Degradation Of Phenolic Pollutants Research Articles

Sustainable utilization of anthraquinone-rich Rheum officinale as electron shuttle in microbial fuel cell: Strategy for stimulating monohydric phenols degradation and bioelectricity generation

In an aim to completely degrade refractory phenolic compounds for effective wastewater treatment, a sustainable strategy using anthraquinone-rich herbal plant contents as electron shuttles is presented. This study is the first attempt of treating four different chemical structures of monohydric phenols, while simultaneously generate low-carbon electricity in a microbial fuel cell. An electron shuttle-mediated strategy was introduced to investigate the effect of electron shuttle against the degradation of phenolic pollutants and bioelectricity generation, by employing Rheum officinale extract as electron shuttle. Results revealed that there was a two-fold increase in chemical oxygen demand (COD) removal, degradation extent of phenol and cresol isomers, output voltage and power density of MFC, compared to the mediator-free MFC system. The degradation of phenol yielded higher COD removal, degradation efficiency, output voltage and power generation over cresol isomers, with and without the application of electron shuttle. A complete removal of COD and phenol, with output voltage of 620.06 mV and power density of 252.49 mW/m2 were obtained. Phenol outperformed cresol isomers with regard to its sole activating hydroxy (−OH) group, lower dipole moment and higher electronic conductivity (8.53 mS/cm). Conversely, meta-cresol exhibited the lowest removal efficiency and power generation, ascribed to greater inductive influence of methyl group in meta position on the dissociation energy of the − OH group. Moreover, detection of the phenolic intermediates by gas chromatograph-mass spectrometer analysis was conducted, and detailed degradation pathways were presented.

Degradation of phenolic pollutants by persulfate-based advanced oxidation processes: metal and carbon-based catalysis

Abstract Wastewater recycling is a solution to address the global water shortage. Phenols are major pollutants in wastewater, and they are toxic even at very low concentrations. Advanced oxidation process (AOP) is an emerging technique for the effective degradation and mineralization of phenols into water. Herein, we aim at giving an insight into the current state of the art in persulfate-based AOP for the oxidation of phenols using metal/metal-oxide and carbon-based materials. Special attention has been paid to the design strategies of high-performance catalysts, and their advantages and drawbacks are discussed. Finally, the key challenges that govern the implementation of persulfate-based AOP catalysts in water purification, in terms of cost and environmental friendliness, are summarized and possible solutions are proposed. This work is expected to help the selection of the optimal strategy for treating phenol emissions in real scenarios.

Two Polyoxometalate-Encapsulated Two-Fold Interpenetrating dia Metal-Organic Frameworks for the Detection, Discrimination, and Degradation of Phenolic Pollutants.

Phenols are widely used for commercial production, while they pose a hazard to the environment and human health. Thus, investigation of convenient and efficient methods for the detection, discrimination, and degradation of phenols becomes particularly important. Herein, two new polyoxometalate (POM)-based compounds, [Co2(btap)4(H2O)4][SiW12O40] (Co-POM) and [Ni2(btap)4(H2O)4][SiW12O40] (Ni-POM) (btap = 3,5-bis(triazol-1-yl)pyridine), are prepared via a hydrothermal synthesis method. The compounds show a fascinating structural feature of a POM-encapsulated twofold interpenetrating dia metal-organic framework. More importantly, besides the novel structures, the compound Co-POM realizes three functions, namely, the simultaneous detection, discrimination, and degradation of phenols. Specifically, Co-POM shows an excellent colorimetric detection performance toward phenol with a detection limit (LOD) ca. 1.32 μM, which is lower than most reported colorimetric detectors for phenol. Also, a new colorimetric sensor system based on Co-POM can discriminate phenol, 4-chlorophenol, and o-cresol with ease. Further, Co-POM exhibits a photocatalytic degradation property for 4-chlorophenol under irradiation of visible light with the highest degradation rate at 62% after irradiation for 5 h. Therefore, this work provides the first example of a POMs-based multifunctional material for achieving the detection, discrimination, and degradation of phenolic pollutants.

Synthesis of silver leaves and their potential application for analysis and degradation of phenolic pollutants.

A one‐pot bottom‐up synthesis method was used to synthesise multi‐level leaf‐like nano‐silver (silver leaf) by simply mixing AgNO3, L‐ascorbic acid, Sodium sodium citrate, and polyvinylpyrrolidone (PVP) in the ethanol‐water mixed solvents. Scanning electron microscopy (SEM) characterisations show that the silver leaves have tertiary structures and their sizes are controllable. In addition, silver leaves exhibit excellent Raman enhancement effect (SERS) and chemical catalytic activities for phenolic molecules. Interestingly, the SERS and catalytic activities increase as the size of the silver leaves decrease within a certain range, but when the size is too small, both of these performances weaken. The nanometre size and interstitial structure have a common amplification effect and influence on these activities. The present work not only showed a new method for the synthesis of silver leaves but also could be generalised to find other metallic leaves that could be used as promising heterogeneous catalysts for various reactions. The production of such small‐sized silver leaves will facilitate the analysis of phenolic pollutants through Raman enhancement and treat these pollutants through catalytic degradation.

