Single Ozonation Process Research Articles

Kinetics and mechanism of thiamethoxam abatement by ozonation and ozone-based advanced oxidation processes

In this study, the abatement of neonicotinoid insecticide, thiamethoxam, by single ozonation, ozone/ultraviolet (O3/UV) and electro-peroxone (EP) process was evaluated. The second-order rate constants for the reaction of thiamethoxam with O3 and hydroxyl radical (OH) at pH 7 were determined to be 15.4 M–1 s–1 and 3.9 × 109 M–1 s–1, respectively. The degradation pathways of thiamethoxam were proposed based on quantum chemical calculations and transformation products were identified using chromatographic and mass-spectrometric techniques. The acute and chronic toxicity of thiamethoxam and its major TPs to various aquatic organisms were assessed. With typical ozone doses applied in water treatment (≤5 mg/L), thiamethoxam was abated by only ∼16–32 % in two real water matrices (groundwater and surface water) during single ozonation, but by ∼100 % and >70 % during the O3/UV and EP treatment, respectively. The energy demand to abate 90 % thiamethoxam in the two water matrices was generally comparable for single ozonation and the EP process (∼0.14 ± 0.03 kW h/m3), but higher for the O3/UV process (0.21–0.22 kW h/m3). These results suggest that single ozonation is unable to sufficiently abate thiamethoxam under typical conditions of water treatment. Therefore, ozone-based advanced oxidation processes are needed to enhance thiamethoxam abatement.

Mass transfer and interfacial reaction mechanisms in a novel electro-catalytic membrane contactor for wastewater treatment by O3

The application of ozone (O3) in wastewater treatment is critically limited by O3 mass transfer and oxidation capacity. An electro-catalytic membrane contactor was designed to improve O3 performance in these two aspects simultaneously. Electro-catalytic membrane contact ozonation (ECMCO) has a higher removal rate for nitrobenzene than that of the single membrane contact ozonation and electrolysis process due to the high oxidation potential of hydroxyl free radicals (OH). O2 mass transfer was promoted through the configuration of the composite membrane; O3 mass transfer was dominated by the liquid boundary layer. ECMCO produced more OH than that from other methods, and most of the OH quenched itself instead of reacting with organic compounds due to the poor mass transfer between the electro-catalytic layer and bulk liquid. The oxidation capacity of the ECMCO process was limited, but a composite membrane with high porosity and thin electro-catalytic layer may significantly mitigate these limits.

Rapid and high purification of olive mill wastewater (OMV) with the combination electrocoagulation-catalytic sonoproxone processes

Background and purpose: Olive Mill Wastewater (OMW) is one of the most problematic wastewater in the food industry. Thus, its ineffective treatment causes severe pollution in the environment. In this study, the treatment of OMW by combining electrocoagulation (EC) and catalytic sonoperoxone processes was investigated. Materials and methods: The efficiency of turbidity removal and mineralization of OMW using EC was investigated by applying the following operation variables: type of electrode (iron and aluminum), reaction time (0- 60 min) and current density (0.08�0.77 A/dm 2 ). Then, a single ozonation process (SOP), a catalytic ozonation process (COP), an ultrasonic process (US), H 2 O 2 , COP/US, a peroxone process (H 2 O 2 /O 3 ) and a catalytic sonoperoxone process (H 2 O 2 /COP/US) were performed. Finally, the biodegradability of OMW was measured by using BOD 5 /TOC index. Results: Maximum removal efficiency of the turbidity, Total Organic Carbon (TOC) and consumed electrode in the EC were 82, 75 and 634 mg of iron electrode/L of OMWW, respectively. The TOC removal efficiency of the pretreated OMW by using the following oxidation processes of US, H 2 O 2 , SOP, O 3 /H 2 O 2 , COP, COP/US and H 2 O 2 /COP/US was 8, 15, 20, 25, 61, 68 and 75, respectively. In addition, the biodegradability index (BOD 5 /TOC) in the catalytic sonoperoxone process increased by as much as 32 compared to raw OMWW. Conclusion: The EC process caused an effective per-treatment of OMW and combined by sonoperoxone process improved its biological biodegradability. So, this process can be used for the efficient treatment of OMWW and the wastewater produced by similar industries. © 2019 Taiwan Institute of Chemical Engineers

