scholarly journals The Effect of Thermal Treatment on the Physicochemical Properties of Minerals Applied to Heterogeneous Catalytic Ozonation

2020 ◽  
Vol 12 (24) ◽  
pp. 10503
Author(s):  
Savvina Psaltou ◽  
Efthimia Kaprara ◽  
Kyriaki Kalaitzidou ◽  
Manassis Mitrakas ◽  
Anastasios Zouboulis
Keyword(s):  
Catalytic Activity ◽  
Thermal Treatment ◽  
Physicochemical Properties ◽  
Hydroxyl Radicals ◽  
Ph Value ◽  
Catalytic Ozonation ◽  
Point Of Zero Charge ◽  
Chlorobenzoic Acid ◽  
Positive Effects ◽  
Heterogeneous Catalytic

In order to enhance the efficiency of heterogeneous catalytic ozonation, the effect of thermal treatment on three commonly used and inexpensive minerals, i.e., zeolite, talc and kaolin (clay), which present different physicochemical properties as potential catalysts, has been examined for the removal of para-chlorobenzoic acid (p-CBA). p-CBA is considered a typical micro-pollutant, usually serving as an indicator (model compound) to evaluate the production of hydroxyl radicals in ozonation systems. The catalytic activity of selected solid catalysts was studied for different pH values (6, 7 and 8) and different temperatures (15 °C, 25 °C and 35 °C). The mechanism of radicals’ production was also verified by the addition of tert-butyl alcohol (TBA). The respective thermal behavior study showed that the point of zero charge (PZC) of these minerals increased with the increase of applied treatment temperature, as it removed crystalline water and hydroxyls, thus improving their hydrophobicity. Circa-neutral surface charge and the presence of hydrophobicity were found to favor the affinity of ozone with solid/catalytic surfaces and the subsequent production of hydroxyl radicals. Therefore, zeolite and talc, presenting PZC 7.2 and 6.5 respectively, showed higher catalytic activity after thermal treatment, while kaolin with PZC equal to 3.1 showed zero to moderate catalytic efficiency. The degradation level of p-CBA by oxidation was favored at 25 °C, while the pH value exerted positive effects when it was increased up to 8.

scholarly journals Transition Metal Ions as Ozonation Catalysts: An Alternative Process of Heterogeneous Catalytic Ozonation

Catalysts ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1091
Author(s):  
Savvina Psaltou ◽  
Konstantina Sioumpoura ◽  
Efthimia Kaprara ◽  
Manassis Mitrakas ◽  
Anastasios Zouboulis
Keyword(s):  
Catalytic Activity ◽  
Metal Ions ◽  
Natural Water ◽  
Transition Metal Ions ◽  
Catalytic Ozonation ◽  
Experimental Conditions ◽  
Chlorobenzoic Acid ◽  
Heterogeneous Catalytic ◽  
Water Matrix ◽  
Phosphate Ions

The aim of this study is to elucidate the mechanism of micropollutants’ removal in drinking water by the application of catalytic ozonation, using transition metals as appropriate catalysts. For that purpose, the degradation of 500 μg/L of p-chlorobenzoic acid (p-CBA) and benzotriazole with the addition of 2 mg/L of ozone in the presence of 1 mg/L of Co(II) or Fe(II) and at pH 7.8 were examined. It was found that in distilled water experiments, both metal ions can be characterized as catalysts, enhancing the ozonation process; however, in the natural water matrix, only iron presented higher removal rates of examined organic pollutants, when compared to single ozonation. The metal ions present catalytic activity, when they can form precipitates, hence converting the initially homogeneous process of catalytic ozonation towards a heterogeneous one. However, when 2 mg/L of ozone was applied in natural water experiments, Co(II)—unlike Fe(II)—could not be oxidized into its trivalent form, hence it cannot precipitate as Co(OH)3. Therefore, under these experimental conditions, this metal was not found to present any catalytic activity. Nevertheless, the addition of phosphates (PO43−) in concentrations higher than 100 mg/L can increase the oxidation ability of the Co(II)/O3 system, due to the resulting sufficient formation of Co3(PO4)2 precipitates. Although cobalt can enhance the •OH production (and therefore, the ozonation procedure) under these conditions, the relatively highly added concentration of phosphate ions makes the treated water non-potable, resulting in the application of further treatment to remove the excess phosphates. Therefore, only Fe(II) can be considered as a sufficient catalyst to enhance the ozonation processes.

