Search

Hypophosphite (P(I)) is ubiquitous in some waste streams. It may contribute to the eutrophication of water bodies, yet conventional methods are ineffective in treating P(I)-laden wastewater. Here, we propose a novel CaO2/ultraviolet (UV) system that can simultaneously remove P(I) and recover Ca-phosphate. This system lies in the simultaneous release of OH-, Ca2+, and H2O2, with the last being activated and producing reactive oxygen species (ROS) under UV irradiation. Subsequently, the generated ROS converts P(I) to phosphite and phosphate, forming Ca-phosphate with the released Ca2+ at pH 11.0. Beyond activating H2O2, UV light also promotes the dissolution of CaO2 powders. The system removes 97.0% of 1.0 mM P(I) in 6 h with dosing 2.0 mM CaO2. The presence of 5.0 mM HCO3- drops P(I) removal from 97.0 to 14.1% by competing with P(V) toward Ca2+. Nitrate and humic acid show similar effects by adsorbing UV light or quenching ROS. However, we may overcome the adverse effects with an enhanced CaO2 dose. For example, with 10 mM CaO2, the CaO2/UV system removed more than 78% of non-ortho P from actual electroless rinse water. These results confirmed that CaO2/UV is an exciting all-in-one system for treating P(I)-laden wastewater and recovering valuable P products.

The aim of this study was to investigate the influence of UV/H2O2 advanced oxidation process on the natural organic matter content and disinfection by-products formation potential of different water matrices. Three water matrices (two natural waters and a synthetic humic acid solution) with different natural organic matter characteristics and concentrations were analysed. The carbonaceous disinfection by-products: trihalomethanes, haloacetic acids and haloketones, as well as nitrogenous disinfection by-products: haloacetonitriles and chloropicrin were investigated after chlorination. The UV/H2O2 treatment resulted in significant trihalomethane and haloacetic acids precursors removal (up to 53% and 30%, respectively) in humic acid solution in conditions ≥ 1.0 mg H2O2/mg DOC, in combination with a dose of UV irradiation ≥ 3000 mJ/cm2. Under the same reaction conditions, in natural groundwater rich in hydrophobic natural organic matter, the advanced process was less effective in DBP precursors removal. On the other hand, the advanced process was very effective in trihalomethaneprecursors removal (up to 76%) in groundwater with hydrophyilic natural organic matter. Haloketones were formed after treatment in very low concentrations. Nitrogenous disinfection by-products were only formed in the natural water containing hydrophilic organic matter, during the advanced process at 3.0 mg H2O2/mg DOC. The UV/H2O2 process resulted in negligible organic matter mineralization, but increased the brominated disinfection by-products formation in waters with low to medium bromide contents. It was concluded that under the same advanced oxidation process reaction conditions different natural organic matter structures showed different reactivities with chlorine toward the formation of the investigated disinfection by-products.

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.

Acid mine drainage (AMD) is a multi-factor pollution formed from complex chemical, physical, and biological interactions that takes place under ambient conditions in abandoned and active mines. Over the years, researchers have been investigating ways to mitigate its potential impact on the environment through various treatment technologies. The aim of this review was to critically analyze the broad spectrum of treatment methods that have been engaged in published literature on the remediation of AMDs. Adsorption treatment using zeolites, fly ash, biochar activated carbon, clay-based minerals and biomass-based adsorbents was discussed. Given an appropriate choice of adsorbent, ions in AMD can be reduced between 50% and 99%. Membrane separation processes like nanofiltration, reverse osmosis and hybrid systems were discovered to be more effective than adsorption and can effect over 90% rejection at optimized conditions. Biological processes showed a far wider range of performance amongst all treatment types due to the selectivity in performance of the different micro-organisms used although Advanced Oxidation Process (AOPs) have been shown to achieve>80% ions removal. In all biological processes studied ranging from wetlands to bioreactors, algal bioreactors seemed the most effective in this domain. Most of these treatment technologies are corrective while preventive techniques can be explored to prevent the production of AMD. Despite the positive outcomes of the different types of treatment, they have associated technical issues. It is recommended that more preventive techniques be explored to reduce the production of AMD. The review discussed how AMD treatment would affect environmental protection and water resource management.

To evaluate the ultraviolet (UV) advanced oxidation process (AOP) in a potable reuse facility, we characterized organic compounds in upstream reverse osmosis (RO)-treated recycled municipal wastewa...

