Fenton-like Advanced Oxidation Processes Research Articles

Constructing Hollow Multishelled Microreactors with a Nanoconfined Microenvironment for Ofloxacin Degradation through Peroxymonosulfate Activation: Evolution of High-Valence Cobalt-Oxo Species.

This study constructed hollow multishelled microreactors with a nanoconfined microenvironment for degrading ofloxacin (OFX) through peroxymonosulfate (PMS) activation in Fenton-like advanced oxidation processes (AOPs), resulting in adequate contaminant mineralization. Among the microreactors, a triple-shelled Co-based hollow microsphere (TS-Co/HM) exhibited optimal performance; its OFX degradation rate was 0.598 min-1, which was higher than that of Co3O4 nanoparticles by 8.97-fold. The structural tuning of Co/HM promoted the formation of oxygen vacancies (VO), which then facilitated the evolution of high-valence cobalt-oxo (Co(IV)═O) and shifted the entire t2g orbital of the Co atom upward, promoting catalytic reactions. Co(IV)═O was identified using a phenylmethyl sulfoxide (PMSO) probe and in situ Raman spectroscopy, and theoretical calculations were conducted to identify the lower energy barrier for Co(IV)═O formation on the defect-rich catalyst. Furthermore, the TS-Co/HM catalyst exhibited remarkable stability in inorganic (Cl-, H2PO4-, and NO3-), organic (humic acid), real water samples (tap water, river water, and hospital water), and in a continuous flow system in a microreactor. The nanoconfined microenvironment could enrich reactants in the catalyst cavities, prolong the residence time of molecules, and increase the utilization efficiency of Co(IV)═O. This work describes an activation process involving Co(IV)═O for organic contaminants elimination. Our results may encourage the use of multishelled structures and inform the design of nanoconfined catalysts in AOPs.

Single-Atom Catalysts in Environmental Engineering: Progress, Outlook and Challenges.

Recently, single-atom catalysts (SACs) have attracted wide attention in the field of environmental engineering. Compared with their nanoparticle counterparts, SACs possess high atomic efficiency, unique catalytic activity, and selectivity. This review summarizes recent studies on the environmental remediation applications of SACs in (1) gaseous: volatile organic compounds (VOCs) treatment, NOx reduction, CO2 reduction, and CO oxidation; (2) aqueous: Fenton-like advanced oxidation processes (AOPs), hydrodehalogenation, and nitrate/nitrite reduction. We present the treatment activities and reaction mechanisms of various SACs and propose challenges and future opportunities. We believe that this review will provide constructive inspiration and direction for future SAC research in environmental engineering.

Degradation of petroleum pollutants in oil-based drilling cuttings using an Fe2+-based Fenton-like advanced oxidation processes.

Oil-based drilling cuttings (OBDC) contain a large amount of total petroleum hydrocarbon (TPH) pollutants, which are hazardous to the environment. In this study, Fe2+-activating hydrogen peroxide (Fe2+/H2O2), peroxymonosulfate (Fe2+/PMS), and peroxydisulfate (Fe2+/PDS) advanced oxidation processes (AOPs) were used to treat OBDC due to the difference in the degradation capacity of TPH caused by the type of free radical generated and effective activation conditions observed for the different oxidants studied. The results showed that the oxidant concentration, Fe2+ dosage, and reaction time in the three AOPs were greatly positively correlated with the TPH removal rate in a certain range. The initial pH value had a significant effect on the Fe2+/H2O2 process, and its TPH removal rate was negatively correlated in the pH range from 3 to 11. However, the Fe2+/PMS and Fe2+/PDS processes only displayed lower TPH removal rates under neutral conditions and tolerated a wider range of pH conditions. The optimal TPH removal rates observed for the Fe2+/H2O2, Fe2+/PMS, and Fe2+/PDS processes were 45.04%, 42.75%, and 44.95%, respectively. Fourier transform infrared spectrometer and gas chromatography-mass spectrometer analysis showed that the alkanes in OBDC could be effectively removed using the three processes studied, and their degradation ability toward straight-chain alkanes was in the order of Fe2+/PMS > Fe2+/PDS > Fe2+/H2O2, among which Fe2+/PMS exhibited the optimal removal effect for aromatic hydrocarbons. Scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction results showed no significant changes in the elemental and mineral composition of OBDC before and after treatment. Therefore, this study provided a theoretical reference for the effective degradation of TPH pollutants in OBDC.

