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To address the problem of petrochemical organic pollutants in water, specifically monoethylene glycol (MEG) present in industrial process streams, in this research, we synthesized and evaluated a multifunctional nanocomposite, Fe3O4@MC/MWCNT-CuO/Ag. The nanocomposite was produced by combining magnetic Fe3O4 nanoparticles, methylcellulose (MC), multi-walled carbon nanotubes (MWCNTs), and CuO/Ag nanoparticles by an integrated synthesis process. A consistent dispersion of nanoparticles, with diameters ranging from 30-40 nm, was discovered by FESEM analysis, showing effective integration without aggregation. Effective synthesis was demonstrated by well-doped and evenly dispersed CuO and Ag nanoparticles. Functional groups that improve electrostatic interactions with contaminants hence enhancing catalytic performance and adsorption efficiency, were validated by FTIR analysis. XRD indicated an unchanged crystal structure with an average crystallite size of 8.67 nm. The anticipated elemental composition was verified by EDS & mapping. A VSM study revealed magnetic characteristics (9.33 emu/g) that simplify nanocomposite separation and reuse. TGA proved thermal stability to be up to 600 °C. A BET study showed a highly specific surface area of 67.661 m2/g, enhancing adsorption. According to DRS and PL studies, the bandgap was lowered by 1.31 eV, which led to better optical absorption. The nanocomposite exhibited notable MEG removal efficiency, with 72 % in adsorption, 65 % in photocatalysis, and 56 % in sonocatalysis. This makes it a promising alternative for the remediation of organic pollutants in water treatment.

Advanced oxidation processes are emerging technologies for the decomposition of organic pollutants in various types of water by harnessing solar energy. The purpose of this study is to examine the physicochemical characteristics of tungsten(VI) oxide (WO3) photoanodes, with the aim of enhancing oxidation processes in the treatment of water. The fabrication of WO3 coatings on conductive fluorine-doped tin oxide (FTO) substrates was achieved through a wet coating process that utilized three different liquid formulations: a dispersion of finely milled WO3 particles, a fully soluble WO3 precursor (acetylated peroxo tungstic acid), and a combination of both (applying a brick-and-mortar strategy). Upon subjecting the WO3 coatings to firing at a temperature of 450 °C, it was observed that their properties exhibited marked variations. The fabricated photoanodes are examined using a range of analytical techniques, including profilometry, thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), and voltammetry. The experimental data suggest that the layers generated through the combination of particulate ink and soluble precursor (referred to as the brick-and-mortar building approach) display advantageous physicochemical properties, rendering them suitable for use as photoanodes in photoelectrochemical cells.

The degradation of diisopropyl methylphosphonate (DIMP) in aqueous solutions was studied using ultrasound irradiation with a fixed frequency of 26.2 kHz, following the first-order kinetic model. The study's primary goal was to determine the influence of the following experimental parameters: the pH (at different values of 2, 7 and 10), the initial concentration of DIMP (at different concentrations: 7, 14, 30, 50, 80 mg/L), the processing time (at different periods: 15, 30, 45, 60, 80, 90 min), and the concentration of the additive CCl4 (at different concentrations: 0.002, 0.004, 0.006, 0.008 mg/L). A DIMP removal efficiency of 98% from aqueous solution was obtained at pH 10 and 0.008 mg/L CCl4, after an ultrasound irradiation time of 45 min, pointing out the influence of the above-mentioned experimental parameters on the DIMP degradation process.

Over the past few decades, peroxymonosulfate (PMS)-driven advanced oxidation processes (AOPs) have garnered substantial interest in the field of organic decontamination. The copper (Cu)/PMS system is intriguing due to its diverse activation pathways and has been extensively employed for the clearance of refractory organic pollutants in water. This article is designed to offer a comprehensive overview of the latest trends in Cu-based catalysts such as single-metal and mixed-metal catalysts aimed at treating recalcitrant pollutants, highlighting PMS activation. Subsequently, investigative methodologies for assessing PMS activation with copper-based catalysts are reviewed and summarized. Then, the implications of pH, PMS and catalytic agent concentrations, anions, and natural organic matter are also addressed. The combination of Cu-based catalyst/PMS systems with other advanced oxidation technologies is also discussed. Following that, the degradation mechanisms in the Cu-based catalyst-activated PMS system are considered and synopsized. Lastly, potential future research avenues are proposed to enhance the technology and offer support for developing of economically viable materials based on copper for activating PMS.

In this research, nanoparticles of NiFe2O4, Zn0.5Ni0.5Fe2O4, TiO2-Zn0.5Ni0.5Fe2O4 and TiO2-Zn0.5Ni0.5Fe2O4-rGO were synthesized respectively by combustion sol-gel method, co-precipitation and two nanocomposite samples by physical mixing method. For the characterization of nanoparticles from Fourier transform infrared (FT-IR) analysis, X-ray diffraction pattern (XRD), Scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), Diffuse Reflectance Spectroscopy (DRS) and porosimetry measurements. Adsorption and desorption have been used with BET. The results show that the synthesized particles are nanoscale ,and the absorption process takes place inside the holes. Also, the advanced oxidation process (AOP) was evaluated using photocatalyst for nanoparticles and the best performance was TiO2-Zn0.5Ni0.5Fe2O4-rGO nanocomposite with saturation magnetism (emu/g) of 65.88 with It showed a destruction of 95%.

Following the goals of the circular economy, this work demonstrates that an industrial by-product can be used in environmental remediation. Metallurgical slag and citric acid were used to form an Fe:Cit complex by simultaneously carrying out the lixiviation of the iron and the chelating stages with an 87% iron recovery. This complex was evaluated in the photo-Fenton process to produce HO• through salicylic acid dosimetry or salicylic acid hydroxylation, producing 0.13 ± 0.1 mM HO• after 30 min of operation; such a value is three orders of magnitude higher than the one reported for the metallurgical slag (as a heterogeneous catalyst, 22 μM) in the photo-Fenton-like process. The system was tested for its ability to degrade a mixture of drugs, including dexamethasone (DEX), naproxen (NAP), and ketorolac (KTR), which are often used to treat the symptoms of COVID-19. The drug degradation tests were performed in two stages. In the first stage, the Fe:Cit complex from the metallurgical slag was compared to the one formed by analytical-grade reactants; the drug degradation was faster for the former, with the major difference being observed at 5 cm and 500 W/m2. Here, 85–90% of the drugs was degraded in 5 min using Fe:Cit from slag, while at least 20 min was necessary to achieve such degradation with the analytical reagent, conceivably because of the trace compounds being lixiviated from the slag. Then, the effects of the liquid depth (5, 10, and 15 cm) and irradiance (250, 500, and 750 W/m2) were tested; the pseudo-first-order kinetic degradation constants for the three model pollutants were in the range of 0.009 > kD > 0.09 min−1, showing that degradation is more feasible for DEX than for NAP and KRT because the radical attack feasibility is related to the molecular structures.

