Abstract Advanced Oxidation Processes Research Articles

Waste eggshell-supported CuO used as heterogeneous catalyst for reactive blue 19 degradation through peroxymonosulfate activation (CuO/eggshell catalysts activate PMS to degrade reactive blue 19).

Advanced oxidation processes play an important role in the removal of organic pollutants from wastewater, in which it is essential to develop an eco-friendly, effective, stable, and inexpensive catalyst. Herein, waste eggshell-supported copper oxide (CuO/eggshell) was synthesized via a facile method and employed as peroxymonosulfate (PMS) activator for the elimination of reactive blue 19 (RB19). CuO/eggshell exhibited high degradation efficiency of RB19 (approximately 100%) by activation of PMS under the optimum conditions of 20 mg/L RB19, 0.2 g/L CuO/eggshell, 0.36 mM PMS, and initial pH 7.12 within 20 min. In addition, the effects of catalyst dosage, PMS concentration, initial pH, inorganic ions, and humic acid on RB19 degradation were investigated. Scavenging experiments and electron paramagnetic resonance revealed that multiple reactive oxygen species, including sulfate radicals (SO4·-), hydroxyl radicals (·OH), superoxide radicals (O2·-), and singlet oxygen (1O2), contributed to RB19 degradation, and 1O2 played a dominant role. Finally, a possible PMS activation mechanism was proposed. This study suggests that loading catalytically active components onto waste eggshell is eco-friendly and effective for enhancing the degradation of dyes from wastewater.

Comparison of reactive azo dye removal with UV/H2O2, UV/S2O82- and UV/HSO5- processes in aqueous solutions.

Advanced oxidation processes (AOPs) are an effective choice for removal of reactive azo dyes used in the textile industry due to high solubility and low degradability. Within the scope of this study, reactive orange 122 (RO122) azo dye was removed using the UV-based AOPs of ultraviolet (UV) radiation, UV/hydrogen peroxide (UV/H2O2), UV/persulfate (UV/S2O82-), and UV/peroxymonosulfate (UV/HSO5-). Oxidant concentration, initial solution pH, initial RO122 concentration, different anions (Cl-, NO3- and SO42-), and solution temperature effects were compared. With only UV radiation (254nm), 19.5% RO122 removal occurred at the end of 120min. The RO122 removal reduced with the UV/oxidant processes at pH 9. Experimental results revealed RO122 removal followed pseudo-first-order (PFO) kinetics. There was a linear correlation identified between initial oxidant concentration and the PFO kinetic rate constant (k1). Among the three UV-based processes, with oxidant concentration 50mg/L, temperature 20°C, and pH 5, RO122 removal efficiency was in the order UV/H2O2 > UV/HSO5- > UV/S2O82-. RO122 removal rate increased as initial oxidant concentration and temperature increased and reduced as initial RO122 concentration increased. Energy requirements and oxidant costs were assessed. The UV/H2O2 process was concluded to be the most efficient and economic process for RO122 removal.

Review: Clay-Modified Electrodes in Heterogeneous Electro-Fenton Process for Degradation of Organic Compounds: The Potential of Structural Fe(III) as Catalytic Sites.

Advanced oxidation processes are considered as a promising technology for the removal of persistent organic pollutants from industrial wastewaters. In particular, the heterogeneous electro-Fenton (HEF) process has several advantages such as allowing the working pH to be circumneutral or alkaline, recovering and reusing the catalyst and avoiding the release of iron in the environment as a secondary pollutant. Among different iron-containing catalysts, studies using clay-modified electrodes in HEF process are the focus in this review. Fe(III)/Fe(II) within the lattice of clay minerals can possibly serve as catalytic sites in HEF process. The description of the preparation and application of clay-modified electrodes in the degradation of model pollutants in HEF process is detailed in the review. The absence of mediators responsible for transferring electrons to structural Fe(III) and regenerating catalytic Fe(II) was considered as a milestone in the field. A comprehensive review of studies investigating the use of electron transfer mediators as well as the mechanism behind electron transfer from and to the clay mineral structure was assembled in order to uncover other milestones to be addressed in this study area.