High 1T phase and sulfur vacancies in C-MoS2@Fe induced by ascorbic acid for synergistically enhanced contaminants degradation

Applicating co-catalyst into Fenton-like advanced oxidation processes to improve the performance for wastewater remediation has attracted widespread attention. Among them, developing highly active and green heterogeneous catalyst integrating homogeneous ferrous ions and inorganic co-catalyst is a great challenge. Herein, ascorbic acid additive was creatively introduced into the precursor composed of thiourea, sodium molybdate and ferric chloride to synthesize carbon intercalated molybdenum disulfide anchoring iron (C-MoS2@Fe) by a simple one-step hydrothermal method. C-MoS2@Fe exhibited an amazing apparent first-order constant as high as 0.739 min−1 about 10 times higher than that of the homogeneous Fe2+/MoS2 system for the sulfamethoxazole (SMX) removal and achieved 68.7% removal of TOC in 6 min, which was attribute to the synergistic enhancement of high 1T phase (82.0%) and sulfur vacancies induced by the introduction of ascorbic acid. Notably, the C-MoS2@Fe was also capable of efficiently degrading multiple organic contaminants such as pharmaceuticals, phenolic compounds, and organic dyes. Compared with the homogeneous Fe2+/PMS system, the C-MoS2@Fe/PMS system expanded the effective pH range (2.0 ∼ 9.0) and the ultralow iron ions leaching (0.204 mg L-1) avoided the formation of iron containing sludge. The results of electron paramagnetic resonance (EPR), radical quenching and probe experiments indicated that •OH was the main active species with the contribution rate about 60.3%. Furthermore, possible degradation pathways were proposed based on the intermediate products of SMX investigated by LC-MS. This study provides novel insights for the development of highly active and green catalysts for wastewater remediation.

Cobalt Oxide on a Nanoporous TUD-1 Catalyst for Methylene Blue Dye Interaction DFT Studies and Degradation

Fenton and Fenton-like advanced oxidation processes (AOP) have been substantially utilized in wastewater treatment for the removal of organic contaminants. The present investigation explores the catalytic activity of cobalt dispersed over nanoporous silicate material (CoO/TUD-1), TUD-1, for the Fenton-type degradation of methylene blue (MB) dye present in wastewater, with hydrogen peroxide (H2O2) as an oxidant. The catalyst, which was prepared using the hydrothermal method, was characterized using analytical and spectroscopic techniques, such as X-ray diffraction (XRD), N2 adsorption–desorption isotherms, UV-visible diffuse reflectance (DR), scanning electron microscope (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR). The results indicated that the CoO/TUD-1 possessed three-dimensional structures with a high surface area and a pore diameter capable of the uniform dispersion of cobalt species. Density functional theory (DFT) simulations were performed to study the most stable tetra coordinate adsorption configuration of a single Co atom on amorphous SiO2. To understand the geometric and electronic structure of this configuration, electron density differences, Bader charge, and partial density of states were examined. The results obtained from the DFT calculations confirmed the occurrence of electron transfer from the Co atom to the amorphous SiO2. The calculated adsorption energy was found to be −1.58 eV, which indicated that the MB dye was strongly adsorbed by parallel configuration mode and degraded more easily. Further, the addition of a 0.1g/L dose of the prepared CoO /TUD degraded the MB dye effectively (~95%) within 240 min of contact. Thus, CoO/TUD-1 is a potential material for the removal of organic contaminants and the degradation of dyes in wastewater treatment.