The microwave enhanced advanced oxidation process (MW-AOP) has been applied to pre-treat different sludge types and high solids content. Secondary sludge not only had the highest solids and nutrient content but also yielded higher treatment efficiency than primary or mixed sludge. In the case of secondary sludge with 4% total solids (TS), the total suspended solids (TSS) concentration was reduced by 32% while soluble chemical oxygen demand concentration increased from 1% to 40% after treatment at 110°C. A high level of nutrient release was also achieved; about 65% total phosphate (TP) solubilized at 110°C. The degree of secondary sludge disintegration was dictated by temperature and hydrogen peroxide dosage. The optimal operating temperature for the system was 110°C, and sludge containing TS up to 8% was treated effectively. Secondary sludge with 8% TS had a TSS reduction of 41% after treatment at 110°C while COD solubilization was about 45%; about 55% TP was solubilized at 10 min holding time. Treatment of sludge with higher solids content would allow for handling larger amounts of sludge at a given period and reduce heating cost per unit of treated sludge. The inter-relationship between the degree of sludge disintegration and changes in chemical and physical properties was also clearly demonstrated here. The treated sludge would be an ideal substrate for anaerobic digestion or phosphorous recovery processes. High levels of nutrients (phosphorus and nitrogen) and metal release, and solids disintegration from sludge containing high solids content would make subsequent resource recovery processes more effective and economical.

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 following work provides a perspective on the degradation of cytostatic pollutants through TiO2 heterogeneous photocatalysis. Cytostatic drugs are emerging pollutants used for cancer treatment found in hospital and domestic wastewater. Small amounts of cytostatic pollutants may pose severe health problems in human beings, animals, and plants after prolonged contact. This research presents a general review of some water treatment methods, such as aerobic activated sludge, enzymatic degradation, nanofiltration and chlorination, that have been used for the degradation or elimination of cytostatic drugs in wastewater. In recent years, photocatalysis has become important to solve this problem; these advanced oxidation process uses pure and modified TiO2 to degrade cytostatic contaminants and convert them into non-harmful substances or to eliminate them completely. This work contains a comprehensive review of the heterogeneous photocatalysis process and mechanism, and its application on the removal of cytostatic pollutants. Even if research on the topic is still scarce, this literature review provides interesting highlights on the scope of the research field, and the path such research could follow.

As an advanced oxidation process, vacuum ultraviolet/ultraviolet (VUV/UV) has been intensively studied for drinking water treatment, but assessment of its feasibility for wastewater treatment has rarely been conducted. This study investigated the treatment of fluorine-containing pharmaceutical wastewater by VUV/UV process and examined the defluorination and therefore the improvement of biodegradability of the wastewater after the process. The results indicated that the degradation of a model fluorine-containing organic compound (namely, 4-fluorophenol) was mainly achieved via the attack of the fluorine atom linking directly to the aromatic ring by the HO• generated from VUV photolysis of water. As the solution pH increased from 4.0 to 10.0, the COD removal efficiency of the real pharmaceutical wastewater decreased slightly from 18.1 to 15.9%, while the release ratio of F− increased from 50.8 to 75.5%. As the dissolved oxygen increased from 0.15 to 12 mg L−1, the removal efficiency of COD and the release ratio of F− increased from 9.2 to 17.1% and from 48.2 to 75.5%, respectively. The biodegradability index (BOD/COD) increased significantly from 0.24 to 0.47 after the VUV/UV irradiation, which confirmed the feasibility of applying the VUV/UV process for improving biodegradability of the pharmaceutical wastewater.

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.

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.

We present an electrochemical advanced oxidation process (eAOP) reactor employing expanded graphite, potassium iodide (KI), and electrical current, which demonstrates an exceptionally high rate of ...

Landfilling in many countries is the most embraced method for disposal of municipal, agricultural and industrial waste. However, the main issue imposed for landfilling is the landfill leachate (LL)...

The following work provides a perspective on the potential application of solar heterogeneous photocatalysis, which is a nonselective advanced oxidation process considered as a sustainable technology, to assist in arsenic removal from water, which is a global threat to human health. Heterogeneous photocatalysis can oxidize trivalent arsenic to pentavalent arsenic, decreasing its toxicity and easing its removal with other technologies, such as chemical precipitation and adsorption. Several lab-scale arsenic photocatalytic oxidation and diverse solar heterogeneous photocatalytic operations carried out in different reactor designs are analyzed. It was found out that this technology has not been translated to operational pilot plant scale prototypes. General research on reactors is scarce, comprising a small percentage of the photocatalysis related scientific literature. It was possible to elucidate some operational parameters that a reactor must comply to operate efficiently. Reports on small-scale application shed light that in areas where other water purification technologies are economically and/or technically not suitable, and the solar energy is available, shed light on the fact that solar heterogeneous photocatalysis is highly promissory within a water purification process for removal of arsenic from water.

