Ozonation System Research Articles

Preparation of SnOx-MnOx@Al2O3 for Catalytic Ozonation of Phenol in Hypersaline Wastewater

ABSTRACT The catalytic ozonation process (COP) is an effective and advanced oxidation technology for the treatment of organic wastewater. However, high salinity has a negative impact on catalytic ozonation performance. In this work, tin oxide (SnOx) and manganese oxide (MnOx) doped γ-Al2O3 catalysts (SnOx-MnOx@Al2O3) were prepared by the incipient wetness impregnation method and characterized by SEM, XRD, BET, XRT, XPS and FT-IR techniques. The SnOx-MnOx@Al2O3 catalyst was applied to the catalytic ozonation of phenol in hypersaline wastewater, and the catalytic performance was evaluated by COD removal efficiency. When the mass ratio of MnOx to SnOx was 1:3, the pH was 7, the catalyst dosage was 40 g/L, the ozone dosage was 6 mg/(L·min), the NaCl concentration was 15 g/L and the COD removal efficiency of hypersaline phenol wastewater reached 93.8% after 240 min of catalytic ozonation treatment. Compared with the single ozonation process (SOP), the introduction of SnOx-MnOx@Al2O3 catalyst improved the COD removal efficiency by 32.3%. Cl− may quench surface •OH species and ozone to form Cl• and Cl2•− with low activity and high selectivity, resulting in the reduction of catalytic ozonation efficiency. The catalytic activity of the SnOx-MnOx@Al2O3 catalyst remained high after eight cycles. In conclusion, the SnOx-MnOx@Al2O3 catalytic ozonation system exhibits efficient and stable mineralization performance and is a promising strategy for the treatment of hypersaline organic wastewater.

Investigations on the Efficacy of Ozone as an Environmental Sanitizer in Large Supermarkets.

Awareness of the importance of the microbial contamination of air and surfaces has increased significantly during the COVID-19 pandemic. The aim of this study was to evaluate the presence of bacteria and fungi in the air and on surfaces within some critical areas of large supermarkets with and without an ozonation system. Surveys were conducted in four supermarkets belonging to the same commercial chain of an Apulian city in June 2021, of which two (A and B) were equipped with an ozonation system, and two (C and D) did not have any air-diffused remediation treatment. There was a statistically significant difference in the total bacterial count (TBC) and total fungal count (TFC) in the air between A/B and C/D supermarkets (p = 0.0042 and p = 0.0002, respectively). Regarding surfaces, a statistically significant difference in TBC emerged between A/B and C/D supermarkets (p = 0.0101). To the best of our knowledge, this is the first study evaluating the effect of ozone on commercial structures in Italy. Future investigations, supported by a multidisciplinary approach, will make it possible to deepen the knowledge on this method of sanitation, in light of any other epidemic/pandemic waves.

Degradation of cefadroxil by photoelectrocatalytic ozonation under visible-light irradiation and single processes

Here, we investigate the degradation of 20 mg L-1 Cefadroxil (CFX) in water using photoelectrocatalytic ozonation (PECO), and compared against its individual processes. A carbon nitrogen-codoped titanium dioxide (CN-TiO2) anode is synthesized using ethylene glycol and ethylenediamine as carbon and nitrogen source, respectively. The X-ray diffraction (XRD) and Scanning Electronic Microscopy (SEM) analysis conducted to this material indicate a crystalline phase anatase with irregular morphology formed on the electrode surface; while the diffuse reflectance spectroscopy (DRS) shows a shift in the photoanode absorbance towards the visible region, unlike undoped TiO2 structure. This behavior results from the inclusion of Carbon and Nitrogen species on the CN-TiO2 electrode in weight percentages of 14.5 and 1.61 wt%, respectively, according to Energy Dispersive Spectroscopy (EDS) analysis. The Cefadroxil (CFX) abatement is monitored UV–Vis spectroscopy, high-performance liquid chromatography (HPLC), and total organic carbon (TOC). All techniques reveal that the highest CFX removal occurs with PECO (Photoelectrocatalytic Ozonation) process, decreasing TOC by 57.6% (96% degradation by HPLC) after 90 min of treatment. The main by-products formed from oxidation with the PECO, PCO (Photocatalytic Ozonation) and O3 (Ozonation) systems were acid species presumably corresponding to short chain carboxylic acids. Finally, the germination of lettuce sativa is carried out in water contaminated with the drug, and compared with water treated by PECO and PCO processes, showing that PECO process improves germination by 23.5% on the contaminated sample and 7.4% on the sample treated with PCO. These findings confirm that synergism of oxidation techniques could be a tractable way to resolve the problems related to recalcitrant compounds contained in wastewater.