Bimetal Cu-Mn porous silica-supported catalyst for Fenton-like degradation of organic dyes in wastewater at neutral pH

Fenton and Fenton-like Advanced Oxidation Processes (AOP) have obtained large applicative use for the removal of organic pollutants from wastewater. Herein, we discuss a novel bimetal Cu-Mn porous silica-supported Fenton-like AOP catalyst with interparticle mesoporosity working under neutral pH and UV-VIS irradiation (CuMnKIL with Mn/Si = 0.01, Mn/Cu = 0.06). The photocatalyst was prepared via solvothermal synthesis (Mn incorporation into porous silica support) followed by incipient wetness impregnation (Cu loading into Mn containing porous silica support) and was tested for the decomposition of methylene blue as a model dye. Copper addition significantly reduced Mn leaching from the porous silica support (from 60 to 30 %) and functioned also as additional surface adsorption site. CuMnKIL (Mn/Si = 0.01, Mn/Cu = 0.06) showed 20 % higher adsorption and 20 % lower efficiency if compared with MnKIL (Mn/Si = 0.01) in Fenton-like AOP system, however, addition of irradiation (photo-Fenton-like system) improved efficiency of Cu/MnKIL (Mn/Si = 0.01, Mn/Cu = 0.06) for 10 % if compared to MnKIL (Mn/Si=0.01) due to the additional •OH radicals produced by the decomposition of H2O2 by the light. No synergistic effects between Cu and Mn were recorded, meaning that Cu and Mn sites were acting as separate sites, which was confirmed with AR-TEM imaging as well as UV spectroscopy studies.

Pd based in situ AOPs with heterogeneous catalyst of FeMgAl layered double hydrotalcite for the degradation of bisphenol A and landfill leachate through multiple pathways.

In situ degradation of organic contaminants by Pd and electro-generated H2 and O2 overcomes the drawbacks to traditional Fenton process, and conducting heterogeneous catalyst of FeMgAl layered double hydrotalcite (LDH) further improved the efficiency and stability. Using bisphenol A (BPA) as the model contaminants, 90% removal can be achieved with 1200mg/L Pd/Al2O3 and FeMgAl-2. The reusability was satisfying due to the very limited leaching of Fe ions at 0.1ppm level. FeMgAl also amplified the window of pH for Pd-catalyzed in situ advanced oxidation processes (AOPs) from 3 by homogenous Fe(II) to 3-7 by FeMgAl LDH. The COD of landfill leachate effluent of the MBR system removed by about 52.3% by this system by the initial pH was 5. Characterizations revealed the distinguishing features associated with LDH structure such as large surface area, good stability, basic character, and strong linage among active sites were accounted for the remarkable performances over a wide pH window. Five reactive intermediates were observed and multiple degradation pathways were proposed in Pd-catalyzed in situ AOP for the first time. Interestingly, because of the unique role of Pd catalyst, these degradation pathways were clearly distinguished from traditional Fenton or Fenton-like AOPs and may provide a new approach of in situ heterogeneous AOPs for refractory contaminants in future.

Ferrous ions reused as catalysts in Fenton-like reactions for remediation of agro-food industrial wastewater

Cassava is the most important tuberous root in tropical and subtropical regions of the world, being the third largest source of carbohydrates. The root processing is related to the production of starch, an important industrial input, which releases a highly toxic liquid wastewater due to its complex composition, which inhibits high performances of conventional effluent treatments. This study aims to evaluate Fenton-like and photo-Fenton-like reactions for treatment of cassava wastewater, reusing ferrous ions from the preliminary coagulation stage. Pre-treated cassava wastewater was submitted to oxidation in three variations of hydrogen peroxide concentrations, with more relevant analytical responses verified in color, turbidity, COD (Chemical Oxygen Demand), and acute toxicity in Artemia salina, besides the action of radicals during Fenton-like reactions. At higher peroxide concentrations, a decrease of 68% in turbidity and 70% in COD on the photo-Fenton-like system was observed, even at slow reaction rates (fastest rate constant k = 2 × 10−4 min−1). Inclusion of UV increases the viability of the Fenton-like reactions by supplementing the reaction medium with hydroxyl radicals, verified by the tert-butanol tests. The oxidation process leads to high EC50 values in 24 h of incubation in Fenton-like reactions and 48 h in photo-Fenton-like reactions. Final COD and turbidity suggests that the reuse of iron, which remains in the preliminary treatment step shows a great potential as a catalyst for Fenton-like advanced oxidation processes. Tertiary treatment can be less expensive and harmful to the environment, reducing production of residual sludge and metal content in the final effluent, which reduces polluting potential of the effluent regarding solid waste.

