scholarly journals Evaluation of Cr(VI) Reduction Using Indigenous Bacterial Consortium Isolated from a Municipal Wastewater Sludge: Batch and Kinetic Studies

Catalysts ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1100
Author(s):  
Buyisile Kholisa ◽  
Mpumelelo Matsena ◽  
Evans M. N. Chirwa
Keyword(s):  
Hexavalent Chromium ◽  
Rate Constants ◽  
Municipal Wastewater ◽  
Agricultural Waste ◽  
Treatment Plant ◽  
Bacterial Consortium ◽  
Second Order ◽  
Wastewater Sludge ◽  
Order Rate ◽  
Wide Range

Hexavalent Chromium (Cr(VI)) has long been known to be highly mobile and toxic when compared with the other stable oxidation state, Cr(III). Cr(VI)-soluble environmental pollutants have been detected in soils and water bodies receiving industrial and agricultural waste. The reduction of Cr(VI) by microbial organisms is considered to be an environmentally compatible, less expensive and sustainable remediation alternative when compared to conventional treatment methods, such as chemical neutralization and chemical precipitation of Cr. This study aims to isolate and identify the composition of the microbial consortium culture isolated from waste activated sludge and digested sludge from a local wastewater treatment plant receiving high loads of Cr(VI) from an abandoned chrome foundry in Brits (North Waste Province, South Africa). Furthermore, the Cr(VI) reduction capability and efficiency by the isolated bacteria were investigated under a range of operational conditions, i.e., pH, temperature and Cr(VI) loading. The culture showed great efficiency in reduction capability, with 100% removal in less than 4 h at a nominal loading concentration of 50 mg Cr(VI)/L. The culture showed resilience by achieving total removal at concentrations as high as 400 mg Cr(VI)/L. The consortia exhibited considerable Cr(VI) removal efficiency in the pH range from 2 to 11, with 100% removal being achieved at a pH value of 7 at a 37 ± 1 °C incubation temperature. The time course reduction data fitted well on both first and second-order exponential rate equation yielding first-order rate constants in the range 0.615 to 0.011 h−1 and second order rate constants 0.0532 to 5 × 10−5 L·mg−1·h−1 for Cr(VI) concentration of 50–400 mg/L. This study demonstrated the bacterial consortium from municipal wastewater sludge has a high tolerance and reduction ability over a wide range of experimental conditions. Thus, show promise that bacteria could be used for hexavalent chromium remediate in contaminated sites.

scholarly journals Reactivities of neutral and cationic forms of 2,2′-dipyridyl disulphide towards thiolate anions. Detection of differences between the active centres of actinidin, papain and ficin by a three-protonic-state reactivity probe

1979 ◽  
Vol 183 (2) ◽  
pp. 233-238 ◽  
Author(s):  
K Brocklehurst ◽  
T Stuchbury ◽  
J P G Malthouse
Keyword(s):  
Rate Constants ◽  
Positive Charge ◽  
Ph Dependence ◽  
Second Order ◽  
Order Rate ◽  
Wide Range ◽  
Thiolate Anion ◽  
Thiolate Anions ◽  
Thiol Proteinase ◽  
Active Centres

The second-order rate constants (k) for the reactions of 2,2′-dipyridyl disulphide (pKa2,45) with 2-mercaptoethanol (pKa9.6) and with benzimidazol-2-ylmethanethiol (pKa values 5.6 and 8.3) were determined at 25 degrees C at I 0.1 by stopped-flow spectral analysis over a wide range of pH. These were used to calculate the pH-independent second-order rate constants (k) for the reactions of neutral 2,2′-dipyridyl disulphide and of its monocation with the 2-mercaptoethanol thiolate anion (associated pKa9.6) and with the benzimidazol-2-ylmethanethiol zwitterion (associated pKa5.6). For both thiolate ions, the rate-enhancement factor (kmonocation/kneutral disulphide) is about 1.5×10(3). The dependence on pH in acidic media of k for the reaction of 2,2′-dipyridyl disulphide with actinidin, the thiol proteinase from Actinidia chinensis, was shown to differ from the forms of pH-dependence observed for the analogous reactions with papain (EC 3.4.22.2) and ficin (3.4.22.3). The reactivity of the 2,2′-dipyridyl disulphide dication and its apparent sensitivity to the presence and location of a positive charge in the attacking thiol are discussed.