Highly efficient catalytic ozonation for oxalic acid mineralization with Ag2CO3 modified g-C3N4: Performance and mechanism

A series of Ag2CO3 doping g-C3N4 composites labeled as AgCNx-T (x represented the weight content of g-C3N4 and T referred to the hydrothermal temperature) were synthesized by a simple precipitation method. Various techniques such as BET, XRD, FTIR, SEM, and XPS were employed to explore the morphology structure and physicochemical properties of catalysts ascribed to the decoration of Ag2CO3 onto g-C3N4 and the results revealed that the hydrothermal temperature played an important role in the size dimension and crystallinity of Ag2CO3. It was worthy noted, the decorating of Ag2CO3 would provide more active sites on the catalyst surface, strengthen the regeneration and transmission of electrons, improve the utilization of O3, and promote the generation of reactive oxygen species, thus improving the catalytic ozonation performance. Amongst, the AgCN0.4-100 composite had the optimal performance with 99.99% of OA degradation efficiency and 93.19% of OA mineralization. Moreover, the AgCN0.4-100 exhibited satisfactory reusability for multiple consecutive cycles (≥5) with low Ag ion release (<0.3 mg L−1). The reactive species (O2•− and 1O2) were verified to take predominant roles in the reaction through the radical scavenger experiments and ESR spectra. Accordingly, an empirical kinetic model was established to predict OA concentration with the given operational parameters. Finally, the synergistic mechanism of OA degradation in catalytic ozonation system was also proposed, which possessed promising prospect in practical water treatment for environmental applications.

Adaptive modeling of nonnegative environmental systems based on projectional Differential Neural Networks observer

A new design of a non-parametric adaptive approximate model based on Differential Neural Networks (DNNs) applied for a class of non-negative environmental systems with an uncertain mathematical model is the primary outcome of this study. The approximate model uses an extended state formulation that gathers the dynamics of the DNN and a state projector (pDNN). Implementing a non-differentiable projection operator ensures the positiveness of the identifier states. The extended form allows producing continuous dynamics for the projected model. The design of the learning laws for the weight adjustment of the continuous projected DNN considered the application of a controlled Lyapunov-like function. The stability analysis based on the proposed Lyapunov-like function leads to the characterization of the ultimate boundedness property for the identification error. Applying the Attractive Ellipsoid Method (AEM) yields to analyze the convergence quality of the designed approximate model. The solution to the specific optimization problem using the AEM with matrix inequalities constraints allows us to find the parameters of the considered DNN that minimizes the ultimate bound. The evaluation of two numerical examples confirmed the ability of the proposed pDNN to approximate the positive model in the presence of bounded noises and perturbations in the measured data. The first example corresponds to a catalytic ozonation system that can be used to decompose toxic and recalcitrant contaminants. The second one describes the bacteria growth in aerobic batch regime biodegrading simple organic matter mixture.

Can the commonly used quenching method really evaluate the role of reactive oxygen species in pollutant abatement during catalytic ozonation?

