Combined Advanced Oxidation Research Articles

Synergistic effects of peroxydisulfate on UV/O3 process for tetracycline degradation: Mechanism and pathways

Tetracycline (TC) as a typical emerging pollutant is becoming a serious threat to the environment and human health. A combined advanced oxidation technology of UV/Ozone (O3)/peroxydisulfate (PDS) process was developed to explore an efficient and economic treatment process of TC in wastewater. Furthermore, the reactive sites and transformation pathways of TC were explored and the toxicity of the intermediates was quantified with a quantitative structure-activity relationship (QSAR) assessment. The degradation performance of TC was substantially enhanced in UV/O3/PDS process with a kobs of 0.0949 min−1, which was 2.3 times higher than UV/O3 and 3.2 times than sole UV. The results demonstrated that there was a superior synergistic effect of PDS on UV/O3 processes for the degradation of TC. Electron paramagnetic resonance (EPR) analysis and quenching experiments show that •OH, SO4•−, O2•− and 1O2 all contributed to TC degradation in the UV/O3/PDS process and exhibited a synergistic effect, which inhibited the generation of harmful products. In addition, the UV/O3/PDS system can effectively degrade TC in a wide range of substrate concentrations and pH, and also showed excellent adaptability to various concentrations of anions (Cl− and HCO3−). This study proves the feasibility of UV/O3/PDS process for treating TC contaminated wastewater with complicated water matrix.

고도산화기술을 적용한 실내공간 휘발성유기화합물 분해 연구

고도산화기술을 적용한 실내공간 휘발성유기화합물 분해 연구

Sonochemical synthesis of Ce-TiO2 nanocatalyst and subsequent application for treatment of real textile industry effluent

Treatment of real textile industry effluent using photocatalysis, sonocatalysis, sonophotocatalysis and H2O2 assisted sonophotocatalysis have been studied based on the use of Ce-TiO2 nanocatalyst synthesized using sonochemical co-precipitation method. Characterization studies of the obtained catalyst revealed crystallite size as 1.44 nm with particles having spherical morphology. A shift of the absorption edge to the visible light range was also observed in UV–Vis diffuse reflectance spectra (UV-DRS) analysis. The effects of different operational parameters viz catalyst dose (0.5 g/L-2 g/L), temperature (30 °C-55 °C) and pH (3–12) on the COD reduction were studied. The reduction in the COD was higher at lower pH and the optimum temperature established was 45 °C. It was also elucidated that the required catalyst dose was lesser in combined sonophotocatalysis when compared with individual photocatalysis and sonocatalysis. Combination of processes and addition of oxidants increased the COD reduction with the sonophotocatalytic oxidation combined with H2O2 treatment showing the best results for COD reduction (84.75%). The highest reduction in COD for photocatalysis was only 45.09% and for sonocatalysis, it was marginally higher at 58.62%. The highest reduction in COD achieved by sonophotocatalysis was 64.41%. Toxicity tests coupled with Liquid Chromatography Mass Spectrometry (LC-MS) analysis revealed that there were no additional toxic intermediates added to the system during the treatment. Kinetic study allowed establishing that generalized kinetic model fits the experimental results well. Overall, the combined advanced oxidation processes showed better results than the individual processes with higher COD reduction and lower requirement of the catalyst.

Ultrasound-Promoted Abatement of Formaldehyde in Liquid Phase with Electrospun Nanostructured Membranes: The Synergy of Combined AOPs.

The present work investigates the effect of ultrasounds in the performance of combined advanced oxidation processes (AOPs) on the degradation of formaldehyde (HCHO)-polluted aqueous solutions for potential application in wastewater treatment. Different heterogeneous nanostructured catalysts based on TiO2 and FeSO4 for photocatalysis and the Fenton process were employed after electrospray deposition on electrospun nanofibrous membranes. Such systems were tested, without the use of any added hydrogen peroxide, by varying the combinations among the selected AOPs in a batch reactor configuration. The results show that, in the absence of a Fenton reaction, ultrasounds provided a significantly increased formaldehyde photocatalytic abatement, probably by increasing the concentration of active species through a different set of reactions while providing a favorable mass transfer regime by the cavitational effect. Due to the faster kinetics of the photo-Fenton process, thanks to its partial homogeneous nature, such a beneficial effect is more limited for the sono-photo-Fenton configuration. On the other hand, the employment of a sono-photocatalytic-Fenton process revealed a synergic effect that provided the best results, reducing the formaldehyde concentration to less than 99% after 240 min. Further analysis showed that, due to a mutual influence, only a tailored TiO2/FeSO4 ratio on the membranes was able to display the best performance.

