Efficient treatment of veterinary pharmaceutical industrial wastewater by catalytic ozonation process: degradation of enrofloxacin via molecular ozone reactions

The study focused on the efficacious performance of bimetallic Fe-Zn loaded 3A zeolite in catalytic ozonation for the degradation of highly toxic veterinary antibiotic enrofloxacin in wastewater of the pharmaceutical industry. Batch experiments were conducted in a glass reactor containing a submerged pump holding catalyst pellets at suction. The submerged pump provided the agitation and recirculation across the solution for effective contact with the catalyst. The effect of ozone flow (0.8-1.55 mg/min) and catalyst dose (5-15 g/L) on the enrofloxacin degradation and removal of other conventional pollutants COD, BOD5, turbidity was studied. In batch experiments, 10 g of Fe-Zn 3A zeolite efficiently removed 92% of enrofloxacin, 77% of COD, 69% BOD5, and 61% turbidity in 1 L sample of pharmaceutical wastewater in 30 min at 1.1 mg/min of O3 flow. The catalytic performance of Fe-Zn 3A zeolite notably exceeded the removal efficiencies of 52%, 51%, 52%, and 59% for enrofloxacin, COD, BOD5, and turbidity, respectively, achieved with single ozonation process. Furthermore, an increase in the biodegradability of treated pharmaceutical industrial wastewater was observed and made biodegradable easily for subsequent treatment.

Catalytic Ozonation of Reactive Black 5 in Aqueous Solution Using Iron-Loaded Dead Leaf Ash for Wastewater Remediation

In the current study, iron-loaded dead leaf ash (Fe-DLA) was used as a novel catalyst in the heterogeneous catalytic ozonation process (HCOP) for textile wastewater containing Reactive Black 5 (RB-5). The research demonstrates a significant boost in removal efficiency, reaching 98.76% with 1.0 g/min O3 and 0.5 g/L catalyst dose, by investigating key variables such as pH, ozone and catalyst doses, initial concentration, and the presence of scavengers in 1 L wastewater. The addition of tert-butyl alcohol (TBA) reduced RB-5 elimination, indicating the involvement of OH radicals. Catalyst reusability decreased slightly (2.05% in the second run; 4.35% in the third), which was attributed to iron leaching. A comparison of single ozonation (Fe-DLA) adsorption and catalytic ozonation processes (Fe-DLA/O3) revealed that the combined process improved dye degradation by 25%, with removal rates ranking as Fe-DLA adsorption O3 Fe-DLA/O3, with an impressive 76.44% COD removal. These results strongly support RB-5 removal using Fe-DLA and HCOP at a basic pH, highlighting the catalyst's utility in practical wastewater treatment.

Application of poly aluminum chloride and alum as catalyst in catalytic ozonation process after coagulation for the treatment of textile wastewater

Textile wastewater is ranked highly contaminated among all industrial waste. During textile processing, the consumption of dyes and complex chemicals at various stages makes textile industrial wastewater highly challenging. Therefore, conventional processes based on single-unit treatment may not be sufficient to comply with the environmental quality discharge standards and more stringent guidelines for zero discharge of hazardous chemicals (ZDHC). In this study, a novel approach was followed by recycling Poly aluminum chloride (PACl) and Alum as a catalyst for the first time in the catalytic ozonation treatment process leading to a nascent method after using them as a coagulant in Coagulation/Flocculation. In the current investigation, six different combinations were studied to remove turbidity, TSS, COD, BOD₅, color, and biodegradability (BOD₅/COD ratios) of wastewater. Moreover, Central Composite Design was implied using RSM in Minitab software. During the combination of treatment processes, it was found that the pre-coagulation/flocculation with coagulant PACl followed by post-catalytic ozonation with recycled PACl, a more effective treatment than others. The optimum R.E of turbidity, TSS, COD, and color were 84%, 86%, 89%, and 98%, respectively. Moreover, a decrease in toxicity and increase in biodegradability (BOD₅/COD ratio from 0.29 to 0.54) was observed as well. The electrical energy demand and operational costs of treatment processes were estimated and compared with other treatment processes.