In the ozonation process, the phenol degradation in wastewater undergoes a low mass transfer mechanism. In this study, ozonized packed bubble column reactor was designed and constructed to remove phenol. The reactor’s inner diameter and height were 150 and 8 cm, respectively. The packing height was kept constant at 1 m in accordance with the reactor hydrodynamics. The gas distributor was designed with 55 holes of 0.5 mm. The phenol removal efficiency was evaluated at ozone concentrations of 10, 15, and 20 mg/L, contact times of 15, 30, 45, 60, 75, 90, 105, and 120 min, and phenol concentrations of 3, 6, 9, 12, and 15 mg/L. The results indicated that the highest phenol removal efficiency of 100% was achieved at 30 min in presence of packing. Moreover, the use of packing improved the contact between the gas and liquid, which significantly enhanced the phenol degradation. Actually, a thin film over a packing surface enhances the mass transfer. Also, it was found that the phenol is degraded into CO2 and H2O through a series of reaction steps. Additionally, a kinetic study of a first-order reaction provided an efficient estimation of reaction parameters with a correlation factor of 0.997.

Soil contamination by polycyclic aromatic hydrocarbons (PAHs) has been an environmental issue worldwide, which aggravates the ecological risks faced by animals, plants, and humans. In this work, the composites of nanoscale zero-valent iron supported on carbonylated activated carbon (nZVI-CAC) were prepared and applied to activate persulfate (PS) for the degradation of PAHs in contaminated soil. The prepared nZVI-CAC catalyst was characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). It was found that the PS/nZVI-CAC system was superior for phenanthrene (PHE) oxidation than other processes using different oxidants (PS/nZVI-CAC > PMS/nZVI-CAC > H2O2/nZVI-CAC) and it was also efficient for the degradation of other six PAHs with different structures and molar weights. Under optimal conditions, the lowest and highest degradation efficiencies for the selected PAHs were 60.8% and 90.7%, respectively. Active SO4−• and HO• were found to be generated on the surface of the catalysts, and SO4−• was dominant for PHE oxidation through quenching experiments. The results demonstrated that the heterogeneous process using activated PS with nZVI-CAC was effective for PAH degradation, which could provide a theoretical basis for the remediation of PAH-polluted soil.

A large variety of pharmaceutical compounds have recently been detected in wastewater and natural water systems. This review highlighted the significance of removing pharmaceutical compounds, which are considered indispensable emerging contaminants, from wastewater and natural water systems. Various advanced oxidation processes (AOPs), including UV-H2O2, Fenton and photo-Fenton, ozone-based processes, photocatalysis, and physical processes, such as sonolysis, microwave, and electron beam irradiation, which are regarded as the most viable methods to eliminate different categories of pharmaceutical compounds, are discussed. All these AOPs exhibit great promising techniques, and the catalytic degradation process of the emerging contaminants, advantages, and disadvantages of each technique were deliberated. Heterogeneous photocatalysis employing metal oxides, particularly anatase TiO2 nanoparticles as catalysts activated by UV light irradiation, was reviewed in terms of the electron–hole separation, migration of the charge carriers to the catalyst surfaces, and redox potential of the charge carriers. This brief overview also emphasized that anatase TiO2 nanoparticles and TiO2-based nanomaterials are promising photocatalysts, and a combination of photocatalysis and other AOPs enhanced photocatalytic degradation efficiency. Finally, the challenges of applying anatase TiO2-based photocatalysis in environmental remediation and wastewater treatments to degrade pharmaceutical compounds, including mass spectroscopic analysis and a biological activity test of by-products of the emerging contaminants resulting from photocatalysis, are summarized.

The release of organic contaminants has grown to be a major environmental concern and a threat to the ecology of water bodies. Persulfate-based Advanced Oxidation Technology (PAOT) is effective at eliminating hazardous pollutants and has an extensive spectrum of applications. Iron-based metal–organic frameworks (Fe-MOFs) and their derivatives have exhibited great advantages in activating persulfate for wastewater treatment. In this article, we provide a comprehensive review of recent research progress on the significant potential of Fe-MOFs for removing antibiotics, organic dyes, phenols, and other contaminants from aqueous environments. Firstly, multiple approaches for preparing Fe-MOFs, including the MIL and ZIF series were introduced. Subsequently, removal performance of pollutants such as antibiotics of sulfonamides and tetracyclines (TC), organic dyes of rhodamine B (RhB) and acid orange 7 (AO7), phenols of phenol and bisphenol A (BPA) by various Fe-MOFs was compared. Finally, different degradation mechanisms, encompassing free radical degradation pathways and non-free radical degradation pathways were elucidated. This review explores the synthesis methods of Fe-MOFs and their application in removing organic pollutants from water bodies, providing insights for further refining the preparation of Fe-MOFs.

The carbonous-based nanocomposites of CoCr layered double hydroxide (LDH) with graphene oxide (GO) and reduced graphene oxide (rGO) were prepared. The successful synthesis of the CoCr LDH in hydrotalcite crystalline structure was deduced from the pattern obtained from X-ray diffraction, and the chemical composition of its surface was checked by X-ray photoelectron spectroscopy. The prosperous decorating of LDH on the sheets of rGO and GO was authenticated by the energy dispersive X-ray spectroscopy analysis and micrographs of scanning electron and transmission electron microscopy. The photo-assisted sonocatalytic activity of the prepared nanocomposites was appraised for the decomposition of dimethyl phthalate (DMP) as a plasticizer. The highest decomposition efficiency of 100% was obtained in the existence of CoCr LDH/rGO nanocomposite (0.5 g/L) during 20 min of reaction time via photo-assisted sonocatalysis. The rGO improved the catalytic activity of the CoCr LDH by increasing the specific surface area from 1.2 m2/g to 4.5 m2/g and reducing the band gap from 1.7 eV to 1.3 eV. Moreover, the results of the colony-forming unit method endorsed antibacterial property improvement of the CoCr LDH via hybridizing with rGO. The results of this research provide an optimistic perspective for applying carbonous-based nanocomposites of CoCr LDH as a novel catalyst with antibacterial properties in photo-assisted sonocatalytic processes.

Water reclamation from lakes needs to be accomplished efficiently and affordably to ensure the availability of clean, disinfected water for society. Previous treatment techniques, such as coagulation, adsorption, photolysis, ultraviolet light, and ozonation, are not economically feasible on a large scale. This study investigated the effectiveness of standalone HC and hybrid HC + H2O2 treatment techniques for treating lake water. The effect of pH (3 to 9), inlet pressure (4 to 6 bar), and H2O2 loading (1 to 5 g/L) were examined. At pH = 3, inlet pressure of 5 bar and H2O2 loadings of 3 g/L, maximum COD and BOD removal were achieved·H2O2 was observed to significantly improve the performance of the HC when used as a chemical oxidant. In an optimal operating condition, a COD removal of 54.5 % and a BOD removal of 51.5 % using HC alone for 1 h is observed. HC combined with H2O2 removed 64 % of both COD and BOD. The hybrid HC + H2O2 treatment technique resulted in a nearly 100% removal of pathogens. The results of this study indicate that the HC-based technique is an effective method for removing contaminants and disinfection of the lake water.