Catalytic ozonation of p-chloronitrobenzene over pumice-supported zinc oxyhydroxide

2013 ◽  
Vol 68 (8) ◽  
pp. 1895-1900 ◽  
Author(s):  
Lei Yuan ◽  
Jimin Shen ◽  
Zhonglin Chen
Keyword(s):  
Hydroxyl Radicals ◽  
Underlying Mechanism ◽  
Catalytic Ozonation ◽  
Point Of Zero Charge ◽  
Hydroxyl Groups ◽  
Ozone Decomposition ◽  
Surface Hydroxyl ◽  
Heterogeneous Catalytic ◽  
Surface Hydroxyl Groups ◽  
Catalytic Ozone

The catalytic ozonation of p-chloronitrobenzene (pCNB) in an aqueous solution using pumice-supported zinc oxyhydroxide (ZMP) as the catalyst was investigated. ZMP significantly enhanced the degradation efficiency in the heterogeneous catalytic ozonation compared with ozonation alone. The decomposition rate of the aqueous ozone increased 2.84-fold in the presence of ZMP. Catalytic ozone decomposition showed that pCNB is oxidized primarily by hydroxyl radicals (•OH) in ozonation/ZMP processes. This modification increases the density of surface hydroxyl groups as well as the pH at the point of zero charge (pHPZC) of pumice, resulting in the appearance of new ZnO and Zn(OH)2 crystalline phases. An investigation of the underlying mechanism confirms that ZnOOH loading promotes •OH initiation, which enhances the degradation of pCNB.

Fe3O4@TiO2preparation and catalytic activity in heterogeneous photocatalytic and ozonation processes

2015 ◽  
Vol 5 (2) ◽  
pp. 1143-1152 ◽  
Author(s):  
L. Ciccotti ◽  
L. A. S. do Vale ◽  
T. L. R. Hewer ◽  
R. S. Freire
Keyword(s):  
Catalytic Activity ◽  
Magnetic Nanoparticle ◽  
Catalytic Ozonation ◽  
Systematic Evaluation ◽  
Hybrid Catalyst ◽  
Heterogeneous Catalytic ◽  
Nanoparticle Preparation ◽  
Ozonation Process

Systematic evaluation of experimental variables in magnetic nanoparticle preparation and hybrid catalyst application in the heterogeneous catalytic ozonation process.

scholarly journals Comparative study on heterogeneous and homogeneous catalytic ozonation efficiency in micropollutants' removal

2021 ◽  
Author(s):  
S. Psaltou ◽  
E. Kaprara ◽  
M. Mitrakas ◽  
A. Zouboulis
Keyword(s):  
Catalytic Activity ◽  
Organic Compounds ◽  
Hydroxyl Radicals ◽  
Ozone Concentration ◽  
Oxidation Reaction ◽  
Physicochemical Characteristics ◽  
Catalytic Ozonation ◽  
Experimental Conditions ◽  
Kinetic Rate ◽  
Kinetic Rate Constants

Abstract Catalytic ozonation was applied for the removal of small concentrations (4 μM) of micropollutants benzotriazole, carbamazepine, p-CBA from aqueous solutions at pH 7. These compounds present different physicochemical characteristics and different kinetic rate constants, when reacting with ozone or hydroxyl radicals in range of <0.15–3 × 105, 5.2 × 109, and 8.8 × 109 M−1s−1, respectively. Calcite was used as heterogeneous catalyst and its catalytic activity evaluated, by applying (and optimized) different experimental conditions (i.e., pH, temperature, ozone concentration), concerning the removal efficiency of p-CBA. Study of micropollutants' removal showed all examined organic compounds can be sufficiently removed by application of catalytic ozonation either by use of calcite, or by presence of Co(II) or Fe(II) (applied as homogeneous catalysts), while the optimum catalyst between them was found to be calcite. Carbamazepine with kO3 = 3 × 105 M−1s−1 can be easily removed, even by application of single ozonation, while benzotriazole and p-CBA resulted in 50% and 68.2% higher removal after application of catalytic ozonation within 3 min of oxidation reaction, due to acceleration of hydroxyl radicals' production by presence of calcite in the ozonation system. The contribution of hydroxyl radicals in removal of all three micropollutants was evaluated by extraction of Rct and f•OH parameters.