Design of Polymer-Embedded Heterogeneous Fenton Catalysts for the Conversion of Organic Trace Compounds

Advanced oxidation processes are the main way to remove persistent organic trace compounds from water. For these processes, heterogeneous Fenton catalysts with low iron leaching and high catalytic activity are required. Here, the preparation of such catalysts consisting of silica-supported iron oxide (Fe2O3/SiOx) embedded in thermoplastic polymers is presented. The iron oxide catalysts are prepared by a facile sol–gel procedure followed by thermal annealing (calcination). These materials are mixed in a melt compounding process with modified polypropylenes to stabilize the Fe2O3 catalytic centers and to further reduce the iron leaching. The catalytic activity of the composites is analyzed by means of the Reactive Black 5 (RB5) assay, as well as by the conversion of phenol which is used as an example of an organic trace compound. It is demonstrated that embedding of silica-supported iron oxide in modified polypropylene turns the reaction order from pseudo-first order (found for Fe2O3/SiOx catalysts), which represents a mainly homogeneous Fenton reaction, to pseudo-zeroth order in the polymer composites, indicating a mainly heterogeneous, surface-diffusion-controlled process.

Special Issue: Application of Advanced Oxidation Processes

Advanced oxidation processes (AOPs) are nowadays not only considered as a complementary treatment option but as an attractive alternative to conventional methods [...]

Enhanced mineralization of Reactive Black 5 by waste iron oxide via photo-Fenton process

Advanced oxidation process is a promising technology for the treatment of azo dye wastewater, owing to its high degradation performance and less secondary contamination. Herein, the mineralization of azo dye Reactive Black 5 (RB5) by the heterogeneous photo-Fenton process was investigated in a three-phase fluidized bed reactor. The waste iron oxide (denoted as BT) obtained from tannery wastewater process with Fenton’s reagent was selected as a heterogeneous catalyst. The introduction of BT to the UV/H2O2 process (UV/H2O2/BT) shows obviously higher mineralization efficiency because ferric complexes of carboxylic acid, the degradation intermediates of RB5, could be readily decomposed by UV irradiation. The decolorization was achieved by homogenous photo-Fenton reaction induced by leached iron, while the mineralization was contributed to heterogeneous oxidation. Under the conditions of 254 nm UV irradiation, 19.00 mM H2O2, 2.0 g L–1 catalyst loading and natural pH0 of 5.0, 90.2% TOC removal of RB5 could be achieved. The catalyst indicated an acceptable stability and reusability after four cycles. The proposed heterogeneous photo-Fenton process with stable performance is environmental-friendly for the mineralization of RB5.

Understanding the by-product formation potential during phenol oxidation from in-situ electro-generated radicals by microalgae harvesting

ABSTRACT Advanced oxidation processes have gained colossal attention owing to the prospect of accessible mineralization, but by-product formation and its toxicity evaluation are still inconclusive. The present study demonstrated the performance of electrochemical oxidation process supported with graphite electrodes for the oxidation of phenol from modulated coke oven wastewater. The results suggested that the hydrogen peroxide along with the in-situ synthesized oxidizing agents has the ability to increase the phenol mineralization 1.5 times and by-product toxicity potential on microalgae, Scenedesmus sp. CBIIT(ISM) also revealed that chlorophyll-a synthesis has increased after the electro-oxidation process in coke oven wastewater. The experimental results for phenol mineralization and by-product formation were validated using a mass spectrophotometer.

Identification of Degradation By-Products of Selected Pesticides During Oxidation and Chlorination Processes

Abstract Advanced oxidation processes (AOPs) are considered to be one of the most effective methods for the decomposition of a wide range of hardly-biodegradable organic compounds, including pesticides. The implementation of such processes in the water streams treatment often leads to the formation of decomposition by-products of micropollutants occurring in water. These compounds, even in concentrations of a few ng/dm3, may negatively affect the water quality. Therefore, there is a need for detailed analyses that will allow to identify intermediates found in the AOP solutions and to assess their impact on the aquatic environment. The paper presents an attempt to identify by-products of three pesticides: triclosan, triallat and oxadiazon during ozonation, chlorination and UV irradiation of their water solutions. The identification of compounds was performed based on the results of the GC-MS analysis using the NIST v17 mass spectral library. It has been shown that during all of tested advanced oxidation processes, incomplete degradation of pesticides occurs. The number of micropollutant decomposition by-products increases with the increase of the applied ozone dose and UV exposure time. During the chlorination process Cl− atoms were added to the tested compound molecules. In the case of triclosan, it led to the generation of compounds containing four or five chlorine atoms in their structure. The toxicological analysis performed by the use of the Microtox® and Lemna sp. Growth Inhibition Test showed the toxic nature of post-process solutions. The decomposition by-products of triclosan and triallate, generated during the UV irradiation process, were highly toxic against the test organisms (toxic effect > 75 %). This makes it impossible to drain these solutions into the natural environment.