Heterogeneous Degradation of Dyes in Industrial Effluent over Fenton-Like Nano-Fe<sub>2</sub>O<sub>3</sub>/Goldmine Complex

Nano-Fe2O3/goldmine complex was obtained by chemical coprecipitation reaction on the surface of goldmine waste-solid. Being used as the heterogeneous catalyst in Fenton-like advanced oxidation processes (AOPs), its treatment effect was studied in the removal performance of industrial dyes effluent. Although the maximal COD removal efficiency would reach 35.4% when 5 mL NaClO was added in 100 mL industrial dyes effluent, it is found that by using nano-Fe2O3/goldmine system, the COD removal efficiency of 13,000 mg/L dyes wastewater could reach up to 75.5% in the presence of 30 g/L nano-Fe2O3/goldmine complex and 50 mL/L NaClO at 50。C.

Effect of Nano-Fe<sub>2</sub>O<sub>3</sub>/Goldmine Complex on Dyeing Wastewater Treatment

Nano-Fe2O3/goldmine complex was obtained by chemical coprecipitation on the surface of goldmine waste-solid. And its application as the heterogeneous catalyst in Fenton-like advanced oxidation processes (AOPs) was discussed for the degradation of dyeing wastewater. It was found that advanced oxidation processes play an important role to the removal of dyeing wastewater. And the best removal rate of 15400mg/L dyeing wastewater reached up to 63.1% with the presence of 50g/L dosage of nano-Fe2O3/goldmine complex and 50mL/L concentration of H2O2 at 50°C with pH=3.

Efficient Adsorption and Combined Heterogeneous/Homogeneous Fenton Oxidation of Amaranth Using Supported Nano-FeOOH As Cathodic Catalysts

Iron oxyhydroxide (FeOOH) as heterogeneous catalyst has been widely used in Fenton-like advanced oxidation processes due to its attractive properties such as wide-operating pH range and controllable iron leaching into solution. However, little is known about the Fe3+/Fe2+ transformation of supported FeOOH catalyst under the external electrical field condition, which is of the essence in electro-Fenton-like oxidation reactions. In this study, activated carbon-supported nano-FeOOH (FeOOH/AC) catalysts were prepared by the air oxidation of ferrous hydroxide suspension method. The as-prepared catalyst was characterized with various characterization techniques and identified as goethite and lepidocrocite mixed crystals. Adsorption and electrochemically assisted oxidation of amaranth with the FeOOH/AC heterogeneous catalysts were investigated at pH 4.0 using graphite felt as cathode. Under weak acidic and external electric field conditions, the supported nano-FeOOH catalyst undergoes proton-promoted dissolution and electrochemical reductive dissolution processes, which facilitates Fe3+/Fe2+ transformation and produces a beneficial enhancement of the heterogeneous/homogeneous electro-Fenton reaction rates. Experimental results demonstrated that the FeOOH/AC heterogeneous catalyst possesses admirable adsorbability, and the electrochemically assisted oxidation of amaranth takes place not only through the heterogeneous Fenton reaction on catalyst/solution interface but also through the homogeneous Fenton reaction in bulk solution due to iron liberation from the supported nano-FeOOH. In addition, a possible electrochemically assisted oxidation mechanism is also proposed.

