Insights into the Time Evolution of Slowly Photodegrading Contaminants

Photochemical degradation plays an important role in the attenuation of many recalcitrant pollutants in surface freshwaters. Photoinduced transformation kinetics are strongly affected by environmental conditions, where sunlight irradiance plays the main role, followed by water depth and dissolved organic carbon (DOC). Apart from poorly predictable weather-related issues, fair-weather irradiance has a seasonal trend that results in the fastest photodegradation in June and the slowest in December (at least in temperate areas of the northern hemisphere). Pollutants that have first-order photochemical lifetimes longer than a week take more than one month to achieve 95% photodegradation. Consequently, they may experience quite different irradiance conditions as their photodegradation goes on. The relevant time trend can be approximated as a series of first-order kinetic tracts, each lasting for one month. The trend considerably departs from an overall exponential decay, if degradation takes long enough to encompass seasonally varying irradiance conditions. For instance, sunlight irradiance is higher in July than in April, but increasing irradiance after April and decreasing irradiance after July ensure that pollutants emitted in either month undergo degradation with very similar time trends in the first 3–4 months after emission. If photodegradation takes longer, pollutants emitted in July experience a considerable slowdown in photoreaction kinetics as winter is approached. Therefore, if pollutants are photostable enough that their photochemical time trend evolves over different seasons, degradation acquires some peculiar features than cannot be easily predicted from a mere analysis of lifetimes in the framework of simple first-order kinetics. Such features are here highlighted with a modelling approach, taking the case of carbamazepine as the main example. This contaminant is almost totally biorecalcitrant, and it is also quite resistant to photodegradation.

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Mechanism-based inactivation of gastric peroxidase by mercaptomethylimidazole

Biochemical Journal ◽

10.1042/bj2960079 ◽

1993 ◽

Vol 296 (1) ◽

pp. 79-84 ◽

Cited By ~ 12

Author(s):

U Bandyopadhyay ◽

D K Bhattacharyya ◽

R K Banerjee

Keyword(s):

Ph Dependence ◽

Order Rate Constant ◽

Order Kinetic ◽

First Order ◽

First Order Kinetics ◽

Mechanism Of Inhibition ◽

Catalytically Active ◽

Pseudo First Order ◽

Inactivation Process ◽

Gastric Peroxidase

The mechanism of inhibition of gastric peroxidase (GPO) activity by mercaptomethylimidazole (MMI), an inducer of gastric acid secretion, has been investigated. Incubation of purified GPO with MMI in the presence of H2O2 results in irreversible inactivation of the enzyme. No significant inactivation occurs in the absence of H2O2 or MMI, suggesting the involvement of peroxidase-catalysed oxidized MMI (MMIOX.) in the inactivation process. The inactivation follows pseudo-first-order kinetics consistent with a mechanism-based (suicide) mode. The pseudo-first-order kinetic constants at pH 8 are ki = 111 microM, k(inact.) = 0.55 min-1 and t1/2 = 1.25 min, and the second-order rate constant is 0.53 x 10(4) M-1 x min-1. Propylthiouracil also inactivates GPO activity in the same manner but its efficiency (k(inact./ki = 0.46 mM-1 x min-1) is about 10 times lower than that of MMI (k(inact./ki = 5 mM-1 x min-1). The rate of inactivation with MMI shows pH-dependence with an inflection point at 7.3, indicating the involvement in the inactivation process of an ionizable group on the enzyme with a pKa of 7.3. The enzyme is remarkably protected against inactivation by micromolar concentrations of electron donors such as iodide and bromide but not by chloride. Although GPO oxidizes MMI slowly, iodide stimulates it through enzymic generation of I+ which is reduced back to I- by MMI. Although MMIOX. is formed at a much higher rate in the presence of I-, a constant concentration of I- maintained via the reduction of I+ by MMI, protects the active site of the enzyme against inactivation. We suggest that MMI inactivates catalytically active GPO by acting as a suicidal substrate.

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Diphasic transfer of oxygen in vertical flow filters: a modelling approach

Water Science & Technology ◽

10.2166/wst.2011.618 ◽

2011 ◽

Vol 64 (1) ◽

pp. 109-116 ◽

Cited By ~ 4

Author(s):

A. Petitjean ◽

A. Wanko ◽

N. Forquet ◽

R. Mosé ◽

F. Lawniczak ◽

...

