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Electrochemical degradation performances of three non-steroidal anti-inflammatory drugs (NSAIDs), acetaminophen (ACT), aspirin (ASP) and ibuprofen (IBP), were investigated and compared in their alone and mixture conditions using Ti/SnO2-Sb/La-PbO2. The pseudo-first-order degradation kinetics (k) order was kIBP-A (0.110 min−1) ˃ kASP-A (0.092 min−1) ˃ kACT-A (0.066 min−1) in their alone condition, while that was kACT-M (0.088 min−1) ˃ kASP-M (0.063 min−1) ˃ kIBP-M (0.057 min−1) in their mixture condition. The •OH apparent production rate constant of 5.23 mmol L−1 min−1 m−2 and an electrical energy per order (EEO) value of 6.55 Wh/L could ensure the synchronous degradation of the NSAIDs mixture. The mineralization efficiency of NSAIDs mixture was 86.9% at 240 min with a mineralization current efficiency of 1.67%. Acetic acid and oxalic acid were the main products in the mineralization process for the both conditions. In the mixture condition, there were higher k values at lower initial concentrations and higher current density, while the presence of carbonate and humic acid inhibited their degradation. The results indicated electrochemical advanced oxidation process can effectively and synchronously mineralize NSAIDs mixture in wastewater.

Peracetic acid (PAA)-based system is becoming an emerging advanced oxidation process (AOP) for effective removal of organic contaminants from water. Various approaches have been tested to activate PAA, while no previous researches reported the application of metal-organic frameworks (MOFs) materials for PAA activation. In this study, zeolitic imidazole framework (ZIF)-67, a representative MOFs, was facile synthesized via direct-mixing method at room temperature, and tested for PAA activation and sulfachloropyridazine (SCP) degradation. The as-synthesized ZIF-67 exhibited excellent performance of PAA activation and SCP degradation with 100% of SCP degraded within 3 min, owing to the specific MOFs structure and abundant Co2+ sites. The pseudo-first-order kinetic model was applied to fit the kinetic data, with rate constant k1 of ZIF-67 activated PAA system 34.2 and 156.5 times higher than those of conventional Co3O4 activated PAA and direct oxidation by PAA. Radical quenching experiments and electron paramagnetic resonance (EPR) analysis indicated that CH3C(O)OO• played a major role in this PAA activation system. Then, the Fukui index based on density functional theory (DFT) calculation was used to predict the possible reaction sites of SCP for electrophilic attack by CH3C(O)OO•. In addition, the degradation pathway of SCP was proposed based on Fukui index values and intermediates detection, which mainly included the S-N bond cleavage and SO2 extrusion and followed by further oxidation, dechlorination, and hydroxylation. Therefore, ZIF-67 activated PAA is a novel strategy and holds strong potential for the removal of emerging organic contaminants (EOCs) from water.

In the past few years, pharmaceutical compounds have appeared as emerging category of environmental pollutants. These microcontaminants can exhibit adverse acute and chronic effects on natural flora and fauna. The detection of pharmaceutical residues in surface waters (rivers, streams, and lakes), seawater, groundwater, soils, sludges, and wastewater treatment plants has been widely documented. Advanced oxidation processes (AOPs) have garnered extensive attention for abetment of emerging pharmaceutical contaminants and minimize their associated environmental risks. Given a clean and efficient oxidizing agent, hydrogen peroxide (H2O2) has been extensively utilized in AOPs. Integration of H(2)O(2 )with different substrates/catalysts boosts up its oxidizing features. H(2)O(2 )may be combined with ozone, UV, Fe2+/Fe3+ ions (Fenton and photo-Fenton-like processes) and with heterogeneous systems (TiO2). The generation of strong oxidative hydroxyl radical (HO:) in H2O2-assisted AOP by various types of activating methods is likely to play a critical role in micropollutants treatment, reusing, and risk reduction. Advanced oxidation process catalyzed by H(2)O(2)may consists of combination of following catalysts: UV/H2O2, O-3/UV/ H2O2, H2O2/TiO2/UV, Fe2+/H2O2, Fe2+/H2O2/UV, Electro-Fenton, O3/H2O2). In this review, we have discussed current reports on various hydrogen peroxide-based advanced oxidation processes for degradation of pharmaceutical pollutants of emerging concern. The ongoing challenges, conclusive remarks and imperative future directions are also outlined. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

In this study, a functionalized Co3O4-Bi2O3-Ti catalytic membrane (CBO-Ti-M) was prepared and applied for removing organic pollutants via activating peroxymonosulfate (PMS) in the dead-end filtration mode. Characterizations including scanning electron microcopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed that the Co3O4-Bi2O3 catalyst was successfully supported on the Ti membrane. The CBO-Ti-M /PMS system could efficiently remove various organic pollutants such as sulfamethoxazole, methyl orange, bisphenol A and methylene blue, achieving removal efficiencies of 98.0%-99.5%. The effects of PMS concentration, flow rate and solution environment on degradation efficiency were investigated in detail. Furthermore, quenching experiments, electron spin resonance (ESR) and in-situ open circuit potential (OCP) tests collectively demonstrated that singlet oxygen as well as the non-radical electron transfer pathway mainly contributed in the reaction mechanism. The synergistic effect of Co and Bi was illustrated according to XPS results, and the possible degradation pathway of MB was proposed based on LC-MS analysis. Reusability test showed that pollutant removal efficiency with the CBO-Ti-M /PMS system remained stable in four runs and limited metal leaching was observed.

Photocatalysis is a promising advanced oxidation process (AOPs). It is often used in the degradation of phenolic derivatives due to their simplicity and easy handling, by converting organic molecules with total mineralisation into nontoxic H2O and CO2. In this study, a combination of microwave-assisted (MW) and facile electrochemical method was applied in the synthesis of catalysts (Fe-MTN and Cu-MZN). The characterisation of catalysts was tested using XRD, UV–Vis DRS and FTIR. It was found that there was no new bonding formed when Fe was introduced onto MTN, while the introduction of Cu onto MZN formed a new Zn-O-Cu. The introduction of Fe and Cu onto MTN and MZN also decreased the bandgap energy from 3.15 to 2.35 eV and 2.92 to 2.63 eV, respectively. The pH of the solution is one of the essential parameters that need to be measured in the photocatalytic process due to the amphoteric properties of semiconductor, which influenced the surface-charged properties of the catalysts. Fe-MTN and Cu-MZN were used in photocatalytic degradation of 2-chlorophenol (2-CP) and 2,4-diclorophenol (2,4-DCP), respectively. After the effect of pH over 2-CP and 2,4-DCP was tested in the range of 3 to 11, the greatest degradation of 2-CP using Fe-MTN was at pH 5 with 99% while 100% degradation of 2,4-DCP at pH 3 for Cu-MZN. These results are probably due to the amphoteric characteristic of catalyst, where it can be tested using point zero charged (pHZPC). The pHZPC value of Fe-MTN and Cu-MZN was 6.1 and 5.5, respectively illustrated that the photoactivity of both catalysts better in acidic condition compared to an alkaline condition.