In this study, an attempt was carried out to degrade ofloxacin (OFX) and metronidazole (MTZ) antibiotics by a new advanced oxidation process. UV/ZnO/sulphite (UZS) was employed for the destruction ...

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.

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.

Ozonation, combined with suitable catalyst represents an interesting option in removing poorly degraded pollutants from stabilized landfill leachate. Therefore, this study aimed to eliminate chemic...

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...

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.

The present study is a “first-of-its-kind” work on an integrated process consisting of a hydrodynamic cavitation (HC)-assisted advanced oxidation process and vacuum membrane distillation (VMD) for ...

Water is one of the most important resource on the planet. Water pollution has become a global problem and have been identified various sources of pollution such as sewage discharge, industrial effluents and agricultural runoff and their potential has been studied in mass. From an environmental view, two approaches to dealing with water pollution are to reduce the sources and to treat the water to remove pollutants or convert them to forms that can be disposed of safely Advanced oxidation processes are widely studied for the treatment of toxic compounds; photocatalysis and radiolysis have been used in the treatment of persistent organic compounds. Radiocatalysis is a process analogous to heterogeneous photocatalysis wherein activation occurs through absorption of ionizing radiation rather than visible or ultraviolet photons. New and emerging pollutants present a new global water quality challenge with potentially-serious threats to human health and ecosystems. Pharmaceuticals, personal care products and endocrine disrupting compounds are among the prime examples of emerging contaminants. Diclofenac is a prevalent anti-inflammatory drug used throughout the world. Its frequent occurrence in freshwater environments and its potential toxicity towards several organisms such as fish and mussels makes diclofenac an emerging environmental contaminant. In this work, radiocatalysis was studied as advanced oxidation process for the degradation of diclofenac. For this, commercial titanium oxide was used as catalyst. The samples were exposed to gamma radiation using an irradiator, which is provided with a 60Co source (gamma ray energies: 1.17 and 1.33 MeV). Some variations in conditions of irradiation (doses and ambient air) were used to determine their effect in process. The effect of adding the deposited catalyst on the degradation of diclofenac was observed and some differences in both processes, photocatalysis and radiocatalysis, were found.

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.

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.

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.

Utilization of the advanced oxidation process (AOP) for degradation of antibiotics into byproducts with low toxicity for enhancing the quality of drinking water and wastewater has remained a huge challenge for environmental aim. In this study, a nanocomposite based on Cobalt zeolite imidazolate framework (ZIF-67), and Fe3O4 nanoparticles (NPs) were prepared using the simple sol-gel method. In this nanocomposite, Fe3O4 NPs were used as an ideal platform for microporous ZIF-67 growth, aiming to create an efficient heterogeneous catalyst with magnetic separation for the activation of peroxymonosulfate (PMS) to expeditiously degrade ciprofloxacin (CIP) antibiotics. The catalytic activity of the proposed nanocomposite was systematically evaluated with several operational factors, such as nanocatalyst and oxidant dosage, initial pH, co-existing anions, and the stability of the catalyst. Furthermore, scavenging technique and electron spin resonance (ESR) demonstrate that the sulfate and hydroxyl radicals play a major role in the degradation process. The findings indicate that ZIF-67/Fe3O4 nanocomposite is a greener and more suitable option for large scale applications and creates new insights into the removal of contaminants from the ecosystem.

Effective pesticide remediation technology demands amendments in the advanced oxidation process for its continuous treatment and catalyst recovery. The evidence of 2,4-dichlorophenoxyacetic acid (2,4-D), an herbicide in water bodies, poses a major environmental threat to both humans and aquatic organisms. In the present study, a recirculation type photocatalytic reactor was developed to treat 2,4-dichlorophenoxyacetic acid using chitosan-TiO2 beads prepared via impregnation method under UV light. At optimized conditions, chitosan-TiO2 beads showed a maximum photocatalytic degradation of 86% than commercial TiO2 (65%) and followed pseudo first-order reaction. The 2,4-D degradation follows pseudo first-order kinetics under UV irradiation with a rate constant of 0.12 h−1, and the intermediates were identified using LCMS analysis. The total operational cost of the chitosan-TiO2 catalyst was found to be profitable (Rs. 1323 for 2 L) than that of TiO2 (Rs. 1679) at optimized conditions. The beads were reusable up to 4 consecutive cycles without loss in efficiency. This study briefs photocatalytic removal of 2,4-dichlorophenoxyacetic acid in a recirculation-type reactor for its reliability, low cost, efficiency, reusability, and commercialization.