Advanced oxidation processes in the treatment of corn stalks

The depletion of fossil fuel reserves and severe environmental damage, resulting in climate change and global warming lead to a necessary shift to alternative renewable resources. Lignocellulose is a valuable feedstock for biorefineries, but its conversion is hindered by the limitations of conventional pretreatments lacking selectivity. This step should also be cost-effective and sustainable. In this paper, combined advanced oxidation techniques were applied for the treatment of corn stalks as a pretreatment for enzymatic hydrolysis. Their effect on delignification and cellulose digestibility was monitored. The combined non-thermal plasma/Fenton treatment appears to be suitable for breaking the complex lignocellulose structure, with a lignin content decrease of 39%. This treatment enhanced carbohydrate hydrolysis, resulting in 2.25 times increase in hexose yield, compared to the untreated sample. Long-term plasma treatment positively affected the textural properties, total porosity, and pore size diameter, of lignocellulose biomass. It enables the creation of materials with a stable system of pores and channels, for the unhindered diffusion of large organic molecules such as enzymes. Additionally, a combination of plasma treatment with Fenton reaction increased selectivity towards lignin degradation in comparison to independently applied Fenton treatment. This could be a significant advantage for a bottleneck in the current valorization of biomass.

Degradation of methylene blue by an E-Fenton process coupled with peroxymonosulfate via free radical and non-radical oxidation pathways

This paper reports a combined advanced oxidation process to degrade methylene blue and investigates its oxidation mechanism and degradation pathway.

Zero valent iron-electro-Fenton-peroxymonosulfate (ZVI-E-Fenton-PMS) process for industrial wastewater treatment.

Advanced oxidation processes are frequently applied to a variety of refractory organic wastewater, but rarely is electro-Fenton combined with activated persulfate technology applied to the removal of refractory pollutants. In this work, the electro-Fenton process was combined with zero-valent iron (ZVI) activated peroxymonosulfate (PMS), two advanced oxidation processes based on different radicals, to form the ZVI-E-Fenton-PMS process to treat wastewater, whose main advantages are the generation of more reactive oxygen species and the reduction of oxidant cost to achieve rapid removal of pollutants. This process can not only produce H2O2 and activate PMS at the cathode, but also reduce Fe(iii) to realize the sustainable Fe(iii)/Fe(ii) redox cycle. The main reactive oxygen species in the ZVI-E-Fenton-PMS process were found to be ˙OH, SO4˙- and 1O2 by radical scavenging experiments and electron paramagnetic resonance (EPR), and the relative contributions of the three reactive oxygen species for the degradation of MB were estimated to 30.77%, 39.62% and 15.38%, respectively. Then, by calculating the ratio of the relative contributions of each component to the removal of pollutants at different PMS doses, it was found that the synergistic effect of the process was better when the proportion of ˙OH in the oxidation of reactive oxygen species (ROS) was higher and the proportion of non-ROS oxidation increased year-on-year. This study provides a new perspective on the combination of different advanced oxidation processes and reveals the advantages and potential of this process for application.