Application of Fe-RGO for the removal of dyes by catalytic ozonation process

Due to continuous industrialization, the discharge of hazardous dyes has enormously disrupted the ecosystem causing environmental problems. Due to the stable recalcitrant nature of dyes, advanced catalytic ozonation processes with the latest catalyst are under investigation. Fe-RGO is an effective oxidation catalyst, and the metal loaded platform provides enhanced catalytic performance. This study aims to investigate the effectiveness of Fe-RGO/O₃ process for the removal of dyes. In the current research, the application of iron-coated reduced graphene oxide (Fe-RGO) was studied as a catalyst in the heterogeneous catalytic ozonation process to remove dyes. Methylene blue (MB) was selected as a model pollutant. RGO was prepared using the improved Hummers method and was coated with iron (Fe) implying the impregnation method. The FTIR, SEM-EDX, XRD, and BET analyses of RG and Fe-RGO were performed to characterize the catalyst. The effect of various parameters such as pH (3-10), catalyst dose (0.01-0.04 g), and radical scavengers (NaHCO₃, NaCl) on removal efficiency was elucidated. The result revealed an excellent catalytic efficiency of Fe-RGO in the ozonation process. At optimum conditions, 96% removal efficiency was achieved in catalytic ozonation at pH 7 with a catalyst dose of 0.02 g and ozone dose 0.5 mg/min, after 10 min. Interestingly, a slight decrease in removal efficiency was observed in the catalytic ozonation process in hydroxyl radical scavengers (NaCl and NaHCO₃), which makes the proposed catalyst more applicable in real conditions. Therefore, it is concluded that Fe-RGO can be used as an excellent catalyst for the removal of dyes in real conditions where radical scavengers may be present in a significant amount.

Interfacial reactions of catalytic ozone membranes resulting in the release and degradation of irreversible foulants

An efficient in-situ self-cleaning catalytic ceramic-membrane tailored with MnO₂-Co₃O₄ nanoparticles (Mn-Co-CM) was fabricated. Density functional theory calculations result substantiated that molecular ozone could be effectively adsorbed by oxygen vacancies (OV) on the Mn-Co-CM surface and then direct activated into a surface-bound atomic oxygen (*O_ad) and a peroxide (*O_{2, ad}), ultimately producing ^·OH. Mn-Co-CM coupling with ozone efficiently removed foulants from the permeate and the membrane surface simultaneously and leading to in-situ formation of ^·OH that changed the nature of the irreversible foulants and ultimately resulted in the rapid release and degradation of humic acid-like substances causing irreversible fouling. However, the commercial CM with ozone mainly removed cake layer fouling including protein-like and fulvic acid-like substances, followed by the slow release and degradation of irreversible foulant, resulting in many humic acid-like substances remain on the membrane surface as irreversible fouling. Based on these, the flux growth rate of Mn-Co-CM was 3.5 times higher than that of CM with ozone. This study provides new insights into the mechanism of in-situ membrane fouling mitigation, when using an efficient catalytic ceramic-membrane. This will facilitate the development of membrane antifouling strategies.

Comparative study of ozonation and ozonation catalyzed by Fe-loaded biochar as catalyst to remove methylene blue from aqueous solution

Ozone-based processes gained much attention in recent years. However, due to low oxidative stability and utilization rate, single ozonation process (SOP) is insufficient for complete mineralization of pollutants. As a result, the single ozonation process is performed in the presence of a catalyst, a process known as catalytic ozonation process (COP). A promising catalyst (Fe/BC) was prepared by impregnating iron on biochar surface to remove methylene blue from aqueous solution via heterogeneous catalytic ozonation process (HCOP). The prepared Fe/BC features were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller method (BET) before and after HCOP. Furthermore, the effect of various operating parameters such as ozone dose, catalyst dose, initial dye concentration, initial pH on the efficiency of SOP and HCOP were compared. In comparison to single ozonation process, the experimental study found that heterogeneous catalytic ozonation process has the highest efficiency. At pH 7.0, approximately 76% of methylene blue is removed during single ozonation process in 60 min. Heterogeneous catalytic ozonation process showed 95% methylene blue elimination from aqueous solution. The efficiency of heterogeneous catalytic ozonation process was decreased by 52% in the presence of hydroxyl radical (^●OH) scavenger, indicating that hydroxyl is the major oxidant during heterogeneous catalytic ozonation process for the removal of methylene blue from aqueous solution. Fe/BC catalyst appears to have a lot of industrial promise, as well as the ability to remove methylene blue from aqueous solution via heterogeneous catalytic ozonation process.