Metal-free activation of peroxydisulfate (PDS) for degrading organic pollutants in water has received increasing attention because it can prevent secondary pollution. However, most of the catalysts that are efficient are derived from non-renewable fossil resources, are very expensive and have complex preparation processes. Also, the emerging non-radical mechanism is still unclear. Herein, 3D sucrose-derived N-doped carbon xerogels (NCXs) were synthesized by a simple and sustainable hydrothermal process and then employed as novel metal-free PDS activators to degrade organic pollutants. The structure, composition and performance of NCXs were regulated by changing the carbonization temperature. The sample carbonized at 900 °C (NCX900) exhibited the best catalytic performance, completely removing bisphenol A in 60 min. Quenching experiments and linear sweep voltammograms demonstrated that PDS was activated mainly through an electron-transfer non-radical mechanism. It was found that graphitic N played a critical role in activating PDS. With this non-radical mechanism, the NCX900/PDS system could adapt well to the wide pH range (3–11) and high Cl− concentration; it selectively oxidized organic pollutants with low ionization potentials. This work provides a sustainable approach to the low-cost and efficient metal-free catalysts for wastewater treatment.

In this study, a rotating microreactor made of Plexiglas was utilized for the removal of methylene blue and methyl oranges from aqueous solutions with these two dyes at different concentrations. To this end, an advanced oxidation process of ultraviolet/hydrogen peroxide/titanium dioxide was performed while setting various conditions for this operation. Box–Behnken experimental design method was implemented to design the experiments. In addition, five variables of initial dye concentration (10, 30, and 50 mg/L), residence time (1, 1.5, and 2 min), hydrogen peroxide concentration (0, 300, and 600 mg/L), titanium dioxide concentration (10, 30, and 50 mg/L), and ultraviolet lamp power (0, 15 and 30 W) were set as the desired variables under the study and a total of 43 tests were performed to remove each dye. Finally, optimal operating conditions for the removal of each of the two items (methylene blue and methyl orange) were obtained. The highest rate of the removal of methylene blue dye (under optimal conditions of initial dye concentration of 36 mg/L, residence time of 2 min, hydrogen peroxide concentration of 235 mg/L, titanium dioxide concentration of 12 mg/L, and ultraviolet lamp power of 30 W) was 99.83% and the highest rate of methyl orange dye removal (under optimal conditions of initial dye concentration of 50 mg/L, residence time of 1.75 min, hydrogen peroxide concentration of 540 mg/L, titanium dioxide concentration of 30 mg/L, and ultraviolet lamp power of 30 W) was 68.69%.

The iron(II)-activated peroxymonosulfate [Fe(II)/PMS] process is effective in degrading organic contaminants with a rapid oxidation stage followed by a slow one. Nevertheless, prior studies have greatly underestimated the degradation rates of organic contaminants in the rapid oxidation stage and ignored the differences in the kinetics and mechanism of organic contaminants degradation in these two oxidation stages. In this work, we investigated the kinetics and mechanisms of organic contaminants in this process under acidic conditions by combining the stopped-flow spectrophotometric method and batch experiments. The organic contaminants were rapidly oxidized with rate constants of 0.18-2.9 s-1 in the rapid oxidation stage. Meanwhile, both Fe(IV) and SO4•- were active oxidants and contributed differently to the degradation of different organic contaminants in this stage. Additionally, the presence of Cl- promoted the degradation of both phenol and estradiol but the effects of Br- and humic acid on phenol degradation differed from those on estradiol degradation in the rapid oxidation stage. In contrast, the degradation of phenol and estradiol was slow and the amounts of Fe(IV) and SO4•- generated were small in the slow oxidation stage. This work updates the fundamental understanding of the degradation of organic contaminants in this process.

In this study, mesoporous TiO2 with various hydrolysis rates were prepared and combined with H2O2 for the photodegradation of unsymmetrical dimethylhydrazine (UDMH) under VUV irradiation. Results showed that the mesoporous TiO2 synthesized by the hydrolysis in water (MT100) exhibited a good mesoporous structure and the largest specific surface area (178.85 m2 g−1). Consequently, MT100 showed the best degradation efficiency, with the rate constant (k) for VUV/MT100 and VUV/MT100/H2O2 of 0.0185 and 0.2595 min−1, respectively, which was 1.4 and 4.0 times of that of P25. The addition of H2O2 significantly enhanced the degradation efficiency by photoactivation of H2O2 and the synergistic effect. The rate constant and the mineralization rate (after a 3-h treatment) increased by 13 and 3.8 times when 40 mM H2O2 was added into VUV/MT100. The weak alkaline condition (pH = 9) would facilitate the degradation of UDMH. The ⋅OH was the key oxidizing species in VUV/MT100/H2O2. Eight intermediates were detected during the degradation and the possible pathways of UDMH degradation in VUV/MT100/H2O2 process were proposed. VUV/MT100/H2O2 provides an efficient method to degrade UDMH.

Organic pollutants, such as synthetic dyes, are treated to prevent them from contaminating natural water sources. One of the treatment methods is advanced oxidation process using a photocatalyst material as the active agent. However, many photocatalysts are hindered by their production cost and efficiency. In this study, nanocomposites consisting of reduced graphene oxide and titanium dioxide (rGO/TiO2) were prepared by a simple and green approach using the microwave-assisted method, and we utilized a graphene oxide (GO) precursor that was fabricated through the Tour method. The ratios of rGO/TiO2 in nanocomposites were varied (2:1, 1:1, and 1:2) to know the influence of rGO on the photocatalytic performance of the nanocomposites for rhodamine 6G degradation. Transmission electron microscopy (TEM) observation revealed that a transparent particle with a sheetlike morphology was detected in the rGO sample, suggesting that a very thin film of a few layers of GO or rGO was successfully formed. Based on scanning electron microscopy (SEM) observation, the rGO/TiO2 nanocomposites had a wrinkled and layered rGO structure decorated by TiO2 nanoparticles with average diameters of 125.9 ± 40.6 nm, implying that rGO layers are able to prevent TiO2 from agglomeration. The synthesized product contained only rGO and TiO2 in the anatase form without impurities that were proven by Raman spectra and X-ray diffraction (XRD). The nanocomposite with rGO/TiO2 ratio 1:2 (composite C) was found to be the best composition in this study, and it was able to degrade 82.9 ± 2.4% of the rhodamine 6G after UV irradiation for 4 h. Based on a time-resolved photoluminescence study at wavelength emission 500 nm, the average decay lifetime of R6G-rGO/TiO2 composites (2.91 ns) was found to be longer than that of the R6G-TiO2 sample (2.05 ns), implying that the presence of rGO in rGO/TiO2 composites successfully suppressed the electron–hole recombination process in TiO2 and significantly improved their photocatalytic performance. This study showed that the rGO/TiO2 nanocomposites synthesized through relatively simple and eco-friendly processes display promising prospects for photocatalytic degradation of dyes and other recalcitrant pollutants in a water stream.

