Oxidation of nitrobenzene by ozone in the presence of faujasite zeolite in a continuous flow gas–liquid–solid reactor

2010 ◽  
Vol 62 (5) ◽  
pp. 1076-1083 ◽  
Author(s):  
J. Reungoat ◽  
J. S. Pic ◽  
M. H. Manéro ◽  
H. Debellefontaine
Keyword(s):  
Liquid Phase ◽  
Chemical Oxygen Demand ◽  
Transfer Coefficient ◽  
Rate Constant ◽  
Decomposition Rate ◽  
Oxidation Rate ◽  
Continuous Flow ◽  
Oxygen Demand ◽  
Decomposition Rate Constant ◽  
Faujasite Zeolite

This work investigates the oxidation of nitrobenzene (NB) by ozone in the presence of faujasite zeolite. Experiments were carried out in a gas–liquid–solid reactor were ozone transfer and NB oxidation took place at the same time. Three configurations of the reactor were compared: empty, filled with inert glass beads and filled with faujasite pellets. First, ozone transfer coefficient (kLa) and decomposition rate constant (kC) were determined for each configuration. In presence of solid, kLa was 2.0 to 2.6 times higher and kC was 5.0 to 6.4 times higher compared to the empty reactor. Then, the various configurations were evaluated in terms of NB removal and chemical oxygen demand (COD) decrease. The faujasite reactor showed higher removal of NB and decrease of COD compared to other configurations under the same conditions suggesting that the faujasite increases the oxidation rate of NB. Oxidation of NB in presence of faujasite also proved to be limited by the transfer of ozone from the gas to the liquid phase.

scholarly journals Wastewater treatment in flow photobioreactors continuous illuminated by artificial and solar light

2020 ◽  
Vol 9 (6) ◽  
pp. e183963748
Author(s):  
Rafael Souza Leopoldino Nascimento ◽  
Ludymyla Marcelle Lima Silva ◽  
Lucas Periard ◽  
Anibal da Fonseca Santiago
Keyword(s):  
Organic Matter ◽  
Wastewater Treatment ◽  
Chemical Oxygen Demand ◽  
Continuous Flow ◽  
Suspended Solids ◽  
Oxygen Demand ◽  
Total Suspended Solids ◽  
Operational Stability ◽  
Artificial Light ◽  
Light Emitting

The technology of microalgae photobioreactors and illuminated by LEDs has been widely studied for the treatment of wastewater. However, sunlight is a free resource and should be taken advantage of. But the question remains whether photobioreactors illuminated by natural (sunlight) light in combination with artificial light can have greater operational stability or greater performance when compared to systems illuminated only by artificial light. In this context, continuous flow photobioreactors illuminated by Light Emitting Diodes (LEDs) combined, or not, with sunlight were operated and had their performance evaluated. The variables analyzed were pH, OD, chemical oxygen demand (COD), chlorophyll - a and total suspended solids. The photobioreactors were effective for removing organic matter, with 75 ± 15% in the photobioreactor illuminated by LED and 65 ± 10% in the photobioreactor illuminated by sunlight and LED. The results showed that the use of combined lighting favors the production of dissolved oxygen and ensures greater operational stability in the removal of carbonaceous organic matter.

scholarly journals Treatment of Bio-Treated Coking Wastewater by Catalytic Ozonation with Semi-Batch and Continuous Flow Reactors

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2532
Author(s):  
Can He ◽  
Jianbing Wang ◽  
Heng Xu ◽  
Xiangyu Ji ◽  
Weiyi Wang ◽  
...  
Keyword(s):  
Chemical Oxygen Demand ◽  
Continuous Flow ◽  
Oxygen Demand ◽  
Catalytic Ozonation ◽  
Cod Removal ◽  
Utilization Efficiency ◽  
Coking Wastewater ◽  
Ozone Absorption ◽  
Flow Reactors ◽  
Continuous Flow Reactors

In this work, the treatment of bio-treated coking wastewater (BCW) by catalytic ozonation was conducted in semi-batch and continuous flow reactors. The kinetics of chemical oxygen demand (COD) removal were analyzed using BCWs from five coking plants. An integral reactor with catalytic ozonation stacked by ozone absorption (IR) was developed, and its efficiency was studied. The catalyst of MnxCe1-xO2/γ-Al2O3 was efficient in the catalytic ozonation process for the treatment of various BCWs. The chemical oxygen demand (COD) removal efficiencies after 120 min reaction were 64–74%. The overall apparent reaction rate constants were 0.0101–0.0117 min−1, which has no obvious relationship with the initial COD of BCW and pre-treatment biological process. The IR demonstrated the highest efficiency due to the enhancement of mass transfer and the utilization efficiency of ozone. Bypass internal circulation can further improve the reactor efficiency. The optimal results were obtained with the ozone absorption section accounting for 19% of the valid water depth in the reactor and 250% of circulation flow ratio. The long-term and full-scale application of the novel reactor in a continuous mode indicated stable removal of COD and polycyclic aromatic hydrocarbons (PAHs). The results showed that the system of IR is a promising reactor type for tertiary treatment of coking wastewater by catalytic ozonation.