Reactive oxygen species (ROS) such as hydroxyl radicals (•OH), superoxide radicals (O2•−), and singlet oxygen (1O2) have often been suggested to play a role in ozone-resistant pollutant abatement during catalytic ozonation. However, there are significant controversies regarding their relative importance in literature. Currently, the role of ROS in pollutant abatement is commonly evaluated by the quenching method based on the assumption that the added ROS quenchers (e.g., tert-butanol (TBA) and para-benzoquinone (pBQ)) quench only the target ROS, but do not considerably influence other reaction mechanisms of catalytic ozonation. However, we hypothesized that this assumption is possibly unrealistic and a main cause for the controversies reported in literature. To test this hypothesis, this study evaluated the effects of six commonly used ROS quenchers (TBA, pBQ, methanol (MeOH), 4-chloro-7-nitrobenzo-2-oxa-1,3-dizole (NBD-Cl), furfuryl alcohol (FFA), and sodium azide (NaN3)) on the mechanism of catalytic ozonation with manganese dioxide. The results show that rather than only quenching their target ROS, these quenchers can profoundly change the catalytic ozonation system through various mechanisms, e.g., interrupting the radical chain reaction of O3 decomposition, blocking the active sites of catalysts, and consuming O3 in the system. Due to the significant confounding effects of ROS quenchers on the reaction mechanism, the quenching method actually cannot reveal the role of ROS in pollutant abatement and often misinterpreted the catalytic ozonation mechanism. The results indicate that the commonly used quenching method is probably not an appropriate way to investigate the role of ROS in pollutant abatement during catalytic ozonation, and many previously reported mechanisms obtained with the quenching method may need a revisit.

Techno-Economic Evaluation of Ozone Application to Reduce Sludge Production in Small Urban WWTPs

In Chile, small wastewater treatment plants (WWTPs) (treatment capacity of less than 4,800 m3/d) are normally not designed with consideration for the potential valorization of generated sludge. For this reason, they are generally operated at high solids residence times (SRT) (15 d) to promote the decay of biomass, promoting less sludge production and reducing the costs associated with biomass management. Operation at high SRT implies the need for a larger activated sludge system, increasing capital costs. The implementation of a sludge-disintegration unit by ozonation in future WWTPs could enable operation at an SRT of 3 d, with low sludge generation. In this work, we evaluate how the implementation of a sludge-ozonation system in small WWTPs (200–4000 m3/d) would affect treatment costs. Four scenarios were studied: (1) a current WWTP operated at an SRT of 15 d, without a sludge ozonation system; (2) a WWTP operated at an SRT of 15 d, with a sludge-ozonation system that would achieve zero sludge production; (3) a WWTP operated at an SRT of 3 d, with a sludge-ozonation system that would provide the same sludge production as scenario 1; (4) a WWTP operated at an SRT of 15 d, with a sludge-ozonation system that would achieve zero sludge production. Economic analysis shows that the treatment costs for scenarios 1 and 2 are similar, while a reduction in cost of up to 47% is obtained for scenarios 3 and 4.

Catalytic Ozonation of the Secondary Effluents from the Largest Chinese Petrochemical Wastewater Treatment Plant—A Stability Assessment

Effluents discharged from petrochemical facilities are complex and composed of various types of highly toxic contaminants, which necessitates the development of sustainable treatment technologies. Stability is among the most important sustainability criteria of the wastewater treatment processes. In the present manuscript, the standard-reaching rate (η) index was used to evaluate the stability of the catalytic ozonation process for treating the secondary effluent from the petrochemical industry. A pilot-scale device was designed and implemented for catalytic ozonation. The effluents were taken from the secondary sedimentation tank of a petrochemical wastewater treatment plant in China. A commercially available γ-Al2O3 was used as the catalyst after a pre-treatment heating step. The catalyst was characterized using scanning electron microscopy. Three mathematical statistics indexes, discrete coefficient (Vσ), skewness coefficient (Cso), and range coefficient (VR), were used to analyze the results achieved from the catalytic ozonation process. Continuous operation of the pilot-scale device was monitored for 9 months under an ozone concentration of 36 mg/L and the contact oxidation time of 1 h. The results demonstrated that the stability evaluation grades of chemical oxygen demand (COD) and suspended solids (SS) in the effluent of the catalytic ozonation system were both 3 and A, indicating that the process was relatively stable over a long period of application. The effluent COD compliance grade was also calculated as B, indicating that the effluent COD does not meet the standard and the process parameters need to be further optimized. When the reflux ratio is 150%, the removal rate of COD is the highest (38.2%) and the COD of effluent is 49.34 mg/L. Meanwhile, to enhance the efficiency and stability of the system, the ozone concentration and the two-stage aeration ratio are 40 mg/L and 4:1, respectively. Moreover, the presence of SS in the water of the catalytic ozonation system will result in the waste of ozone and reduce the utilization rate of ozone.