In this study, photocatalytic degradability of Floxin antibiotic by UV/ZnO/sulfite (UZS) advanced oxidation process was evaluated. The degradation rate of Floxin antibiotic by UV/ZnO (UZ) and UV alone processes were 30% and 15%, respectively, within 5 min. It was observed sulfite has a synergistic effect on the performance of UZ, as the complete destruction of Floxin was achieved when sulfite was introduced into the photocatalytic medium. The complete degradation of Floxin by UZS was obtained at pH of 12.0, sulfite/ZnO molar ratio of 1:3 after 5 min of reaction. According to kinetic studies, the observed rate of Floxin degradation (robs (mg L-1 min)) by UZS was 63 and 25 times that of UV alone and UZS, respectively. The values of energy consumption and the total cost for UV alone, UZ and UZS processes were estimated to be (50 kWh m-3 and 1.4 $ m-3), (20 kWh m-3 and 0.98 $ m-3) and (0.78 kWh m-3 and 0.82 $ m-3), respectively.

Chlorinated organic pollutants are highly toxic and widespread in the environment, which cause ecological risk and threaten the human health. Chlorinated pollutants are difficult to degrade and mineralize by the conventional advanced oxidation process as the C-Cl bond is resistant to reactive oxygen species oxidation. Herein, we designed a bifunctional Fe/Cu bimetallic single-atom catalyst anchored on N-doped porous carbon (FeCuSA-NPC) for the electro-Fenton process, in which chlorinated pollutants are dechlorinated on single-atom Cu and subsequently oxidized by the ·OH radical produced from O2 conversion on single-atom Fe. Benefitting from the synergistic effect between dechlorination on single-atom Cu and ·OH oxidation on single-atom Fe, the chlorinated organic pollutants can be efficiently degraded and mineralized. The mass activity for chlorinated organic pollutant degradation by FeCuSA-NPC is 545.1-1374 min-1 gmetal-1, excessing the highest value of the reported electrocatalyst. Moreover, FeCuSA-NPC is demonstrated to be pH-universal, long-term stable, and environment friendly. This work provides a new insight into the rational design of a bifunctional electrocatalyst for efficient removal of chlorinated organic pollutants.

The advanced oxidation process (AOPs) has caused great concern in recent years. Among them, biochar has been widely studied as a catalyst for advanced oxidation process because of its low price and low environmental risk. In this study, a novel ball milling assisted KOH activation biochar (MKBC) was prepared and applied in peroxydisulfate (PDS) activation to degrade tetracycline hydrochloride (TC-H). In comparison with the oxidation (3.48%) by PDS alone and adsorption (36.19%) by MKBC alone, the removal rate of TC-H was increased to 84.15% in the MKBC/PDS system, indicating that MKBC can successfully activate PDS. Besides, the catalytic activity of the MKBC to activate PDS for the degradation of TC-H is 58.33% higher than that of pristine biochar (PBC). In addition, MKBC has outstanding stability that after three repeated experiments, the removal rate of TC-H by the MKBC/PDS system still remains 77.35%. Meanwhile, the mechanism was investigated that the singlet oxygen (1O2) seized the principal position in the degradation of TC-H in the PDS/MKBC system. This study explored a novel, solvent-free and economic method to propose this extraordinary biochar, which provided a new strategy for the future research of biochar.

Photocatalysis has been regarded as a kind of environmentally friendly advanced oxidation process to eliminate pollutants. In this work, Phosphorus-doped carbon nitride tube (PCN) was synthesized via a hydrothermal calcination method and applied to degrade tetracycline (TC) through combing with peroxydisulfate (PDS) under visible light irradiation. Experimental results showed that the optimized catalysts PCN-5 exhibited superior degradation performance and reusability for TC degradation. 96.4% TC could be degraded for optimal PCN-5 with 0.3 g·L−1 catalysts and 1.0 g·L−1 PDS under visible light within 60 min. In addition, the degradation rate constant for TC of PCN + PDS + Vis system was still above 85% after five uses. Radical trapping experiment indicating that O2·− is the dominant radical for TC degradation. The findings of this work revealed the potential application of the PCN + PDS + Vis system toward degrading contaminants in wastewater. HIGHLIGHTS Phosphorus-doped carbon nitride tube was successfully synthesized.; PCN-5 + PDS + Vis system exhibited excellent TC degradation performance and reusability.; O2·− is the dominant radical for TC degradation.

Stable and recyclable catalysts are crucial to the peroxymonosulfate (PMS) based advanced oxidation process (AOPs) for wastewater treatment. Herein, nitrogen-rich carbon wrapped Fe3C (Fe3C@CN) on carbon felt (CF) substrate was synthesized by using Prussian blue (PB) loaded CF as the precursors. The obtained Fe3C@CN/CF catalyst was applied for degradation of bisphenol A (BPA) via the heterogeneous catalytic activation of PMS. Results showed that ~91.7%, 95.2%, 98.1% and 99.1% of BPA (20 mg/L) were eliminated in the Fe3C@CN/CF + PMS system within 4, 10, 20 and 30 min, respectively. The fast degradation kinetics is attributed to the production of abundant reactive species ( OH, SO4 − and 1O2) in the Fe3C@CN/CF + PMS system, as demonstrated by the electron paramagnetic resonance spectroscopy and quench experiments. The Fe3C@CN/CF catalyst was stable and can be easily recycled by using an external magnet. The results indicated that the nanoconfined Fe3C endowed Fe3C@CN/CF with high stability and magnetic property and enabled the efficient electron transfer for PMS activation. This study provides a cost-effective approach for the fabrication of stable and recyclable Fe3C@CN/CF catalyst, and shed a new light on the rational design of multifunctional catalyst for advanced water remediation.

Using the bulk g-C3N4 as a precursor, four g-C3N4 nanosheets were further prepared by ultrasonic, thermal, acid, and alkali exfoliation. The structures of these materials were characterized by various techniques such as X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The synergistical Fenton catalysis of these materials with Cu2+ was evaluated by using rhodamine B as a simulated organic pollutant. The results showed that there existed a significant synergistical Fenton catalysis between Cu2+ and g-C3N4. This synergistic effect can be observed even when the concentration of Cu2+ was as low as 0.064 mg L−1. The properties of g-C3N4 strongly influenced the catalytic activity of the Cu2+/g-C3N4 system. The coexistent of Cu2+ and the alkali exfoliated g-C3N4 showed the best catalytic activity. Hydroxyl radicals as oxidizing species were confirmed in the Cu2+/g-C3N4 system by electron paramagnetic resonance spectra. The synergistic catalysis may be attributed to the easier reduction of Cu2+ adsorbed on the g-C3N4. This study provided an excellent Fenton catalytic system, and partly solved the rapid deactivation of heterogeneous Fenton catalysts caused by the leaching of metal ions. HIGHLIGHTS There exists a significant synergistical Fenton catalysis between trace Cu2+ and g-C3N4.; The Cu2+ concentration is lower than the maximum acceptable limit in drinking water.; This study partly solved the rapid deactivation caused by the leaching of metal ions.; This study reminds researchers to pay attention to the possible synergistic catalysis between leached ions and supports.