Degradation of Blue KN-R Dye in Batik Effluent by an Advanced Oxidation Process Using a Combination of Ozonation and Hydrodynamic Cavitation

The popularity of batik has been increasing since it was declared as a world cultural heritage by UNESCO in 2009. Correspondingly, the content of textile dyes in textile industry wastewater is also increased. These dyes contain functional groups which make them quite stable in the environment and causes pollution. In this work, degradation of 100 ppm Blue KN-R has been investigated using ozonation, hydrodynamic cavitation, and a combination of the two for 60 min. The three configuration methods were optimized in terms of different operating parameters, namely flowrate, initial pH and dosage of ozone, to obtain the maximum degradation of Blue KN-R. It was found that the highest decolorization level for a single method was 70.16% for the single ozonation process at pH 11 and 156.48 mg/h of ozone and 1.79% for the single hydrodynamic cavitation process at pH 4. The highest decolorization level was 79.39%, achieved by the combination at pH 11 and 156.48 mg/h of ozone. The mineralization level in the form of a percentage of Total Organic Carbon (TOC) removal by ozonation, hydrodynamic cavitation, and their combination was 14.81, 1.85, and 19.9%, respectively. Due to its better performance, degradation of Blue KN-R was conducted by the hybrid method for 120 min, resulting in 92.63% of decolorization and 24.54% of TOC removal. The degree of synergetic decolorization and mineralization was due to the mechanical and chemical effect of hydrodynamic cavitation in increasing ozone solubility and production of hydroxyl radicals. Degradation of batik effluent has been investigated in optimum conditions for 120 min. The color, COD, BOD, and TSS removal were 67.96, 68.72, 66.54, and 79.84%, respectively.

Mechanism and kinetics of catalytic ozonation for elimination of organic compounds with spinel-type CuAl2O4 and its precursor

CuAl2O4 based mixed oxides were used as heterogeneous catalysts for ozone activation to degrade organics in aqueous solution. The solids were thoroughly characterized by SEM/EDS, N2 physisorption, XRD, FTIR, Pyridine-FTIR, TEM and XPS. We demonstrated that the solid precursor calcined at 300 °C exhibited the best catalytic ozonation activity with respect to CuAl2O4 spinel phase obtained at higher temperatures. Such performance was attributed to the better textural properties and a higher density of active sites (hydroxyl groups and Lewis acidity). Specifically, the mixed oxide/O3 process allows to reach a near complete color removal of the dye solution (100 mg L−1) in 25 min at neutral pH. Corresponding reaction rate value was measured at 0.112 min−1 and was clearly higher compared with the single oxide ozonation process (0.071 min−1 for CuO/O3 and 0.074 min−1 for Al2O3/O3). Then, we proposed that such catalytic performance was related to a synergistic function between ≡Cu2+ and ≡Al3+, which took part of a mechanism of radical formation. In such mechanism, present ≡Al3+ could act as a reservoir for surface active sites such as hydroxyl groups and Lewis acid sites, while ≡Cu2+ could provide the possibility of electron transfer with ozone for the enhancement of radical generation. We suggested that the interaction between chemisorbed ozone and surface hydroxyl groups initially stabilized on ≡Al3+ initiated the generation of reactive radical species. This interaction led as well to the formation of surface adsorbed HO and few O2− on ≡Cu2+ Lewis acid sites. Besides, the interfacial redox reaction with ozone is favored by the presence of ≡Cu2+ following the sequence of ≡Cu2+/≡Cu+/≡Cu2+ redox cycle.