Removal of 4-nonylphenol in activated sludge by peroxymonosulfate activated with sorghum distillery residue-derived biochar

The presence of 4-nonylphenol (4-NP), an endocrine disrupting chemical, waste activated sludge (WAS) or biosolids at elevated content requires effective method for 4-NP reduction in total sludge management. Herein, sorghum distillery residue-based biochar-activated peroxymonosulfate (SDRBC/PMS) system was studied as pretreatment of WAS. Results indicated 91% of 4-NP removal at pH 6.0 in the presence of 3.1 × 10−6 M and 0.8 g L−1 PMS and SDRBC500, individually. The synergetic effects of singlet oxygen (1O2) and the abundant functional sites (C = O/C–O content) of SDRBC significantly improved 4-NP degradation. The decreased fluorescent dissolved organic matter (DOM) in the sludge also enhanced the pretreatment efficiency. Moreover, the enrichment of the Nitrospira functional bacteria in the microbial community yielded the highest 4-NP degradation in the SDRBC/PMS-pretreated sludge. The SDRBC/PMS system functions mainly via nonradical-mediated oxidation pathway in pretreating WAS in particular and potentially by combined advanced oxidation and biodegradation processes for wastewater treatment in general.

Treatment of Wastewater Containing New and Non-biodegradable Textile Dyes: Efficacy of Combined Advanced Oxidation and Adsorption Processes

Treatment of Wastewater Containing New and Non-biodegradable Textile Dyes: Efficacy of Combined Advanced Oxidation and Adsorption Processes

O3/H2O2 and UV-C light irradiation treatment of oil sands process water

The oil sands industry generates large volumes of oil sands process water (OSPW). There is an urgent need for OSPW treatment to reduce process water inventories and to support current reclamation approaches. This study discusses how efficient ozone (O3)-based combined advanced oxidation processes (AOPs), including hydrogen peroxide (H2O2) and UV-C, are at achieving mineralization while reducing the toxicity arising from such organic components as naphthenic acids (NAs) in OSPW. The results showed that the dissolved organic carbon (DOC) removals of 45%, 84%, 84% and 98%, obtained after 90-min treatments with O3, O3/H2O2, UVC/O3 and UVC/O3/H2O2, respectively, at a production rate of 6 g/L·h O3 were considerably higher than at lower O3 production rates. The acute toxicity on Vibrio fischeri was significantly reduced by all the treatments, which explains the high percentages of NA removal (up to 99% as confirmed by UPLC-QTOF-HRMS.) Mineralization (expressed as DOC removal) was highest with UVC/O3/H2O2 at ca. 2 mg C/L in the treated effluent, which means that it could be used as cooling/boiling process water in bitumen upgrading units. However, considering the energy demand of the treatments tested, the treatment using O3/H2O2 was found to be the most realistic for large-scale applications.

Pilot-scale and mechanistic study of the degradation of typical odors and organic compounds in drinking water by a combined UV/H2O2-BAC process

Odor problems are challenging issues in water treatment. Advanced oxidation has a significant degradation effect on these odors; however, some issues, such as oxidant residues and disinfection byproducts, exist in the use of advanced oxidation in actual water treatment. Because of the above issues, a combined advanced oxidation process has emerged—the UV/H2O2 -biological activated carbon (BAC) process can play a strong oxidizing role in advanced oxidation and uses the physical adsorption and biological effects of activated carbon. However, there have been few studies on the odor degradation mechanism and characteristics of activated carbon biofilms in actual water treatment. This paper systematically studied the organic and odor substances removal effects and mechanism of a pilot combined UV/H2O2-BAC process. The results showed that UV/H2O2-BAC technology had a good removal effect on odor substances under long-term stable operation. The concentrations of geosmin (GSM) and 2-methylisoborneol (2-MIB) after systemic treatment were below 5 ng/L. The removal rates of DOC, UV254 and H2O2 by the combined process were 53.60%, 73.08% and 60.20%, respectively. The results of full-scan determination of GSM and 2-MIB degradation by gas chromatography–mass spectrometry (GC–MS) were consistent with those of front-track analysis. The diversity, richness and evenness of microorganisms in the lower activated carbon layer were higher than those in the middle and upper activated carbon layers. The greater the difference in the carbon layer height was, the greater the difference in the biological community structure.

