Single Ozonation Research Articles

Continuous versus single H2O2 addition in peroxone process: Performance improvement and modelling in wastewater effluents

Ozonation combined with continuous addition of H2O2 was studied as potential strategy for the effective abatement of ozone-resistant micropollutants from wastewater effluents. Oxidant doses within and beyond immediate ozone demand completion were tested. Through experiments involving the continuous addition of H2O2 in a semi-continuous contactor, it was demonstrated that this new approach could lead to a 36 % reduction of the overall O3 needs for a constant H2O2/O3 molar ratio of 0.25 compared to single ozonation, representing a 28 % reduction in energy consumption. This improvement was mainly attributed to H2O2 addition during the secondary ozonation stage, where the direct ozone demand becomes less important. The OH-exposure per consumed ozone (i.e., ROHO3 concept) calculation demonstrated that higher (0.5–1) and lower (0.25) oxidant relationships work better in improving the process performance during initial and secondary stages, respectively. Moreover, continuous versus total initial addition of H2O2 were compared and the first one showed better performance, representing differences in energy costs up to 21 %. Finally, two strategies for the real-time control of the O3-recalcitrant MPs fate were tested, one based on the ROHO3 concept and the other on UVA254 monitoring. Both resulted in accurate predictions (R2 > 0.96) for different compounds, effluents and processes.

Optimization of synthesis a new composite of nano-MgO, CNT and Graphite as a catalyst in heterogeneous catalytic ozonation for the treatment of pesticide-laden wastewater

The production of an efficient, reusable, stable and easily separable catalyst in the ozonation process through a reliable procedure is one of the essential requirements of the catalytic ozonation process (COP). In this study, the nano-MgO/CNT/Graphite composite was synthesized to use as a new catalyst in the COP. Synthesis of the nano-MgO/CNT/Graphite was carried out based on the extreme vertices mixture design (EVMD) using three components; MgO nanoparticles, carbon nanotubes (CNTs) and Graphite. Based on EVMD, 9 compositions were produced. For assessing the catalytic activity of synthesized compositions, pesticide manufacturing plant wastewater (PMPW) (initial COD=617 mg/L and TOC = 121) was treated in COP with new synthesized catalytic. The highest COD and TOC removal and destruction efficiencies were attained with composition C-9. The surface area of the optimum nano-MgO/CNT/Graphite was calculated to be had 221.631 m2 g−1 and a high density of basic surface functional groups. Kinetics of PMPW oxidation indicated that the rate of COD and TOC removal efficiencies in the optimum nano-MgO/CNT/Graphite/O3 process were 12.73 (13.24/1.04 mg COD/L.min) and 7.11 (1.44/0.2 mg TOC/L.min) times as high as those in the single ozonation (SOP), respectively. Clearly, the optimum nano-MgO/CNT/Graphite showed a significant ability in catalysis of the ozonation process of organic materials by means of increasing O3 decomposition and OH production. The synthesized optimum nano-MgO/CNT/Graphite was reusable because of the stability and durability of the catalytic activities.

Catalytic ozonation of an azo-dye using a natural aluminosilicate

Catalytic ozonation of Orange II (100 mg/L) was studied using aluminosilicate Montanit300® (M) modified with H2SO4 (MS) and HCl (MH). Characterization of these samples was performed through several techniques: SEM/EDX, FTIR, XRD, FRX, TPD pyridine, surface area, pHPZC. Acid treatment increased surface area, Si:Al ratio and quantity of acid sites, but reduced pHPZC and Fe and Mn content.Ozonation experiments achieved complete decoloration and remarkable TOC conversions of 66, 65, 88 and 91 % by single ozonation and catalytic ozonation with MH, MS and M, respectively. Higher M and MS activity under acidic pH was attributed to Mn leaching. Decreased mineralization efficiency in the presence of tert-butanol suggested a radical mechanism. At neutral pH, M showed no activity, while MS presented mild activity owing to its enlarged hydrophobicity.The M sample sustained mineralization levels over 20 h. Lower O3 dose caused quick MS deactivation. However, it was reversed through calcination and prevented with a higher oxidant dose.Mn is naturally found in Montanit300®, thus making it an inexpensive catalyst. The development of a dynamic cycle combining reduced and oxidized forms of Mn was key to the outstanding activity observed.