Degradation Characteristics and Mechanism of Ibuprofen by Ozone Catalyzed by Nitrogen-Doped Biochar

This study used a novel nitrogen-doped biochar (N-C) to catalyze the oxidative degradation of IBP in water by ozone and studied the catalytic ozone oxidation degradation of ibuprofen (IBP) efficiency and mechanism. Furthermore, it explored the influence of pH, ozone dosing quantity, catalyst dosing quantity, different anions, and background of water quality conditions on the IBP degradation efficiency. The results showed that, compared with that of some common carbon-based catalysts (g-C3N4, biochar, and granular-activated carbon) and metal catalysts (MnO2 and Fe3O4), the N-C catalytic ozone system had a very outstanding oxidation degradation performance of organic pollutants; the removal rate of IBP reached 100% in 5 min, and the utilization rate of ozone was increased from 10% to 46%. The treatment efficiency of the system was enhanced with the increase in pH. Compared with that by increasing the ozone dosage, the treatment capacity of the system was significantly improved by increasing the concentration of catalyst. The quenching experiment and EPR further confirmed that N-C could effectively catalyze ozone to produce more reactive oxygen species, such as superoxide radicals (·O2-) and H2O2. It was also found that·O2- was the main active substance in the reaction system and played a leading role in the degradation of IBP.

Insights into mechanism of catalytic ozonation of cinnamyl alcohol over core–shell Fe3O4@SiO2@La2O3 catalyst

In this study, a magnetic Fe3O4@SiO2@La2O3 nano-catalyst with a core–shell structure was synthesized to improve the efficiency of catalytic ozonation of cinnamyl alcohol. The structure, morphology, and elemental composition of the catalyst were analyzed with the help of catalyst characterization methods. The mechanism of strengthened degradation efficiency and mineralization of cinnamyl alcohol in catalytic ozonation system in the existence of the catalyst were further discussed according to the analysis results. The results showed that the Fe3O4@SiO2@La2O3 catalyst can not only greatly improve the degradation of cinnamyl alcohol, but also has good reusability and stability. And its economic efficiency is relatively good. The degradation rate of cinnamyl alcohol could reach up to 99.8% at 30 min, and the COD could be removed by 28.5% at 60 min with the help of the catalyst. The degradation efficiency of cinnamyl alcohol by ozone oxidation alone was only 52.1% at 30 min, and the COD removal rate was only 24.2% at 60 min in the same experimental conditions. Besides, the possible degradation pathway and degradation mechanism of cinnamyl alcohol were proposed according to the intermediate products detected by gas chromatography-mass spectrometry.

Are microbubbles magic or just small? a direct comparison of hydroxyl radical generation between microbubble and conventional bubble ozonation under typical operational conditions