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.

In this work, bismuth-doped titania (BixTiO2) with improved oxygen vacancies was synthesized by sol-gel protocol as a novel peroxymonosulfate (PMS, HSO5-) activator. HSO5- and adsorbed oxygen molecules could efficiently be transformed into their respective radicals through defect ionization to attain charge balance after their trapping on oxygen vacancies of the catalyst. XRD study of BixTiO2 with 5 wt% Bi (5BiT) revealed anatase, crystalline nature, and successful doping of Bi into TiO2 crystal lattice. The particle size obtained from BET data and SEM observations was in good agreement. PL spectra showed the formation rates of •OH by 3BiT, 7BiT, 5BiTC, and 5BiT as 0.720, 1.200, 1.489, and 2.153 μmol/h, respectively. 5BiT catalyst with high surface area (216.87 m2 g-1) and high porosity (29.81%) was observed the excellent HSO5- activator. The catalytic performance of 0BiT, 3BiT, 5BiT, and 7BiT when coupled with 2 mM HSO5- for recalcitrant flumequine (FLU) removal under dark was 10, 27, 55, and 37%, respectively. Only 5.4% decrease in catalytic efficiency was observed at the end of seventh cyclic run. Radical scavenging studies indicate that SO4•- is the dominant species that caused 62.0% degradation. Moreover, strong interaction between Bi and TiO2 through Bi-O-Ti bonds prevents Bi leaching (0.081 mg L-1) as shown by AAS. The kinetics, degradation pathways, ecotoxicity, and catalytic mechanism for recalcitrant FLU were also elucidated. Cost-efficient, environment-friendly, and high mineralization recommends this design strategy; BixTiO2/HSO5- system is a promising advanced oxidation process for the aquatic environment remediation.

This work presents a bibliographic review of the literature regarding the simultaneous removal of contaminants of emerging concern (CECs) and disinfection in domestic wastewater matrices. These two responses are usually evaluated independently, as most attention has been centered on the discussion over the removal of CECs in the last 10 years. However, the simultaneous removal of CECs and pathogens from wastewater has been recently brought to the spotlight, especially considering the removal of antibiotics and antibiotic-resistant bacteria. Aiming at a reproducible and nonbiased methodology, a combination of the construction of a bibliometric portfolio with systemic analysis was performed with peer-reviewed manuscripts published between 2008 and 2019 in five distinct databases. Several keyword combinations were necessary to achieve a relevant portfolio according to strict criteria. As a result, five highly cited papers and authors were selected. Among the advanced oxidation processes (AOPs) explored for simultaneous removal of CECs and disinfection in these papers, detailed results have been elucidated mainly for ozonation. Thus, revealing the broad range of questions that have yet to be investigated in depth for new technologies such as irradiated solar processes. In addition, there is a lack of information associated with simultaneous assessment of CEC removal and disinfection in real samples and in wastewater matrices originated from different secondary treatment technologies in diverse locations.

The substantial growth of industrial development and challenging regulations associated with environmental protection demands new and advanced technologies for the effective treatment of the effluents. The applications of the classical Fenton process are versatile and effective particularly for the treatment of recalcitrant compounds among advanced oxidation processes. However, the classical Fenton process possesses some shortcomings like the requirement of a narrow pH range, production of a high amount of iron sludge, and high chemical involvement. These drawbacks are the environmental barriers that restricted its widespread application. Several modifications have been adopted by many researchers as possible solutions to overcome these restrictions. Although several types of research and reviews have been reported in the literature on Fenton’s types and applications, nevertheless, a review with emphasis on the restrictions of the Fenton process and their possible solutions is lacking. The present review delineates the restrictions of the classical Fenton process and recent approaches to overcome these limitations with a special focus on Fenton sludge reuse systems as a sustainable approach. The Fenton sludge reuse systems for various wastewater treatment are also highlighted. The sludge reuse systems without regeneration, with optimized addition of reagents dosage, are the most effective method for treatment. To the best of our knowledge, this is the first review article focusing Fenton sludge reuse system for wastewater treatment. The review also addresses the possible areas for future research as reported in the literature, to make the process cost-effective, environmentally friendly, and its feasibility for large-scale applications.