Catalytic ozonation of high concentrations of catechol over TiO2@Fe3O4 magnetic core-shell nanocatalyst: Optimization, toxicity and degradation pathway studies

Abstract TiO2@Fe3O4 magnetic core-shell nanocomposite was coupled with ozone for catalytic ozonation of catechol in a batch environment. The catalyst features were characterized using FE-SEM, EDS, XRD, VSM and TEM techniques. The effect of several operating parameters including solution pH, catalyst loading, initial catechol concentrations and scavengers was assessed in parallel with a single ozonation process (SOP). Possible mechanism, intermediates identification and pathway of degradation were also performed. In all experiments, catalytic ozonation showed better performance, compared to SOP in the degradation and mineralization of catechol. The experimental data were in good agreement with pseudo-first-order kinetic model. Over 99% of catechol were removed by TiO2@Fe3O4/O3 system under optimum conditions within 60 min reaction and the mineralization degree was obtained >91%. The entire degradation of 50, 100 and 250 mg/L concentrations was obtained within 30 min treatment by TiO2@Fe3O4/O3. The bioassay and biodegradability tests indicated that the organic matters were removed effectively by TiO2@Fe3O4/O3 process and the biodegradability indices was improved as well. Particularly, hydroxyl radicals were dominant species during catechol degradation in the catalytic ozonation process. After ten consecutive use cycles, the degradation efficiency was reduced slightly (

Rapid decolorization and mineralization of molasses by catalytic ozonation process with a nanocomposite from fermentation industry wastewater

Molasses is a byproduct of sugar and fermentation factories and a mixture of sucrose with other mono/poly saccharides and the conventional biological treatments are unable effectively to mineralize and decolorize them from the wastewater effluent. In this study, the efficacy of catalytic ozonation process (COP) with magnetic carbonaceous nanocomposite, as a novel catalyst, on dye degradation and mineralization of molasses were investigated and the results were compared with those obtained from single ozonation process (SOP) and granular activated carbon (GAC) catalyst. For this purpose, the nanocomposite synthesized with co-precipitation method and applied with ozonation in COP. Then the influential parameters such as pH, catalyst dosage and synergistic effect were all evaluated. The residual dye concentration, chemical oxygen demand (COD) and total organic carbon (TOC) were analyzed using american dye manufactures institute, acid digestion, and total organic carbon analyzing methods, respectively. The results showed that the degradation efficiency of dye, COD and TOC in COP was 95, 51 and 74%, respectively, and the highest efficiency of the nanocomposite was achieved at optimal pH of 8. However the results of dye removal in COP (95%) were higher than SOP (71%) and GAC/ozonation (86%). Furthermore, this catalyst has synergistic property on dye decomposition, so that the greatest synergistic effect on the dye removal efficiency is 15% which occurred in the first 15 min, and the catalytic role of magnetic carbon is not affected by dye adsorption. This finding revealed that the applied approach is technically suitable for the effective degradation and mineralization of dye contaminant form molasses industrial wastewaters.

Effective catalytic ozonation for oxalic acid degradation with bimetallic Fe‐Cu‐MCM‐41: operation parameters and mechanism

AbstractBACKGROUNDThe formation of carboxylic acid, especially oxalic acid (OA), limits the complete mineralization of organic pollutant in both ozonation and catalytic ozonation. Bimetallic catalyst is well known for its catalytic activity. In this study, bimetallic Fe‐Cu‐MCM‐41 is synthesized to accelerate ozone decomposition to ·OH and enhance OA degradation.RESULTSAfter the employment of Fe‐Cu‐MCM‐41/O3, 95% OA was removed at 60 min, which was much higher than that in Fe‐MCM‐41/O3 (23.4%), Cu‐MCM‐41/O3 (69.7%) and a single ozonation process (16.5%). Using pyridine adsorption–IR, ESR and XPS, a relationship was found between catalytic activity of catalysts, Lewis acid sites and electron transfer effect. OA degradations were found to follow a hydroxyl radical mechanism. The Fe‐Cu‐MCM‐41/O3 process was sensitive to pH value; a higher removal efficiency was achieved under alkaline conditions. Fe‐Cu‐MCM‐41 significantly accelerated ozone decomposition, hydroxyl radicals and hydrogen peroxide generation.CONCLUSIONSCo‐incorporating Fe and Cu successfully increased the number of Lewis acid sites on MCM‐41. Electron transfers between Fe(II/III), Cu(I/II) and O3 were also found. The joint function of Lewis sites and the electron transfer effect enhanced ·OH generation and OA degradation. Fe‐Cu‐MCM‐41 showed bright prospects for use in water treatment processes. © 2017 Society of Chemical Industry