The application of microbubbles for water treatment is an emerging technology which has been shown to significantly enhance gas–liquid contacting processes. When applied to ozonation, microbubble technology has been shown to enhance mass transfer and the speed and extent of compound removal compared with conventional bubbling techniques. One explanation as to why microbubble systems outperform conventional systems is that microbubbles shrink, collapse and spontaneously generate hydroxyl radicals which is thought to enhance the speed of compound removal. This study compared microbubble (mean diameter 37 μm) and conventional bubble (mean diameter 5.4 mm) ozonation systems under identical conditions. The experiments were normalised for effective ozone dose to determine whether microbubble ozonation generated significantly more hydroxyl radicals than conventional bubble ozonation. 4-chlorobenzoic was used as the hydroxyl radical probe and the proportion of hydroxyl radicals generated for a given effective ozone dose was quantified. The •OH-exposure to O3-exposure (the Rct) was used to compare the systems. The ratio of the mean RctMicrobubble to mean RctConventional was 0.73, 0.84 and 1.12 at pH 6, 7 and 8 respectively. Statistical assessment of the Rct showed that there was no significant difference between the bubble systems. No evidence was found to support the hypothesis that microbubble systems generate more •OH. Instead, the level of •OH-exposure is linked to the effective dose and pH of the system and future designs should focus on those factors to deliver •OH based benefits.

Magnetically separable NiFe2O4/sepiolite catalyst for enhanced ozonation treatment of quinoline and bio-treated coking wastewater in a catalytic ozonation system

In a quest to eliminate the bio-refractory organic pollutants in industrial wastewater, the NiFe2O4/SEP composites were synthesized via a sol-gel method and investigated by XRD, SEM, XPS, FTIR, VSM. The TOC removal increased from 16.82% to 69.35% in NiFe2O4/SEP+O3 system using quinoline as a target contaminant after 30 min, which is about 4.12 times as that in O3 system. The evolution of acetic acid, oxalic acid and formic acid in quinoline degradation was analyzed, saturated carboxylic acids were inertia to ozone molecules. However, 93.54% of oxalic acid was removed after 10 min, and 77.66% of acetic acid was degraded after 30 min in catalytic ozonation. The generation of small molecular organic acids could promote the Fe3+/Fe2+ redox cycle by complexing with Fe3+ on NiFe2O4/SEP, and then accelerated the formation of reactive oxygen species. In the presence of NiFe2O4/SEP, the high oxidation potential of •OH and •O2- contributed to an excellent TOC removal rate. Meanwhile, NiFe2O4/SEP was proved to be active for bio-treated coking wastewater in catalytic ozonation. The naturally fluorescent constituents in bio-treated coking wastewater were almost entirely removed by NiFe2O4/SEP+O3 system in 60 min. These findings indicated the good potential of NiFe2O4/SEP for practical applications in industrial wastewater treatment.

Treatment of C.I Reactive Blue 160 by ozonation system

This study was carried out to assess the treatment ability of color, dye, and COD in the dyeing wastewater containing C.I Reactive Blue 160 by ozonation system. Both batch and continuous operating modes with concurrent and counter-current flows were investigated. The effects of the ozone gas flow rate, pH, temperature, Na2CO3 concentration, and initial dye concentration were evaluated. The decolorization, dye removal efficiencies, and mineralization ability of COD by ozonation were determined. The results indicated that ozonation had high efficiency in the treatment of dyeing wastewater containing C.I Reactive Blue 160. The treatment performance was affected by the ozone gas flow rate, pH, temperature, Na2CO3 concentration, and initial dye concentration. The removal efficiency of color, dye, and COD were 98.04%, 99.84%, and 87.31% for the treatment of 200 mg/L initial dye concentration in batch mode with 30 min ozonation time, respectively. In the continuous operation and counter-current flow, the color, dye, and COD removal efficiencies reached 97.24%, 99.76%, and 86.38% after 30 min HRT, respectively, and higher than concurrent flow. The reaction of ozone and C. I Reactive Blue 160 was the first-order reaction in both batch and continuous operation. The complete mineralization required 90 min ozonation time.

Enhanced degradation of dimethyl phthalate in wastewater via heterogeneous catalytic ozonation process: performances and mechanisms.