Unsubstituted metallophthalocyanine catalysts for the removal of endocrine disrupting compounds using H2O2 as oxidant

Advanced oxidation processes have become increasingly important to treat non-biodegradable compounds entering environmental waters. In recent decades, water-soluble metallophthalocyanines have been shown to catalyse H2O2-containing oxidation reactions through the production of unique reactive species, nucleophilic metal-peroxo complexes. Few reports in the literature have examined water insoluble metallophthalocyanines (MPc). The oxidative catalytic activity of water insoluble manganese- and iron-phthalocyanine (MnPc, FePc) at pH7 has been shown through the decolourisation of methylene blue and removal of bisphenol A. These studies expand on this previous study, exploring the catalytic activity of a range of metallophthalocyanines catalysts under both acidic and neutral conditions. FePc, while only active under neutral conditions, was the best performing catalyst. This activity was significantly improved upon by the addition of acetonitrile as a co-solvent, as well as increasing the ratio of H2O2 to catalyst. MnPc was catalytically active at both pH3 and 7. FePc and MnPc catalysts showed the ability to remove bisphenol A in the presence of dam water. Reaction rates were reduced for bisphenol A removal with FePc as a catalyst but were unchanged in the presence of MnPc. The removal of 17β-estradiol, estrone, and coumestrol was successfully demonstrated, with greater than 96% removal of all tested EDC's achieved. This is the first reported study showing the removal of the phytoestrogen, coumestrol. Even though considerably lower concentrations of costly catalysts and oxidation reagents were used in our work, the removal extent of EDC's by the MPc-catalysed oxidation reactions achieved here compares favourably with literature.

Co3O4/TiO2 hetero-structure for methyl orange dye degradation.

Advanced oxidation processes based on sulphate radical generated by peroxymonosulphate (PMS) activation is a promising area for environmental remediation. One of the biggest drawbacks of heterogeneous PMS activation is catalyst instability and metal ion leaching. In this study, a simple organic binder mediated route was explored to substitute Ti4+ ions into the Co3O4 host lattice structure to create a Co-O-Ti bond to minimise cobalt leaching during methyl orange degradation. The catalyst was characterised by X-ray diffraction, and scanning and transmission electron microscopy. The as-prepared catalysts with Co3O4:TiO2 ratio of 70:30 exhibited minimal leaching (0.9 mg/L) compared to other ratios studied. However, the pristine Co3O4 exhibited highest catalytic activity (rate constant = 0.41 min-1) and leaching (26.7 mg/L) compared to composite material (70:30 Co3O4:TiO2). Interestingly, the morphology of the composite and leaching of Co2+ ions were found to be temperature dependent, as an optimum temperature ensured strong Co-O-Ti bond for prevention of Co2+ leaching. The classical quenching test was utilised to determine the presence and role of radical species on methyl orange degradation. The fabricated catalyst also exhibited good catalytic activity in degrading mixed dyes and good recyclability, making it a potential candidate for commercial application.

Experimental and theoretical study on chemical reactions and species diffusion by a nano-pulse discharged bubble for water treatment

Advanced oxidation processes using hydroxyl radicals (⋅OH) generated inside bubbles in water has drawn widely interest for the high oxidation potential of OH radical to decompose persistent organic pollutants such as dioxins and humic acid for water purification. In this study, a two-dimensional diffusion model for a nano-pulse discharged bubble in water is established. Based on the experimental results of streamer propagation inside a bubble, the diffusion processes around the bubble interface and reactions of chemical species in liquids are simulated. The simulation results show that OH radicals can diffuse only several micrometers away from the bubble interface in water. Furthermore, the optimal operating voltage and frequency conditions for OH generation is obtained by comparing the OH concentration in water obtained from numerical simulation with that measured by spectroscopy in experiment.