The efficiency of catalytic ozonation using carbosieve in xylene removal from waste air stream

Catalytic ozonation process (COP) is a new method of single ozonation process that has recently received considerable attention in air pollution control industry. The present study aimed to evaluate the efficiency of catalytic ozonation using carbosieve in xylene removal from the waste air stream. An experimental-laboratory study was conducted at the pilot scale, and the performance of carbosieve adsorbent system, simple ozonation, and catalytic ozonation was studied. A lab-scale pilot was designed and launched at the chemical laboratory of the Faculty of Health, Hamadan. Xylene liquid with purity of 99.5 was prepared from Merck (German) and carbosieve from Aldrich Co. (USA). The specific surface rate and the used catalyst size in this study were 972 m2/g and 1.8–2.3 mm, respectively. Results showed that by increasing xylene concentration in the beginning of the system, the time of bed saturation and adsorbent breakpoint decreased, and removal efficiency by ozone gas declined by increasing xylene concentrations in the reactor inlet from 20 to 200 ppm. The findings showed that the carbosieve breakpoint and saturation in catalytic ozonation can happen later from the absorbent carbosieve system alone. It seems that the catalytic ozonation was more efficient in xylene removal compared with absorbent carbosieve system and simple ozonation. The COP by carbosieve could be a promising alternative to conventional volatile organic compounds; removal systems are particularly toxic compounds from waste air stream. © 2017 Desalination Publications. All rights reserved.

Synthesis of MnOx/SBA-15 for Norfloxacin degradation by catalytic ozonation

Abstract Norfloxacin, a kind of widely used fluoroquinolone antibiotics, was degraded by MnOx/SBA-15/O3 process. The prepared catalyst possessed a large surface area ranging from 405 to 671 m2 g−1, which was beneficial for surface reaction. The loaded MnOx on SBA-15 successfully increased its the adsorption ability and catalytic activity, and its surface property played an importance role in catalytic process. Under the adopted condition, both O3 and MnOx/SBA-15/O3 systems were effective for Nofloxacin removal. A high mineralization efficiency (54%) was achieved by MnOx/SBA-15/O3 process at 60 min, 1.36 times higher than that of single ozonation process. The protonated surface hydroxyl groups were the main reaction sites and more hydroxyl radicals generation were found after the presence of MnOx/SBA-15. Three kinds of common small molecule acid (oxalic acid, formic acid, acetic acid) were detected, and the concentration of oxalic acid in MnOx/SBA-15/O3 process was lower than that in sole ozonation process because more OH generated in catalytic ozonation. Toxicological tests were also conducted to evaluate their detoxification ability. As the accumulation of transformation products, the toxicity of solution increased at first and reached the highest after 15 min reaction time. And a high detoxification was achieved after 30 min.

Oxalic acid degradation from aqueous solution using ozonation process in the presence of magnesium oxide nanoparticles catalyst stabilized on activated carbon

