Search query: organic contaminant degradation

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abstract: Abstract Photocatalysis is one of the promising technologies because of its potential application in degrading pollutants, reducing CO2 levels, and producing sustainable hydrogen (H2) fuel. Though inorganic semiconductors have shown tremendous progress in different fields of application, there are some inherent challenges in these photocatalysts. Various types of photocatalytic materials and reactors have been studied for the degradation of pollutants in wastewater. The photocatalytic efficiency and the reaction rate highly depend on the different operational parameters. In this connection, this chapter deals with the basic photocatalytic mechanism, different performance parameters, challenges, and their strategy to overcome the challenges. This chapter also addresses some key issues that should be addressed in future research.
author_names: Biju Mani Rajbongshi
title: Photocatalyst: mechanism, challenges, and strategy for organic contaminant degradation
year: 2020

abstract: We investigated the activation of hydrogen peroxide (H2O2) by biochars (produced from pine needles, wheat, and maize straw) for 2 chlorobiphenyl (2 CB) degradation in the present study. It was found that H2O2 can be effectively activated by biochar, which produces hydroxyl radical )OH) to degrade 2 CB. Furthermore, the activation mechanism was elucidated by electron paramagnetic resonance (EPR) and salicylic acid (SA) trapping techniques. The results showed that biochar contains persistent free radicals (PFRs) typically 10(18) unpaired spins/gram. Higher trapped )OH] concentrations were observed with larger decreases in PFRs concentration, when H2O2 was added to biochar, indicating that PFRs were the main contributor to the formation of )OH. This hypothesis was supported by the linear correlations between PFRs concentration and trapped )OH] as well as kobs of 2 CB degradation. The correlation coefficients (R(2) were 0.723 and 0.668 for PFRs concentration vs trapped )OH] and PFRs concentration vs kobs, respectively, when all biochars pyrolyzed at different temperatures were included. For the same biochar washed by different organic solvents (methanol, hexane, dichloromethane, and toluene) the correlation coefficients markedly increased to 0.818 0.907. Single electron transfer from PFRs to H2O2 was a possible mechanism for H2O2 activation by biochars, which was supported by free radical quenching studies. The findings of this study provide a new pathway for biochar implication and insight into the mechanism of H2O2 activation by carbonaceous materials (e.g. activated carbon and graphite)
author_names: Guodong Fang

Juan Gao

Cun Liu

Dionysios D Dionysiou

Yu Wang

Dongmei Zhou
title: Key role of persistent free radicals in hydrogen peroxide activation by biochar: implications to organic contaminant degradation.
venue: Environmental science technology
year: 2014

abstract: We propose a multi element isotope modeling approach to simultaneously predict the evolution of different isotopes during the transformation of organic contaminants. The isotopic trends of different elements are explicitly simulated by tracking position specific isotopologues that contain the isotopes located at fractionating positions. Our approach is self consistent and provides a mechanistic description of different degradation pathways that accounts for the influence of both primary and secondary isotope effects during contaminant degradation. The method is particularly suited to quantitatively describe the isotopic evolution of relatively large organic contaminant molecules. For such compounds, an integrated approach, simultaneously considering all possible isotopologues, would be impractical due to the large number of isotopologues. We apply the proposed modeling approach to the degradation of toluene, methyl tert butyl ether (MTBE) and nitrobenzene observed in previous experimental studies. Our model successfully predicts the multi element isotope data (both 2D and 3D) and accurately captures the distinct trends observed for different reaction pathways. The proposed approach provides an improved and mechanistic methodology to interpret multi element isotope data and to predict the extent of multi element isotope fractionation that goes beyond commonly applied modeling descriptions and simplified methods based on the ratio between bulk enrichment factors or on linear regression in dual isotope plots.
author_names: Biao Jin