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.

Heterogeneous catalytically ozonation as a novel disinfectant for inhibition of Legionella pneumophila virulence

The aim of this study was investigating the effects of hertogeneous catalytic ozonation process with copper (HCO) as a new designed disinfectant for inhibition of virulence factors in L. pneumophila in hospital water.The hospital water was selected as a natural contaminant source for L. pneumophila. The samples were exposed with ozone with MIC = 0.5 μg/mL for single ozonation (SO) in 20 min, and HCO for 15 min. HCO led to complete removal of bacteria after 10 min.The mRNA of the exposed and unexposed samples with SO and HCO was extracted by GmbH Jena bioscience (Germany). Then, the cDNA of the samples was synthesized and the change of expression levels of the selected genes was evaluated.The effects of modified disinfectant against gene expression inhibition t2ss and t4ss were studied by the RT-PCR.Both SO and HCO led to completely L.P. removal, in which the second system was fast. Gene expression of t2ss and t4ss decreased after exposure to the disinfectant but did not change the expression level of housekeeping gene mip. Also, HCO reduced gene expression more than SO. The removal efficiency of L.P in HCO was higher than SO. There was an interaction effect between the two types of ozonation processes, and the exposure time colonies to removal (p ≤ .001). The MIC results for both SO at 20 min and HCO with copper at 15 min were 0.5 μg/mL.HCO successfully can inhibit the expression of virulence genes of L. pneumophila. Therefore, this system can be used for hospital water disinfection and control of L. pneumophil concerns in health care systems.

Advanced oxidation processes for recalcitrant compounds removal comparison with biofiltration by Corbicula fluminea

Conventional treatments cannot remove the emerging contaminants due to their refractory character, therefore improved methodologies should be applied for obtaining their total removal. The need of development of suitable technologies to treat these recalcitrant compounds is related with the wastewater reclamation. Advanced oxidation technologies such as photocatalysis and ozonation appear as suitable solutions for recalcitrant compounds removal. Moreover, the biofiltration can be applied as a pest management approach integrated with wastewater treatment. Due to the invasive character of Corbicula fluminea their usage as biofilter hosts can work as a reduction of their impact over native species or industrial damage. These methodologies were used to promote the degradation of a mixture of SMX, CBZ and LRZ at initial concentration of 1 mg/L of each one. Single ozonation was capable to remove totally SMX and CBZ in 5 min. Whereas only 50% of LRZ were removed in 60 min. The weather can affect the sunlight radiation photon flux which will promote impact on the photocatalytic oxidation using 1 wt% of Ag and Pd-TiO2 as catalysts, for SMX, CBZ and LRZ abatement. C. fluminea was capable to remove about 30% of CBZ and LRZ in 24h.

A char-clay composite catalyst derived from spent bleaching earth for efficient ozonation of recalcitrants in water

Catalytic ozonation is an efficient process that can be utilized to degrade recalcitrant organics. Char-clay composite derived from refinery spent bleaching earth (SBE) is an economical and readily available catalyst that can be used during the ozonation treatment of recalcitrants in wastewater. Four catalysts of SBE-N2-650, SBE-N2-850, SBE-O2-650, and SBE-O2-850 were prepared by heating the SBE at 650 and 850 °C under N2 or O2 conditions. High surface OH sites in the SBE-N2-650 and SBE-O2-650 relative to the SBE-N2-850 and SBE-O2-850 resulted in an increase in catalytic activity. Additional carbon (C), that existed in the SBE-N2-650 and SBE-N2-850, had a positive effect on catalytic activity. The SBE-N2-650 exhibited the highest activity among those prepared catalysts. During catalytic ozonation, the SBE-N2-650 increased the mineralization rate of benzoic acid by 36% when compared with single ozonation. Molecular ozone was decomposed at the surface active sites on SBE-N2-650, generating active •OH, •O2−, or 1O2 species. Gas and liquid products having calorific values that are generated during SBE-N2-650 preparation can be further utilized. This study introduces a potential use of SBE for the ozonation treatment of recalcitrant wastewaters.