Treatment and valorization of municipal solid waste gasification effluent through a combined advanced oxidation – microalgal phytoremediation approach

Liquid effluents generated during the gasification process of municipal solid wastes (MSW) represent highly heterogenous and recalcitrant substrates, and thus require energy-intensive treatments prior to their discharge into the environment. However, these streams represent untapped carbon sources which can be converted, under the right conditions, to platform molecules, decreasing thus the elevated costs of current mitigation approaches. Thus, the present study describes a novel two-step chemical and biological effluent treatment process which co-generates microalgal biomass containing valuable functional components. The detoxification potential of ozone, ultrasonication and a combination of both of these advanced oxidation processes (AOPs) were initially evaluated using wastewater generated from scrubbing primary syngas produced from the gasification of MSW. The pretreated effluents were subsequently used to cultivate Chlorella vulgaris microalgae under various illumination (light/dark cycles of 24h/0h, 12h/12h and 0h/24h) and nutrient (supplementation of yeast extract) regimes, in order to assess their potential to further convert the remaining carbon into value-added functional biomolecules, such as photosynthetic pigments. The use of ozone, either individually or combined with ultrasounds, showed the best performances for the substrate detoxification prior to the biological treatment step. It was determined that 20 min of oxidative reaction using ozone coupled with ultrasounds was sufficient to degrade up to 70% of the total phenol compounds, 64% of the COD, and 75% of the color initially present in the gasification wastewater. The further microalgal phytoremediation and conversion experiments showed that 12 h of illumination per day, together with 0.5 g/L of yeast extract, generated the highest microalgae growth rate (0.29 d−1), biomass productivity (244 mg/L/d), photosynthetic pigment accumulation (12.0 and 4.5 mg/L of total chlorophyll and carotenoids, respectively) as well as total carbon removal (57 %). Therefore, the combination of AOPs with mixotrophic cultivation of C. vulgaris demonstrates for the first time an alternative to current treatment strategies of highly-recalcitrant industrial wastewaters, which includes the further valorization of the carbon available in these streams.

Degradation of chloramphenicol in water by oxidation on a boron-doped diamond electrode under UV irradiation

A combined advanced oxidation process based on the electrochemical oxidation of chloramphenicol (CHL) on a boron-doped diamond (BDD) electrode under UV irradiation was investigated. The influence of the main process parameters (current density, pH, temperature, and chloride concentration) on CHL degradation and mineralization was assessed. An estimation of the energy consumption required to mineralize CHL was also made.The results showed that CHL can be completely degraded and extensively mineralized by 3-h UV-assisted anodic oxidation on BDD. The process can be further accelerated by chlorides, as these species act as precursors for the photo-induced formation of radical species contributing to CHL oxidation. Under optimal conditions (300 mA m–2, 0.01 M NaCl, ambient temperature, and pH 10), complete CHL removal occurred after 150 min of treatment, and approximately 95 % mineralization was achieved in 180 min.Overall, the results obtained suggest that the investigated process may represent a promising approach to treat wastewaters containing CHL or other recalcitrant antibiotics.

Fenton/ozone-based oxidation and coagulation processes for removing metals (Cu, Ni)-EDTA from plating wastewater

Wastewater containing heavy metals has caused many serious problems to land and marine environments. These heavy metal-laden wastewaters containing organic complexing agents are the consequence of using large-scale industrial applications for dissolving metals. Ethylenediaminetetraacetate (EDTA) is a widely used complexing agent in plating, metal finishing and chemical cleaning industries. However, due to the dramatic increase in the solubility of metal ions, EDTA has negative impact on heavy metals removed in wastewaters by conventional precipitation processes. This study aims to find the optimal conditions of combined/hybrid process of advanced oxidation and coagulation to treat metals-EDTA containing Cu, Ni plating wastewater from an electroplating manufacturer in Vietnam. The effects of pH, H2O2 dose, Fe2+ dose, ozone, reaction time and poly acrylic acid (PAA) dose were investigated. Results indicated that the 3-stage treatment process at the optimal conditions could remove 99.7 % of Ni and 99.72 % of Cu. The effluent of wastewater after the whole treatment process met the Vietnamese national regulation on industrial wastewater (QCVN 40:2011/BTNMT) for NH4+, Cu and Ni at column A and COD at column B. In short, the combined advanced oxidation processes and coagulation/flocculation could successfully be applied for plating wastewater treatment.