Coffee consumption over the past four years has continued to increase the amount of used coffee grounds. Usually, the used coffee grounds are simply thrown away. In fact, it can still be used as other materials that are more efficient and environmentally friendly, such as activated carbon. Activated carbon can be utilized as an adsorbent to adsorb compounds that are carcinogenic and potentially last a long time in the environment, such as phenols. Phenol decomposition through chemical can be carried out by Advanced Oxidation Process (AOP) which utilize hydroxyl radicals. This method used a catalyst such as iron(III) oxide under ultraviolet light. Phenol decomposition can also be carried out using ultrasound. This study presents the performance of the combination of activated carbon-catalyst with ultrasound in phenol decomposition. The results showed that the mass of the composite influenced the 0.1 M phenol degradation by the activated carbon–iron(III) oxide assisted with ultraviolet light, ultrasound, and 0.01 M hydrogen peroxide. for 45 minutes. The best degradation of phenol was obtained when 0.5 g adsorbent was applied with the adsorption capacity of phenol was 704.37 mg/g. The concentration of hydrogen peroxide also affects the decomposition of phenol in solution. From the variation of the hydrogen peroxide solution used (0.01; 0.02; and 0.03 M), the optimal concentration in degrading phenol was 0.01 M with the adsorption capacity of phenol was 393.70 mg/g.

The combination of Co(II) and peracetic acid (PAA) is an important alternative advanced oxidation process (AOPs), in which R-O• radicals including acetyloxyl radicals (CH3C(O)O•) and acetylperoxyl ...

Ultraviolet (UV)/chlorine draws increasing attention for the abatement of recalcitrant organic pollutants. Herein, it was found that TiO2 would significantly promote the degradation of dimethyl phthalate (DMP) in the UV/chlorine system (from 19 to 84%). Hydroxyl radicals (HO•) and chlorine radicals (Cl•) were the dominant reactive species for DMP degradation in the UV/chlorine/TiO2 system. Chlorine decayed much faster in UV/chlorine/TiO2 compared with UV/chlorine, which is possibly because photogenerated electrons (ecb-) and superoxide radicals (O2•-) have high reactivity with chlorine. As a result, the recombination of photogenerated holes (hvb+) and ecb- was inhibited and the accumulation of HO• and Cl• was facilitated. A kinetic model was established to simulate the reaction process, and it was found that the concentrations of HO• and Cl• were several times to dozens of times higher in UV/chlorine/TiO2 than that in UV/chlorine. The contributions of HO• and Cl• to DMP degradation were 70.3 and 29.7% by model simulation, respectively, and were close to the probe experiment result. In the UV/chlorine/TiO2 system, the degradation of DMP did not follow pseudo-first-order kinetics but the degradation of benzoate fitted well with pseudo-first-order kinetics. This phenomenon was elucidated by the structure of the pollutant and TiO2 and further tested by calculating the adsorption energy (Eads)/binding energy (Eb) with density functional theory. Due to faster decay of chlorine, lower amounts of disinfection byproducts formed in UV/chlorine/TiO2 compared with UV/chlorine. Adding TiO2 into the UV/chlorine system can promote the degradation of recalcitrant organic pollutants in an aqueous environment.

Carboxylic acids are the main pollutant of industrial wastewater during the advanced oxidation process (AOPs). In this study, a resin-based spherical activated carbon (RSAC, AF5) as an adsorbent was examined and acetic acid was used as a model substrate for adsorption investigation. The pH = 3, temperature = 298 K were fixed by batch technique. The pseudo-second-order kinetic model, the intraparticle and external models are fitted well, and it was found that the adsorption of acetic acid onto AF5 was controlled by liquid film diffusion. A Freundlich model indicated that the adsorption process was heterogeneous multimolecular layer adsorption on the surface. AF5 shows good regenerative ability; the recovery rate of adsorption capacity was ∼88% after five cycles. Chemical oxygen demand (COD) adsorption removal rate could be maintained at 100% for over 35 h in an actual AOPs effluent, and could be eluted for 100% after 8 h by 0.8wt% NaOH. Characterizations, including XRF, XRD, TG/DSC,FTIR, SEM and N2 adsorption, showed that the excellent adsorption performance was mainly due to the microporous structure and large specific surface area (1,512.88 m2/g), the adsorption mechanism mainly included pore filling effect and electrostatic attraction. After five adsorption recycles, AF5's pore characteristic did not change significantly. This study provides a scientific basis for the wastewater standard discharge process of AOPs coupled adsorption. HIGHLIGHTS The reusability of the acetic acid wastewater was increased by adsorption methods.; Resin-spherical activated carbon was used as an adsorbent in acetic acid diluent.; Freundlich isotherm and pseudo-second-order adsorption kinetics were the most suitable models.; The effluent of CWAO/adsorption process effluent could reach the discharge standard.

The residual antibiotics in different environmental media pose a serious threat to human health and the ecosystem. The high-efficient elimination of antibiotics is one of the foremost works. In this study, chloramphenicol (CAP) was eliminated efficiently by electrocatalytic advanced oxidation process with carbon nanotubes/agarose/indium tin oxide (CNTs/AG/ITO) electrode. The influences of different experimental parameters on the degradation efficiency were systematically studied. Under the optimal conditions (4 V potential, 10 wt% CNTs dosage, and pH = 10), the maximum degradation efficiency of CAP (20 mg L− 1) achieved 88% within 180 min. Besides, the electrocatalytic degradation pathway and mechanism for CAP were also investigated, •O2− played a major role in the process of electrocatalytic degradation. Based on the QSAR (quantitative structure-activity relationship) model, the toxicities of CAP and identified intermediates were analyzed. Compared with the parent compound, the maximal chronic toxicity of intermediate ((E)-3-(4-nitrophenyl)prop-1-ene-1,3-diol) for daphnid increased 197-fold. Besides, the hybrid toxicity of the degradation system was further confirmed via disk agar biocidal tests with Escherichia coli ATCC25922, which changed slightly during the degradation process. Based on the above results, it is worth noting that the degradation pathway and toxicity assessment should be paid more attention to the treatment of antibiotic wastewater.

In the present study, the sol–gel method is used to synthesize pure TiO2, TiO2–ZnO and TiO2–ZnO–NiO (TZN) nanoparticles. The study aims at investigating the photocatalytic efficiency of the synthesized nanoparticles used in order to remove methyl orange (MO, as a model water pollutant) dye, as exposed to black light radiation. Moreover, it also addresses the factors that may positively or negatively affect the efficiency of the photocatalytic process. XRD, SEM and DRS analyses were used to determine the nanocatalysts’ properties. The response surface method (RSM) was used to investigate the effect of four operating parameters [including the catalyst loading (TZN), basic dye concentration, pH and H2O2 concentration] and optimize the photocatalytic process of MO dye degradation in 60 min. Maximum dye removal percentage was obtained under the best operating conditions (catalyst loading = 0.3 g/l, dye concentration = 15 mg/l, pH 3 and H2O2 concentration = 15 ml/l). The high correlation coefficient (R2 = 0.9930) showed that there is an acceptable level of consistency between the experimental data and the resulted MO dye degradation predictions using the response surface model. Appropriate modules were used to carry out the two-dimensional steady-state computational fluid dynamic (CFD) simulation of the advanced oxidation process in the photocatalytic reactor. A quasi-first-order kinetic equation derived from the Langmuir–Hinshelwood model (kapp = 0.015 min−1) was used to account for the photocatalytic process of MO dye degradation. The value of R2 = 0.8865 indicated the significant consistency between the simulated CFD concentration values and experimental data.