In this work, the activated persulfate oxidation of ciprofloxacin (CIP) using a low-grade titanium ore under sunlight or simulated sunlight were conducted to analyze the CIP degradation efficiency and to identify the transformation products (TPs) generated during oxidation under both types of irradiation sources by using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). All advance oxidation process experiments were performed in a 2700-mL raceway reactor at a pH value of ~ 6.5 and an initial CIP concentration of 1 mg/L, during 90 min of reaction time. The control experiments carried out under simulated sunlight achieved a 97.7 ± 0.6% degradation efficiency, using 385 W/m2 of irradiation with an average temperature increase of 11.7 ± 0.6 °C. While, the experiments under sunlight reached a 91.2 ± 1.3% degradation efficiency, under an average irradiation value of 19.2 ± 0.3 W/m2 in October–November 2019 at hours between 11:00 am and 3:00 pm with an average temperature increase of 1.4 ± 0.8 °C. Mass spectrometry results indicated that 14 of the 108 possible TPs reported in the literature were detected. The calculated exact mass, measured accurate mass, and its characteristic diagnostic fragment ions were listed, and two new TPs were tentative identified. The TP generation analysis showed that some specific compounds were detected in different time intervals with kinetic variations depending on the irradiation used. Consequently, two CIP degradation pathways were proposed, since the type of irradiation determines the CIP degradation mechanism.

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG [Abstract] The removal of emerging pollutants from municipal wastewater was studied for the first time using a three-step pilot-scale system: 1) hybrid digester (HD) as first step, 2) subsurface vertical flow constructed wetland (VF) as second step, and 3) photodegradation (PD) unit as third step or post-treatment. The HD and VF units were built and operated in series with effluent recirculation at pilot scale. For the PD post-treatment, three alternatives were studied at lab-scale, i) UVC irradiation at 254 nm (0.5 h exposure time), ii) UVA irradiation at 365 nm using a TiO2-based photocatalyst and iii) sunlight irradiation using a TiO2-based photocatalyst, the last two for 1 and 2 h. Alternative iii) was also tested at pilot-scale. Degradation of nine compounds was evaluated: acetaminophen (ACE), caffeine (CAF), carbamazepine (CBZ), ketoprofen (KET), ibuprofen (IBU), diclofenac (DCL), clofibric acid (ACB), bisphenol A (BPA), and sotalol (SOT). Overall, the HD-VF-UVC system completely removed (>99.5 %) ACE, CAF, KET, IBU, DCL and ACB, and to a lesser extent SOT (98 %), BPA (83 %) and CBZ (51 %). On the other hand, the HD-VF-UVA/TiO2 system (at 2 h) achieved >99.5 % removal of ACE, CAF, KET, IBU and DCL while ACB, BPA, CBZ and SOT were degraded by 83 %, 81 %, 78 % and 68 %, respectively. Working also at 2 h of exposure time, in summer conditions, the HD-VF-Sol/TiO2 system achieved >99.5 % removal of ACE, CAF, KET, IBU, DCL and ACB, and to a minor extent BPA (80 %), SOT (74 %) and CBZ (69 %). Similar results, although slightly lower for SOT (60 %) and CBZ (59 %), were obtained in the pilot sunlight plus TiO2 catalyst unit. However, the use of sunlight irradiation with a TiO2-based photocatalyst clearly showed lower removal efficiency in autumn conditions (i.e., 47 % SOT, 31 % CBZ). This research was funded by the Spanish Ministerio de Economía y Competitividad through project CTQ2015-71238-R (MINECO/FEDER), and the Xunta de Galicia (project GPC ED431B 2020/52 and project GPC ED431B 2019/44), respectively. Funding for open access charge: Universidade da Coruña/CISUG Xunta de Galicia; GPC ED431B 2020/52 Xunta de Galicia; GPC ED431B 2019/44