Aims: In this work, activated carbon, magnesium oxide (MgO), and MgO stabilized on activated carbon derived from sweet corn were applied as catalysts for oxalic acid degradation from aqueous. Materials and Methods: Sweet corn pile was used for the production of activated carbon, and magnesium nitrate applied for the production of MgO. Ozone concentration determined using iodometry method, and oxalic acid concentration was determined by a spectrophotometer at 210 nm. Moreover, the effect of MgO, activated carbon and oxalic acid concentration, pH, contact time, and oxalic acid mineralization were investigated. Results: The results showed that ozonation in the presence of activated carbon or MgO and/or MgO stabilized on activated carbon, increased the decomposition rate of oxalic acid. Removal efficiency of oxalic acid with increasing catalysts dose of 0.05–1 g, pH of 3–11, and time of 1–30 min have increased from 72% to 85%, 72% to 85%, and 92% to 95% respectively. Furthermore with increasing of oxalic acid from 40 to 100 mg/L, the removal efficiency decreased from 96% to 88%. Conclusion: According to this study, catalytic ozonation processes have shorter time and more removal efficiently than the single ozonation process. Moreover, the results showed that oxalic acid was mineralized significantly and interfering factors have negligible effect on the catalytic ozonation process than the single ozonation.

Heterogeneous catalytic ozonation of 2, 4-dinitrophenol in aqueous solution by magnetic carbonaceous nanocomposite: catalytic activity and mechanism

Herein, the catalytic properties of a carbonaceous nanocomposite in the catalytic ozonation process (COP) of 2, 4-dinitrophenol (2, 4-DNP) were investigated and the results were compared with those obtained from single ozonation process (SOP). Magnetic carbonaceous nanocomposite, as a novel catalyst, was applied to optimize the condition for the removal of 2, 4-DNP in the COP, and the influential parameters such as pH, catalyst dosage, addition of radical scavengers, and durability were all evaluated. The results showed that the degradation efficiency of 2, 4-DNP and COD in the COP (98.2, 92%) was higher compared to the SOP (75, 61%) and the highest catalytic potential was achieved at an optimal pH of 6. The first-order modeling demonstrated that the reactions were dependent on the concentration of the catalyst, with the kinetic constants varying from 0.022 (1/min) in the SOP to 1.377 (1/min) in the COP at the catalyst dosage of 4 g/L and the optimum concentration of catalyst (2 g/L). The addition of radical scavenger noticeably diminished the removal efficiency of 2, 4-DNP in the SOP from 75% down to 54%, while the corresponding values for the COP dropped from 98.2 to 93%. Furthermore, a negligible reduction in the catalytic properties of the catalyst was observed (~5%) after five-time reuse. The results also revealed that the applied method is effectively suitable for the removal of 2, 4-DNP contaminant from industrial wastewaters.

Manganese Sand Ore Is an Economical and Effective Catalyst for Ozonation of Organic Contaminants in Petrochemical Wastewater

Catalytic ozonation process (COP) is a promising advanced oxidation process for petrochemical wastewater (PCW) treatment. However, the lack of economical and effective catalysts limits its application. Manganese sand ore (MSO) was utilized as a heterogeneous catalyst for ozonation of organic contaminants in PCW in this study. The calcined MSO-assisted COP (cMSO-COP) of aniline exhibited greater degradation than natural MSO-assisted COP or single ozonation process (SOP). The cMSO significantly promoted hydroxyl radical-mediated oxidation, decreased the ozonation activation energy by about 20 %, and doubled the reaction rates in comparison with SOP. The cMSO-COP increased the chemical oxygen demand (COD) removal of PCW twofold relative to SOP. The number of polar organic contaminants decreased by 50 % after cMSO-COP treatment. This study demonstrated the potential use of cMSO for efficient ozonation of petrochemical-derived contaminants at low cost.