Photocatalytic degradation of Reactive Red 24 in Aqueous Media by Photo-Fenton Reagent

Advanced oxidation processes (AOPs) are widely used for the removal of health hazardous organic pollutants from industrial and municipal wastewater. Reactive Red 24, which has a complex molecular structure with azo aromatic groups, is widely used in textile industry. Degradation of Reactive Red 24 by Photo-Fenton regent has been investigated under irradiation of visible light in aqueous solution. The parameters that influence degradation such as concentration of Reactive Red 24, FeSO4, H2O2, light intensity and pH of the experimental solution were studied. The optimum condition for the photocatalytic degradation of dye was established. The degradation of dye in the dilute solution follows the first order kinetics.

Greener And Expedient Approach for the Wastewater Treatment by Fenton and Photo-Fenton Processes: A Review

Advanced Oxidation Processes (AOPs) have emerged as a promising technology for the treatment of wastewaters containing toxic, recalcitrant organic compounds such as dyes, pesticides etc. This review paper focuses on the Fenton and photo- Fenton technique which is one of the most efficient AOPs developed to decolorize and/or degrade organic pollutants. This oxidation method can produce biodegradable intermediates and mineralize complex organic pollutants effectively and efficiently. In this paper Fenton and photo-Fenton methods are categorised into two broad groups as homogeneous and heterogeneous Fenton and photo-Fenton processes. Applications of fundamental and advanced combined Fenton and photo-Fenton processes are also discussed.

Generation of Hydrogen Peroxide in Gas Bubbles Using Pulsed Plasma for Advanced Oxidation Processes

Advanced oxidation process (AOP) is one of the most effective methods of decomposing persistent organic pollutants in water using OH radicals. The O3/H2O2 method is widely used to form OH radials for AOP; however, this method needs a continuous H2O2 supply. The continuous generation of H2O2 using plasma is appropriate for the O3/H2O2 method, since plasma is readily available anywhere electricity is. This paper presents suitable conditions for pulsed plasma generation in oxygen bubbles for effective and rapid formation of H2O2. The experimental results show that low-voltage-driven and long pulsewidth plasma is best for H2O2 generation. The highest H2O2 generation rate of 61.8 mg/h and energy yield of 2.1 g/kWh were obtained at 2.5-kV voltage, 4-kHz pulse frequency, and 1- $\mu \text{s}$ pulsewidth.

Determinação das condições operacionais para o tratamento terciário de efluente frigorífico pelo processo integrado Fenton Coagulação

Advanced oxidation processes (AOPs) appear to be effective methods for tertiary wastewater treatment because they are able to destroy pollutants and not only transfer them from one phase to another without destroying them as is the case with conventional tertiary processes applied in the slaughterhouse industries. Biological processes are the main

Evaluation of the solar photocatalytic degradation of organochlorine compound trichloroethanoic acid using titanium dioxide and zinc oxide in the Caribbean region

Advanced oxidation processes driven by solar energy can be an efficient method in removing organochlorine compounds from river water especially in tropical environments like the Caribbean region. The feasibility of solar photocatalytic degradation of an organochlorine compound, namely trichloroethanoic acid (TCA), which is commonly used in the Caribbean islands of Trinidad and Tobago, was separately assessed using titanium dioxide and zinc oxide as photocatalysts in suspended solution. Overall the prototype solar photoreactor operated and performed efficiently for the photodegradation of TCA. This study showed that a basic photocatalytic oxidation method for treating water using solar energy as the primary driver gives enhanced decomposition rates of the organochlorine compound when coupled to the additional application of the two separate semiconductor photocatalysts. The results further showed that for varying concentrations of TCA and photocatalysts alike, the organochlorine compound could be completely photocatalytically degraded using short exposure times under the applied influx of solar radiation. This means that this process could be optimised by judicious use of sensors so that dosage rates of the photocatalyst could be altered with variations in influent contamination levels, and the exposure time in the reactor could be altered according to daily variations in solar radiation intensity.