Water is one of the major sources that spread human diseases through contamination with bacteria and other pathogenic microorganisms. This review focuses on microbial hazards as they are often present in water and wastewater and cause various human diseases. Among the currently used disinfection methods, sonochemical reactors (SCRs) that produce free radicals combined with advanced oxidation processes (AOPs) have received significant attention from the scientific community. Also, this review discussed various types of cavitation reactors, such as acoustic cavitation reactors (ACRs) utilizing ultrasonic energy (UE), which had been widely employed, involving AOPs for treating contaminated waters. Besides ACRs, hydrodynamic cavitation reactors (HCRs) also effectively destroy and deactivate microorganisms to varying degrees. Cavitation is the fundamental phenomenon responsible for initiating many sonochemical reactions in liquids. Bacterial degradation occurs mainly due to the thinning of microbial membranes, local warming, and the generation of free radicals due to cavitation. Over the years, although extensive investigations have focused on the antimicrobial effects of UE (ultrasonic energy), the primary mechanism underlying the cavitation effects in the disinfection process, inactivation of microbes, and chemical reactions involved are still poorly understood. Therefore, studies under different conditions often lead to inconsistent results. This review investigates and compares other mechanisms and performances from greener and environmentally friendly sonochemical techniques to the remediation of microbial hazards associated with water and wastewater. Finally, the energy aspects, challenges, and recommendations for future perspectives have been provided.

Water pollution has become one of the most serious environmental issues recently, especially in relation to chemical-containing wastewater. Uncontrolled industrial waste, including large amounts of dye-containing wastewater from textile industries, needs intensive attention. In this work, the synthesis of Fe3O4@SiO2 nanocomposite biogenic silica from Salacca zalacca leaf ash was conducted for the photo-Fenton-like degradation of dye waste. The use of Salacca zalacca leaf ash and the nanoflake form is the novelty of this work. The physicochemical characterization of the material was conducted using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and diffuse reflectance UV-visible spectroscopy (UV-DRS) analyses, and photocatalytic activity of material was investigated in wet peroxidation of rhodamine B and batik wastewater. The results showed homogeneously dispersed Fe3O4 in SiO2 support with a nanoflake form, and a crystallite size of 44.9 nm was obtained. XRD investigation revealed the single phase of Fe3O4, which is consistent with the TEM analysis. The bandgap energy of 2.21 eV was reported from UV-DRS measurements, which influenced the increasing photocatalytic activity and reusability of the nanocomposite compared to pure Fe3O4. The photocatalyst showed the maximum degradation efficiency (DE) of 99.9% after 60 min, and the reusability feature was expressed, as there was an insignificant change in the DE over the fifth cycle of use. The material exhibited photocatalytic oxidation of batik wastewater as the removal of total suspended solids, chemical oxygen demand, and color reached 95.55%, 89.59%, and 90.00%, respectively.

Triclosan (TCS), a broad-spectrum bacteriostatic agent with bactericidal and disinfectant properties, is one of the emerging pollutants of great interest. The electrically activated persulfate-coupled carbon membrane system was studied in this paper. The removal of triclosan achieved 90% within 40 min. Complete degradation can be achieved within 90 min. The electrode was characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The optimal reaction conditions were explored. The catalytic mechanism of the reaction was investigated. It was proved that hydroxyl radicals, sulfate radicals, and singlet oxygen were the main reactive oxygen species in the reaction process by the free radical quenching experiment and electron paramagnetic resonance spectrometer. The degradation path and mechanism of triclosan were investigated.

The visible-light-driven photocatalytic degradation of pharmaceutical pollutants in aquatic environments is a promising strategy for addressing water pollution problems. This work highlights the use of bromine-ion-doped layered Aurivillius oxide, Bi2WO6, to synergistically optimize the morphology and increase the formation of active sites on the photocatalyst’s surface. The layered Bi2WO6 nanoplates were synthesized by a facile hydrothermal reaction in which bromine (Br−) ions were introduced by adding cetyltrimethylammonium bromide (CTAB)/tetrabutylammonium bromide (TBAB)/potassium bromide (KBr). The as-synthesized Bi2WO6 nanoplates displayed higher photocatalytic tetracycline degradation activity (~83.5%) than the Bi2WO6 microspheres (~48.2%), which were obtained without the addition of Br precursors in the reaction medium. The presence of Br− was verified experimentally, and the newly formed Bi2WO6 developed as nanoplates where the adsorbed Br− ions restricted the multilayer stacking. Considering the significant morphology change, increased specific surface area, and enhanced photocatalytic performance, using a synthesis approach mediated by Br− ions to design layered photocatalysts is expected to be a promising system for advancing water remediation.

ENVIRONMENTAL APPLICATIONS OF PERSULFATE: REMEDIATION OF CONTAMINATED GROUNDWATER AND SOILS. Environmental remediation represents a major technological challenge due to the complexity of the environmental matrices and the high treatment cost. In recent years, in situ chemical oxidation technologies (ISCO) have shown a good cost/benefit ratio, which has favored their use in the degradation of several relevant environmental pollutants. In this context, persulfate-mediated processes are of relevant importance once persulfate can be activated in situ, promoting the formation of highly oxidative radical species. Persulfate-based treatments have been frequently reported in environmental remediation studies because they guarantee the effective degradation of pollutants without producing significant changes in the remediated matrix. Given these statements, this study aims to discuss the main ways of activating persulfate and the relevant applications in the remediation of groundwater and soils contaminated with resistant organic pollutants.

Photocatalytic removal of bisphenol A, one of the most widely and emerging pollutants in the aquatic environment, was investigated by advanced oxidation process under natural sunlight. The removal process by a metal-organic framework, synthesized with phosphonic acid ligand, namely STA-12 (Fe) and hydrogen peroxide revealed excellent results. Therefore, the optimal conditions for the degradation of bisphenol A by the photo-Fenton mechanism were studied. The removal process follows the first-order kinetics with respect to the contaminant and a significant synergy was observed in the catalytic system of hydrogen peroxide/sunlight/STA-12 (Fe). The Optimal values for pH, irradiation time, catalyst amount and H2O2 dosage for oxidation of bisphenol A in 30 mg / l aqueous solution were determined to be 5, 90 minutes, 10 mg and 12 μl, respectively. Under these conditions, the best removal efficiency was 79.8%. Also, the mineralization value of organic pollutant was determined to equal 51% by measuring TOC. To determine the most important species that affected the photocatalytic reduction, trapping experiments were carried out, using various kinds of scavengers and the results showed that the hydroxyl radicals (•OH) are the main oxidizing agent in the photocatalytic system and superoxide radical and the holes in the photocatalyst surface are less involved in the process of contaminant degradation. Finally, a probable reaction mechanism has been investigated in detail. In addition, the catalyst has recyclability and stability in the photocatalytic reaction. This study is the first report for application of a phosphonate-based MOF for the removal of an emerging pollutant with a photo-Fenton mechanism and presents a new example of solar-driven advanced oxidation process for the treatment of aquatic sources and environmental protection.

