Seasonal variations of adsorption/desorption equilibrium concentrations of P at water-sediment interface in different trophic states of Taihu Lake, China

2006 ◽  
Vol 25 (S1) ◽  
pp. 164-164
Author(s):  
Xiangcan Jin ◽  
Xia Jiang ◽  
Dongmei Liu
Keyword(s):  
Seasonal Variations ◽  
Taihu Lake ◽  
Equilibrium Concentrations ◽  
Desorption Equilibrium ◽  
Adsorption Desorption ◽  
Sediment Interface

scholarly journals Mechanism and Influencing Factors of REY Enrichment in Deep-Sea Sediments

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 196
Author(s):  
Jiangbo Ren ◽  
Yan Liu ◽  
Fenlian Wang ◽  
Gaowen He ◽  
Xiguang Deng ◽  
...  
Keyword(s):  
Deep Sea ◽  
Research Progress ◽  
Bottom Current ◽  
Knowledge Map ◽  
P2o5 Content ◽  
Deep Sea Sediments ◽  
Potential Resource ◽  
And Migration ◽  
Adsorption Desorption ◽  
Sediment Interface

Deep-sea sediments with high contents of rare-earth elements and yttrium (REY) are expected to serve as a potential resource for REY, which have recently been proved to be mainly contributed by phosphate component. Studies have shown that the carriers of REY in deep-sea sediments include aluminosilicate, Fe-Mn oxyhydroxides, and phosphate components. The ∑REY of the phosphate component is 1–2 orders of magnitude higher than those of the other two carriers, expressed as ∑REY = 0.001 × [Al2O3] − 0.002 × [MnO] + 0.056 × [P2O5] − 32. The sediment P2O5 content of 1.5% explains 89.1% of the total variance of the sediment ∑REY content. According to global data, P has a stronger positive correlation with ∑REY compared with Mn, Fe, Al, etc.; 45.5% of samples have a P2O5 content of less than 0.25%, and ∑REY of not higher than 400 ppm. The ∑REY of the phosphate component reaches n × 104 ppm, much higher than that of marine phosphorites and lower than that of REY-phosphate minerals, which are called REY-rich phosphates in this study. The results of microscopic observation and separation by grain size indicate that the REY-rich phosphate component is mainly composed of bioapatite. When ∑REY > 2000 ppm, the average CaO/P2O5 ratio of the samples is 1.55, indicating that the phosphate composition is between carbonate fluoroapatite and hydroxyfluorapatite. According to a knowledge map of sediment elements, the phosphate component is mainly composed of P, Ca, Sr, REY, Sc, U, and Th, and its chemical composition is relatively stable. The phosphate component has a negative Ce anomaly and positive Y anomaly, and a REY pattern similar to that of marine phosphorites and seawater. After the early diagenesis process (biogeochemistry, adsorption, desorption, transformation, and migration), the REY enrichment in the phosphate component is completed near the seawater/sediment interface. In the process of REY enrichment, the precipitation and enrichment of P is critical. According to current research progress, the REY enrichment is the result of comprehensive factors, including low sedimentation rate, high ∑REY of the bottom seawater, a non-carbonate depositional environment, oxidation conditions, and certain bottom current conditions.

Heterojunctions of silver–iron oxide on graphene for laser-coupled oxygen reduction reactions

2018 ◽  
Vol 54 (57) ◽  
pp. 7900-7903 ◽  
Author(s):  
Wei-Quan Chen ◽  
Min-Chuan Chung ◽  
Joey Andrew A. Valinton ◽  
David P. Penaloza ◽  
Shiow-Huey Chuang ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Oxygen Reduction ◽  
Oxygen Adsorption ◽  
Reduction Reactions ◽  
Oxygen Reduction Reactions ◽  
Doped Graphene ◽  
Desorption Equilibrium ◽  
Adsorption Desorption

We report a two-step hybridization of N-doped graphene and Ag-decorated Fe2O3 hematite to realize a balanced oxygen adsorption/desorption equilibrium and a laser-coupled ORR (LORR).

scholarly journals Modification to L-H Kinetics Model and Its Application in the Investigation on Photodegradation of Gaseous Benzene by Nitrogen-Doped TiO2

Catalysts ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 326 ◽  
Author(s):  
Peng Sun ◽  
Jun Zhang ◽  
Wenxiu Liu ◽  
Qi Wang ◽  
Wenbin Cao
Keyword(s):  
Adsorption Equilibrium ◽  
Illumination Intensity ◽  
Desorption Process ◽  
Doped Tio2 ◽  
Coverage Ratio ◽  
Nitrogen Doped ◽  
Desorption Equilibrium ◽  
Adsorption Desorption ◽  
Kinetics Of ◽  
Gaseous Benzene