Inhibition in Purified Systems and in Human Plasma of Chimaeric Plasminogen Activators Consisting of the NH2-Terminal Region of Tissue-Type Plasminogen Activator and the COOH-Terminal Region of UrokinaseType Plasminogen Activator

1988 ◽  
Vol 60 (02) ◽  
pp. 247-250 ◽  
Author(s):  
H R Lijnen ◽  
L Nelles ◽  
B Van Hoef ◽  
F De Cock ◽  
D Collen
Keyword(s):  
Plasminogen Activator ◽  
Rate Constants ◽  
Plasminogen Activators ◽  
Second Order ◽  
Tissue Type ◽  
Single Chain ◽  
Chain Molecules ◽  
Order Rate ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator

SummaryRecombinant chimaeric molecules between tissue-type plasminogen activator (t-PA) and single chain urokinase-type plasminogen activator (scu-PA) or two chain urokinase-type plasminogen activator (tcu-PA) have intact enzymatic properties of scu-PA or tcu-PA towards natural and synthetic substrates (Nelles et al., J Biol Chem 1987; 262: 10855-10862). In the present study, we have compared the reactivity with inhibitors of both the single chain and two chain variants of recombinant u-PA and two recombinant chimaeric molecules between t-PA and scu-PA (t-PA/u-PA-s: amino acids 1-263 of t-PA and 144-411 of u-PA; t-PA/u-PA-e: amino acids 1-274 of t-PA and 138-411 of u-PA). Incubation with human plasma in the absence of a fibrin clot for 3 h at 37° C at equipotent concentrations (50% clot lysis in 2 h), resulted in significant fibrinogen breakdown (to about 40% of the normal value) for all two chain molecules, but not for their single chain counterparts. Preincubation of the plasminogen activators with plasma for 3 h at 37° C, resulted in complete inhibition of the fibrinolytic potency of the two chain molecules but did not alter the potency of the single chain molecules. Inhibition of the two chain molecules occurred with a t½ of approximately 45 min. The two chain variants were inhibited by the synthetic urokinase inhibitor Glu-Gly-Arg-CH2CCl with apparent second-order rate constants of 8,000-10,000 M−1s−1, by purified α2-antiplasmin with second-order rate constants of about 300 M−1s−1, and by plasminogen activator inhibitor-1 (PAI-1) with second-order rate constants of approximately 2 × 107 M−1s−1.It is concluded that the reactivity of single chain and two chain forms of t-PA/u-PA chimaers with inhibitors is very similar to that of the single and two chain forms of intact u-PA.

Determination of the Nucleophilicity of Tricarbonyliron Coordinated Cyclohepta-1,3,5-triene

1999 ◽  
Vol 64 (11) ◽  
pp. 1770-1779 ◽  
Author(s):  
Herbert Mayr ◽  
Karl-Heinz Müller
Keyword(s):  
Gibbs Energy ◽  
Ambient Temperature ◽  
Rate Constants ◽  
Second Order ◽  
Order Rate ◽  
Electrophilic Additions ◽  
Kinetics Of

The kinetics of the electrophilic additions of four diarylcarbenium ions (4a-4d) to tricarbonyl(η4-cyclohepta-1,3,5-triene)iron (1) have been studied photometrically. The second-order rate constants match the linear Gibbs energy relationship log k20 °C = s(E + N) and yield the nucleophilicity parameter N(1) = 3.69. It is concluded that electrophiles with E ≥ -9 will react with complex 1 at ambient temperature.