Photocatalytic Degradation of Methyl tert-Butyl Ether (MTBE): A review

Advanced oxidation processes using UV and catalysts like TiO2 and ZnO have been recently applied for the photocatalytic degradation of MTBE in water. Attempts have been made to replace the UV radiation by the solar spectrum. This review intends to shed more light on the work that has been done so far in this area of research. The information provided will help in crystallizing the ideas required to shift the trend from UV photocatalysis to sunlight photocatalysis. The careful optimization of the reaction parameters and the type of the dopant employed are greatly responsible for any enhancement in the degradation process. The advantage of shifting from UV photocatalysts to visible light photocatalysts can be observed when catalysts like TiO2 and ZnO are doped with suitable metals. Therefore, it is expected that in the near future, the visible light photocatalysis will be the main technique applied for the remediation of water contaminated with MTBE.

Integrated Sono-Fenton ultrafiltration process for 4-chlorophenol removal from aqueous effluents: assessment of operational parameters (Part 1)

Advanced oxidation processes (AOPs) and membrane separation processes are successfully used in the final stages of wastewater treatment for recycling and reuse purposes. This research proposes a new two stage process including in the first step a homogeneous Sono-Fenton process (as an AOP), coupled with ultrafiltration (UF), as a cleaner and safer alternative for advanced wastewater treatment, designed specially to enhance the removal of priority organic pollutants which are difficult to eliminate by means of conventional treatments. The aim of this study is to analyze experimentally the performances of an integrated ultrasonication-UF process for the removal of 4-chlorophenol (4CP) (as a model-pollutant for priority organic compounds from wastewaters), both from the removal efficiency (expressed as phenolic concentration and chemical oxygen demand reduction) and the energy consumption point of view. The most important factors with influence on both stages of the proposed process, such as acoustic amplitude, power density, and operating mode for the Sono-Fenton process and pressure, time, operating mode, and cleaning operations for the UF stage, were assessed in this paper (Part 1). The experimental results indicate that the process can be applied for such aqueous effluents, in laboratory scale equipments and represent the basis for modeling the process steps and scale-up of different process arrangements (Cailean et al. (2014): “Integrated Sono-Fenton UF Process for 4CP Removal from Aqueous Effluents: Process Modeling and Simulation (Part 2)”), with the purpose to analyze and control such a process, under various conditions and to understand better its advantages and disadvantages.

Enhanced Transformation of Atrazine by High Efficient Visible Light-Driven N, S-Codoped TiO2Nanowires Photocatalysts

Advanced oxidation process using titanium dioxide as a photocatalyst under solar irradiation is one of the most attractive technologies to eliminate atrazine, an endocrine disrupting and carcinogen contaminant. The N, S-codoped TiO2nanowires at the calcination of 600°C obtained by a facile hydrothermal method revealed the best photocatalytic performance for the degradation of atrazine under visible light irradiation compared to N, S-codoped TiO2nanoparticles and S-doped TiO2nanowires. TOC removal experiment also exhibited the similar result and achieved 63% of atrazine mineralization within 6 h. The degradation of atrazine was driven mainly by•OH and holes during the photocatalytic process. Reactive species quantities such•OH andO2•-generated by N, S-codoped TiO2nanowires under visible light irradiation were much more than those of S-doped TiO2nanowires and N, S-codoped TiO2nanoparticles. These results were mainly attributed to the synergistic effect of N and S doping in narrowing the band gap, remarkable increase in electron-hole separation, extending the anatase-to-rutile transformation temperature above 600°C, and preferentially exposing high reactive{001}crystal facets of anatase.

Using of AOP Process for Phenol Removal from Wastewater

Advanced oxidation processes (AOPs) have been developed as an emerging technology for hazardous organic treatment in industrial wastewater. For phenol removing from wastewater traditional disinfection by chlorine is not appropriate because of generating more toxic pollutants - chlorophenols so AOPs are widely used for disinfection of this kind of water. In this paper for phenol degradation is used physico-chemical method (ozonization). Also influence of catalyst is monitored. As catalyst red mud and black nickel mud are used. These catalysts are waste from metal production. Results from analyses are compared.