Hydrodynamic cavitation (HC) has been extensively investigated for effluent treatment applications. Performance of HC devices or processes is often reported in terms of degradation of organic pollutants rather than quantification of hydroxyl (OH) radicals. In this study, generation of OH radicals in vortex based cavitation device using coumarin dosimetry was quantified. Coumarin was used as the chemical probe with an initial concentration of 100 µM (15 ppm). Generation of OH radicals was quantified by analysing generated single hydroxylated products. The influence of operating parameters such as pH and type of acid used to adjust pH, dissolved oxygen, and inlet and outlet pressures was investigated. Acidic pH was found to be more conducive for generating OH radicals and therefore subsequent experiments were performed at pH of 3. Sulphuric acid was found to be more than three times effective than hydrochloric acid in generating OH radicals. Effect of initial levels of dissolved oxygen was found to influence OH radical generation. Performance of vortex based cavitation device was then compared with other commonly used cavitation devices based on orifice and venturi. The vortex based cavitation device was found to outperform the orifice and venturi based devices in terms of initial per-pass factor. Influence of device scale (nominal flow rate through the device) on performance was then evaluated. The results presented for these devices unambiguously quantifies their cavitational performance. The presented results will be useful for evaluating computational models and stimulate further development of predictive computational models in this challenging area.

Biochar-supported copper/manganese oxide composite (CuOx-MnOy@BC) as a useful Fenton-like catalyst was synthesized and characterized. The nanocatalyst was applied to eliminate metronidazole (MNZ) from an aqueous wastewater. 99.7% of MNZ and 55.2% of the total organic carbon (TOC) removal were achieved at 20 mM of H2O2, 0.75 mg/L of CuOx-MnOy@BC, and 20 mg/L of MNZ under neutral pH, and the catalyst remained active under a wide range of pH. Free radicals quenching studies verified the dominant role of hydroxyl radicals produced through activation of H2O2 with the synergistic effect of Cu2+, Mn2+, persistent free radicals, and visible light. The reusability of catalyst was confirmed through five repeated uses.

This work provides new insight into the development of the TiO2/Oxone/UV-LED process for organic contaminant degradation as well as hospital waste management. The Moxifloxacin (MOX) degradation using Oxone activated TiO2 under UV-LED was studied. The TiO2/Oxone/UV LED process was carried out by the addition of Oxone (0.025, 0.05, 0.1 and 0.2 mM) activated by TiO2 different concentrations 0.0125, 0.025, 0.05, 0.1 and 0.5 g/L. The degradation efficiency was studied by HPLC having UV/Vis detector, C18 column (5µ, 4.6 × 250 mm2). The complete removal of 10 ppm of MOX occurred at 0.1 g/L TiO2 and 0.1 mM Oxone with UV-LED exposure time of 12 min. The TOC analysis was performed and 55% TOC reduction was observed at described procedure. The parameters such as drug initial concentration, Oxone, TiO2 dosages and pH were optimized and their effects on degradation were noted. The pseudo-first order reaction kinetics was observed for MOX degradation. It was revealed from the mechanism of activation that SO4-. and OH. have played a key role in the degradation. The effect of pH (3.6–11) was observed to evaluate the degradation rate of Moxifloxacin. The pH 9.4 achieved the maximum degradation. The UPLC-ESI-MS analysis was performed to identify the intermediates and degraded end-products.

The shortage of water resources has caused extensive research to be conducted in this field to develop effective, rapid, and affordable wastewater treatment methods. For the treatment of wastewater, modern oxidation techniques are desirable due to their excellent performance and simplicity of implementation. In this project, wet impregnation and the hydrothermal technique were applied to synthesize a modified catalyst. Different analysis methods were used to determine its characteristics, including XRD, BET, FT-IR, NH3−TPD, and FE-SEM. The catalyst features a spherical shape, large surface area, high crystallinity, and uniform active phase dispersion. In order to eliminate the methylene blue dye as a modeling effluent, the catalyst’s performance was examined in a heterogeneous quasi-electro-Fenton (EF) reaction. The impact of various performance characteristics, such as catalyst concentration in the reaction medium, solution pH, and current intensity between the two electrodes, was elucidated. According to the results, the best operational circumstances included a pH level of 2, a catalyst concentration of 0.15 g/L, and a current of 150 mA, resulting in the greatest elimination efficiency of 101%. The catalyst’s performance was stable during three consecutive tests. A pseudo-first-order model for the elimination reaction’s kinetics was developed, which showed acceptable agreement with the experimental results. This study’s findings help clarify how well the heterogeneous zeolite catalyst functions in the pseudo-EF reaction. The results revealed the method’s potential to be implemented in wastewater treatment. An artificial neural network model is utilized to predict the removal percentage. The hyperparameter tuning is used to find the best model, and the model achieved an MAE of 1.26% and the R2 was 0.99.

Iron-based materials are widely applied in Fenton chemistry, and they have promising prospects in the processing of wastewater. The composition complexity and rich chemistry of iron and/or oxides, however, hamper the precise understanding of the active sites and the working mechanism, which still remain highly controversial. Herein, iron oxides of four different model systems are designed through a conventional precipitation method plus H2 reduction treatment. These systems feature Fe@Fe3O4 with abundant oxygen vacancy, Fe0 and Fe3O4 particles with interface structures, and Fe3O4-dominated nanoparticles of different sizes. These materials are applied in the decomposition of methyl orange as a model reaction to assess the Fenton chemistry. The Fe@Fe3O4 with core–shell structures exhibits significantly higher decomposition activity than the other Fe3O4-rich nanoparticles. A thin Fe3O4 layer formed by auto-oxidation of iron particles when exposed to air can boost the activity as compared with the Fe0 and Fe3O4 particles with interface structures but poor oxygen vacancy. The unique hetero-structure with the co-existence of both metallic iron and oxygen vacancy displays excellent redox propensity, which might account for the superior Fenton activity. This finding provides a new perspective to understand and design highly efficient iron-based Fenton catalysts.

In this paper, high-activity manganese oxide was prepared from electrolytic manganese anode slime to realize the efficient removal of antibiotics. The effects of sulfuric acid concentration, ethanol dosage, liquid–solid ratio, leaching temperature and leaching time on the leaching of manganese from electrolytic manganese anode slime were systematically studied. Under the optimal conditions, the leaching rate of manganese reached 88.74%. In addition, a Mn3O4 catalyst was synthesized and used to activate hydrogen persulfate (PMS) to degrade tetracycline hydrochloride (TCH). The synthesized Mn3O4 was characterized by XRD, XPS, Raman, SEM and HRTEM. As a result, the prepared Mn3O4 is spherical, with high purity and crystallinity. The catalytic activity of Mn3O4 for PMS to degrade TCH was increased to 82.11%. In addition, after four cycles, the performance remained at 78.5%, showing excellent stability and recyclability. In addition, O2− and 1O2 are the main active species in the degradation reaction. The activity of Mn3O4 is attributed to it containing Mn(II) and Mn(III) at the same time, which can quickly realize the transformation of high-valence and low-valence manganese, promote the transfer of electrons and realize the degradation of organic pollutants.