Massimo Rolle
title: Mechanistic approach to multi element isotope modeling of organic contaminant degradation.
venue: Chemosphere
year: 2014

abstract: Advanced oxidation processes (AOPs) generating nonselective hydroxyl radicals (HO* provide a broad spectrum contaminant destruction option for the decontamination of waters. Halide ions are scavengers of HO* during AOP treatment, such that treatment of saline waters would be anticipated to be ineffective. However, HO* scavenging by halides converts HO* to radical reactive halogen species (RHS) that participate in contaminant destruction but react more selectively with electron rich organic compounds. The effects of Cl Br and carbonates (H2CO3+HCO3 +CO3(2 on the UV/H2O2 treatment of model compounds in saline waters were evaluated. For single target organic contaminants, the impact of these constituents on contaminant destruction rate suppression at circumneutral pH followed the order Br >carbonates>Cl Traces of Br in the NaCl stock had a greater effect than Cl itself. Kinetic modeling of phenol destruction demonstrated that RHS contributed significantly to phenol destruction, mitigating the impact of HO* scavenging. The extent of treatment efficiency reduction in the presence of halides varied dramatically among different target organic compounds. Destruction of contaminants containing electron poor reaction centers in seawater was nearly halted, while 17beta estradiol removal declined by only 3% Treatment of mixtures of contaminants with each other and with natural organic matter (NOM) was evaluated. Although NOM served as an oxidant scavenger, conversion of nonselective HO* to selective radicals due to the presence of anions enhanced the efficiency of electron rich contaminant removal in saline waters by focusing the oxidizing power of the system away from the NOM toward the target contaminant. Despite the importance of contaminant oxidation by halogen radicals, the formation of halogenated byproducts was minimal.
author_names: Janel E Grebel

Joseph J Pignatello

William A Mitch
title: Effect of halide ions and carbonates on organic contaminant degradation by hydroxyl radical based advanced oxidation processes in saline waters.
venue: Environmental science technology
year: 2010

abstract: Abstract The performance of two redox mediating compounds, namely 1 hydroxybenzotriazole (HBT) and syringaldehyde (SA) was compared in terms of enhancement of enzymatic degradation of a diverse set of 14 phenolic and 16 non phenolic trace organic contaminants (TrOCs) and the toxicity of the treated media. Extracellular enzyme extract (predominantly containing laccase) from Trametes versicolor culture achieved efficient degradation (70 95% of nine phenolic and one non phenolic TrOCs. Mediator dosing extended the spectrum of efficiently degraded TrOCs to 13 phenolic and three non phenolic compounds, with moderate improvements in removal of a few other non phenolic compounds. TrOC removal efficiency improved significantly as the HBT dose was increased from 0.1 to 0.5 mM, while SA achieved similar removal over dosage range of 0.1 1 mM. A particular concern was the toxicity of the treated media (1200 2200 times that of the control) for all SA dosages applied. Overall, HBT at a concentration of 0.5 mM achieved the best removal without raising concern regarding toxicity of the treated media. The results are discussed in the light of the redox potential of the enzyme mediator cocktail, the balance between the stability and reactivity of the radicals generated and their cytotoxic effects.
author_names: Luong Ngoc Nguyen

Faisal I Hai

Jinguo Kang

Frederic D L Leusch

Felicity A Roddick

Saleh Faraj Magram

William Evan Price

Long Duc Nghiem
title: Enhancement of trace organic contaminant degradation by crude enzyme extract from Trametes versicolor culture: Effect of mediator type and concentration
year: 2014

author_names: Emily Palmer
title: The impact of soluble microbial products on trace organic contaminant degradation
year: 2016

abstract: TiO2 composites with zeolite templated carbon (TiO2 ZTC) and activated carbon (TiO2 AC) were prepared and used as the photocatalysts for comparative studies with pure TiO2. TiO2 ZTC exhibited the highest rate of methylene blue degradation with a rate approximately 4 and 400 times higher than those of TiO2 AC and pure TiO2, respectively. Moreover, the highest catalytic performance of TiO2 ZTC in gas phase degradation of acetone was approximately 1.1 and 12.9 times higher than TiO2 AC and pure TiO2, respectively. These outstanding performances could be attributed to high surface area, pore volume, and hydrophobic surface properties, leading to improvement in the adsorption properties of organic molecules.
author_names: Waleeporn Donphai