Heterogeneous Activation of Persulfate by LaMO3 (M=Co, Fe, Cu, Mn, Ni) Perovskite Catalysts for the Degradation of Organic Compounds

Sulfate radical-based advanced oxidation processes (SR-AOPs) are lately applied for the degradation of various pollutants through the formation of reactive oxidant species (ROS) from activation of oxidants, such as persulfate (PS) or peroxymonosulfate (PMS). In this study, LaMO3 (M=Co, Fe, Cu, Mn, Ni) perovskite catalysts were synthesized, characterized by several techniques, and tested for the activation of persulfate towards the degradation of phenolic pollutants. The effect of substitution of position B of La-based perovskites as well as calcination temperature was studied. Overall, the results showed that the decisive role in the catalytic activity was the presence of structures that enhance the transfer of electrons between perovskite and oxidant. LaNiO3 followed by LaCoO3 were found as the most active catalysts. Finally, the stability of the catalysts was studied, showing that B-metal leaching is significant for both catalysts, with LaCoO3 being the most stable one.

Graphitic Carbon Nitride Nanosheets Decorated with Cu-Doped Carbon Dots for the Detection and Degradation of Phenolic Pollutants

Graphitic Carbon Nitride Nanosheets Decorated with Cu-Doped Carbon Dots for the Detection and Degradation of Phenolic Pollutants

Acid-induced molecule self-assembly synthesis of Z-scheme WO3/g-C3N4 heterojunctions for robust photocatalysis against phenolic pollutants

Searching for effective strategies of boosting charge carrier separation and improving photooxidation ability are highly desirable to design graphitic carbon nitride-based photocatalysts for efficient organic pollutant degradation. Here we demonstrate an in situ acid-induced self-assembly of melamine and sodium tungstate method combined with hydrothermal treatment, by forming WO3/melamine-cyanuric acid supramolecular complex, to fabricate porous sheet-like WO3/g-C3N4 heterojunctions with oxygen doping; meanwhile, the morphology of WO3/g-C3N4 nanosheets can be further regulated by selecting different short-chain carboxylic acids. The heterojunctions exhibit enhanced visible-light photocatalytic activity than bulk g-C3N4 and supramolecule-based g-C3N4 in degradation of phenolic pollutants, acetaminophen and methylparaben. The tests including active species trapping, photoelectrochemistry and photoluminescence firmly evidence that the extraordinary Z-scheme charge transfer manner plays dominated role to this excellent activity, which can accelerate charge carrier separation and retain powerful redox ability of electrons on conduction band of g-C3N4 and holes on valence band of WO3 simultaneously; additionally, porous sheet-like nanostructures and oxygen doping also positively influence the activity via improving light harvesting, providing plentiful active sites, shortening charge carrier migration distance and further facilitating charge carrier separation. LC–MS analysis and TOC monitoring find the target pollutants are completely degraded under oxidation of holes, superoxide and hydroxyl radicals.

(Invited) Electrocatalysis and Photoelectrochemistry Based on Modified Titanium Dioxide Nanomaterials

With an ever-increasing population, the importance of industrial processes to ensuring enough food and energy are produced to meet increasing demand cannot be understated. Unfortunately, these processes often produce byproducts that become waste and cause ecological damage. A large concern arises when these waste products enter the water system, resulting in serious consequences for the environment. Various methods have been explored towards the removal of these pollutants. Catalysis plays a key role in chemical production, energy conversion and storage, air purification, water treatment, food processing, and the life sciences. In this presentation, we report on the preparation and modification of TiO2 nanostructured materials as advanced electrocatalysts and photocatalysts for environmental applications and water disinfection. TiO2 nanopores and nanotubes were directly grown on a titanium substrate using anodization processes. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction were employed to characterize the formed TiO2 nanostructures. The electrocatalytic and photocatalytic activities of the nanoporous and nanotubular TiO2 were investigated by the degradation of phenolic pollutants and lignin, a byproduct of the pulp and paper industry, as the model pollutants. The formed TiO2 nanostructures were further treated using electrochemical methods in enhance their catalytic activities. The effectiveness of electrochemical and photoelectrochemical degradation of phenolic species and lignin was determined by UV-Visible spectroscopy and total organic carbon analyzer. The effect of the growth time, the morphology, and the electrochemical treatment on the performance of the formed nanoporous and nanotubular TiO2 is discussed. In addition, the increasing lack of drinking water around the globe is of great concern. The synergistic effect of the integration of photocatalysis and electrocatalysis on bacterial disinfection is highlighted.