In this paper, the Langmuir-Hinshelwood (L-H) model has been used to investigate the kinetics of photodegradation of gaseous benzene by nitrogen-doped TiO2 (N-TiO2) at 25 °C under visible light irradiation. Experimental results show that the photoreaction coefficient kpm increased from 3.992 × 10−6 mol·kg−1·s−1 to 11.55 × 10−6 mol·kg−1·s−1 along with increasing illumination intensity. However, the adsorption equilibrium constant KL decreased from 1139 to 597 m3·mol−1 when the illumination intensity increased from 36.7 × 104 lx to 75.1 × 104 lx, whereas it was 2761 m3·mol−1 in the absence of light. This is contrary to the fact that KL should be a constant if the temperature was fixed. This phenomenon can be attributed to the breaking of the adsorption-desorption equilibrium by photocatalytically decomposition. To compensate for the disequilibrium of the adsorption-desorption process, photoreaction coefficient kpm was introduced to the expression of KL and the compensation form was denoted as Km. KL is an indicator of the adsorption capacity of TiO2 while Km is only an indicator of the coverage ratio of TiO2 surface. The modified L-H model has been experimentally verified so it is expected to be used to predict the kinetics of the photocatalytic degradation of gaseous benzene.

Modelling stream water chemistry with snowmelt

1984 ◽  
Vol 305 (1124) ◽  
pp. 427-439 ◽  
Keyword(s):  
Ion Exchange ◽  
Water Chemistry ◽  
Seasonal Variations ◽  
Stream Water ◽  
Acid Precipitation ◽  
Exchange Reactions ◽  
Stream Water Chemistry ◽  
Reservoir Models ◽  
Southern Norway ◽  
Adsorption Desorption

Simple hydrochemical reservoir models based on the mobile anion concept are described for the Birkenes and Storgam a catchments in southern Norway with acidified stream water. Key processes modelled include water routing, sulphate adsorption-desorption, ion-exchange reactions, weathering and a gibbsite equilibrium condition. The models reproduce much of the daily and seasonal variations in stream water chemistry which have been observed over several years. Model considerations have been used in an attempt to explain the acidification of stream water in these two areas. It is hypothesized that soil acidification has occurred and that acid precipitation is at least partly responsible. The results are tentative largely because the models are derived from present-day stream water chemistry.

scholarly journals Adsorption and Decomposition of Peroxides on the Surfaces of Dispersed Oxides Fe2O3, Cr2O3 and V2O5

2019 ◽  
Vol 3 (1) ◽  
pp. 13
Author(s):  
Volodymyr Dutka ◽  
Olena Aksimentyeva ◽  
Nataliya Oschapovska ◽  
Yaroslav Kovalskyi ◽  
Halyna Halechko
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Effective Activation Energy ◽  
Equilibrium Constants ◽  
Langmuir Equation ◽  
Effective Activation ◽  
Activation Energy Of Degradation ◽  
Degradation Reaction ◽  
Desorption Equilibrium ◽  
Adsorption Desorption

The adsorption of peroxides on dispersed oxides Fe2O3, Cr2O3 and V2O5 was studied. It is shown that the adsorption of peroxides is described by the Langmuir equation. The adsorption of benzoyl peroxide grows within Fe2O3<Cr2O3<V2O5. Adsorption-desorption equilibrium constants (K) for Cr2O3 and V2O5 are the same, but for Fe2O3 this value is 6 times higher. The decomposition of peroxides is observed in the solution and on the surface of adsorbents. The effective activation energy (E) of the thermal decomposition of peroxides in the studied systems is in the range of 80–140 kJ/mol. The activation energy of degradation of peroxides on the surface (Es) of the dispersed oxides studied is lower. The degradation reaction of peroxides on the surface of Fe2O3 and V2O5 has an oxidation-reducing nature, during which free radicals are produced. On the surface of Cr2O3, there is a heterolytic decay of peroxides. The parameters of the reaction of peroxides decomposition are found. The decomposition of peroxides in the presence of Fe2O3, Cr2O3 and V2O5 in styrene is accompanied by the formation of polystyrene both in the solution and on the surface of the adsorbent.

scholarly journals The effect of different nanocatalysts for photocatalytic degradation of methylene blue

2019 ◽  
Vol 6 (2) ◽  
pp. 79-83
Author(s):  
Ayşegül Pala ◽  
Güneş Kurşun
Keyword(s):  
Methylene Blue ◽  
Photocatalytic Oxidation ◽  
Uv Light ◽  
Performance Tests ◽  
Methylene Blue Solution ◽  
Blue Solution ◽  
Desorption Equilibrium ◽  
Adsorption Desorption ◽  
Zno And Tio2 Nanoparticles ◽  
Commercial Tio2

The aim of this study was to investigate photodegradation of Methylene Blue (MB) in water by using ZnO and TiO2 nanoparticles. Adsorption and photocatalytic oxidation studies were carried out by using produced TiO2, commercial TiO2 and commercial ZnO nanoparticles. In order to evaluate performance tests, 5 mg/l of MB solution was used. The samples were mixed in the dark for 2 hours for establishing adsorption-desorption equilibrium. The photocatalytic tests of the samples were performed by assessing the decomposition rate of MB solutions under UV light. The results of the photocatalytic showed that the highest color removal efficiencies was obtained by TiO2 catalyst where Methylene blue solution was completely degraded.

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