It is important to further enhance the performance of green and efficient non-homogeneous catalysts for advanced oxidation process of Peroxymonosulfate (PMS-AOP) for green treatment of industrial wastewater. In this paper, nitrogen–sulfur co-doped MOFs-derived carbon material (CoSN@C) was prepared by one-pot synthesis followed by carbonization, and its morphological structure was characterized by XRD and SEM. After pyrolysis, the CoSN@C still maintained the dodecahedral morphology and structure of ZIF-67. The synergistic effects of S and N significantly elevated the activation of PMS. The results show that the CoSN@C + PMS system can effectively activate PMS to degrade Rhodamine B (RhB), with a rate constant (1.85 min−1) four times higher than that of the CoN@C + PMS system (0.44 min−1). The optimal catalytic process parameters of material dosage, PMS concentration, temperature, pH, and other parameters were also investigated for the activation of PMS to remove Rhodamine B. The cyclic experiment shows that the CoSN@C has excellent recyclability and the degradation rate of RhB still reached 88.9% after four cycles. Radical capture experiments and EPR tests showed that the CoSN@C + PMS system generated a large amount of SO4·− and ·OH radicals adsorbed on the catalyst surface and a certain amount of singlet oxygen, and the free radical pathway and non-radical pathway worked together to degrade RhB efficiently and rapidly. While non-radical pathway with singlet oxygen as main reactive oxygen species played a key role in the CoN@C + PMS system. This work provides a new idea for the rational design of non-homogeneous catalysts for PMS-AOP system.

The purpose of this study is to convert bauxite mining tailing waste into magnetic nanocomposite as catalyst in catalytic wet peroxidation of tetracycline. The preparation of material was performed via hydrothermal method of immobilized iron oxide precursor of Fe2+ and Fe3+ in alkaline condition, followed by calcination. The obtained nanocomposite was characterized using X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and vibration sample magnetometer. The results from XRD, XPS and TEM analyses showed that the composite composed as the dispersed γ-Fe2O3 in combination with Fe3O4 nanoparticles. The catalytic activity studies of the nanocomposite showed the capability of material to remove tetracycline with supportive adsorption capability. The oxidation of tetracycline was recorded to follow pseudo-first kinetics with removal efficiency of 89.7 % for 20 ppm of tetracycline. Insignificant change of removal efficiency at varied tetracycline concentration ranging at 2–40 ppm indicated its potential to be active in wide range of concentration. In addition, the nanocomposite showed stability as studied by XRD analysis along with the easy in separation as the magnetic properties with magnetism of 9.8 emu/g.

In this study, ZnCr layered double hydroxide (LDH), ZnCr LDH/carbon nanotube (CNT), and ZnCr LDH/Biochar (BC) were synthesized and characterized by various analyses. The successful synthesis and the great crystallinity of the samples were consented by XRD analysis. SEM and TEM were applied to study the morphology of the synthesized samples. The simultaneous presence of C, Zn, and Cr elements was well confirmed by EDX and dot mapping analyses demonstrating the successful preparation of nanocomposites. According to the BET analysis, ZnCr LDH nanocomposites with BC and CNT had more specific surface area compared to ZnCr LDH alone. The catalytic performances of the samples were determined for the degradation of rifampicin (RF). The degradation efficiency of the sonophotocatalytic process in the presence of 0.6 g L−1 of ZnCr LDH/BC toward 15 mg L−1 of RF under 150 W ultrasound and visible light irradiation was found to be about 100% within 40 min. The influence of the reactive species on the sonophotocatalytic process was assessed via the addition of different scavengers (para-benzoquinone (p-BQ), formic acid (FA), isopropyl alcohol (IPA)), and enhancers (hydrogen peroxide and potassium persulfate). The GC–MS analysis was carried out and eleven by-products during the RF decomposition were detected.

Removal of recalcitrant organic pollutants by degradation or mineralization from industrial waste streams is continuously being explored to find viable options to apply on the commercial scale. Herein, we propose a titanium nanotube array (based on a non-ferrous Fenton system) for the successful degradation of a model contaminant azo dye, methyl orange, under simulated solar illumination. Titanium nanotube arrays were synthesized by anodizing a titanium film in an electrolyte medium containing water and ethylene glycol. Characterization by SEM, XRD, and profilometry confirmed uniformly distributed tubular arrays with 100 nm width and 400 nm length. The non-ferrous Fenton performance of the titanium nanotube array in a minimal concentration of H2O2 showed remarkable degradation kinetics, with a 99.7% reduction in methyl orange dye concentration after a 60 min reaction time when illuminated with simulated solar light (100 mW cm−2, AM 1.5G). The pseudo-first-order rate constant was 0.407 µmol−1 min−1, adhering to the Langmuir–Hinshelwood model. Reaction product analyses by TOC and LC/MS/MS confirmed that the methyl orange was partially fragmented, while the rest was mineralized. The facile withdrawal and regeneration observed in the film-based titanium nanotube array photocatalyst highlight its potential to treat real industrial wastewater streams with a

The removal of water pollutants by photocatalysis is a promising technique, mainly due to its environmentally friendly and sustainable nature. In this study, the degradation of a recalcitrant organic pollutant, malachite green (MG), was investigated in water by a microstructured silver oxide photocatalyst. The silver oxide (Ag2O) microparticles (MPs) were synthesized by a low-cost, green method, mediated by green tea leaves extract. The surface, morphological and optical properties of the synthesized Ag2O MPs were determined by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-visible) spectrophotometry. The synthesized Ag2O MPs showed good photoactivity, represented by 83% degradation of malachite green (MG) ([C]0 = 0.4 mM, Ag2O loading = 0.1 g L−1) at neutral pH, in 3 h. Persulfate ions (PS) showed a strong synergistic effect on the efficiency of solar/Ag2O photocatalysis, represented by complete MG removal in 15 min, in the presence of 1.6 mM PS. The results revealed that solar/Ag2O, particularly solar/Ag2O/PS photocatalysis is a promising method for the elimination of toxic organic pollutants, such as malachite green, from the water environment.

The sulphate radical based advanced oxidation processes (AOPs) are highly in demand these days, owing to their numerous advantages. Herein, the Fe-Mn bimetallic oxide particle was used to activate peroxymonosulphate (PMS) for Rhodamine B (RhB) degradation. Three bimetallic catalysts were synthesized via the chemical precipitation method with different concentrations of metals; Fe-Mn (1:1), Fe-Mn (1:2) and Fe-Mn (2:1). The best performance was shown by Fe-Mn (2:1) system at optimized conditions; 96% of RhB was removed at optimized conditions. Scavenging experiments displayed the clear dominance of hydroxyl radical in pH 3, while sulphate radical was present in a large amount at pH 7 and 10. The monometallic Fe and Mn oxides were also synthesized to confirm the synergistic effect that was present in the bimetallic oxide system. The application of optimized condition in real textile wastewater was conducted, which revealed the system works efficiently at high concentrations of PMS and catalyst dosage.