In this study, removal of P-Nitrophenol (PNP) as a nitro-aromatic contaminant from the aqueous medium have been investigated using the photochemical oxidation process by UV-activated periodate. The...

This paper presents an advanced oxidation process (AOP) of peracetic acid (PAA) and ruthenium(III) (Ru(III)) to oxidize micropollutants in water. Studies of PAA-Ru(III) oxidation of sulfamethoxazole (SMX), a sulfonamide antibiotic, in 0.5-20.0 mM phosphate solution at different pH values (5.0-9.0) showed an optimum pH of 7.0 with a complete transformation of SMX in 2.0 min. At pH 7.0, other metal ions (i.e., Fe(II), Fe(III), Mn(II), Mn(III), Co(II), Cu(II), and Ni(II)) in 10 mM phosphate could activate PAA to oxidize SMX only up to 20%. The PAA-Ru(III) oxidation process was also unaffected by the presence of chloride and carbonate ions in solution. Electron paramagnetic resonance (EPR) measurements and quenching experiments showed the dominant involvement of the acetyl(per)oxyl radicals (i.e., CH3C(O)O• and CH3C(O)OO•) for degrading SMX in the PAA-Ru(III) oxidation process. The transformation pathways of SMX by PAA-Ru(III) were proposed based on the identified intermediates. Tests with other pharmaceuticals demonstrated that the PAA-Ru(III) oxidation system could remove efficiently a wide range of pharmaceuticals (9 compounds) in the presence of phosphate ions in 2.0 min at neutral pH. The knowledge gained herein on the effective role of Ru(III) to activate PAA to oxidize micropollutants may aid in developing Ru(III)-containing catalysts for PAA-based AOPs.

Effect of acidification on advanced oxidation performance of ozone-electrolysis was explored by experimental and theoretical approaches. A series of experiments revealed that ozone-electrolysis had...

Explosive compounds are hazardous to the environment, posing a serious risk to human and animal health and the ecosystem. The primary goal of research was to compare the efficiency of UV/H2O2, photo-Fenton, electro (EO)/UV/H2O2 processes at near-neutral pH (pH=6) on the degradation of nitramine explosives (NAs), such as hexogen (RDX), octogen (HMX), and tetryl (TET), in an aqueous solution. The effect of operational conditions, likely pH of the solution, initial H2O2 concentration, initial Fe2+ concentration, and solution temperature, was observed. The removal kinetics fit with first-order kinetics and were in the order: photo-Fenton >EO/UV/H2O2 > UV/H2O2. The results showed higher rate constant values for TET, RDX and HMX removal by UV/H2O2 (k = 0.07778, 0.03791 and 0.03786 min-1), EO/UV/H2O2 (k = 0.16599, 0.1475 and 0.08674 min-1) and photo-Fenton (k = 0.18018, 0.1501 and 0.09336 min-1) processes. Furthermore, TET, RDX and HMX were mineralized at 59.7%, 45.1%, and 25.1 %, respectively, under optimum conditions after 60 min of the photo-Fenton process. From the economic perspective, photo-Fenton only requires 2.132–4.113 kWh m-3 to completely reduce NAs. Finally, acute toxicity towards Vibrio fischeri was defeated after usage of near-neutral photo-Fenton. Thus, photo-Fenton at circum-neutral is promising for low-cost, eco-friendly and efficient processes for treating nitramine explosives in aqueous solutions.

The combination of sulfate radical-mediated advanced oxidation process (SA-AOP) and photocatalysis is researched as a highly efficient strategy for pollutant degradation in recent decades. To systematically study the synergistic effect between photocatalysis and peroxymonosulfate (PMS) induced SA-AOP, graphene oxide (GO) coupled graphitic carbon nitride (CN) composites were synthesized as catalyst. About 98% of bisphenol A was decomposed in CNGO/PMS/light system, which was significantly higher than that in CNGO/PMS or CNGO/light system, demonstrating the strong synergistic effect between photocatalysis and SA-AOP. CNGO was deactivated in catalyst/PMS system, but not in catalyst/PMS/light system, showing that the deactivation of CNGO in the presence of sulfate radicals was inhibited by the photocatalysis. The photogenerated electrons may directly reduce the oxidized GO, or react with the oxidative species which may oxidize GO, and thus maintain the activity of CNGO. In addition, the system temperature was elevated due to the light-to-heat conversion on GO. The increased reaction temperature accelerated the degradation reaction due to the improved the charge separation and molecular collision. This work explains the synergy effect between photocatalysis and SA-AOP from different perspectives, and provides a new idea to improve the reusability of carbonaceous catalyst.

2–4 Dichlorophenoxy acetic acid is most publicly applied from chlorinated phenoxy acids herbicides. In this research, central composite design for optimization of photo-Elecro/persulfate/nZVI process to degradation and mineralization of this herbicide in aqueous solution to environment protection was applied. The initial pH (2–4), persulfate anion concentration (0.25–0.5 mg/L), direct electrical (0.5–1 A), herbicide concentration (50–100 mg/l), nZVI dose (0.05–1 mg/L), and reaction time (50–100 mg/l) are independent variables optimized. Also, the synergist effect, COD and TOC removal, the effect of radical scavengers, and by-products were investigated. The fitting of the model, suggested a quadratic model (R(2) = 0.9926). F-value and P value of ANOVA were 719.81 and 0.0001 respectivelty. After optimizing the PEP/nZVI process, the proposed optimal conditions was pH = 3.4, persulfate concentration equal to 0.49 mg/l, in 1 A direct current, nZVI dose equal to 0.1 mg/l, in 50.05 mg/l herbicide concentration as an initial concentration, in 80 min reaction time. The theoretical and actual removal was evaluated 91.99% and 92%, respectively. In the optimum condition, 45.4% synergist effect indicated. 78.3% and 66.5% of initial COD and TOC were decreased. 39.02% of Cl ion was released form 2,4-D structure. The presence of radical scavengers have an adverse impact on the performance of process. The highest amount of radical scavenging was in methanol, tert-butyl alcohol and bicarbonate ions at concentrations at 50 mM/l. The kinetic data was fitted via pseudo-first-order reaction (R(2) = 0.99).The direct and indirect oxidation process lead to formation of several organic by-products which were confirmed by GC-MS analysis.