Keyword(s):

Multiphase Model ◽

Vertical Flow ◽

Treatment Efficiency ◽

Two Phase ◽

Convection Diffusion ◽

First Order ◽

First Order Kinetics ◽

First Results ◽

Diffusion Phenomena ◽

Modelling Approach

Oxygen renewal, as a prominent phenomenon for aerobic bacterial activity, deeply impacts vertical flow constructed wetland (VFCW) treatment efficiency. The authors introduce a multiphase model able to simulate oxygen transfer in VFCWs. It is based on a two-phase flow module, and a transport module. The transport module is able to deal with convection/diffusion phenomena, inter-phase (air–water) mass exchange, and first-order kinetics. The first results displayed for the air phase allow us to draw the following ideas on the design of vertical filters. The ponding phenomenon is more efficient for oxygen renewal than non-ponding batch loading: it provides a higher value, sooner, and deeper in the filter. In non-colonised filters and for standard batch loading, oxygen convection in the air phase is predominant for oxygen renewal. The seepage front limits oxygen renewal through the bottom of the filter and leads to an insufficient oxygen concentration on the lowest part of the filter.

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Kinetics and reaction mechanism of photochemical degradation of diclofenac by UV-activated peroxymonosulfate

RSC Advances ◽

10.1039/d0ra10178h ◽

2021 ◽

Vol 11 (12) ◽

pp. 6804-6817

Author(s):

Yunlan Peng ◽

Hongle Shi ◽

Zhenran Wang ◽

Yongsheng Fu ◽

Yiqing Liu

Keyword(s):

Reaction Mechanism ◽

Kinetic Model ◽

Order Kinetic ◽

Photochemical Degradation ◽

First Order ◽

Order Kinetic Model ◽

Pseudo First Order

Compared to UV alone and PMS alone systems, diclofenac was removed more efficiently in UV/PMS system at pH 7.0 due to the contribution of SO4˙− and HO˙ and its degradation followed the pseudo-first order kinetic model.

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Photocatalytic Degradation of Erythrosin-B using Cadmium Cobaltite for Water Reuse: Efficiency and Degradation Pathway

Asian Journal of Chemistry ◽

10.14233/ajchem.2020.22713 ◽

2020 ◽

Vol 32 (9) ◽

pp. 2143-2148

Author(s):

JAYANTI SAMOTA ◽

SURAJ SHARMA ◽

SHIPRA BHARDWAJ ◽

KUMUD INTODIA

Keyword(s):

Photocatalytic Degradation ◽

Water Reuse ◽

Reaction Rate ◽

Degradation Pathway ◽

Photochemical Degradation ◽

Erythrosin B ◽

First Order ◽

First Order Kinetics ◽

Pseudo First Order ◽

The Impact

In present work, a photocatalytic degradation of Erythrosin-B has been studied using cadmium cobaltite. The impact of different parameters such as pH, amount of cadmium cobaltite, concentration of Erythrosin-B and light intensity have been observed on the reaction rate. Radical quenching experiments revealed that hydroxyl radicals are primarily responsible for the degradation of Erythrosin-B. The progress of reaction monitored spectrophotometrically and it followed pseudo first-order kinetics. An experimental mechanism is proposed for the photochemical degradation of Erythrosin-B.

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Nano-Catalytic Ozonation of 4-Nitrochlorobenzene in Aqueous Solutions

E-Journal of Chemistry ◽

10.1155/2012/696418 ◽

2012 ◽

Vol 9 (4) ◽

pp. 1968-1975 ◽

Cited By ~ 3

Author(s):

S. M. Tabatabaei ◽

A. Mehrizad ◽

P. Gharbani

Keyword(s):

Particle Size ◽

Degradation Rate ◽

Batch Reactor ◽

Kinetic Studies ◽

Catalytic Ozonation ◽

Main Role ◽

Order Kinetic ◽

Nano Zno ◽

First Order ◽

Pseudo First Order

In this paper, efficiency of nano-ZnO particles on catalytic ozonation of 4-nitrochlorobenzene (4NCB) using semi-batch reactor has been studied at various pHs. During the catalytic ozonation, TOC and concentration of nitrate ions was monitored. Results indicate that degradation of 4NCB was improved by combination of nano-ZnO with ozone. The effect of ZnO particle size and pH are also examined. According to the results, concentration of 4NCB decreased with increasing of particle size from nanosized to microsized and pH from 3.0 to 9.0. Based on the results, it suggests radical hydroxyl does not affect on the degradation of 4NCB in catalytic ozonation, but the surface of catalyst plays main role. Kinetic studies showed degradation of 4NCB followed pseudo-first-order kinetic and maximum degradation rate was observed at pH=3.