Degradation of domoic acid toxin by UV-promoted Fenton-like processes in seawater

Domoic acid ([2 S-[2α,3β,4β(1 Z,3 E,5 S*)]]-2-carboxy-4-(5-carboxy-1-methyl-1,3-hexadienyl)-3-pyrrolidineacetic acid, DA), a harmful algal toxin produced by several microorganisms genus involved in red tides, was tested for degradation in de-ionized and synthetic sea water using Fenton and Fenton-like advanced oxidation processes (AOPs). Four different AOPs—Fenton, photo-Fenton, cobalt/peroxymonosulfate and cobalt/peroxymonosulfate/UV—were tested. Cobalt/PMS/UV demonstrated the highest initial reaction rate when compared with the other oxidation processes tested. Results obtained from tests performed in synthetic sea water were similar for the case of Co/PMS/UV process whereas important decrease in degradation reaction rate was observed for photo-Fenton reaction probably due to the formation of chlorine–Fe 2+ or sulfate–Fe 2+ complexes.

Degradation of sodium dodecyl sulphate in water using solar driven Fenton-like advanced oxidation processes

Synthetic wastewater samples containing a model surfactant were treated using two different Fenton-like advanced oxidation processes promoted by solar radiation; the photo-Fenton reaction and Co/PMS/UV processes. Comparison between the different experimental conditions was performed by means of the overall surfactant degradation achieved and by obtaining the initial rate in the first 15 min of reaction (IR 15). It was found that, for dark Fenton reaction, the maximum surfactant degradation achieved was 14% under low iron and oxidant concentration. Increasing Fenton reagents by one magnitude order, surfactant degradation achieved 63% in 60 min. The use of solar radiation improved the reaction rate by 17% under same conditions and an additional increase of 12.5% was obtained by adjusting initial pH to 2. IR 15 values for dark and irradiated Fenton reactions were 0.143 and 0.154 mmol/min, respectively, for similar reaction conditions and this value increased to 0.189 mmol/min when initial pH was adjusted. The use of the Co/PMS system allow us to determine an increase in the degradation rate, for low reaction conditions (1 mM of transition metal; 4 mM oxidant) similar to those used in dark Fenton reaction. Surfactant degradation increased from 3%, for Fenton reaction, to 44.5% in the case of Co/PMS. When solar irradiation was included in the experiments, under same reaction conditions described earlier, surfactant degradation up to 64% was achieved. By increasing Co/PMS reagent concentration by almost 9 times under irradiated conditions, almost complete (>99%) surfactant degradation was reached in 5 min. Comparing IR 15 values for Co/PMS and Co/PMS/UV, it allow us to observe that the use of solar radiation increased the degradation rate in one magnitude order when compared with dark experiments and further increase of reagent concentration increased reaction rate twice.

Degradation of atrazine using solar driven fenton-like advanced oxidation processes

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) was degraded using cobalt-peroximonosulfate (Co/PMS) advanced oxidation process (AOP). Three Co concentrations (0.00, 0.25 and 0.50 mM) and five peroximonosulfate (PMS) concentrations (0, 5, 8, 16 and 32 mM) were tested. Maximum degradation reached was 88% using dark Co/PMS in 126 minutes when 0.25 mM of cobalt and 32 mM of PMS were used. Complete atrazine degradation was achieved when the samples were irradiated by the sun under the same experimental conditions described. Tests for identification of intermediate products allowed identification and quantification of deethylatrazine in both dark and radiated conditions. Kinetic data for both processes was calculated fitting a pseudo-first order reaction rate approach to the experimental data. Having kinetic parameters enabled comparison between both conditions. It was found that the kinetic approach describes data behavior appropriately (R2 ≥ 0.95). Pseudo-kinetic constants determined for both Co/PMS processes, show k value of 10−4 for Co/PMS and a k value of 10−3 for Co/PMS/ultraviolet (UV). This means, that, with the same Co/PMS concentrations, UV light increases the reaction rate by around one order of magnitude than performing the reaction under dark conditions.