70% depletion of ozone, cooling the ozone layer and allowing more ultraviolet-B to reach Earth where it photo-dissociates ground-level ozone pollution, raising air temperatures, especially in the most polluted areas. Ultraviolet-B also penetrates oceans tens of meters, efficiently raising ocean heat content. Earth’s surface warmed 0.6°C from 1970 to 1998 with warming twice as great in the northern hemisphere containing 90% of global population. In 2014, Bárðarbunga volcano in central Iceland extruded 85 km2 of basaltic lavas in six months, depleting the ozone layer and warming Earth another 0.3°C by 2016. Throughout Earth history, basaltic lava flows covering areas of up to millions of square kilometers are contemporaneous with sudden global warming—the larger the lava flow, the greater the warming. Large explosive volcanic eruptions, on the other hand, typically form aerosols in the lower stratosphere that spread throughout the world, reflecting and scattering sunlight, cooling Earth approximately 0.5°C for two to four years. Computer modelling shows the effects of this global cooling can still be observed in ocean temperatures a century later. Several large explosive volcanic eruptions per century, continuing for millennia, cool oceans incrementally down into ice-age conditions. Detailed measurements of air temperatures in ice cores at Summit Greenland over the past 122,000 years show that the footprints of climate change are sudden warming within years, followed by slow, incremental cooling over millennia, in highly erratic sequences averaging only a few thousand years in length. Ozone depletion and aerosols are particularly effective because they occur worldwide.
Abstract: A molecule of oxygen absorbing solar ultraviolet-C radiation is photo-dissociated into two atoms of oxygen that fly apart at high velocity, converting kinetic energy of oscillation of the molecular bond directly and completely into kinetic energy of linear motion of the oxygen atoms. This increases air temperature. Two oxygen atoms can then collide...
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