Investigating the potential of carbon activated with NH4Cl for catalyzing the degradation and mineralization of antibiotics in ozonation process

The catalytic activity of carbon activated with NH4Cl (NAC) was compared with a standard analytical grade activated carbon (SAC) for ozonation of amoxicillin. The results indicate that the NAC had greater catalytic potential than SAC for degradation and mineralization of amoxicillin by ozonation. Complete degradation and 54.1% mineralization of 50mg/L amoxicillin was obtained using the catalytic ozonation process with NAC as catalyst (COP/NAC) at a solution pH of 6.8, ozone dosage of 0.8mg/min, catalyst concentration of 100mg/L and reaction time of 50min. The catalytic ozonation process with SAC as the catalyst (COP/SAC) degraded 64.7% of amoxicillin while the single ozonation process (SOP) degraded 22% and COP/SAC mineralized 32.4% of amoxicillin while SOP mineralized 8.3% under similar conditions. The rates of degradation and mineralization of amoxicillin for COP/NAC were 3.2 and 1.8 times, respectively, those for COP/SAC. These findings demonstrate the high catalytic activity of NAC, suggesting it is a promising and efficient material for catalyzing the ozonation of emerging water contaminants.

P‐Nitrophenol Removal by Bauxite Ore Assisted Ozonation and its Catalytic Potential

The catalytic ozonation process (COP) has attracted wide attention in the treatment of recalcitrant organic contaminants because of its high efficiency and easy operation. In this study, the bauxite ore (BO) was used as a heterogeneous catalyst to catalyze ozonation of p‐nitrophenol in water. Calcined BO (CBO) assisted COP (CBO–COP) exhibited a higher degradation and mineralization performance for p‐nitrophenol in comparison with raw BO assisted COP and single ozonation process (SOP). The CBO–COP was dominated by hydroxyl radical mediated oxidation on the CBO surface, following a pseudo‐first order kinetics with a reaction rate constant of 0.1944 min−1 at 298.15 K and an activation energy of 6.476 kJ mol−1. The reaction rate constants increased by about 76% at 298.15 K and 45% at 308.15 K and activation energy decreased by approximately 70% in CBO–COP compared to those in SOP. p‐Nitrophenol in CBO–COP was first transformed into 4‐nitrocatechol, pyrocatechol, hydroquinone, phenol p‐benzoquinone, and o‐benzoquinone, and then into benzoquinone, maleic acid, fumaric acid, acetic anhydride, acetic acid, formic acid, or directly mineralized to carbon dioxide and water. The results demonstrated the catalytic potential of BO for ozonation of recalcitrant organic contaminants considering low cost and earth‐abundant reserves.

Photocatalytic ozonation of phenazopyridine using TiO2 nanoparticles coated on ceramic plates: mechanistic studies, degradation intermediates and ecotoxicological assessments

Removal of phenazopyridine (PhP), an analgesic drug, from water with different oxidation processes including photocatalysis, ozonation and photocatalytic ozonation was studied. The experiments were conducted using a semi-batch reactor where TiO2 nanoparticles were immobilized on ceramic plates irradiated by UV-A light in the proximity of oxygen and/or ozone. The surface morphology, topography and roughness of the bare and TiO2-coated ceramic plates were analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Comparing the processes of photocatalysis, ozonation and photocatalytic ozonation revealed that using photocatalytic ozonation led to the highest efficiency (85% at 35min) in PhP removal. The influence of pH, PhP initial concentration and ozone gas flow rate on the removal of PhP was investigated in both individual and combined processes. The presence of synergy was investigated under various operational parameters. The mechanism of photocatalytic ozonation process was investigated in the presence of various reactive oxygen species (ROS) scavengers. The main intermediate products of PhP produced in ozonation and photocatalytic ozonation processes were verified by the GC–MS technique. The chronic phytotoxicity of PhP and its intermediate compounds formed in ozonation and photocatalytic ozonation was evaluated using aquatic species Spirodela polyrrhiza (S. polyrrhiza). It was found that the photocatalytic ozonation process, in contrast to the single ozonation process, can efficiently reduce the phytotoxicity of the PhP from aqueous solutions.