Catalytic ozonation by metal ions for municipal wastewater disinfection and simulataneous micropollutants removal

Several works in literature demonstrated that catalytic ozonation using metal ions promotes the decomposition of ozone and generation of hydroxyl radicals (HO•). The purpose of this study was to assess the effects of different metal ions (Fe2+, Co2+ and Al3+) in disinfection of urban wastewater through E.coli and Pseudomonas spp inactivation along with cellular adenosine triphosphate (ATP) depletion. Simultaneously, the effect of catalytic ozonation of secondary effluent on the selected micropollutants removal with different ozone kinetics (acetamiprid, dichlorvos and atrazine) was evaluated in semi-continuous operation. Results demonstrated that E.coli and Pseudomonas spp inactivation increased almost 20% with 1 mg L−1 Fe2+, Co2+, Al3+ and 40% with 10 mg L−1 Fe2+ compared with single ozonation. Fe2+ was the most effective metal ion on inhibiting regrowth after the treatments. The cellular ATP followed the same trend as the indicators microorganisms inactivation, with significant reduction of ATP over the treatment to single ozonation comparison. The ROH,O3 was applied for the treatments to quantify and compare the micropollutants removal by the radical pathway. The improvement of metal ions on ROH,O3 values occurred significantly for both stages of ozonation (before and after initial ozone demand) for all tested metals. Thus, metal ions addition to ozonation process provided an increase in simultaneous disinfection and pesticides removal as well as in the inhibition of bacterial reactivation, which resulted in savings between 30–50% of ozone dose needs compared with the same attainment in single ozonation.

The role of metal ions on p-CBA degradation by catalytic ozonation

The homogeneous catalytic ozonation, through the addition of dissolved metal ions, acting as catalysts, was applied for the removal/degradation of small concentrations of p-CBA, used as model micropollutant, from aqueous solutions. For this purpose five different transition metal ions, i.e. Co(II), Fe(II), Mn(II), Ni(II) and Zn(II), were studied at pH 7 and concentrations ranges of 0.25–1 mg/L. It was found that only the application of O3/Co(II) and O3/Fe(II) systems can be characterized as effective catalytic ozonation processes. The addition of these metals resulted in 95.5% and 92.5% p-CBA degradation respectively, mainly due to the low solubility of respectively formed oxy-hydroxides (Co(OH)3 and Fe(OH)3). These oxy-hydroxides are relatively hydrophobic and positively charged at pH 7, whereas the respective aquatic species, i.e. Co(OH)2+ and Fe(OH)2+, can also favor the attraction of negatively charged p-CBA. The optimum conditions for both metal ions were: catalyst concentration 1 mg/L, ozone concentration 2 mg/L and pH value 8, where p-CBA residual concentration was found to diminish below the respective analytical detection limit of 0.025 μM after only 3 min of reaction/oxidation time. Additionally, it was found that the presence of Co(II) and Fe(II) can increase the decomposition of ozone, as well as the production of hydroxyl radicals, hence resulting in faster and more effective p-CBA degradation in comparison to single ozonation (i.e. without the presence of catalytically acting dissolved metal cations).

Simultaneous membrane fouling mitigation and emerging pollutant benzophenone-3 removal by electro-peroxone process