Luminescence Quenching of Rhodamines by Cyclooctatetraene

1987 ◽  
Vol 42 (9) ◽  
pp. 1009-1013 ◽  
Author(s):  
P. Targowski ◽  
B. Ziętek ◽  
A. Bączyński
Keyword(s):  
Rhodamine B ◽  
Rate Constants ◽  
Internal Conversion ◽  
Rhodamine 6G ◽  
Second Order ◽  
Luminescence Quenching ◽  
Intersystem Crossing ◽  
Order Rate ◽  
Quenching Process

Cyclooctatetraene (COT) as a quencher of fluorescence of a series of Rhodamine solutions was studied. The second order rate constants for the quenching process of Rhodamine 110, Rhodamine 19 pchl., Rhodamine 6G pchl., Rhodamine 6G, Tetramethylrhodamine, Rhodamine B and Rhodamine 3B pchl. are given. It was found that COT enhances rather intersystem crossing than internal conversion.

A Study on the β-Elimination Reaction from N-[2-(p-nitrophenyl)ethyl]quinuclidinium and 2-(p-nitrophenyl)ethyl bromide induced by amines in dimethylsulfoxide with formation of p-nitrostyrene

2000 ◽  
Vol 2000 (2) ◽  
pp. 62-63
Author(s):  
Sergio Alunni ◽  
Arianna Rocchi
Keyword(s):  
Rate Constants ◽  
Second Order ◽  
Ethyl Bromide ◽  
Elimination Reaction ◽  
Order Rate

Second order rate constants kE M−1 s−1 for the β-elimination reaction from N-[2-( p-nitrophenyl)ethyl]quinuclidinium and 2-( p-nitrophenyl)ethyl bromide induced by amines of different structure in dimethylsulfoxide at 50 °C have been measured. Application of the Brønsted equation shows a similar behaviour of the two substrates, with values of β = 0.649 and 0.584 respectively.

Improved alkaline stabilization of municipal wastewater sludge

2002 ◽  
Vol 46 (10) ◽  
pp. 139-146 ◽  
Author(s):  
J.M. Mendez ◽  
B.E. Jiménez ◽  
J.A. Barrios
Keyword(s):  
Municipal Wastewater ◽  
Treatment Plant ◽  
Physicochemical Process ◽  
Wastewater Sludge ◽  
The Other ◽  
Stabilization System ◽  
Municipal Wastewater Treatment ◽  
Faecal Coliforms ◽  
Salmonella Spp ◽  
Closed Systems

In Mexico, physicochemical sludge contains high levels of pathogens; and alkaline stabilization is an alternative for their control. However, the odours caused mainly by ammonia generation represent a disadvantage. On the other hand, the ammonia is known as an effective disinfectant. The aim of this study was to evaluate the disinfectant properties of ammonia in sludge, and use it in a closed alkaline stabilization system, which, not only copes with odours but also increases the efficiency of the process. Raw sludge from a municipal wastewater treatment plant using a physicochemical process was used. Ammonia was applied in doses from 10 to 50% w/w; also, doses from 5 to 40% of CaO were applied in open and closed systems and raw and treated sludge quality was evaluated. Results showed that ammonia removed 6 and 5 logs of faecal coliforms and Salmonella spp., respectively and up to 94% of viable helminth ova. The closed system was more efficient than the open system when applying doses from 5 to 20% of CaO. Finally, the results indicate that the ammonia represents an alternative to disinfecting wastewater sludge and it can be used to enhance alkaline stabilization processes.

KINETICS OF THE AQUEOUS ALKALINE HOMOGENOUS HYDROLYSIS OF HIGH EXPLOSIVE 1, 3,5,7-TETRAAZA- 1, 3,5,7-TETRANITROCYCLOOCTANE (HMX)

1994 ◽  
Vol 30 (3) ◽  
pp. 53-61 ◽  
Author(s):  
Harro M. Heilmann ◽  
Michael K. Stenstrom ◽  
Rolf P. X. Hesselmann ◽  
Udo Wiesmann
Keyword(s):  
Temperature Dependence ◽  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Elevated Temperatures ◽  
Second Order ◽  
Order Rate ◽  
Subsequent Calculation ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Order Rate Equation