The treatment of acid wastewater to remove organic matter in acid wastewater and recycle valuable resources has great significance. However, the classical advanced oxidation process (AOPs), such as the Fenton reaction, encountered a bottleneck under the conditions of strong acid. Herein, making use of the oxidation properties of CeAY (CeO2@acid clay), we built an AOPs reaction system without H2O2 under a strong acid condition that can realize the transformation of organic matter in industrial wastewater. The X-ray photoelectron spectroscopy (XPS) proved that the CeAY based on Ce3+ as an active center has abundant oxygen vacancies, which can catalyze O2 to produce reactive oxygen species (ROS). Based on the electron spin-resonance spectroscopy spectrum and radical trapping experiments, the production of •O2– and •OH can be determined, which are the essential factors of the degradation of organic compounds. In the system of pH = 1.0, when 1 mg CeAY is added to 10 mL of wastewater, the degradation efficiency of an aniline solution with a 5 mg/L effluent concentration is 100%, and that of a benzoic acid solution with a 100 mg/L effluent concentration is 50% after 10 min of reaction. This work may provide novel insights into the removal of organic pollutants in a strong acid water matrix.

The ozone/peroxymonosulfate (O3/PMS) system has attracted widespread attention from researchers owing to its ability to produce hydroxyl radicals (•OH) and sulfate radicals (SO4•−) simultaneously. The existing research has shown that the O3/PMS system significantly degrades refinery trace organic compounds (TrOCs) in highly concentrated organic wastewater. However, there is still a lack of systematic understanding of the O3/PMS system, which has created a significant loophole in its application in the treatment of highly concentrated organic wastewater. Hence, this paper reviewed the specific degradation effect, toxicity change, reaction mechanism, various influencing factors and the cause of oxidation byproducts (OBPs) of various TrOCs when the O3/PMS system is applied to the degradation of highly concentrated organic wastewater. In addition, the effects of different reaction conditions on the O3/PMS system were comprehensively evaluated. Furthermore, given the limited understanding of the O3/PMS system in the degradation of TrOCs and the formation of OBPs, an outlook on potential future research was presented. Finally, this paper comprehensively evaluated the degradation of TrOCs in highly concentrated organic wastewater by the O3/PMS system, filling the gaps in scale research, operation cost, sustainability and overall feasibility.

Light-harvesting of titanium oxide (TiO2) was enhanced by copper (Cu) doping, and its performance was evaluated by gabapentin (GBP) degradation under UVA-LED irradiation. The morphology and structure of TiO2 and Cu-TiO2 were characterized using XRD, FTIR, FE-SEM, EDX, TEM, PL, DRS, and BET analysis. The complete degradation of 10 mg/L GBP was obtained in the developed photocatalytic process under the optimal conditions: catalyst loading, 0.4 g/L; pH solution, 8; and reaction time, 20 min. The reactive species trapping was studied to identify the degradation mechanism in this system. Among the water matrix experiments, phosphate (PO43−) anion indicated an inverse effect in increasing efficiency. Finally, the main intermediates generation during the GBP degradation was investigated based on LC-MS analysis, and a decomposition pathway was proposed. Accordingly, doping TiO2 with Cu resulted in the development of a UVA-activated photocatalyst for efficiently degrading and mineralizing GBP as a model of a pharmaceutical compound.

The use of parabens in personal care products can result in their leakage into water bodies, especially in public swimming pools with insufficient water treatment. We found that ferrite-based nanomaterials could catalytically enhance ozone efficiency through the production of reactive oxygen species. Our objective was to develop a catalytic ozonation system using ternary nanocomposites that could minimize the ozone supply while ensuring the treated water was acceptable for disposal into the environment. A ternary CuFe2O4/CuO/Fe2O3 nanocomposite (CF) delivered excellent degradation performance in catalytic ozonation systems for butylparaben (BP). By calcining with melamine, we obtained the CF/g-C3N4 (CFM) nanocomposite, which had excellent magnetic separation properties with slightly lower degradation efficiency than CF, due to possible self-agglomeration that reduced its electron capture ability. The presence of other constituent ions in synthetic wastewater and actual discharge water resulted in varying degradation rates due to the formation of secondary active radicals. 1O2 and •O2− were the main dominant reactive species for BP degradation, which originated from the O3 adsorption that occurs on the CF≡Cu(I)–OH and CF≡Fe(III)–OH surface, and from the reaction with •OH from indirect ozonation. Up to 50% of O3-treated water resulted in >80% ELT3 cell viability, the presence of well-adhered cells, and no effect on the young tip of Ceratophyllum demersum L. Overall, our results demonstrated that both materials could be potential catalysts for ozonation because of their excellent degrading performance and, consequently, their non-toxic by-products.

In this work are presented and discussed the results related to the obtaining of the best conditions for the treatment of a real paint wastewater by combining the chemical coagulation methods and solar photo-Fenton process. The best conditions for the coagulation-flocculation process involved the use of 8 mL of chemical coagulant (ferric chloride) for every 1.0 L of wastewater. At this condition, total removal of turbidity and color (visual inspection) of the wastewater were achieved. For the solar photo-Fenton process, the concentration of Fe2+ and H2O2 at 105 mg L-1 and 2.0 g L-1, respectively, resulted in the complete removal of organic matter and odor (olfactory perception). Therefore, the combined use of these techniques in the treatment of the real paint wastewater presented quite relevant results from the environmental standpoint, as evidenced by the reduction/elimination of important environmental parameters, with the real possibility of disposal and/or reuse proposals of treated water. DOI: http://dx.doi.org/10.17807/orbital.v11i2.1365

Here, we control the surface activity of hydroxyapatite (HAp) in wastewater treatment which undergoes peroxodisulfate (PDS) activation. Loading the catalytically active Cu species on HAp forms a copper phosphate in the outer layer of HAp. This modification turns a low active HAp into a high catalytically active catalyst in the dye degradation process. The optimal operational conditions were established to be [Cu–THAp]0 = 1 g/L, [RhB]0 = 20 mg/L, [PDS]0 = 7.5 mmol/L, and pH = 3. The experiments indicate that the simultaneous presence of Cu-THAp and PDS synergistically affect the degradation process. Additionally, chemical and structural characterizations proved the stability and effectiveness of Cu-THAp. Therefore, this work introduces a simple approach to water purification through green and sustainable HAp-based materials.

Bimetallic catalysts have significantly contributed to the chemical community, especially in environmental science. In this work, a CoAl2O4 spinel bimetal oxide was synthesized by a facile co-precipitation method and used for the degradation of organic pollutants through peroxymonosulfate (PMS) activation. Compared with Co3O4, the as-prepared CoAl2O4 possesses a higher specific surface area and a larger pore volume, which contributes to its becoming increasingly conducive to the degradation of organic pollutants. Under optimal conditions (calcination temperature: 500 °C, catalyst: 0.1 g/L, and PMS: 0.1 g/L), the as-prepared CoAl2O4 catalyst could degrade over 99% of rhodamine B (RhB) at a degradation rate of 0.048 min−1, which is 2.18 times faster than Co3O4 (0.022 min−1). The presence of Cl− could enhance RhB degradation in the CoAl2O4/PMS system, while HCO3− and CO32− inhibit RhB degradation. Furthermore, the considerable reusability and universality of CoAl2O4 were testified. Through quenching tests, 1O2 and SO4•− were identified as the primary reactive species in RhB degradation. The toxicity evaluation verified that the degraded solution exhibited lower biological toxicity than the initial RhB solution. This study provides new prospects in the design of cost-effective and stable cobalt-based catalysts and promotes the application of PMS-based advanced oxidation processes for refractory wastewater treatment.