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U(VI) adsorption in water by sodium alginate modified Bacillus megaterium

Royal Society Open Science ◽

10.1098/rsos.202098 ◽

2021 ◽

Vol 8 (2) ◽

Author(s):

Dianxin Li ◽

Yiqing Yang ◽

Peng Zhang ◽

Jiangang Liu ◽

Tao Li ◽

...

Keyword(s):

Adsorption Capacity ◽

Sodium Alginate ◽

Bacillus Megaterium ◽

Adsorption Process ◽

Batch Adsorption ◽

Maximum Adsorption Capacity ◽

Order Kinetic ◽

First Order ◽

First Order Kinetics ◽

Pseudo First Order

The surface of Bacillus megaterium was modified by coating sodium alginate. The modified B. megaterium before and after adsorption were characterized by SEM, FTIR and XPS. The effects of pH, reaction time, initial U(VI) concentration and adsorbent dosage on the adsorption of U(VI) by the modified B. megaterium were studied by batch adsorption experiments. The adsorption process was studied by pseudo-first-order kinetics and pseudo-second-order kinetic models, Langmuir and Freundlich isotherms. The results showed that the maximum adsorption capacity of U(VI) was 74.61 mg g −1 under the conditions of pH 5.0, adsorbent 0.2 g l −1 , 30°C and initial U(VI) concentration of 15 mg l −1 . The adsorption process accords with pseudo-first-order kinetics and Langmuir isotherm. The adsorption capacity of U(VI) by the modified B. megaterium was still higher than 80% after five times of desorption and reuse experiments. In conclusion, the sodium alginate modified B. megaterium was an ideal material for U(VI) biosorption.

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Degradation of biotansformation products of nonylphenol ethoxylates by ozonation and UV/TiO2 treatment

Water Science & Technology ◽

10.2166/wst.2002.0727 ◽

2002 ◽

Vol 46 (11-12) ◽

pp. 127-132 ◽

Cited By ~ 33

Author(s):

M. Ike ◽

M. Asano ◽

F.D. Belkada ◽

S. Tsunoi ◽

M. Tanaka ◽

...

Keyword(s):

Degradation Rate ◽

Degradation Kinetics ◽

Chemical Oxidation ◽

Order Kinetic ◽

Oxidation Processes ◽

First Order ◽

First Order Kinetics ◽

Biotransformation Products ◽

Kinetics Of ◽

Dioxide Suspension

The degradation kinetics of biotransformation products of nonylphenol polyethoxylates (NPEOs), nonylphenol (NP), nonylphenol monoethoxylate (NP1EO) and nonylphenoxy carboxylic acid (NP1EC), by ozonation and UV/TiO2 (ultraviolet photocatalytic degradation in the presence of titanium dioxide suspension as a catalyst) were investigated using lab-scale reactors. The degradation rate of NP by UV/TiO2 was the highest among the tested NPEOs metabolites, while NP1EC showed the lowest degradation rate. In contrast, ozonation was especially effective for the breakdown of NP1EC. NP could be also degraded efficiently by ozonation, however, it was much less effective for NP1EO decomposition. Degradation of NP by both chemical oxidation processes followed first-order kinetics. The degradation curves of NP1EO and NP1EC could be approximately described by first-order kinetics also, although the degradation of NP1EC by ozonation seemed to follow a second-order kinetic.

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Iron Supported on Ion Exchange Resin as Source of Iron for Fenton Reagent: A Heterogeneous or a Homogeneous Fenton Reagent Generation?

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2017-0026 ◽

2017 ◽

Vol 15 (5) ◽

Cited By ~ 3

Author(s):

Orlando García-Rodríguez ◽

Jennifer A. Bañuelos ◽

Luis A. Godínez ◽

Hortencia C. Arredondo Valdez ◽

Evelyn Zamudio ◽

...