Decomposition rate constants of Picea abies logs in southeastern Norway

1999 ◽  
Vol 29 (3) ◽  
pp. 372-381 ◽  
Author(s):  
Erik Næsset
Keyword(s):  
Picea Abies ◽  
Rate Constant ◽  
Cross Sections ◽  
Decomposition Rate ◽  
Rate Constants ◽  
Initial Density ◽  
Decomposition Rate Constant ◽  
Negative Exponential Function ◽  
Standing Trees ◽  
Negative Exponential

Decomposition rate constants were estimated from 384 cross sections of Norway spruce (Picea abies (L.) Karst.) logs with base diameter >7.0 cm collected in open areas at five different study sites in southeastern Norway. Fresh wood core samples were taken from 95 standing trees adjacent to the logs to estimate the initial density of these cross sections. Based on this chronosequence, a simple negative exponential function of time showed an average decomposition rate constant for all cross sections of 0.033 per year. Cross-section diameter, ground contact, soil moisture, and aspect were all found to have significant impacts on the decomposition rate constant. For different combinations of these characteristics the decomposition rate constant ranged from a minimum of 0.0165 per year to a maximum of 0.0488 per year.

Kinetics and mechanism of the oxidation of oxalate ion by tris(acetylacetonato)-manganese(III) and its hydrolytic derivatives in aqueous perchlorate media

1993 ◽  
Vol 71 (12) ◽  
pp. 2155-2159 ◽  
Author(s):  
Subrata Mukhopadhyay ◽  
Swapan Chaudhuri ◽  
Rina Das ◽  
Rupendranath Banerjee
Keyword(s):  
Free Radicals ◽  
Rate Constant ◽  
Decomposition Rate ◽  
Rate Constants ◽  
Kinetics And Mechanism ◽  
Unimolecular Decomposition ◽  
Decomposition Rate Constant ◽  
Mixed Complexes ◽  
Ph Range ◽  
Oxalate Ion

In the pH range 6.6–8.6, [MnL2(H2O)2]+ and [MnL2(H2O)(OH)] (HL = acetylacetone) oxidize oxalate ion (ox2−) to CO2 through the inner-sphere intermediates [MnL2(ox)]− and [MnL2(OH)(ox′)]2−, where ox′ is a half-bonded (unidentate) oxalate ion. Their rate constants of decomposition are 1.0 × 10−4 s−1 and 11.2 × 10−2 M−1 s−1 at 30 °C and at I = 1.0 M (NaClO4). Decomposition of these mixed complexes produces free radicals, presumably CO2−, which is further oxidized to CO2 by another Mn(III) in a fast step. At pH 4.2, [Mn(ox)3]3− is produced quantitatively when [ox]0 ≥ 0.12 M, which has been characterized spectrally, and its unimolecular decomposition rate constant k (= 2.7 × 10−4s−1 at 30 °C and I = 1.0 M) compares well with that reported earlier (2.44 × 10−4 s−1 at 25 °C and I = 1.0 M).

scholarly journals Leaf-litter decomposition and nutrient dynamics of five selected tropical tree species

2020 ◽  
Vol 30 (1) ◽  
pp. 32-38
Author(s):  
S. Bhattarai ◽  
B. Bhatta
Keyword(s):  
Weight Loss ◽  
Leaf Litter ◽  
Litter Decomposition ◽  
Rate Constant ◽  
Decomposition Rate ◽  
Tree Species ◽  
Nutrient Dynamics ◽  
Decomposition Rate Constant ◽  
Tropical Tree Species ◽  
One Year