A photocatalytic sulfate radical-based advanced oxidation process was studied to degrade 4-chlorophenol (4-CP) using persulfate (PS) catalyzing UV light and heterogeneous catalyst. In this regards, ferroferric oxide nanoparticles anchored on activated carbon (FOC) was applied as a supporter of TiO2 nanoparticles for fabricating of a recoverable photocatalyst (FOCT). Some analysis techniques including PL, UV–vis DRS, XRD, FESEM-EDS, BET, TEM and VSM were utilized to determine the optical, structural, textural and physicochemical characteristics of FOCT. The reaction mechanisms of PS activation and the generation of free radicals were described in details. Moreover, degradation intermediate products were identified and reaction pathway were proposed. It was found that photocatalytic activity and oxidation performance of pure TiO2 were improved after decoration on FOC. An excellent elimination efficiency was achieved in coupling of FOCT and UV irradiation with PS. Over 99 % of 4-CP (60 mg/L) and 49 % of TOC were removed by FOCT/UV/PS at optimum operational conditions. Furthermore, high PCP decontamination rate (> 86 %) was obtained, even at high concentrations (100 mg/L). During consecutive five runs of catalyst use, the degradation rate was decreased slightly to 88 % with a negligible decline in Fe and Ti leaching, demonstrating the excellent reusability and durability of FOCT in oxidation process. SO4 – and HO radicals were detected as main reactive species that involved in the degradation of 4-CP over FOCT/UV/PS system. Thanks to good performance and easy recovery of catalyst, FOCT/UV/PS hybrid system has a great potential for environmental remediation perspectives.

During the water treatment process, some by-products could be produced by combining the disinfectant with the organic compounds. For example, chlorine can effectively convert humic acid derivatives to trihalomethane. Trihalomethanes are important organohalogen compounds with a hazardous effect on human health. In the present research, Cr-doped ZnO nano-photocatalyst was synthesized using a microwave-assisted solution combustion method, and its ability to degradation of trihalomethane, humic acid and fulvic acid were evaluated by an advanced oxidation process. To investigate the structural morphology and characterization of the synthesized nano-photocatalyst, field emission scanning electron microscopy, X-ray diffraction and diffuse reflectance spectroscopy analysis were used. The influence of various factors such as nano-photocatalyst dosage, pollutant initial concentration, reaction time and pH was evaluated to obtain an optimum condition for degradation. Also, isotherms, kinetic and thermodynamic studies were carried out in the optimum condition. According to the results, the removal process of fulvic acid and humic acid follows the Langmuir and Freundlich isotherm models and second-order kinetic equation. Also, the thermodynamic parameters such as entropy (> 0) and enthalpy (> 0) confirmed a higher degradation efficiency for fulvic acid in comparison with humic acid using the developed method due to less require energy. Isotherms and kinetic studies were carried out in the case of trihalomethane, and the results showed that trihalomethane photodegradation was followed the Langmuir–Hinshelwood isotherm model and more fitted by the first-order kinetic.

Most of the white sugar production is based on the clarification of sugarcane juice through sulfitation. In this work, alternative clarification technologies, namely ozonation and the electrochemical advanced oxidation process using the DSA® anode, are compared for the first time. In the first case, the effects of temperature and ozone concentration in the gas bubbled into raw sugarcane juice were investigated; for the electrochemical process, the effects of applied electric potential and temperature were considered. Central composite experimental designs were used to study the effects of these process variables on ICUMSA color removal, remaining sucrose content, rheology of the juice and energy consumption. For ozonation, the highest ICUMSA color removals at the end of 60 min were 75% (55 °C; 22.9 mg O3 L−1), 71.4% (33.7 °C; 14.5 mg O3 L−1), and 57.6% (55 °C; 14.5 mg O3 L−1), with energy consumptions of 532, 442 and 642 kWh m−3 order−1, respectively. In contrast, the highest ICUMSA color removal achieved by anodic electrooxidation was around 35%, at 33.8 °C and 18 V or 40 °C and 28 V, with 199 and 587 kWh m−3 order−1, respectively. In both cases, no losses of sucrose or appreciable variation in juice viscosity were observed. Considering equivalent clarification performances, the electrochemical process was shown to be more energy-efficient. Conversely, given the best performances achieved in each case, the clarification technologies studied did not reveal significant differences regarding energy consumption, sounding promising for industrial application, while further detailed process design and economic evaluation are needed.

4-chlorophenol (4-CP) is recognized as a highly toxic organic which can cause damage effects on human life and the aquatic environment. Since conventional wastewater techniques were unable to remove non-biodegradable chlorophenols, advanced oxidation process was investigated to achieve this goal. Amongst them, non-thermal plasma was recently proposed as an alternative and promising technique. However, the energy efficiency of most non-thermal plasma technique is very low as well as the input energy is dissipated in many forms such as heat, UV radiation, electromagnetic waves, etc., that are not totally involved in the pollutant degradation. In this work, quantitative analyses of UV radiation and H2O2 in a moist air gliding arc plasma (glidarc) were performed using potassium ferrioxalate actinometry and peroxytitanyl complex method, respectively. The role of UV light emitted in gliding arc plasma was elucidated by performing parallel experiments: H2O2, glidarc alone, glidarc + H2O2, glidarc + H2O2 + Fe3+ (plasma-Photo-Fenton). The results show that the incorporation of Fenton reagents in 4-CP solution exposed to the plasma enhanced the yields of chemical active species, which were available for efficient removal and mineralization of 4-CP.

Bisphenol A (BPA) is an emerging pollutant with endocrine disrupting properties that can be found at trace levels in various aqueous environments. Conventional water and wastewater treatments are not designed to efficiently remove these substances. Therefore, this work investigates the removal of BPA by an Advanced Oxidation Process (AOP), specifically heterogeneous photocatalysis using TiO2. The influences of the TiO2 concentration (1.0–10.0 mg L-1), pH (5.3 and 8.5) and effects matrix composition were studied for the removal of BPA at a concentration of 0.8 mg L-1. The results indicated that BPA was completely removed after 45 min of treatment using 7.5 and 10 mg L-1 of TiO2, under constant aeration and artificial UV irradiation, at the different pH values. The use of solar radiation as an UV source was also effective, removing BPA after 60 min of irradiation at pH without adjustment, as well as at pH 8.5. Ecotoxicological evaluation indicated that the post-treatment samples did not present acute effects towards Daphnia similis. Evaluation of chronic toxicity with Raphidocelis subcapitata showed that there was a reduction in the negative effect of BPA under the growth rate of algae biomass after 60 min of treatment, compared to the initial sample.