Catalytic Effect of Hydrogen Peroxide in the Electrochemical Treatment of Phenolic Pollutants using a BDD Anode

AbstractPhenolic pollutants are recalcitrant substances that cannot be removed from wastewater using the current treatments. In this study, degradation of phenolic pollutants was studied on the basis of the application of hydrogen peroxide during the electrooxidation process using BDD as anode (EO−H2O2 coupled process). The process was optimized using 4‐chlorophenol (4‐CP) as model compound and later an emerging pollutant, Nonylphenol Ethoxylate‐10 (NP10EO), was degraded using the optimized experimental conditions found. To ascertain treatment effectiveness, experiments with hydrogen peroxide (H2O2), electrooxidation (EO) and EO−H2O2 (coupled process) were carried out. The variables considered in this investigation were pH, current density, quantity of H2O2, and reaction time. It was observed that the coupled process (EO−H2O2) increases degradation efficiency, reaching 81.9 % for 4‐CP and 94.3 % for NP10EO. UV/VIS spectrophotometry, COD and HPLC analysis verified these results. The results of the analysis by cyclic voltammetry after the EO−H2O2 coupled process indicate that pollutants in the solution were efficiently oxidized. It was concluded that small amounts of hydrogen peroxide (250 μL 30 % w/v solution per 1.1 L) are sufficient to attain good results; larger amounts of H2O2 produce inhibitory effects during degradation. The slow cathode (SS) oxidation during the experiments was confirmed by XPS and AFM analysis.

Enhanced adsorption and degradation of phenolic pollutants in water by carbon nanotube modified laccase-carrying electrospun fibrous membranes

The advantages of two nanomaterials were combined to improve the activity and stability of laccase, and its purification ability for phenols.

Degradation of phenolic pollutants using KrCl and XeBr excilamps in the presence of dye: A comparative study

Phenolic compounds removal in colourless and non turbid water systems has been widely studied. In this work, the oxidation of phenol and 4-chlorophenol in the presence of the dye methyl green has been studied using a combined advanced treatment based on photodegradation with UV radiation generated by KrCl and XeBr excimer lamps in the presence of H 2O 2. Experiments suggest that pollutants removal is practically independent of the presence of the dye in the reaction matrix. The KrCl excilamp was found to require a shorter treatment period than the XeBr to totally degrade the phenolics. Increasing phenol or 4-chlorophenol concentrations has a negative influence on methyl green degradation, whereby maximum dye degradation rate is achieved when there are no phenolic compounds in the aqueous matrix. It was also evident in the experimental range tested, that the H 2O 2:phenolic compound molar ratio does not significantly influence the removal of phenol and 4-chlorophenol using both excimer lamps. Nevertheless, the removal of methyl green is improved with high molar ratios. Based on the experimental data, a pseudo-first order kinetic model for the KrCl excilamp and a pseudo-second order for the XeBr were proposed. A good correlation between experimental and calculated data was obtained.

Sonochemical degradation of phenolic pollutants in aqueous solutions

The sonochemical degradation of phenol, 2‐chlorophenol and 3,4‐dichlorophenol in aqueous solutions as a function of several operating conditions has been investigated. Experiments were performed at initial substrate concentrations of 0.1, 0.5 and 1 g l−1, liquid phase volumes of 0.05, 0.07 and 0.08 1, electric power outputs of 125, 187.5 and 250 W, liquid bulk temperatures of 20, 35, 50 and 70°C and an ultrasound frequency of 20 kHz. Substrate concentration was determined as a function of time by means of high performance liquid chromatography. At the conditions under consideration, the rate of degradation follows first order kinetics with respect to the substrate concentration and increases with increasing electric power and decreasing liquid volume. The relative reactivity appears to decrease in the order: 2‐chlorophenol>3,4‐dichlorophenol>phenol. Measurements of liquid phase total organic carbon content showed that degradation by‐products are more recalcitrant than the original substrate. The rate of 2‐chlorophenol degradation was also found to decrease with decreasing liquid bulk temperature and increasing initial concentration. Addition of t‐butanol as a hydroxyl radical scavenger only partially inhibited degradation, thus implying that degradation is likely to proceed via both radical‐induced and thermal reactions. Addition of Fe2+ ions at concentrations as low as about 0.2×10−3 g l−1 resulted in increased degradation rates; this is attributed to iron being capable of readily decomposing hydrogen peroxide (generated by water sonolysis) in a Fenton‐like process to form hydroxyl radicals as well as being an effective oxidation catalyst. The implications of the use of ultrasound in wastewater treatment are also discussed.