Two-dimensional layered carbon-based catalytic ozonation for water purification: Rational design of catalysts and an in-depth understanding of the interfacial reaction mechanism

This review renewed insight into the existing complex and contradictory mechanisms of catalytic ozonation by two-dimensional layered carbon-based materials (2D-LCMs) for degradation toxic refractory organics in aqueous solution. Migration and capture of active electrons are central to catalytic ozonation reactions, which was not studied or reviewed more clearly. Based on this perspective, the catalytic ozonation potential of 2D-LCMs synthesized by numerous methods is firstly contrasted to guide the design of subsequent carbon based-catalysts, and not limited to 2D-LCMs. Matching ROS to active sites is a key step in understanding the catalytic mechanism. The structure-activity relationships between reported numerous active sites and ROS evolution is then constructed. Result showed that OH could be produced by -OH, -C=O, -COOH groups, defective sites, immobilized metal atoms, doped heteroatoms and photo-induced electrons; and O₂^- could be produced by -OH groups and sp²-bonded carbon. The normalized model further be used to visually compare the contribution degree of various regulatory methods to performance improvement. More importantly, this review calls for 2D-LCMs-based catalytic ozonation to be studied without circumventing the issue of structural stability, which would lead to many proposals of catalysts and its involved catalytic reaction mechanism being meaningless.

Energy-efficient removal of carbamazepine in solution by electrocoagulation-electrofenton using a novel P-rGO cathode

In this study, carbamazepine (CBZ) decay in solution has been studied by coupling electrocoagulation with electro-Fenton (EC-EF) with a novel P-rGO/carbon felt (CF) cathode, aiming to accelerate the in-situ generation of •OH, instead of adding Fe²⁺ and H₂O₂. Firstly, the fabricated P-rGO and its derived cathode were characterized by XRD, SEM, AFM, XPS and electrochemical test (EIS, CV and LSV). Secondly, it was confirmed that the performance in removal efficiency and electric energy consumption (EEC) by EC-EF (k_obs=0.124 min^-1, EEC=43.98 kWh/kg CBZ) was better than EF (k_obs=0.069 min^-1, EEC=61.04 kWh/kg CBZ). Then, P-rGO/CF (k_obs=0.248 min^-1, EEC=29.47 kWh/kg CBZ, CE=61.04%) showed the best performance in EC-EF, among all studied heteroatom-doped graphene/CF. This superior performance may be associated with its largest layer spacing and richest C=C, which can promote the electron transfer rate and conductivity of the cathode. Thus, more H₂O₂ and •OH could be produced to degrade CBZ, and almost 100% CBZ was removed with k_obs being 0.337 min^-1 and the EEC was only 24.18 kWh/kg CBZ, under the optimal conditions (P-rGO loading was 6.0 mg/cm², the current density was 10.0 mA/cm², the gap between electrode was 2.0 cm). Additionally, no matter the influent is acidic, neutral or alkaline, no additional pH adjustment is required for the effluent of EC-EF. At last, an inconsecutive empirical kinetic model was firstly established to predict the effect of operating parameters on CBZ removal.

Catalytic ozonation for the removal of reactive black 5 (RB-5) dye using zeolites modified with CuMn2O4/gC3N4 in a synergic electro flocculation-catalytic ozonation process

This study aims to investigate the decolourization efficiency of reactive black 5 (RB-5) dye by using CuMn₂O₄/gC₃N₄ coated zeolites (zeolite 4A) for the first time in a hybrid electro-flocculation-catalytic ozonation process. A comparison between various treatment options such as electro-flocculation, electro-flocculation in the presence of a catalyst, and catalytic ozonation in combination with electro-flocculation was explored. Moreover, the effect of different factors such as pH, time, catalyst dose, ozone dose, radical scavenger, and voltage has been studied in each treatment option mentioned earlier. The results indicated that the best treatment option was found to be catalytic ozonation in combination with electro-flocculation with removal efficiency (RE) of 90.31% at pH 10 after 30 min of the treatment process. The hydroxyl radical scavenger effect indicated that the synergistic catalytic process follows a radical mechanism. It is therefore concluded that CuMn₂O₄/gC₃N₄-zeolite catalysts in synergic electro-flocculation-catalytic ozonation process may be effectively used for the treatment of textile wastewaters.