Magnetic heterogeneous catalytic ozonation: a new removal method for phenol in industrial wastewater

In this study, a new strategy in catalytic ozonation removal method for degradation of phenol from industrial wastewater was investigated. Magnetic carbon nano composite as a novel catalyst was synthesized, characterized and then used in the catalytic ozonation process (COP) and compared with the single ozonation process (SOP). The influential parameters were all investigated. The results showed that the removal efficiency of phenol and COD (chemical oxygen demand) in COP (98.5%, 69.8%) was higher than those of SOP (78.7%, 50.5%) and the highest catalytic potential was achieved at optimal neutral pH. First order modeling demonstrated that the reactions were dependent on the concentration of catalyst, with kinetic constants varying from 0.023 1/min (catalyst = 0 g/L) to 0.071 1/min (catalyst = 4 g/L), whereby the optimum dosage of catalyst was found to be 2 g/L. Furthermore, the catalytic properties of the catalyst remained almost unchanged after 5-time reuse. The results regarding the biodegradability of the effluent showed that a 5-min reaction time in COP reduced the concentrations of phenol and COD to the acceptable levels for the efficient post-treatment in the SBR in a 4-h cycle period. Finally, this combined system is proven to be a technically effective method for treating phenolic contaminants.

Catalytic activity of aluminum silicate for ozonation of chloronitrobenzenes in aqueous solution

Chemical oxidation using ozone with appropriate catalysts offers an attractive option for removing inhibitory and toxic pollutants in micro-polluted water. This work investigated the catalytic ozonation of three chloronitrobenzenes (CNBs, i.e. p-CNB, o-CNB, and m-CNB) in the presence of a novel and efficient synthesized aluminum silicate catalyst. Experiments were carried out with focus on the degradation efficiency of CNBs at different reaction pH values, water matrices and repeated uses, as well as the possible catalytic mechanism. Regardless of the water matrix, the results showed that the catalytic ozonation had considerably higher degradation efficiency of CNBs than the single ozonation process at the same ozone dose. The change of pH had an obvious effect on the removal efficiency of CNBs, which suggested that the aluminum silicate catalyst was more appropriate for application in the neutral pH condition. Ozonation processes in the presence of the aluminum silicate were significantly influenced by tert-butyl alcohol, which confirmed that the aluminum silicate catalytic ozonation followed a hydroxyl radical-type mechanism.

Degradation and mineralization of furfural in aqueous solutions using heterogeneous catalytic ozonation

The main aim of this experiment was to study the degradation of furfural in wastewater using catalytic ozonation process with granular activated carbon as a catalyst. Influences of the following parameters were investigated on furfural degradation; initial furfural concentration, solution pH, GAC dosage, and reaction time. In order to gain an understanding of the mechanism, involved these experiments were done in the presence of some radical scavengers. A significant synergistic effect between ozone and activated carbon was obtained in the oxidation and mineralization of furfural compared to single ozonation and adsorption on GAC processes, thus verifying the positive effect of coupling ozonation and GAC to degrade toxic compounds such as furfural. Furthermore, this study demonstrated that the efficiency of furfural removal increased with a decreasing size of AC particles due to an increased surface area. Measurements of COD in SOP and COP showed that more degradation and mineralization of furfural occurred in COP (80.2%) compared to single ozonation process (42.4%). Desorption studies were performed and they showed that percentages for recovery of furfural from GAC used in COP and single adsorption processes were 3.5 and 85.4, respectively.

Catalytic ozonation of Acid Red B in aqueous solution over a Fe–Cu–O catalyst

The catalytic ozonation of Acid Red B (ARB) solution in the presence of Fe–Cu oxide (Fe–Cu–O) catalysts was investigated under different operating conditions. The effects of solution pH (3–11), ozone flow (3.6–30mg/min) and initial ARB concentration (100–500mg/L) on color and COD removal were evaluated. The optimum pH and ozone flow were determined to be 6.8 and 30mg/min, respectively. In the presence of 1g/L Fe–Cu–O powder, after 60min, the color and the COD removal efficiency was 90% and 70%, while that of the single ozonation process was 66% and 48%, respectively. The repeated use of the catalyst proved that the Fe–Cu–O catalyst had a good reusability and stability. Finally, the possible mechanism of the catalytic ozonation of ARB was proposed, and the kinetics model of the color and COD degradation were established.