In this work, the effects of electro-peroxone (E-peroxone, i.e. combination of ozonation and electrolysis using a carbon based cathode) assistance on microfiltration (MF) was systematically investigated from the performance and mechanism viewpoints. Results show that E-peroxone oxidation exhibited better ability than individual processes in membrane fouling mitigation when using bovine serum albumin (BSA), humic acid (HA) and silicon dioxide (SiO2) particles as model foulants. The relative fluxes at 250 s E-peroxone assisted MF treatment were determined to be ~0.30–0.71, which are > 15% higher than those in single ozonation or electrolysis assisted MF process. The efficiency of E-peroxone process in membrane fouling reduction was positively correlated with the applied voltage (0–4 V) and inlet ozone concentration (0–48.6 mg/L). The experimental data combined with three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs) analysis indicate that simultaneous fouling mitigation and emerging pollutant benzophenone-3 (BP3) removal could be obtained during actual river water treatment. Furthermore, the comparison tests reveal that generation of hydroxyl radicals (HO) via enhanced O3/H2O2 decomposition had a significant role on the organic contaminant degradation and membrane fouling mitigation in E-peroxone assisted MF process, and the introduced electrostatic repulsion force could also contribute to the fouling reduction. These observations suggest that E-peroxone maybe a feasible assistive method for membrane filtration water treatment.

Catalytic ozonation of sulfamethoxazole over Fe3O4/Co3O4 composites

In this study, Fe3O4/Co3O4 composites were prepared and applied in the catalytic ozonation of sulfamethoxazole (SMX). Various parameters including initial solution pH, Fe3O4/Co3O4 composites dose, O3 dose and SMX concentration were investigated. Results showed that Fe3O4/Co3O4 composites could significantly improve the mineralization of SMX by catalytic ozonation system and a synergic effect between Fe3O4 and Co3O4 was observed. Only about 16% total organic carbon (TOC) could be removed in 60 min by single ozonation under the condition of 20 mg/L SMX, 6.0 mg/min O3, pH 5.1 and room temperature, While in the presence of 0.10 g/L Fe3O4/Co3O4 composites at the same conditions, 60% TOC removal were obtained by catalytic ozonation process. SMX could be degradation by O3 rapidly and the removal was not significantly affected by the changing parameters. However, those operating parameters exerted different effects on SMX mineralization. Furthermore, the generation of hydroxyl radicals (OH) and the utilization efficiency of O3 would increase with the addition of Fe3O4/Co3O4 composites. The quenching experiments indicated that OH might account for the enhancement of SMX mineralization and the mechanism of catalytic ozonation was proposed. Additionally, the intermediates were detected by using a high-performance liquid chromatography-mass spectrometry (LC-MS), from which some plausible transformation pathways were proposed.

Catalytic Ozonation of Recalcitrant Organic Chemicals in Water Using Vanadium Oxides Loaded ZSM-5 Zeolites.

The discharge of wastewater having recalcitrant chemical compositions can have significant and adverse environmental effects. The present study investigates the application of a catalytic ozonation treatment for the removal of recalcitrant organic chemicals (ROCs) from the water. Novel catalytic materials using vanadium (V) oxides deposited onto the surface of NaZSM-5 zeolites (V/ZSM) were found to be highly efficient for this purpose. The highly-dispersed V oxides (V4+ and V5+) and Si-OH-Al framework structures were determined to promote the surface reaction and generation of hydroxyl radicals. The constructed V1/ZSM450 (0.7 wt% of V loading and 450°C of calcination) exhibited the highest activity among the developed catalyst compositions. The V1/ZSM450-COP increased the mineralization rate of nitrobenzene and benzoic acid by 50 and 41% in comparison to single ozonation. This study demonstrates the enhanced potential of V/ZSM catalysts used with catalytic ozonation process (COP) for the treatment of chemical wastewaters.

Ozonation of ammonia at low temperature in the absence and presence of MgO.

Ozone oxidation and ozonation catalyzed with MgO were applied to remove ammonia in water at low temperature (10℃). Results show that pH played a critical role in both ozonation and catalytic ozonation for ammonia removal, especially in the ozonation rate of ammonia and the types of oxidation products. For single ozonation, both O3 and OH contributed to ammonia degradation. Lower pH is beneficial to high selectivity of gaseous products (N2 or N2O) in the presence of Cl-. Significantly enhanced efficiency of ammonia removal was obtained under the catalysis of MgO, which worked as a solid alkali as well as a catalyst, facilitating ammonia oxidation both in the solution and on the MgO surface. Molecular O3 dominated ammonia removal in the heterogeneous catalytic ozonation system, while the contribution of OH was not significant in quantity and a small part of ammonia was degraded by the reaction of ClOx- with NH4+. A relatively high removal efficiency (77.53%˜80.17%) of ammonia could also be achieved in the temperature range of 0℃˜10℃, which indicates that catalytic ozonation over catalysts like MgO may be a potential method to control ammonia pollution during cold weather or under other conditions difficult for biological treatment.