FeS2/carbon felt as an efficient electro-Fenton cathode for carbamazepine degradation and detoxification: In-depth discussion of reaction contribution and empirical kinetic model

Carbamazepine (CBZ) decay by electro-Fenton (EF) oxidation using a novel FeS₂/carbon felt (CF) cathode, instead of a soluble iron salt, was studied with the aim to accelerate the reaction between H₂O₂ and ferrous ions, which helps to produce more hydroxyl radicals (^•OH) and eliminate iron sludge. First, fabricated FeS₂ and its derived cathode were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Anodes were then screened, with DSA (Ti/IrO₂-RuO₂) showing the best performance under EF oxidation regarding CBZ degradation and electrochemical characterization. Several operating parameters of this EF process, such as FeS₂ loading, current density, gap between electrodes (GBE), initial [CBZ], and electrolyte type, were also investigated. Accordingly, a nonconsecutive empirical kinetic model was established to predict changes in CBZ concentration under the given operational parameters. The contribution of different oxidation types to the EF process was calculated using kinetic analysis and quenching experiments to verify the role of the FeS₂-modified cathode. The reaction contributions of anodic oxidation (AO), H₂O₂ electrolysis (EP), and EF oxidation to CBZ removal were 12.81%, 7.41%, and 79.77%, respectively. The ^•OH exposure of EP and EF oxidation was calculated, confirming that ^•OH exposure was approximately 22.45-fold higher using FeS₂-modified CF. Finally, the 19 intermediates formed by CBZ degradation were identified by ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry. Accordingly, four CBZ degradation pathways were proposed. ECOSAR software was used to assess the ecotoxicity of intermediates toward fish, daphnia, and green algae, showing that this novel EF oxidation process showed good toxicity reduction performance. A prolonged EF retention time was proposed to be necessary to obtain clean and safe water, even if the targeted compound was removed at an earlier time.

Subcritical and supercritical water oxidation for dye decomposition

The total annual output of synthetic dyes exceeds 7 × 10⁵ tons. About 1,000 tons of non-biodegradable synthetic dyes are released every year into the natural streams and water sources from textile wastes. The release of these colored wastewater exerts negative impact on aquatic ecology and human beings because of the poisonous and carcinogenic repercussions of dyes involved in coloration production. Therefore, with a growing interest in the environment, efficient technologies need to be developed to eliminate dyes from local and industrial wastewater. Supercritical water oxidation as a promising wastewater treatment technology has many advantages, such as a rapid reaction and pollution-free products. However, due to corrosion, salt precipitation and operational problems, supercritical water oxidation process did not gain expected industrial development. These technical difficulties can be overcome by application of non-corrosive subcritical water as a reaction medium. This work summarizes the negative impacts of dyes and role of subcritical and supercritical water and their efficiencies in dye oxidation processes.

A study on the influence of pH changes during catalytic ozonation process on alumina, zeolites and activated carbons for the decolorization of Reactive Red-241

The current study focuses on a prime effect of pH changes in the catalytic ozonation process (COP) by using three main classes of catalysts such as zeolites (alumina-silicates), alumina (metal oxides), and activated carbons for decolorization of Reactive Red 241 (RR-241). The role of pH changes, point of zero charges and the effect of catalyst dose on pH change was studied. The results reveal that the overall removal efficiency of RR-241 in the case of COPs was the highest compared with single ozonation process (at pH = 7 the efficiency was 80, 65 65.5 and 60% for AC/O₃, Al₂O₃/O₃, Zeolite/O₃ and O₃ respectively). At initial acidic pH 4, the highest pH variations in COPs and ozonation processes were observed. Moreover, the pH changes were not found to be significant near the point of zero charges of materials (pH_pzc = 6.8, 8.4 and 8.8 for zeolite, activated carbons and Al₂O₃, respectively. The COP in the presence of activated carbon shows the highest removal efficiency (82%) at pH 7. The material dose effect indicates that increasing the amount of catalyst (from 1 gm to 2 gm) significantly leads to a change in the pH of the solution. Results reveal the prominent effect and significance of pH changes on the efficiency of COP to determine true catalytic efficiency.

Treatment of leachate through constructed wetlands using Typha angustifolia in combination with catalytic ozonation on Fe-zeolite A

Leachate control and management is a major challenge faced during solid waste management as it may pollute surface and groundwaters. In the current research, constructed wetlands (CWs) vegetated with Typha angustifolia plant in combination with catalytic ozonation by ferrous (Fe)-coated zeolite A was studied for the treatment of leachate. The CWs treatment with 9 days detention reduced the chemical oxygen demand (COD) and biochemical oxygen demand (BOD) up to 75.81% and 69.84%, respectively. Moreover, total suspended solids (TSS), total dissolved solids (TDS), and total kjeldahl nitrogen (TKN) removal of 91.16%, 33.33%, and 25.22% were achieved, respectively. The Fe-coated zeolite A catalytic ozonation further reduced the COD up to 90.7%. Comparison of the processes showed the effective performance of the combined process (CW/O₃/Fe-zeolite) with 97.76% COD reduction of leachate. It is, therefore, concluded that the studied combined process (CW/O₃/Fe-zeolite A) was more efficient as compared with single ozonation and CW alone, hence it can be implied for the leachate treatment in real conditions.