In this research work, we investigated the ability of the oxidative degradation of 2, 4-Dichlorophenoxy acetic acid herbicide via ultrasonic-assisted in electro-activation of the persulfate system in the presence of nano-zero valent iron. The effect of experimental parameters such as pH value [4–8], electrical current (0.5–1 A), persulfate concentration (0.25–0.5 mg.l(−1)), nano zero-valent iron dose (0.05–0.1 mg.l(−1)), and initial organic pollutant concentration (50–100 mg.l(−1)) on the ultrasonic-electropersulfate process performance was assessed via central composite design. The combination of ultrasonic waves with the electrochemical process to activation of persulfate showed better efficiency into 2, 4-Dichlorophenoxy acetic acid herbicide degradation compared to their implementation in individual and binary systems. Following optimal conditions (pH = 5.62, 0.80 A applied electrical current, 0.39 mg/L persulfate concentration, 0.07 mg/L nano-zero valent iron, and 50 mg/L 2,4-Dichlorophenoxy acetic acid concentration in 40 min reaction), nearly 91% removal was done. Moreover, the complete removal of 2, 4-Dichlorophenoxy acetic acid, 92% COD, and 88% TOC removal was achieved by this process near 140 min reaction. The scavenging experiment confirmed the role of free oxidizing species in the degradation of 2, 4-Dichlorophenoxy acetic acid during the process. Approximately 50% improved 2, 4-Dichlorophenoxy acetic acid removal in the process against the inclusive efficiency of single mechanisms. The obtained results were fitted to the pseudo-first-order kinetic model with a high correlation coefficient (R(2) = 0.96). Five important intermediate products of 2, 4-D oxidation were 2, 4-dichlorophenol (2, 4-DCP), 2, 6-dichlorophenol (2, 6-DCP), 4, 6 dichlororesorcinol (4, 6-DCR), 2-chlorohydroquinone (2-CHQ), and 2-chloro-1, 4-benzoquinone (2-CBQ). In the end, can be employed as a satisfactory advanced oxidation process in high mineralization of 2, 4-D and refractory organic pollutants.

TiO2 photocatalyst is one of the advanced oxidation process strategy which may be very potential to be implemented to deal with wastewater. The properties of the organic solvents and alkoxide precursors can impose significant effects on the final products’ microstructures and properties of TiO2. In this case, two organic compounds, ethanol, and methanol were selected for sol-gel synthesis. Besides these two solvents, two precursors, tetra isopropyl orthotitanate and tetra-n-butyl orthotitanate were used. Attention was paid to the structure, bad-gap, morphology, and photocatalytic activity of the samples. XRD confirmed the anatase crystal structure for all samples. The formation of brookite phase was facilitated by the use of tetra isopropyl orthotitanate with ethanol as solvent. The photoluminescence spectra displayed a broad, intense emission in the upper UV region. A band-gap near the theoretical band-gap at 3.2 eV was observed; hence, the photoactivity will occur in the ultraviolet area. TNBm was observed to have a higher percentage (66.5%) and a higher rate (0.5/min) of methylene blue degradation to test the photoactivity of synthesized TiO2 NPs.

The release of volatile organic compounds (VOCs) from stationary and mobile sources increases the concentration of these pollutants in the environment. These compounds have the potential to cause adverse effects on human health and the environment. The adoption of management and engineering procedures to control the emission of these pollutants to the air has become essential. The aim of this study was to use an advanced oxidation process namely the catalytic ozonation to reduce the concentration of these pollutants in industrial output. In this experimental study, the catalytic ozonation process in the presence of ZnO nanoparticles coated on zeolite media was used in a laboratory scale to treat the air contaminated with BTEX compounds as indicators of VOCs. For this purpose, First the nanocomposites were synthesized based on chemical co-precipitation method. SEM, XRD, BET and FT-IR analyses were performed to investigate the characteristics of nanocomposites. The variables including initial concentrations of BTEX (50–200 ppm), polluted air flow rate (5–20 l/h), humidity (0–75%) and ozone dose (0.25–1 g/h) were investigated. The concentration of BTEX compounds was measured by the Gas Chromatography (GC) technique according to the NIOSH 1501 manual. The results of SEM, XRD, BET and FT-IR analyses showed the proper synthesis of nanocomposites. According to the laboratory results, the optimal conditions of the process were found to be as follows: the initial concentration of pollutants equal to 50 ppm, inlet air flow rate of 5 l/h, relative air humidity of 25–35%, and inlet ozone concentration equal to 1 g/h. Under these conditions, the removal efficiency of the compounds: benzene, toluene, ethylbenzene and xylene were obtained 98, 96, 92 and 91%, respectively. Simple ozonation and adsorption processes were less efficient than catalytic ozonation. This process had the ability to reduce the concentration of BTEX compounds to standard level.

The UV/permanganate process is an innovative advanced oxidation process (AOP) that generates oxidative species, such as hydroxyl radicals (HO•) and reactive manganese species (RMnS), and adsorptive...

In this study, we introduced SnO2-Sb2O3 intermediate layer and Bi oxide into the PbO2 electrode based on Ti mesh, and investigated the improvement of electrochemical decolorization efficiency and i...

In this work, a flower-shaped ZnO/GO/Fe3O4ternary nanocomposite was synthesized via the co-precipitation method. Two significant goals of the study were boosting the degradation efficiency of ZnO and achieving a fast and simple synthesis approach. The structure, properties, and morphology of the product were characterized, and the effect of the ZnO flower-shaped structure in combination with GO nanosheets and magnetite nanoparticles was investigated on the photocatalytic activity. The structure and quality of the prepared nanocomposite were assessed by X-ray diffraction pattern, UV-visible DRS spectroscopy, Field Emission Scanning Electron Microscopy (FE-SEM). The catalytic activity of the nanocomposite was assessed by spectrophotometric analysis. The developed nanocomposite offered high photodegradation efficiency in Rhodamine B degradation under UV-C light in comparison with pure ZnO. At a specific period, the efficiency of the synthesized sample was about two times greater than that of pristine ZnO particles. Our nanocomposite is anticipated to have practical benefits in wastewater treatment given its good performance, economic savings through reducing the amount of catalyst consumption and saving time, and being a facile and fast synthesis method.

Water contamination is a critical and severe issue all over the world. The nano-based particles have the potency to overcome water contamination. In the present work, CuO and Ag/CuO nanoparticles (NPs) were synthesized by Cyperus pangorei extract using the co-precipitation method. The plant extract acts as a reducing and stabilizing agent. The purpose of plant extract is to reduce the negative impact of the synthesis method and its derivatives. The Ag+ and Cu+ reduction were confirmed through the surface plasmon resonance in the DRS spectrum. The bandgap decreasing is informed that the results have opted in the optical and catalytical applications. CuO bandgap is higher than the Ag/CuO NPs (∆Eg = 0.55 eV) reveals the Ag/CuO NPs have remarkable optical and catalytic applications. The NPs crystalline nature and size were analyzed by XRD. SEM and TEM analyses characterized the morphology and size variation of the CuO and Ag/CuO NPs. The EDX analysis analyzed the composition of the elements in the synthesized NPs. The FTIR analysis was performed to confirm the possible functional groups of plant extract involved in chemical reduction and bondings. Copper and silver metals and oxygen valencies and binding energies were examined by XPS. Occasionally, contagious diseases shake the world and affected human healthiness because of their pathogenic activity. Mostly, they are resolved by nanoparticles. The biosynthesized CuO and Ag/CuO NPs were performed against Gram-positive (Staphylococcus aureus—S. aureus) and Gram-negative (Escherichia coli—E. coli) bacteria. The results showed better activity in E. coli compared to S. aureus in both CuO and Ag/CuO NPs. The photocatalytic activity of CuO and Ag/CuO NPs were analyzed against Rhodamine B (Rh-B) dye under visible light irradiation. The metallic Ag-doped with CuO NPs improves the catalytic compared to pure CuO NPs. The pseudo-first-order kinetics were found to increase the rate of dye degradation by adding Ag ions to the CuO surface. The advanced oxidation process would increase the electron–hole pair activity and reactive oxygen species (ROS) formation. The AOP photocatalyst is widely used to remove the toxicity of wastewater. There is no secondary product formation and rich activated electrons. The obtained results indicate the CuO and Ag/CuO NPs may further use in wastewater treatment and biomedical applications.