Keyword(s):

Ion Exchange ◽

Exchange Resin ◽

Dye Decolorization ◽

Ion Exchange Resin ◽

Order Kinetic ◽

Fenton Reagent ◽

First Order ◽

Relative Contribution ◽

First Order Kinetics ◽

Pseudo First Order

Abstract The aim of this work is to discuss the relative contribution of homogeneous and heterogeneous Fenton processes in the treatment of Orange II dye solutions at pH 3 and 7 using an ion exchange resin as iron support. While at pH 3, 99% of the colour was removed, under neutral conditions a decoloration of 56% was observed. Studying the release of iron from the resin, we found a concentration of 1.49 mg/L of ferric ion and 0.31 mg/L of ferrous ion at pH 3 and 1.08 mg/L and 0.11 mg/L at pH 7, revealing that as expected, dissolution of iron ions at pH 3 is larger. Using these concentrations in a homogeneous process, 45% of the colour can be removed at pH 3 and 10% at pH 7, so it was infered that there is an effect of the iron that is still supported on the resin. In this way, a mixed homogeneous/heterogeneous mechanism could be proposed. While the experimental data for the desorption of iron at pH 3 was well suited to a pseudo second order kinetic model, the desorption of iron at pH 7 was fit to pseudo-first order kinetics. Experimental results of dye decolorization were on the other hand, fitted to a pseudo first order kinetics.

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Photo-catalytic degradation of gaseous pollutants in paper mills of southern China

TAPPI Journal ◽

10.32964/tj17.03.167 ◽

2018 ◽

Vol 17 (03) ◽

pp. 167-178 ◽

Cited By ~ 2

Author(s):

Xin Tong ◽

Jiao Li ◽

Jun Ma ◽

Xiaoquan Chen ◽

Wenhao Shen

Keyword(s):

Degradation Rate ◽

Southern China ◽

Catalytic Degradation ◽

Pulp And Paper ◽

Gaseous Pollutants ◽

Pulp And Paper Mills ◽

Paper Mills ◽

Initial Concentration ◽

First Order ◽

First Order Kinetics

Studies were undertaken to evaluate gaseous pollutants in workplace air within pulp and paper mills and to consider the effectiveness of photo-catalytic treatment of this air. Ambient air at 30 sampling sites in five pulp and paper mills of southern China were sampled and analyzed. The results revealed that formaldehyde and various benzene-based molecules were the main gaseous pollutants at these five mills. A photo-catalytic reactor system with titanium dioxide (TiO2) was developed and evaluated for degradation of formaldehyde, benzene and their mixtures. The experimental results demonstrated that both formaldehyde and benzene in their pure forms could be completely photo-catalytic degraded, though the degradation of benzene was much more difficult than that for formaldehyde. Study of the photo-catalytic degradation kinetics revealed that the degradation rate of formaldehyde increased with initial concentration fitting a first-order kinetics reaction. In contrast, the degradation rate of benzene had no relationship with initial concentration and degradation did not conform to first-order kinetics. The photo-catalytic degradation of formaldehyde-benzene mixtures indicated that formaldehyde behaved differently than when treated in its pure form. The degradation time was two times longer and the kinetics did not reflect a first-order reaction. The degradation of benzene was similar in both pure form and when mixed with formaldehyde.

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Leaching Kinetics of Atrazine and Inorganic Chemicals in Tilled and Orchard Soils

International Agrophysics ◽

10.2478/intag-2014-0012 ◽

2014 ◽

Vol 28 (2) ◽

pp. 231-237 ◽

Cited By ~ 2

Author(s):

Lech W. Szajdak ◽

Jerzy Lipiec ◽

Anna Siczek ◽

Artur Nosalewicz ◽

Urszula Majewska

Keyword(s):

Reaction Rate ◽

Inorganic Compounds ◽

Model Performance ◽

Order Reaction ◽

First Order Reaction ◽

Order Kinetic ◽

Time Data ◽

First Order ◽

Concentration Changes ◽

Reaction Constants

Abstract The aim of this study was to verify first-order kinetic reaction rate model performance in predicting of leaching of atrazine and inorganic compounds (K+1, Fe+3, Mg+2, Mn+2, NH4 +, NO3 - and PO4 -3) from tilled and orchard silty loam soils. This model provided an excellent fit to the experimental concentration changes of the compounds vs. time data during leaching. Calculated values of the first-order reaction rate constants for the changes of all chemicals were from 3.8 to 19.0 times higher in orchard than in tilled soil. Higher first-order reaction constants for orchard than tilled soil correspond with both higher total porosity and contribution of biological pores in the former. The first order reaction constants for the leaching of chemical compounds enables prediction of the actual compound concentration and the interactions between compound and soil as affected by management system. The study demonstrates the effectiveness of simultaneous chemical and physical analyses as a tool for the understanding of leaching in variously managed soils.

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