Takashi Kamegawa

Metta Chareonpanich

Khanin Nueangnoraj

Hirotomo Nishihara

Takashi Kyotani

Hiromi Yamashita
title: Photocatalytic performance of TiO2 zeolite templated carbon composites in organic contaminant degradation.
venue: Physical chemistry chemical physics PCCP
year: 2014

abstract: Abstract Electrochemical oxidation (EO) is by most researchers considered as a treatment method within the advanced oxidation processes family and has attracted a lot of attention within the last two decades. Oxidative electrochemical technologies offer an alternative solution to many environmental problems in the process industry, because electrons provide a versatile, efficient, cost effective, easily automatable, safe and clean reagent Comninellis et al. 2008 Rajeshwar and Ibanez, 1997 As this chapter will demonstrate, EO has the potential to become a significant treatment method in industrial or municipal wastewater treatment, when toxic and bioincompatible organic compounds and other recalcitrant pollutants need to be removed. Different possibilities for implementation exist and will be discussed along with case studies of uses in the areas of polluted ground water and process water treatment. Finally, the many possible applications within water disinfection result in a very attractive technique with a large market potential.
author_names: Jens Muff
title: Electrochemical Oxidation A Versatile Technique for Aqueous Organic Contaminant Degradation
year: 2014

abstract: This study investigated the removal of five selecte d non phenolic trace organic contaminants (TrOC) by extracellular enzyme extract from a white rot fungus. Except dicl ofenac, no other investigated non phenolic TrOC were degraded by the extracellular enzyme extract. Improvement of enzymatic degradation of all TrOC was achieved in the presence of a redox mediator, namely, 1 hydroxybenzotriazole (HBT) However, the enhancement of degradation was mediator concentration specific. A significant impr ovement in degradation at higher dosage than 0.1 mM (HBT) was achieved.
author_names: Ngoc-Luong Nguyen

Faisal I Hai

Jinguo Kang

Saleh Faraj Magram

William Evan Price

Long Duc Nghiem
title: Impact of 1 Hydroxybenzotriazole Dosing on Trace Organic Contaminant Degradation by Laccase
year: 2014

abstract: Abstract A series of coupled measurements was made at the Naval Air Station North Island (NASNI) Installation Restoration Site 5, Unit 2 during July and August 2013. Preliminary samples were taken in March 2013. Coupled measurements included CO2 respiration rate, proportion of the CO2 attributable to chlorinated hydrocarbon (CH) mineralization and a zone of influence (ZOI) model. This coupling led to calculating CH degradation per unit time per unit area. These coupled measurements represent the first analysis where carbon is followed from contaminant to final degradation product (CO2) directly without need for inference or lines of evidence. In order to determine a mass removal for this study, the average contaminant mineralization rate (0.673 g C m 3 d 1) was multiplied by the total area within the sampling grid (1,225 m2) then multiplied by the ZOI depth to give the total carbon mass removal from the CH pool: 14.5 g C d 1. The wells on site are screened at the groundwater:vadoze zone interface and the vertical ZOI characteristics are likely very different above and below the water table (vadoze versus saturated zone) However, if the assumption is made that the entire surface soil lens (sandy silt) to a depth of approximately 3 meters has similar CH degradation rates, an optimistic estimate of 246 g C d 1 over the entire sampled site area can be calculated. In terms of dissolved CH, an estimate of 0.100 g CH carbon L 1 was assumed based on reported values (from 2009) Over the site, within the ZOI, residence time for CH averaged just over 4 years, assuming no additional input (desorbing from soils) At the lowest measured turnover rates, residence time was calculated at 2,400 years and the highest measured rate, 11 months.
author_names: Thomas J Boyd

Michael T Montgomery

Richard H Cuenca

Yutaka Hagimoto
title: CO2 Radiocarbon Analysis to Quantify Organic Contaminant Degradation, MNA, and Engineered Remediation Approaches
year: 2014