Leaf-litter decomposition in terrestrial ecosystems has a major role in recycling the nutrients to the soil. Nutrient dynamics is the way nutrients cycle in an ecosystem. The present study was conducted for five selected tropical tree species viz. Shorea robusta, Ficus hookeri, Mallotus philippensis, Artocarpus lakoocha and Dillenia pentagyna at Hetauda, Makawanpur. This paper aims to determine the litter decomposition rate-constant and nutrient mineralization pattern of the selected species. The litter-bag method was used to assess the decomposition and nutrient dynamics for one year. Both decomposition rate-constant and weight loss were highest for M. philippensis (% weight loss = 73.49; k = 0.33) and lowest for S. robusta (% weight loss = 54.01; k = 0.18). In general, weight remaining showed a strong negative correlation with N and P concentration but a slightly negative with K. However, the remaining weight of litter showed a strong positive correlation with C : N ratio, thus indicating a good predictor of mass loss and mineralization. The study showed that there was no net release of nitrogen during the one-year study period; however, the net P release was found to be highest for S. robusta followed by D. pentagyna and the net K release was highest in F. hookeri followed by A. lakoocha.

scholarly journals Modelling the temperature of a compost microreactor in isolation

2020 ◽  
Author(s):  
◽  
Mitchell Hawse
Keyword(s):  
Rate Constant ◽  
Decomposition Rate ◽  
Dry Mass ◽  
Small Scale ◽  
Conductive Heat ◽  
Wood Biomass ◽  
Decomposition Rate Constant ◽  
Plastic Container ◽  
Waste Wood ◽  
Municipal Biosolids

A mixture of waste-wood biomass and municipal biosolids waste was composted in a plastic container inside of an insulated chamber. The mixture of biomass and biosolids was approximately 50:50 and weighed 82.6 kg. The peak temperature of the compost was 32.4◦C. The small scale of the compost system allowed the lower limit of the compost decomposition rate to be studied. A model was successfully developed to predict the core temperature of the compost using the ambient temperature in the insulated chamber. A literature review was conducted to determine literature values for the overall convective and conductive heat transfer coefficient, the dry mass fraction, and heat of combustion for both biomass and biosolids. The model used an optimization algorithm to calculate the rate constant for the experimental setup. The calculated decomposition rate constant was 0.0525 Day−1.

scholarly journals Patterns of Leaf Litter Decomposition as Related to Litter Traits in the Sudano-Guinea Savannahs of Ngaoundere, Cameroon

2019 ◽  
pp. 1-19
Author(s):  
A. Ibrahima ◽  
P. Souhore ◽  
A. A Mang A Menick
Keyword(s):  
Phenolic Compounds ◽  
Leaf Litter ◽  
Litter Decomposition ◽  
Plant Species ◽  
Rate Constant ◽  
Decomposition Rate ◽  
Dry Mass ◽  
Specific Mass ◽  
Decomposition Rate Constant ◽  
Litter Mass

Litter decomposition processes are poorly studied in the savannahs. Leaf litter decomposition of the twenty-four contrasting plant species including trees, shrubs and grass species, was studied in the sudano-guinea savannahs of Ngaoundere, Cameroon. The litterbag technique was used to assess litter mass loss and single exponential model was adopted to estimate decay rate constants. Initial litter thickness varied from 0.02 to 1.11 mm, area from 4.27 to 245.89 mm2, sclerophyllous index from 0.01 to 1.75 mg.mm-2, density from 0.21 to 87.50 mg.mm-3, and specific mass area from 0.57 to 185.46 mm2.mg-1. Litter cellulose content varied from 3.79 to 11.84%; lignin from 2.84 to 8.12%, NDF from 21.35 to 80.41%, and total phenolic compounds from 0.47 to 17.76%. During the 52 weeks of the field experiment, mean dry mass remaining of litter samples was significantly between 8.05 and 75.22% of initial litter dry mass for C. papaya and C. regidus respectively. Litter decomposition rate constant (k) significantly ranged from 0.003 (C. regidus) to 0.121 %.week-1 (C. papaya). Litter mass remaining (LMR) was positively related to thickness (R2 = 0.605, P<0.01), Sclerophyllous index (R2 = 0.446, P<0.05), Specific mass area (R2 = 0.569, P<0.001), lignin (R2 = 0.631, P<0.01) and phenolic compounds (R2 = 0.618, P<0.001). The litter decomposition rate constant (k) was negatively related to thickness (R2 = 0.602, P<0.01, n=12), Sclerophyllous index (0.542; P<0.05), Specific mass area (0.419; P<0.05) and phenolic compounds (0.530; P<0.01). It can be concluded that litter decomposition is affected by plant species diversity, plant groups and physico-chemical traits of litters in the sudano-guinea savannahs of Ngaoundere, Cameroun. These preliminary results would contribute to understanding the mechanism of litter decomposition in general and in these savannahs in particular.

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