Elimination of basic blue 9 by electrocoagulation coupled with pelletized natural dead leaves (Sapindus mukorossi) biosorption

Elimination of basic blue 9 (BB-9), a cationic textile dye, by electrocoagulation coupled with biosorption exploiting pelletized natural dead leaves (PNDL) of Sapindus mukorossi, an economic alternative biosorbent, was investigated. The experimental runs were conducted in a laboratory-scale hybrid reactor loaded with Al electrodes, aeration spargers and PNDL packed twin suspended buckets. The pelletized adsorbents offer key advantages of good mechanical stability, lesser clogging risk, and easy disengagement as compared to powdered adsorbents. The parameters of current density, pH, PNDL dose, and initial dye concentration were studied for the decolorization and COD removal efficiency. The experimental results revealed that up to 99.9% decolorization and 90.01% COD removal efficiency achieved after 8 min at optimum condition of current density (j)=20.27 mA/cm², pH = 9, PNDL dose = 6 g/L, and initial dye concentration = 50 mg/L. The BB-9 elimination followed the first-order kinetics with K₁=0.318 min^-1 and R²=0.997. The results revealed the potential of PNDL as a feasible biosorbent with the effective performance of the coupled process.

Catalytic ozonation of emerging pollutant and reduction of toxic by-products in secondary effluent matrix and effluent organic matter reaction activity

In this study, the performance of LaCoO₃ (LCO) catalytic ozonation was evaluated comprehensively, including the degradation efficiency of benzotriazole (BZA) as a typical emerging pollutant, toxic bromate reduction and the disinfection by-products (DBPs) precursors removal ability in effluent organic matter (EfOM), as well as EfOM reactive activity in catalytic ozonation. Additionally, the reduction of toxic halogenated by-products in (catalytic) ozonation was reported, which was not focused on previous researches before. Results showed that LCO catalytic ozonation improved the removal efficiency of BZA, UV₂₅₄ and SUVA via enhanced HO· formation. Interestingly, LCO catalytic ozonation showed the ability on the reduction of aldehydes and toxic halogenated organic by-products. Moreover, the formed [trichloromethane (TCM)], [bromochloroacetonitrile (BCAN)] and [dichloroacetamide (DCAcAm)] decreased significantly in catalytic ozonation. Catalytic ozonation was also able to remove DBPs precursors to decline the formation of DBPs, such as TCM, bromodichloromethane (BDCM), trichloroacetonitrile (TCAN) and trichloronitromethane (TCNM). This process was involved in the transformation of EfOM in catalytic ozonation, which was confirmed by multi-spectrum methods, two-dimensional correlation spectroscopy (2D-COS) and hetero-spectral 2D-COS. In summary, LCO was shown to be an effective catalyst to improve the performance of the sole ozonation on the removal of emerging contaminants and DBPs precursors, as well as toxic by-products reduction. Additionally, the strategy of toxic by-products reduction in catalytic ozonation was proposed. Results indicated this technology was an important contribution on removal of refractory organics and formation of toxic by-products in water supply and wastewater treatment industry.

Degradation of safranin by heterogeneous Fenton processes using peanut shell ash based catalyst

Today, dyes are one of the major problematic pollutants in the environment and are broadly used in several industrial sectors. In the current research work, decolorization of safranin (basic dye) from aqueous solution was investigated using iron-impregnated peanut shell ash (Fe-PSA) as a catalyst in the UV-assisted heterogeneous Fenton process (Fe-PSA/H₂O₂/UV). The effect of parameters such as H₂O₂ concentration, catalyst dose, pH, initial dye concentration, temperature, and agitation speed was studied. The maximum decolorization of safranin was achieved at optimum parametric values of reagent dose = 8 mM, catalyst dose = 0.5 g, pH = 3, initial concentration of safranin = 50 ppm, temperature = 25 °C, and agitation speed = 200 rpm. The results revealed the efficient performance of Fe-PSA as catalyst in the Fe-PSA/H₂O₂/UV process for safranin treatment.