This study aimed to remove the antibiotic tetracycline from a sample of synthetic wastewater using an advanced oxidation process by Fenton's reagent treatment. Central Composite Design (CCD) software was used to reduce the number of tests required to remove tetracycline. The independent variables identified in batch oxidation experiments are the concentrations of tetracycline (40–250 mg / L), hydrogen peroxide (20–600 mg / L), and Fe(II) (0–60 mg / L). The rate of tetracycline degradation was significantly influenced by the concentration of hydrogen peroxide and tetracycline. The reaction time required for tetracycline removal was determined to be 15 minutes. The optimal ratio of independent variants leading to complete degradation 100% of tetracycline was hydrogen peroxide / Fe2 + / tetracycline 310/30/145 mg / l.

TiO2/H2O2 mediated UV photocatalysis was studied for estimating the degradation of cypermethrin in a synthetic aqueous solution. All the experiments were performed in a laboratory scale photo-reactor under UV-A (~365 nm) irradiation. Optimisation of the process parameters was done to achieve maximum degradation of cypermethrin. The process parameters chosen for this investigation were concentration of TiO2 (0.5 to 2 g/L), concentration of H2O2 (50 to 350 mg/L) and initial pH of the reaction mixture (2 to 10). A three-level Box-behnken factorial design (BBD) in combination with Response Surface Methodology (RSM) was adopted to perform the optimisation process. Further, thermal treatment method was adopted to regenerate the TiO2 particles and their reusability was assessed. The findings of this analysis revealed that after 3 h of reaction time and at optimised conditions (i.e., concentration of TiO2 = 0.65 g/L; concentration of H2O2 = 179 mg/L and pH = 3.9), 48.30% of cypermethrin was degraded and subsequent biodegradability index, of the reaction mixture, improved from 0.55 to 0.3. Also, it was estimated that the adsorption and photocatalytic degradation processes followed Langmuir isotherm and first-order kinetics, respectively. The TiO2 particles were observed to be reusable as, after five cycles only 12.6% reduction was observed in its degradation efficiency. The findings of this study may prove beneficial for treating the pesticides’-contaminated water bodies, in the tropical countries, where sunlight is intense and pesticides are continuously entering into the water bodies from nearby agricultural fields.

This study has systematically reviewed all of the research articles about the photocatalytic degradation of pesticides using titanium dioxide (TiO2) nanoparticles (NPs) and ultraviolet (UV) irradiation. Online databases were searched for peer-reviewed research articles and conference proceedings published during 2009-2019, and ultimately 112 eligible articles were included in the review. Fifty-three active ingredients of pesticides and one mixture had been investigated, most of them were organophosphorus (22%), followed by triazine derivatives (11%), chloropyridines (9%), and organochlorines (9%). Sixteen types of TiO2 with an average photodegradation efficiency of 71% were determined. Based on the type of pesticide and experimental conditions such as irradiation time, the complete photodegradation had been observed. The removal of each group of pesticides has been sufficiently discussed in the article. Effect of experimental conditions on photocatalytic activity has been investigated using linear and polynomial regressions. The strategies to reduce the required energy for this process, doping TiO2 with metal and non-metal agents, innovative reactor designs, etc., were also discussed. In conclusion, TiO2 NPs have been successful for degradation of pesticides. Future direction for research incorporates developing and application of heterogeneous doped and immobilized titania having optimized characteristics such as surface area, reactive centers, recombination rate, and phase, and capable to photo-degrade low levels of pesticides residues under solar light in an efficient full-scale size.

Different technologies such as physical, chemical, biological, advanced oxidations and electro-chemical methods are involved in the treatment of industrial effluent. The widely followed biological treatment techniques are required more time, wide operational space and are not effective for wastewater contains heavy metal and hazardous elements. The advanced oxidation process needs tremendous operational cost and is usually procure high immaculate water. The chemical coagulation process is time delaying and brings about a huge volume of sludge. In the electrostatic coagulation process, the electrode plates are dissolved in the wastewater by a direct current source of metal electrodes immersed in the effluent. Electrocoagulation (EC) has a newly followed method used for treating industrial effluent due to its adaptability and cost-effective eco-friendly method. EC has been used for treating a wide range of industrial effluent. These metal ions combine with hydroxide ions to form metal hydroxide which acts as the coagulant for the destabilization of suspended as well as dissolved pollutants in the industrial wastewater. Therefore, the intention of this review paper is the possibility of EC for the treatment of industrial effluents as well as energy consumption in the EC.

Degradation of nonbiodegradable organic compounds into harmless substances is one of the main challenges in environmental protection. Electrically-activated persulfate process has served as an efficient advanced oxidation process (AOP) to degrade organic compounds. In this study, we synthesized three nitrogen-doped carbon materials, namely, nitrogen-doped activated carbon plus graphene (NC), and nitrogen-doped activated carbon (NAC), nitrogen-doped graphene (NGE), and three nitrogen-doped carbon material-graphite felt (GF) cathodes. The three nitrogen-doped carbon materials (NC, NGE, NAC) were characterized using X-ray diffraction, Raman spectroscopy, X-ray electron spectroscopy, and nitrogen desorption–adsorption. The electron spin resonance technique was used to identify the presence of hydroxyl radicals (˙OH), sulfate radicals (SO4˙−) and singlet oxygen (1O2) species. The results showed that NC was more conducive for the production of free radicals. In addition, we applied NC-GF to an electro-activated persulfate system with the degradation of p-nitrophenol and investigated its performance for contaminant degradation under different conditions. In general, the nitrogen-doped carbon electrode electro-activated persulfate process is a promising way to treat organic pollutants in wastewater.

Catalytic ozonation with nano-perovskite oxides is a more efficient and advanced oxidation process for the mineralization of organic pollutants. In this study, by regulating the amount of polyethylene glycol during the synthesis of CaZrO3 perovskite-type oxides by the co-precipitation method, efficient surface oxygen vacancies were formed in CaZrO3. Owing to the presence of abundant oxygen vacancies, CaZrO3 modified by PEG exhibited a much higher catalytic activity than unmodified CaZrO3. It was further discovered from the EPR results that the main active oxygen species depend on the surface structure of CaZrO3. The variation of oxygen vacancies on the surface of the catalyst with PEG addition stimulated ozone decomposition to generate a large number of superoxide radicals. This study not only proposed a method to improve the activity of the catalyst, but also further studied the reaction mechanism of CaZrO3 catalyzed ozonation. It provides a solid theoretical basis for the industrial application of catalytic ozonation technology.