Ozonation process is a promising yet challenging method for the removal of refractory organic matter due to the sluggish reaction for generating hydroxyl radical (˙OH) at a neutral pH condition. Herein, an efficient heterogeneous catalytic ozonation system using CeO2/Al2O3 catalyst was developed to remove dimethyl phthalate (DMP) from wastewater. Under a neutral condition of pH = 6, this system achieved almost 100% DMP removal within 15 min at an optimized catalyst dosage of 30 g L-1 and the ozone flow rate of 22.5 mg min-1. Moreover, the catalytic ozonation system exhibited a stable degradation performance of DMP in a wider pH range (pH = 5-10). The results of electron paramagnetic resonance (EPR) and quantitative tests confirmed the ultrafast conversion of O3 to ˙OH (0.774 μM min-1) on the surface of CeO2 based ceramic catalyst. The quenching experiments further supported the predominant role of ˙OH in the mineralization of DMP. These results highlight the potential of using the heterogeneous catalytic ozonation system for the efficient removal of refractory organic matter from wastewater.

Enhanced Ozone Oxidation by a Novel Fe/Mn@γ−Al2O3 Nanocatalyst: The Role of Hydroxyl Radical and Singlet Oxygen

Catalytic ozonation is a potential alternative to address the dye wastewater effluent, and developing an effective catalyst for catalyzing ozone is desired. In this study, a novel Fe/Mn@γ−Al2O3 nanomaterial was prepared and successfully utilized for catalytic ozonation toward dye wastewater effluent components (dimethyl phthalate and 1−naphthol). The synthesized Fe/Mn@γ−Al2O3 exhibited superior activity in catalytic ozonation of dimethyl phthalate and 1−naphthol in contrast to Fe@γ−Al2O3 and Mn@γ−Al2O3. Quench and probe tests indicated that HO° contributed to almost all removal of dimethyl phthalate, whereas O3, HO°, and singlet oxygen participated in the degradation of 1−naphthol in the Fe/Mn@γ−Al2O3/O3 system. The results of XPS, FT−IR, and EPR suggested that HO° and singlet oxygen were generated from the valence variations of Fe(II/III)and Mn(III/IV). Moreover, the Fe/Mn@γ−Al2O3/O3 system could also have excellent efficacy in actual water samples, including dye wastewater effluent. This study presents an efficient ozone catalyst to purify dye wastewater effluent and deepens the comprehension of the role and formation of reactive species involved in the catalytic ozonation system.

Lyapunov stable learning laws for multilayer recurrent neural networks

This study aims to develop stable learning laws (in the sense of Lyapunov) for a general class of multilayer recurrent neural network (RNN) non-parametric identifier. The application of control Lyapunov functions in the discrete-time domain ensures the ultimate boundedness for the identification error enforcing it to reach a boundary set related to the power of parametric uncertainties and the modeling error. This work presents a general algorithm to design RNNs with n layers: one input layer, n-2 hidden layers, and one output layer. Numerical simulations support the theoretical results showing the advantages of increasing the number of layers in an RNN structure. A first example identifies the unknown states of the Van Der Pol oscillator. Then, a second example demonstrates the behavior of an RNN in a third-order system with high nonlinear dynamics describing an ozonation system of a single contaminant. For both cases, the application of the developed learning laws succeeds in estimating the uncertain dynamics. Moreover, the numerical simulations show how the identification error decreases as the number of layers increases.

Fischer–Tropsch synthetic wastewater treatment with Fe/Mn@CH: Catalytic ozonation and process evaluation

• Fe-Mn@CH with high catalytic activity was prepared. • The organic matter is transformed into protein-like and tryptophan-like substances. • Ozone catalytic oxidation process is closer to the secondary reaction kinetics. • A multi-level-gray relational evaluation model is established. In this study, the honeycomb ceramic catalyst Fe/Mn@CH with high catalytic activity was prepared. The effect of preparation conditions on the catalytic performance of Fe/Mn@CH was systematically studied. Scanning electron microscope; X-ray energy spectrum analysis; X-ray diffraction; specific surface area, pore distribution and adsorption performance analysis; X-ray fluorescence spectroscopy; and X-ray photoelectron spectroscopy were performed to analyze the structural characteristics of the catalyst. The optimal working conditions of the catalytic ozonation system for the degradation of Fischer–Tropsch synthesis wastewater were also studied. The metal elements Fe and Mn were successfully loaded on the surface of the honeycomb ceramic carrier in the form of α-MnO 2 and α-Fe 2 O 3 oxides. The optimal COD removal rate could reach 64.37% at pH of 9, ozone dosage of 6 g/h, Fe/Mn@CH dosage of 50 g/300 mL, and reaction time of 60 min. The specific mechanism of catalytic ozonation in the presence of tert -butanol was explored through ultraviolet absorption spectroscopy and three-dimensional fluorescence spectroscopy. The COD removal efficiency for Fischer–Tropsch synthesis wastewater was analyzed on the basis of catalytic oxidation reaction kinetics. Finally, a multilevel gray correlation evaluation model was established for the quantitative evaluation of the ozonation catalytic oxidation of Fischer–Tropsch wastewater.