Recently, microplastics (MPs) became a big name in the world since their presence in bodies of different species, environmental media, and even in bottled drinking water was frequently reported. Several studies reported MPs’ potential threat to health of humans, animals and the ecosystem. Therefore, it is of great importance to develop reliable technologies for removing MPs in the environment. Advanced oxidation processes (AOPs) are widely studied and applied for the decomposition of different refractory contaminants in the environment. Because reactive oxygen species produced in AOPs could effectively degrade many pollutants, several AOPs were applied for MPs decomposition. Homogeneous and heterogeneous AOPs, including photolysis, UV/H2O2, O3, UV/visible light-induced photocatalysis, and heat activated PS and PMS, could effectively decompose various types of MPs with different sizes. However, the decomposition mostly occurred on the surface of MPs even though several studies reported complete removal of MPs. Interestingly, several studies demonstrated that treated MPs could become pollutant carriers for animals and human beings by adsorbing contaminants in the environment. However, a limited number of studies on MPs removal by AOPs are available and only few types of AOPs are recently studied even though current studies demonstrated the potential of AOPs for complete MPs removal. Therefore, more effort must be put into investigating different AOPs for complete removal of MPs in the environment. AOPs will play a key role for MPs removal in the environment in the near future, definitely.

Polycyclic aromatic hydrocarbons (PAHs) are the toxic and persistent micro-pollutants recalcitrant to biodegradation. Photo-Fenton process is a commonly adopted advanced oxidation process. Advanced oxidation processes generate highly reactive hydroxyl radicals (OH·) which completely mineralise the organic contaminants. This study aims to find the efficiency of photo-Fenton oxidation process in the removal of PAHs and COD from landfill leachate, and investigate its effect on 16 PAHs according to their number of aromatic rings. Experiments were designed using central composite design, a module of response surface methodology (RSM) in the Design-Expert software. pH, Fe2+ concentration, H2O2 concentration, reaction time and UV intensity were the five experimental variables which were optimised and modeled successfully. The statistical analysis proved that all the variables have significant effect on the model. The value of R2 (0.94) showed a high reliability in the estimation of chemical oxygen demand and polycyclic aromatic hydrocarbons removal efficiency. Optimum experimental conditions of pH 6.5, Fe2+ 1.1 g/L, H2O2 concentration 5.5 g/L, reaction time 40 min and UV intensity 13.5 W resulted in the maximum chemical oxygen demand and polycyclic aromatic hydrocarbons removal efficiency of 84.43% and 92.54%, respectively. Validation was carried out by conducting additional set of experiments, and the small gap between observed and predicted values confirmed that central composite design is the effective tool to optimise the photo-Fenton oxidation process in the degradation of chemical oxygen demand and polycyclic aromatic hydrocarbons.

Chloramines applied to control microfiltration and reverse osmosis (RO) membrane biofouling in potable reuse trains form the potent carcinogen, N-nitrosodimethylamine (NDMA). In addition to degrading other contaminants, UV-based advanced oxidation processes (AOPs) strive to degrade NDMA by direct photolysis. The UV/chlorine AOP is gaining attention because of its potential to degrade other contaminants at lower UV fluence than the UV/hydrogen peroxide AOP, although previous pilot studies have observed that the UV/chlorine AOP was less effective for NDMA control. Using dimethylamine (DMA) as a model precursor and secondary municipal wastewater effluent, this study evaluated NDMA formation during the AOP treatment via two pathways. First, NDMA formation by UV treatment of monochloramine (NH2Cl) and chlorinated DMA (Cl-DMA) passing through RO membranes was maximized at 350 mJ/cm2 UV fluence, declining at higher fluence, where NDMA photolysis outweighed NDMA formation. Second, this study demonstrated that chlorine addition to the chloramine-containing RO permeate during the UV/chlorine AOP treatment initiated rapid NDMA formation by dark breakpoint reactions associated with reactive intermediates from the hydrolysis of dichloramine. At pH 5.7, this formation was maximized at a chlorine/ammonia molar ratio of 3 (out of 0-10), conditions typical for UV/chlorine AOPs. At 700 mJ/cm2 UV fluence, which is applicable to current practice, NDMA photolysis degraded a portion of the NDMA formed by breakpoint reactions. Lowering UV fluence to ∼350 mJ/cm2 when switching to the UV/chlorine AOP exacerbates effluent NDMA concentrations because of concurrent NDMA formation via the UV/NH2Cl/Cl-DMA and breakpoint chlorination pathways. Fluence >700 mJ/cm2 or chlorine doses greater than the 3:1 chlorine/ammonia molar ratios under consideration for the UV/HOCl AOP treatment are needed to achieve NDMA control.