The coupling use of electro-chemical and advanced oxidation to enhance the gaseous elemental mercury removal in flue gas

A novel diffusion electro-chemical combined advanced oxidation reactor offers potential for elemental mercury (Hg0) removal in flue gas and shown excellent performance. This study introduced an ultraviolet light into the electric catalytic system to form an UV-electric oxidation system to strengthen Hg0 removal. Hg0 removal efficiency in the combined UV-electric oxidation system reached up to 65%. Hg0 is excited by UV lamp with a wavelength of 253.7 nm, and a very small amount of oxygen contained in high-purity nitrogen can still participate in Hg0 oxidation reaction. In addition, the Fenton method has also been introduced into the simple electrolysis system. Both the above combined system can improve the efficiency of Hg0 removal. The electro-chemical GDE was characterized by SEM, BET, and contact angle and gas permeability. The electro-chemical and advanced oxidation process (Fenton method and UV illumination) combined within a system or individually in series were explored the different influencing factors. The gaseous elemental mercury removal mechanism of the combined electro-chemical and advanced oxidation was investigated via combining the experimental data and theoretical reasoning. Electrochemical coupling with other advanced oxidation technologies is a promising technology.

A confined micro-reactor with a movable Fe3O4 core and a mesoporous TiO2 shell for a photocatalytic Fenton-like degradation of bisphenol A

Photocatalysis and Fenton process are two primary and promising advanced oxidation processes to degrade organic pollutants. However, the practical applications of single photocatalysis and Fenton process are still limited. Introducing one of them into another to form a combined photocatalytic Fenton-like system has shown great potential but still faces challenges in designing a well-tailored catalyst. Herein, a confined photocatalytic Fenton-like micro-reactor catalyst with a movable Fe3O4 core and a mesoporous TiO2 shell has been constructed via a successive Stöber coating strategy, followed by an ultrasound assisted etching method. The resulting micro-reactor possesses well-defined yolk-shell structures with uniform mesopores (∼4 nm), a large Brunauer-Emmett-Teller (BET) surface area (∼166.7 m2/g), a high pore volume (∼0.56 cm3/g) and a strong magnetization (∼51 emu/g), as well as tunable reactor sizes (20−90 nm). When evaluated for degrading bisphenol A under solar light in the presence of peroxymonosulfate, the micro-reactor exhibits a superior catalytic degradation performance with a high magnetic separation efficiency and an excellent recycle ability. The outstanding performance can be attributed to its unique textual structure, which leads to a great synergistic effect from the photocatalytic and Fenton-like process. This study gives an important insight into the design and synthesis of an advanced micro-reactor for a combined advanced oxidation processes (AOPs).

A feasibility study on optimization of combined advanced oxidation processes for municipal solid waste leachate treatment

Municipal solid waste (MSW) leachate, mostly comprised of organic and inorganic substances originated from discarded organic matters, chemicals, and liquors at MSW dumpsite. Pollutant composition and toxic compounds of leachate necessitate the effective treatment before its disposal. In the current study, advanced oxidation processes; ozonation, peroxone process and photolytic ozonation were employed for the treatment of complex MSW leachate. Central Composite Design (CCD) of Response Surface Methodology (RSM) was applied to optimize the various operating parameters in the treatment system. The optimized condition of pH: 9.0; contact time: 60 min and Ozone dose: 5 g/h for a litre of leachate provided the maximum COD and NH3–N reduction of 72 % and 80 % respectively for photolytic ozonation (under 15 W–UVC; λ:254 nm) whereas under the same operating conditions, ozonation process provided 45 % of COD removal and 50 % of NH3-N removal. Peroxone process with H2O2 concentration of 800 mg/L, showed the maximum COD and NH3-N removal efficiencies of 61 % and 59.7 % respectively. The developed models have confirmed the interaction between the selected parameters; have good agreement with each other; have the best fit. The present approach provided the knowledge to adopt an efficient way of treatment to the complex MSW leachate to proceed further for pilot-scale treatment.