Water pollution by dyes is a huge environmental problem; there is a necessity to produce new decolorization methods that are effective, cost-attractive, and acceptable in industrial use. Magnetic cyclodextrin polymers offer the advantage of easy separation from the dye solution. In this work, the β-CD-EPI-magnetic (β-cyclodextrin-epichlorohydrin) polymer was synthesized, characterized, and tested for removal of the azo dye Direct Red 83:1 from water, and the fraction of non-adsorbed dye was degraded by an advanced oxidation process. The polymer was characterized in terms of the particle size distribution and surface morphology (FE-SEM), elemental analysis (EA), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), infrared spectrophotometry (IR), and X-ray powder diffraction (XRD). The reported results hint that 0.5 g and pH 5.0 were the best conditions to carry out both kinetic and isotherm models. A 30 min contact time was needed to reach equilibrium with a qmax of 32.0 mg/g. The results indicated that the pseudo-second-order and intraparticle diffusion models were involved in the assembly of Direct Red 83:1 onto the magnetic adsorbent. Regarding the isotherms discussed, the Freundlich model correctly reproduced the experimental data so that adsorption was confirmed to take place onto heterogeneous surfaces. The calculation of the thermodynamic parameters further demonstrates the spontaneous character of the adsorption phenomena (ΔG° = −27,556.9 J/mol) and endothermic phenomena (ΔH° = 8757.1 J/mol) at 25 °C. Furthermore, a good reusability of the polymer was evidenced after six cycles of regeneration, with a negligible decline in the adsorption extent (10%) regarding its initial capacity. Finally, the residual dye in solution after treatment with magnetic adsorbents was degraded by using an advanced oxidation process (AOP) with pulsed light and hydrogen peroxide (343 mg/L); >90% of the dye was degraded after receiving a fluence of 118 J/cm2; the discoloration followed a pseudo first-order kinetics where the degradation rate was 0.0196 cm2/J. The newly synthesized β-CD-EPI-magnetic polymer exhibited good adsorption properties and separability from water which, when complemented with a pulsed light-AOP, may offer a good alternative to remove dyes such as Direct Red 83:1 from water. It allows for the reuse of both the polymer and the dye in the dyeing process.

In recent decades, the increasing use of pesticides to improve food productivity has led to the release of effluents that contaminate the environment. To prepare a material that may help to treat effluents generated during agricultural practice, we used a new method based on the non-hydrolytic sol-gel route to obtain zinc photocatalysts in aluminophosphate matrixes. IR spectroscopy, X-ray diffraction, thermal analysis, differential scanning electron microscopy, energy dispersion spectroscopy, and specific surface area and pore volume determined from the nitrogen adsorbed were used to characterize materials treated at different temperatures. X-ray analysis showed how heat-treatment affected the structure of the material: Zn-AlPO4 in the trigonal and orthorhombic phase was obtained at 750 and 1000 °C, respectively. These phases directly influenced the ability of the material to generate OH radicals. The capacity of the materials to treat effluents was tested in the photodegradation of the pesticide Fipronil. The photocatalytic reactions were monitored by ultraviolet-visible spectroscopy and gas chromatography-mass spectrometry analyses. Zn-AlPO4 treated at 750 °C showed better photodegradation results--it removed 80% of the pesticide in 2 h when higher mass (150 mg) was tested. Long-time treatment of the effluent with Zn-AlPO4 treated at 750 °C completely photodegraded Fipronil. GC-MS analysis confirmed the photodegration profile, and only traces of Fipronil were observed after photocatalytic reaction for 120 min in the presence of Zn-AlPO4 treated at 750 °C under UV radiation.

Advanced treatment of biologically processed palm oil mill effluent (BIOTPOME), which possesses a potential danger to the water sources is required to meet the Malaysian discharge standard, as BIOTPOME contains high level of chemical oxygen demand (COD), suspended solids and oil and grease even after going through conventional treatment process. The significant but insufficient treatment efficiency of ponding system in Malaysia urged an alternative method to treat the recalcitrant organic compounds. Thus, post-treatment of BIOTPOME using oxidation by thermally activated persulfate process was proposed to solve this issue. In order to maximize the removal of COD and color, the central composite design (CCD) module of the response surface approach was used to optimize the interactions of the process variables temperature, S2O82−/COD ratio, and reaction time. In order to identify the significant terms of interacting process factors, CCD performed a batch study from which statistical models of responses were created. All models were confirmed by analysis of variance (ANOVA) showing significances with Prob > F less than 0.1. The optimal performance was obtained at the temperature of 67.4 °C, S2O82−/COD ratio of 9.8 and reaction time of 120 min, rendering COD removal of 85.65% and color removal of 85.74%. The total cost for the treatment process was RM0.94 per liter.

Advanced oxidation processes (AOPs) utilizing heterogeneous catalysts have attracted great attention in the last decade. The use of solid catalysts, including metal and metal oxide nanoparticle support materials, exhibited better performance compared with the use of homogeneous catalysts, which is mainly related to their stability in hostile environments and recyclability and reusability. Various solid supports have been reported to enhance the performance of metal and metal oxide catalysts for AOPs; undoubtedly, the utilization of clay as a support is the priority under consideration and has received intensive interest. This review provides up-to-date progress on the synthesis, features, and future perspectives of clay-supported metal and metal oxide for AOPs. The methods and characteristics of metal and metal oxide incorporated into the clay structure are strongly influenced by various factors in the synthesis, including the kind of clay mineral. In addition, the benefits of nanomaterials from a green chemistry perspective are key aspects for their further considerations in various applications. Special emphasis is given to the basic schemes for clay modifications and role of clay supports for the enhanced mechanism of AOPs. The scaling-up issue is suggested for being studied to further applications at industrial scale.

UV/persulfate (UV/PS) could effectively degrade algal cells and micro-organic pollutants. This process was firstly applied to remove Microcystis aeruginosa (M. aeruginosa) and 2,4,6-trichlorophenol (TCP) simultaneously in bench scale. Algal cells can be efficiently removed after 120 min reaction accompanied with far quicker removal of the coexisted TCP, which could be totally removed within 5 min in the UV/PS process. Both SO4•- and HO• were responsible for algal cells and TCP degradation, while SO4•- and HO• separately dominated TCP degradation and algal cells removal. Apart from the role of radicals (SO4•- and HO•) for algal cells and TCP degradation, UV also played a role to some extent. Increased PS dose (0–4.5 mM) or UV intensity (2.71–7.82 mW/cm2) could enhance the performance of the UV/PS process in both TCP and algae removal. Although some intracellular organic matters can be released to the outside of algal cells due to the cell lysis, they can be further degraded by UV/PS process, which was inhibited by the presence of TCP. This study suggested the good potential of the UV/PS process in the simultaneous removal of algal cells and micro-organic pollutants.