Kaolinite based catalysts for efficient ozonation of recalcitrant organic chemicals in water

Kaolinite has been widely utilized as a raw material in industrial and agricultural fields. Kaolinite derived materials can be used as catalysts in a catalytic ozonation process (COP) of recalcitrant organic chemicals in wastewater with decreased costs and improved profitability. The silicon (Si), aluminum (Al) and oxygen (O) in layered silicate of kaolinite and amorphous aluminum silicate of metakaolinite contribute to the formation of catalytic active sites. Kaolinite contains surface OH groups, SiO and AlO structures that promote oxidation through the formation of hydroxyl radicals (OHs) mineralizing the pollutant p-nitrophenol. Different metakaolinite has surface SiO and AlO structures that enhance mineralization through surface reaction. Catalytic ozonation of p-nitrophenol using kaolinite and metakaolinite increased the total organic carbon removal (46% and 41%, respectively) relative to single ozonation (32%). Introduction of Mn into kaolinite and metakaolinite further accelerate OH generation, improving the catalytic activity. Among the catalysts, the highest activity was observed using Mn loaded kaolinite (TOC removal 66%). Its enhanced activity may be mainly attributed to cooperative interactions from the distributed Mn oxides (Mn2+, Mn3+, and Mn4+) and surface OH groups. This study introduces the potential application of kaolinite and metakaolinite for the treatment of recalcitrant chemical wastewaters in catalytic ozonation processes.

Degradation of atrazine by catalytic ozonation in the presence of iron scraps: performance, transformation pathway, and acute toxicity

Degradation of atrazine by catalytic ozonation in the presence of iron scraps (ZVI/O3) was carried out. The key operational parameters (i.e., initial pH, ZVI dosage, and ozone dosage) were optimized by the batch experiments, respectively. This ZVI/O3 system exhibited much higher degradation efficiency of atrazine than the single ozonation, ZVI, and traditional ZVI/O2 systems. The result shows that the pseudo-first-order constant (0.0927 min−1) and TOC removal rate (86.6%) obtained by the ZVI/O3 process were much higher than those of the three control experiments. In addition, X-ray diffraction (XRD) analysis indicates that slight of γ-FeOOH and Fe2O3 were formed on the surface of iron scrap after ZVI/O3 treatment. These corrosion products exhibit high catalytic ability for ozone decomposition, which could generate more hydroxyl radical (HO•) to degrade atrazine. Six transformation intermediates were identified by liquid chromatography-mass spectrometry (LC-MS) analysis in ZVI/O3 system, and the degradation pathway of atrazine was proposed. Toxicity tests based on the inhibition of the luminescence emitted by Photobacterium phosphoreum and Vibrio fischeri indicate the detoxification of atrazine by ZVI/O3 system. Finally, reused experiments indicate the approving recyclability of iron scraps. Consequently, the ZVI/O3 system could be as an effective and promising technology for pesticide wastewater treatment.

Performance and kinetic modelling of photolytic and photocatalytic ozonation for enhanced micropollutants removal in municipal wastewaters

In this work, the performances of ozonation, photolytic ozonation (UV-C/O3), and photocatalytic ozonation (UV-A/TiO2/O3) in degrading ozone recalcitrant micropollutants in four different real domestic wastewaters were evaluated in semi-continuous operation, together with the influence of water matrices in the ozone mass transfer and pollutant degradation rates. The OH exposure per consumed ozone ratio, defined as ROH,O3, was applied for single ozonation and modified for light-assisted ozonation processes to evaluate and compare the contribution of radical pathway on micropollutants abatement for the different wastewaters studied. ROH,O3 plots presented good fitting (R2 > 0.95) in two stages, corresponding to different ozone mass transfer regimes, for all cases. Light-assisted ozonation attained higher pollutant degradation for all water matrices compared to single ozonation, although the performance of UV-assisted processes was more sensitive to matrix factors like composition and turbidity. Moreover, the improvement brought by both light-based processes on ROHO3 values mainly took place during the second stage. Thus, photocatalytic ozonation reached ROHO3 values higher than double for all wastewaters, compared with single ozonation (between 105% and 127% increase). These values represent a saving of almost half of the overall ozone needs (42%) for the same ozone recalcitrant micropollutant depletion, although it would require the adoption of higher ozone doses than the currently employed for ozonation in wastewater treatment plants.