Effect of calcination temperature on the catalytic activity of nanosized TiO2 for ozonation of trace 4-chloronitrobenzene

2012 ◽  
Vol 66 (3) ◽  
pp. 479-486 ◽  
Author(s):  
Miaomiao Ye ◽  
Zhonglin Chen ◽  
Tuqiao Zhang ◽  
Weiyun Shao
Keyword(s):  
Catalytic Activity ◽  
Ph Value ◽  
Average Pore Size ◽  
Average Crystallite Size ◽  
Catalytic Ozonation ◽  
Solution Ph ◽  
Average Pore ◽  
Paramagnetic Resonance ◽  
Calcination Temperatures ◽  
Titanium Dioxides

Nanosized titanium dioxides were synthesized by hydrolysis of TiCl4 followed by calcination at different temperatures ranging from 300 to 1,000 °C. The as-prepared samples were characterized by X-ray diffraction, N2 adsorption–desorption, and zeta potential analysis. The catalytic activities of the TiO2 nanoparticles were tested by catalytic ozonation of trace 4-chloronitrobenzene (4-CNB) in water. Moreover, the catalytic ozonation activity of a sample calcined at 400 °C (denoted as T400) was tested in aqueous solution using electron paramagnetic resonance (EPR) spin trapping technique with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin trap. It was found that with increasing calcination temperatures, the average crystallite size and average pore size increased, in contrast the BET surface areas decreased. However, the isoelectric point (IEP) first increased, and then decreased. The ozone adsorption on the catalyst surface played an important role in determining their catalytic activity. Sample T400 with the IEP of 7.0, farthest away from the 4-CNB solution pH value (pH = 5.3), showed the best catalytic activity. The EPR experiments further confirmed that the hydroxyl radicals TiO2-catalyzed ozonation followed a radical-type mechanism.

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

2015 ◽  
Vol 57 (43) ◽  
pp. 20447-20456 ◽  
Author(s):  
Yousef Dadban Shahamat ◽  
Mahdi Sadeghi ◽  
Ali Shahryari ◽  
Niloofar Okhovat ◽  
Farshad Bahrami Asl ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Catalytic Activity ◽  
Catalytic Ozonation ◽  
Heterogeneous Catalytic

Catalytic ozonation of bisphenol A in aqueous solution using Mn-Ce/HZSM-5 as catalyst

2015 ◽  
Vol 72 (5) ◽  
pp. 696-703 ◽  
Author(s):  
Yanfang Liu ◽  
Junna Zhao ◽  
Zaixing Li ◽  
Guixia Li ◽  
Wei Li ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Catalytic Activity ◽  
Bisphenol A ◽  
Heterogeneous Catalysts ◽  
Butyl Alcohol ◽  
Catalytic Ozonation ◽  
Point Of Zero Charge ◽  
Toc Removal ◽  
Tert Butyl Alcohol ◽  
Bpa Removal

Mixed manganese and cerium oxide supported on HZSM-5 were synthesized and used as heterogeneous catalysts for ozonation of bisphenol A (BPA) in aqueous solution. The prepared catalysts of Mn-Ce/HZSM-5 were characterized by X-ray diffraction, scanning electron microscopy and Fourier transform-infrared spectroscopy. The results indicated that Mn-Ce/HZSM-5 exhibits extraordinary catalytic activity for the degradation of BPA. Removal of 89.3% of BPA and 90.4% of total organic carbon (TOC) was achieved in 30 min, compared to non-catalytic ozonation, where only 50.5% BPA and 28.1% TOC removal were reached under the same conditions. Adsorption of BPA on HZSM-5 support and Mn-Ce/HZSM-5 catalysts was negligible. The strong inhibition of BPA removal by tert-butyl alcohol indicated that the attack of hydroxyl radicals was responsible for the improvement of catalytic ozonation. It was observed that at neutral pH, which is near the point of zero charge of the catalyst, the catalytic activity reached its maximum. Increasing the amount of Mn-Ce/HZSM-5 catalyst until it exceeded 3 g/L did not show a strong effect on BPA removal. The catalysts showed high stability and reusability.

scholarly journals Heterogeneous Catalytic Ozonation of p-Chlorobenzoic Acid in Aqueous Solution by FeMnOOH and PET

Separations ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 42 ◽  
Author(s):  
Savvina Psaltou ◽  
Stylianos Stylianou ◽  
Manasis Mitrakas ◽  
Anastasios Zouboulis
Keyword(s):  
Organic Compound ◽  
Adsorption Capacity ◽  
Treatment Process ◽  
Catalyst Concentration ◽  
Catalytic Ozonation ◽  
Total Removal ◽  
Chlorobenzoic Acid ◽  
Heterogeneous Catalytic ◽  
Hydrophobically Modified ◽  
Typical Model