In order to get basic data for the design of a novel treatment scheme for high explosives we investigated the kinetics for the aqueous alkaline hydrolysis of 1,3,5,7-tetraaza-1,3,5,7-tetranitrocyclooctane (HMX) and the temperature dependence of the rate constants. We used an HPLC procedure for the analysis of HMX. All experimental data could be fit accurately to a pseudo first-order rate equation and subsequent calculation of second-order rate constants was also precise. Temperature dependence could be modeled with the Arrhenius equation. An increase of 10°C led to an average increase in the second-order rate constants by the 3.16 fold. The activation energy of the second-order reaction was determined to be 111.9 ±0.76 kJ·moJ‒1. We found the alkaline hydrolysis to be rapid (less than 2.5% of the initial HMX-concentration left after 100 minutes) at base concentrations of 23 mmol oH‒/L and elevated temperatures between 60 and 80°C.

scholarly journals The accessibility of protein-bound dinitrophenyl groups to univalent fragments of anti-dinitrophenyl antibody

1976 ◽  
Vol 159 (2) ◽  
pp. 323-333 ◽  
Author(s):  
C G Knight ◽  
N M Green
Keyword(s):  
Dissociation Constant ◽  
Rate Constants ◽  
Alkyl Chain ◽  
Dissociation Constants ◽  
Tryptophan Fluorescence ◽  
Thiol Group ◽  
Second Order ◽  
Thiol Compounds ◽  
Order Rate ◽  
Chain Lengths

A series of N-(N-dinitrophenylaminoalkyl)maleimides were sythesized with alkyl-chain lengths of two, four and six carbon atoms. When these compounds reacted with the thiol group of mercaptalbumin, the tryptophan fluorescence of the protein was quenched. This change in fluorescence was used to determine the rate of reaction of the Dnp (dinitrophenyl)-maleimides with mercaptalbumin. The second-order rate constants were similar to those observed in reactions between low-molecular-weight thiol compounds and maleimides. When N-(N-Dnp-aminoalkyl)succinimidomercaptalbumins were added to univalent fragments of anti-Dnp antibody the antibody fluorescence was quenched. Florescence-quenching titrations showed that the protein-bound Dnp groups were fully available to the antibody even when the alkyl chain was short. The apparent dissociation constants were significantly > that of the interaction between anti-Dnp antibody and the free hapten, 6-(N-Dnp)-aminohexanoate. The antibody fluorescence was quenched efficienty by [dnp-Lys41]ribonuclease A, also with an increased dissociation constant. It could be concluded from the increase in dissociation constant that the Dnp group spent no more than 0.1% of its time in the dissociated state, available to antibody. The second-order rate constants for the association between the Dnp-mercaptablumins and the antibody were determined and were similar in magnitude to those observed in other interactions between protein and anti-protein antibody.

Studies of Reactions between Flavins and Quinones, Mercaptans, and Enolates

1972 ◽  
Vol 27 (9) ◽  
pp. 1016-1020 ◽  
Author(s):  
Morton J. Gibian ◽  
D. Lauriston Elliott ◽  
Charles Kelly ◽  
Brad Borge ◽  
Kirklen Kupecz
Keyword(s):  
Electron Transfer ◽  
Rate Constants ◽  
Redox Reaction ◽  
Radical Anion ◽  
Second Order ◽  
Ph Values ◽  
Order Rate

A. Equilibrium and second-order rate constants have been measured for the redox reaction between phthaloquinone and dihydroriboflavin (and its reverse) at a number of pH values. The equilibria and kinetic determinations are in agreement. No intermediates could be found in the reaction, and it is proposed that with this and other quinones electron transfer occurs within a complex of the flavin and hydroquinone (or dihydroflavin and quinone). B. A survey of the reaction between mercaptans and flavins is reported, as well as data showing that with mercaptoethanol the reaction is reversible, the disulfide and reduced flavin giving mercaptan and flavin. C. The reaction of alkylphenone enolates with isoalloxazine is described. This reaction leads t 50% isoalloxazine radical anion and an adduct of the enolate with the ketone. A possible route for this process is discussed.

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