Ultrafine bubbles as an augmenting agent for ozone-based advanced oxidation.

In this study, the influence of nanobubbles (NBs) application in ozone (O3) based advanced oxidation processes (AOP) is investigated. The results demonstrate the potential of NBs application to O3 - based AOP. It was observed that NBs suppress the negative influence of pH and operating temperatures on the efficiency of ozonation. In addition, the application of NBs tends to improve the solubility of O3 and the rate of mass transfer under the influence of a broad range of temperature and pH conditions. The results of this research indicate that application of NBs minimized the reduction in concentration of dissolved O3 with an increase in temperature. Furthermore, application of NBs highly improved the OH radical formation in acidic conditions. The results of this research depicted for first time that the application of NBs strongly encourages the initiation of reactions involving OH radicals. It was found by this research that NBs can boost the concentration of OH radicals up to 3.5 fold compared to equivalent MB-supported ozonation systems. This is assumed to improve the efficiency of currently existing conventional bubble supported O3 - based AOP systems.

Recent Development in Sludge Biochar-Based Catalysts for Advanced Oxidation Processes of Wastewater

Sewage sludge as waste of the wastewater treatment process contains toxic substances, and its conversion into sludge biochar-based catalysts is a promising strategy that merges the merits of waste reutilization and environmental cleanup. This study aims to systematically recapitulate the published articles on the development of sludge biochar-based catalysts in different advanced oxidation processes of wastewater, including sulfate-based system, Fenton-like systems, photocatalysis, and ozonation systems. Due to abundant functional groups, metal phases and unique structures, sludge biochar-based catalysts exhibit excellent catalytic behavior for decontamination in advanced oxidation systems. In particular, the combination of sludge and pollutant dopants manifests a synergistic effect. The catalytic mechanisms of as-prepared catalysts in these systems are also investigated. Furthermore, initial solution pH, catalyst dosage, reaction temperature, and coexisting anions have a vital role in advanced oxidation processes, and these parameters are systematically summarized. In summary, this study could provide relatively comprehensive and up-to-date messages for the application of sludge biochar-based catalysts in the advanced oxidation processes of wastewater treatment.

Removal of pharmaceuticals by advanced treatment methods

The removal of endocrine disrupting compounds (EDCs) remains a big challenge in water treatment in terms of public health. The aim of the study was evaluating the performance of nano TiO2, ozone, and UV system for removal of EDCs. In this study, the efficiency of the nano TiO2 to degrade target EDCs under catalytic and photocatalytic ozonation was examined at different operational conditions. The maximum removal of target pollutant was obtained with pH 6.8; ozone concentration 10 mg/L; catalyst dosage 0.050 g/L and the duration time of the photocatalytic performances was 10 min showing the most treatment conditions respectively. In addition, the surface reaction mechanism of endocrine disrupting compound removal by catalytic and photocatalytic ozonation was investigated. The results showed that the catalyst can significantly enhance the removal of target compound. The 99.0%, 88.3% and 51.8% removal rates were obtained at photocatalytic ozonation, catalytic ozonation and sole ozonation, respectively. These results indicated that the Ozone/TiO2/UV process was favorable for engineering applications for removal of endocrine disrupting compounds such as steroid hormone and likely similar micro pollutants.