Degradation of pesticide Cartap in Padan 95SP by combined advanced oxidation and electro-Fenton process

The electro-Fenton process combined with a boron-doped diamond-positive electrode in a one-compartment cell has shown efficient degradation of Cartap (95% in Padan 95SP) by hydroxyl radicals (•OH) generated in the electro-Fenton and the electrochemical oxidation processes. The influence of added NaOCl in a pretreatment step, effects of H2O2 concentration, Fe2+-ion addition, presence of further metals acting as co-catalysts, and solution pH on the efficiency of Cartap degradation were studied. The concentration of Cartap was determined by UV-vis spectroscopy according to the 5,5-dithiobis-(2-nitrobenzoic acid) procedure. The efficiency reaches approximately 80% when measured as total carbon concentration decrease, even with increased concentrations of H2O2, Fe2+, or metal ions added as co-catalyst. This limitation is presumably due to recalcitrant intermediates, which cannot be destroyed by •OH.

Potential of combined advanced oxidation – Biological process for cost-effective organic matters removal in reverse osmosis concentrate produced from industrial wastewater reclamation: Screening of AOP pre-treatment technologies

While reverse osmosis (RO) technology is playing an important role in industrial wastewater reclamation, safe and cost-effective RO concentrate (ROC) disposal becomes challenging due to high levels of organic pollutants. The present study assessed the feasibility of combined advanced oxidation – biological process for organics removal in real ROC. Four advanced oxidation processes (AOPs) were evaluated for ROC pre-treatment, including UV/H2O2, UV/Persulfate (PS), Fenton and Fluidized bed reactor (FBR)-Fenton processes. Based on the results of process optimization and cost evaluation, FBR-Fenton was identified as the most cost-effective pre-treatment technology with a chemical cost of S$0.519/m3. Under the optimum operating conditions with 10 mM H2O2, 1.25 mM Fe2+, pH 3 and HRT of 1 h, continuous FBR-Fenton process increased the BOD5/COD ratios in ROC by 4.2–10.0 times, while the COD removal efficiency was in the range of 30.9–59.8%. A biological activated carbon (BAC) column with EBCT of 120 min was combined with FBR-Fenton for continuous treatment of ROC. Over the 120-day operation, the combined system performed consistent organics removal in ROC with an average COD removal efficiency of 69%. The average effluent COD level in ROC was observed to be 26 mg/L. Both LC-OCD data and fluorescence EEM spectra suggested humic substances to be the dominant organic species in ROC, FBR-Fenton could achieve significant humic substances removal and biodegradability enhancement in ROC. High-throughput sequencing demonstrated Planctomycetes to be top dominant phylum in BAC media with high salinity influent, and FBR-Fenton process promoted its proliferation for higher COD removal efficiency in ROC.

Microbiological evaluation of combined advanced chemical-biological oxidation technologies for the treatment of cork boiling wastewater

This paper contains a multidisciplinary approach that will contribute to design and properly evaluate a treatment line for complex biorecalcitrant wastewaters. To demonstrate this approach a specific industrial wastewater (cork boiling wastewater, CBW) was used. A treatment line based on a coagulation-flocculation step followed by an Advanced Oxidation Process (AOP) (solar photo-Fenton) and combined with an aerobic biological system was evaluated. Applied microbiological techniques: optical microscopy, plate count, DNA extraction and qPCR, indicated that some communities disappeared after the activated sludge adaptation period to the partially treated wastewater, while communities that did not disappear were damaged: 2-log reduction of total heterotrophic bacteria (THB) and a decrease in DNA concentration from 200 ng/μL to 65 ng/μL were observed. Therefore, chemical and microbiological results obtained along the set of experiments, suggested the inefficiency of the combined treatment option between solar photo-Fenton and advanced aerobic biological systems for CBW. This led to the necessity of applying solar photo-Fenton without combining with biotreatment and with the objective of improving the effluent quality enough for being reused in the own industry. Toxicity tests, based on different organisms (after coagulation-flocculation followed by solar photo-Fenton), showed increase on acute toxicity (from 46% to 71% by respirometric assays) and the development of chronic toxicity (from 21–29% to 83–90% also measured by respirometric assays), made evident the incompatibility of this type of wastewater with a biological treatment even after the application of an AOP.