The oxidation of p-chlorobenzoic acid (p-CBA), used as a typical-model refractory organic compound, in aqueous solutions during the heterogeneous catalytic ozonation treatment process by applying the hydrophilic tetravalent manganese feroxyhyte (TMFx), as well as modified hydrophobic TMFx and the polyethylene terephthalate (PET) as solid (powdered) catalysts was examined in this study. TMFx was hydrophobically modified by using trichloromethylsilane (TriClMS) solutions in toluene at the concentration range 10–1000 mg/L. TMFx catalysts were characterized by the application of scanning electron microscopy (SEM), as well as by Brunauer-Emmet-Teller (BET) and surface charge density determinations. TMFx catalyst, which was modified by 50 mg/L trichloromethylsilane (TriClMS) solution (TMFx-50), was found to present the higher adsorption capacity of studied organic compound (250 μg p-CBA/g) when compared with all the other investigated catalysts, which in turn resulted in the higher removal of p-CBA (>99%) by the subsequent application of ozonation, as compared to hydrophilic TMFx (96.5%) and to single ozonation (96%) applications. PET-catalyst concentration in the range 0.5–10 g/L led to almost total removal of p-CBA within 15 min of reaction/oxidation time at pH 7. Conclusively, the experimental results for both catalysts indicated that hydrophobicity and adsorption capacity are crucial steps for the process of heterogeneous catalytic ozonation of refractory organic compounds.

scholarly journals Calcite Mineral Catalyst Capable of Enhancing Micropollutant Degradation during the Ozonation Process at pH7

2020 ◽  
Vol 2 (1) ◽  
pp. 26
Author(s):  
Savvina Psaltou ◽  
Efthimia Kaprara ◽  
Manassis Mitrakas ◽  
Anastasios Zouboulis
Keyword(s):  
Reaction Time ◽  
Hydroxyl Radicals ◽  
Advanced Oxidation Process ◽  
Oxidation Process ◽  
Catalytic Ozonation ◽  
Batch Mode ◽  
Heterogeneous Catalytic ◽  
Physico Chemical ◽  
Oxidative Species ◽  
Ozonation Process

Catalytic ozonation is an Advanced Oxidation Process (AOPs) based on the production of hydroxyl radicals, which are very reactive oxidative species. The aim of this study is to evaluate the catalytic activity of calcite on the ozonation of four different typical micropollutants (atrazine, benzotriazole, carbamazepine, and p-CBA) at pH 7 and for low initial concentrations (4 μΜ) by performing batch mode experiments. These compounds have different physico-chemical characteristics, as well as different rate constants, when reacting with ozone and hydroxyl radicals (•OH), being in the range of <0.15 − 3 × 105 M−1s−1 and 2.4 − 8.8 × 109 M−1s−1, respectively. It was found that most of these micropollutants can be sufficiently removed by the application of heterogeneous catalytic ozonation, using calcite as the catalyst, except for the case of atrazine, which was the compound that was most difficult to degrade, when compared to the application of single ozonation. Carbamazepine with kO3 = 3 × 105 M−1s−1 can be easily removed even by single ozonation after the first minute of the reaction time, and the addition of the catalyst eliminated the oxidation/reaction time. The application of catalytic ozonation resulted in 50% and 68.2% higher removals of benzotriazole and p-CBA, respectively, in comparison with single ozonation, even during the first 3 min of the reaction/oxidation time, due to the higher production of hydroxyl radicals, caused by the catalytic ozonation. For the case of atrazine, the addition of calcite did not enhance the micropollutant degradation, and its removal reached 83% after a 30 min application of catalytic ozonation, whereas during the single ozonation, the removal under the same reaction time was 90%.

scholarly journals Heterogeneous Catalytic Ozonation of Micropollutants in a Pilot Scale Continuous Flow System

2020 ◽  
Vol 2 (1) ◽  
pp. 24
Author(s):  
Efthimia Kaprara ◽  
Chrysovalantou Koutsiantzi ◽  
Savvina Psaltou ◽  
Anastasios Zouboulis ◽  
Manassis Mitrakas
Keyword(s):  
Continuous Flow ◽  
Flow System ◽  
Pilot Scale ◽  
Catalytic Ozonation ◽  
Hydrophobic Membrane ◽  
Chlorobenzoic Acid ◽  
Heterogeneous Catalytic ◽  
Complete Degradation ◽  
Scale Unit ◽  
Micropollutant Removal

The present study evaluates micropollutant degradation from water by catalytic ozonation in a pilot scale unit comprising of a hydrophobic membrane for ozone dilution and a column filled with granules of the catalyst. The catalysts examined are alumina, calcite, dolomite, goethite, pearlite, polyethylene terephthalate (PET) and zeolite. Experimental results revealed zeolite as the most effective material achieving complete degradation of benzotriazole and carbamazepine, as well as 70% degradation of atrazine and about 50% of p-chlorobenzoic acid (p-CBA). The rest of the catalysts tested presented a moderate performance in micropollutant removal, reaching 30%–50% for atrazine, 25%–35% for p-CBA, more than 90% for benzotriazole and complete degradation of carbamazepine. Adsorption capacity of all materials examined did not exceed 5%.

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