An economical corncob biochar-based magnetic iron–copper bimetallic nanomaterial (marked as MBC) was successfully synthesized and optimized through a co-precipitation and pyrolysis method. It was successfully used to activate H2O2 to remove ciprofloxacin (CIP) from aqueous solutions. This material had high catalytic activity and structural stability. Additionally, it had good magnetic properties, which can be easily separated from solutions. In MBC/H2O2, the removal efficiency of CIP was 93.6% within 360 min at optimal reaction conditions. The conversion of total organic carbon (TOC) reached 51.0% under the same situation. The desorption experiments concluded that adsorption and catalytic oxidation accounted for 34% and 66% on the removal efficiency of CIP, respectively. The influences of several reaction parameters were systematically evaluated on the catalytic activity of MBC. OH was proved to play a significant role in the removal of CIP through electron paramagnetic resonance (EPR) analysis and a free radical quenching experiment. Additionally, such outstanding removal efficiency can be attributed to the excellent electronic conductivity of MBC, as well as the redox cycle reaction between iron and copper ions, which achieved the continuous generation of hydroxyl radicals. Integrating HPLC-MS, ion chromatography and density functional theory (DFT) calculation results, and possible degradation of the pathways of the removal of CIP were also thoroughly discussed. These results provided a theoretical basis and technical support for the removal of CIP in water.

Advanced oxidation procedures (AOPs) refer to a variety of technical procedures that produce OH radicals to sufficiently oxidize wastewater, organic pollutant streams, and toxic effluents from industrial, hospital, pharmaceutical and municipal wastes. Through the implementation of such procedures, the (post) treatment of such waste effluents leads to products that are more susceptible to bioremediation, are less toxic and possess less pollutant load. The basic mechanism produces free OH radicals and other reactive species such as superoxide anions, hydrogen peroxide, etc. A basic classification of AOPs is presented in this short review, analyzing the processes of UV/H2O2, Fenton and photo-Fenton, ozone-based (O3) processes, photocatalysis and sonolysis from chemical and equipment points of view to clarify the nature of the reactive species in each AOP and their advantages. Finally, combined AOP implementations are favored through the literature as an efficient solution in addressing the issue of global environmental waste management.

In this work, photoactive nanocomposites of ZnO/SiO2 porous heterostructures (PCHs) were prepared from montmorillonite clay. The effects of preparation methods and Zn content on the physicochemical features and photocatalytic properties were investigated. Briefly, a comparison of the use of hydrothermal and microwave-assisted methods was done. The Zn content was varied between 5 and 15 wt% and the characteristics of the nanomaterials were also examined. The physical and chemical properties of the materials were characterized using X-ray diffraction, diffuse-reflectance UV-Vis, X-ray photoelectron spectroscopy, and gas sorption analyses. The morphology of the synthesized materials was characterized through scanning electron microscopy and transmission electron microscopy. The photocatalytic performance of the prepared materials was quantified through the photocatalytic degradation of methyl violet (MV) under irradiation with UV and visible light. It was found that PCHs exhibit greatly improved physicochemical characteristics as photocatalysts, resulting in boosting photocatalytic activity for the degradation of MV. It was found that varied synthesis methods and Zn content strongly affected the specific surface area, pore distribution, and band gap energy of PCHs. In addition, the band gap energy was found to govern the photoactivity. Additionally, the surface parameters of the PCHs were found to contribute to the degradation mechanism. It was found that the prepared PCHs demonstrated excellent photocatalytic activity and reusability, as seen in the high degradation efficiency attained at high concentrations. No significant changes in activity were seen until five cycles of photodegradation were done.

In this study, the effectiveness of a rhodamine B (RhB) dye degradation process at a concentration of 20 mg/L in different advanced oxidation processes—H2O2/UV, O3/UV and PDS/UV—has been studied. The use of UV in a photo-assisted ozonation process (O3/UV) proved to be the most effective method of RhB decolorization (90% after 30 min at dye concentration of 100 mg/L). The addition of sulfate radical precursors (sodium persulfate, PDS) to the reaction environment did not give satisfactory effects (17% after 30 min), compared to the PDS/UV system (70% after 30 min). No rhodamine B decolorization was observed using hydrogen peroxide as a sole reagent, whereas an effect on the degree of RhB degradation was observed when UV rays strike the sample with H2O2 (33% after 30 min). The rhodamine B degradation process followed the pseudo-first-order kinetics model. The combined PDS/O3/UV process has shown 60% color removal after 30 min of reaction time at an initial dye concentration of 100 mg/L. A similar effectiveness was obtained by only applying ozone or UV-activated persulfate, but at a concentration 2–5 times lower (20 mg/L). The results indicated that the combined PDS/O3/UV process is a promising method for high RhB concentrations (50–100 mg/L) comparing to other alternative advanced oxidation processes.

The petroleum industry is one of the most rapidly developing industries and is projected to grow faster in the coming years. The recent environmental activities and global requirements for cleaner methods are pushing the petroleum refining industries for the use of green techniques and industrial wastewater treatment. Petroleum industry wastewater contains a broad diversity of contaminants such as petroleum hydrocarbons, oil and grease, phenol, ammonia, sulfides, and other organic composites, etc. All of these compounds within discharged water from the petroleum industry exist in an extremely complicated form, which is unsafe for the environment. Conventional treatment systems treating refinery wastewater have shown major drawbacks including low efficiency, high capital and operating cost, and sensitivity to low biodegradability and toxicity. The advanced oxidation process (AOP) method is one of the methods applied for petroleum refinery wastewater treatment. The objective of this work is to review the current application of AOP technologies in the treatment of petroleum industry wastewater. The petroleum wastewater treatment using AOP methods includes Fenton and photo-Fenton, H2O2/UV, photocatalysis, ozonation, and biological processes. This review reports that the treatment efficiencies strongly depend on the chosen AOP type, the physical and chemical properties of target contaminants, and the operating conditions. It is reported that other mechanisms, as well as hydroxyl radical oxidation, might occur throughout the AOP treatment and donate to the decrease in target contaminants. Mainly, the recent advances in the AOP treatment of petroleum wastewater are discussed. Moreover, the review identifies scientific literature on knowledge gaps, and future research ways are provided to assess the effects of these technologies in the treatment of petroleum wastewater.

In this work, discoloration of basic yellow 28 using sonoelectrochemical method in presence of titanium dioxide nanoparticles was investigated. The respond surface methodology (RSM) was applied for optimization of discoloration. The influence of different factors such as applied potential, amount of titanium dioxide nanoparticles, time and solution pH was evaluated on discoloration. A mathematical model was presented to prediction of discoloration with RSM. The results shown that time has highest effect on discoloration efficiency, pH, applied potential and amount of titanium dioxide nanoparticles has also effective factors. The sonoelectrochemical route in presence of TiO2 nanoparticles has better performance on discoloration comparing with other methods including sonoelectrochemistry, sonochemistry in presence of hydrogen peroxide, sonochemistry in presence of hydrogen peroxide/TiO2 nanoparticles and electrochemistry in presence of TiO2 nanoparticles at optimum condition, i.e. pH= 8.0, 1.1 V applied potential, 0.96 g/L TiO2 nanoparticles and 119 min.