Catalytic performance and an insight into the mechanism of CeO2 nanocrystals with different exposed facets in catalytic ozonation of p-nitrophenol

Ceria based catalysts have been widely applied in ozonation of organic pollutants in wastewater treatment. Ceria with different exposed facets have not been used in catalytic ozonation. In this study, ceria nanorods (R-CeO2), nanocubes (C-CeO2) and nanooctahedra (O-CeO2) with different exposed facets (110) + (100), (100) and (111)) respectively were used in catalytic ozonation of p-nitrophenol. Two calcination temperatures 300 and 500 °C were selected for comparative catalytic activity. Ceria nanoparticles (NP-CeO2) were also prepared for comparative catalytic activity. Approximately 86%, 71%, 68%, 64%, 60% and 40% TOC was removed by ozonation catalyzed by R300-CeO2, C300-CeO2, CeO2-NP, O300-CeO2, R500-CeO2 and ozonation alone respectively. Nanorod calcined at 500 °C (R500-CeO2) showed lower catalytic activity as compared to R300-CeO2. O3 was also rapidly decomposed by R300-CeO2 as compared to other catalysts and single ozonation. Inorganic hydroxyl radical scavengers and several characterization techniques were applied for investigating the underlying mechanism of catalytic ozonation. Hydroxyl radicals, surface peroxide and surface atomic oxygen as reactive oxygen species were generated for enhancing the catalytic activity. Furthermore, irrespective of surface area, the difference in catalytic activity of ceria nanoshapes were assigned to the differences in the abundance of surface basic sites, defects densities/oxygen vacancies (OVs) and coordination number of surface atoms. This study provides an insight to use other metals with variety of exposed facets for catalytic ozonation.

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

Catalytic Ozonation of Sulfonamide, Fluoroquinolone, and Tetracycline Antibiotics Using Nano-Magnesium Hydroxide from Natural Bischofite

Huge amounts of natural bischofite (MgCl2∙6H2O) resulting from the mining process of salt lakes often cannot be utilized effectively and are discarded; techniques for reutilization of the discarded bischofite as magnesium resources are limited. The nano-magnesium hydroxide (nano-Mg(OH)2) synthesized from natural bischofite was firstly used as catalyst for ozonation of antibiotics including sulfathiazole (ST), ofloxacin (OFL), and tetracycline (TC). Rapid ozonation of ST, OFL, and TC was achieved using nano-Mg(OH)2 as catalyst. The removal rate constant of OFL in the catalytic ozonation treatment (kOFL = 0.512 min−1) was nearly 2.1 times higher than the single ozonation (kOFL = 0.249 min−1). The removal rate constant of ST and TC increased by 23.5% and 32.8% from 0.298 min−1 and 0.384 min−1 to 0.368 min−1 and 0.510 min−1, respectively, when the catalyst was added into the reaction system. The removal rate constant of ST sharply increased from 0.259 to 0.604 min−1 when the reaction temperature increased from 15 to 35 °C while those of OFL and TC changes slightly. The removal efficiency sharply decreased when the initial concentration of ST, OFL, and TC increased from 10 to 500 mg L−1. Both anions and cations could inhibit the removal of ST, OFL, and TC at relatively higher concentrations. The prepared nano-Mg(OH)2 catalyst could maintain its catalytic activity in the repeated use process. High removal efficiency of typical antibiotics and heavy metals free indicated that nano-Mg(OH)2 from natural bischofite is a promising ozonation catalyst in terms of antibiotics removal.

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.