Advanced Oxidation System Research Articles

Oxygen vacancies mediate the degradation of refractory organics in the interflow around a simple landfill: Based on Mg-Fe3O4/PMS system

The interflow around simple landfills in villages and towns contains high-risk and trace refractory organics (TRO), which can have serious effects on the rural living environment. Here, an iron-based catalyst containing oxygen vacancies was prepared by doping with Mg, and the Mg-Fe3O4/peroxymonosulfate (PMS) advanced oxidation system was constructed to mediate the efficient degradation of the pollutants in the interflow around simple landfills. The parameters of the system were optimized to maximize the degradation of the pollutants in interflow via single-factor and response surface experiments. Electron paramagnetic resonance revealed that oxygen vacancies can effectively form in the catalyst by doping co-precipitation. The rate of chemical oxygen demand removal from the interflow was 96.01 ± 1.12% under the following conditions: 10% Mg doping, 1.03 g·L−1 catalyst dosage, and 13.47 mmol·L−1 PMS dosage. UV254 and E280 decreased from 0.403 and 0.305 cm−1 to 0.199 and 0.164 cm−1, respectively, and E300/E400 increased from 5.56 to 8.92 after the reaction. Excitation–emission matrix spectra showed that the corresponding absorption peaks of fulvic acid and tyrosine analogs were heavily attenuated. Gas chromatography–mass spectrometry analysis showed that the number of TRO decreased from 57 to 9, indicating that a large amount of TRO had been removed. A mechanistic analysis revealed that SO4·- and OH· might play a major role in the reaction process and that 1O2 plays an important role in the degradation process.

O2-Involved Electro-activation of Persulfate on Oxidized Carbon Black for Effective Sulfamethoxazole Degradation: Key Role of Side-Reactive Oxygen Reduction

The oxygen reduction reaction (ORR) was an unavoidable side reaction in the electro-activating persulfate (PS) process, especially on the ORR-active carbon materials, which has usually been ignored in previous reports. In this work, the O2/N2-involved electro-activation of the PS system was constructed to confirm the role of side-reactive ORR on oxidized carbon black (OCB) for sulfamethoxazole (SMX) degradation. With O2 involvement, 820.8 μM •OH was produced by PDS electro-activation, over 7 times more than 115.8 μM under N2 aeration, leading to a high SMX removal of 90.6% (only 67.8% under N2 aeration). Such a huge difference in •OH yield and SMX removal performance was mainly attributed to side-reactive 2e– ORR, in which as-generated H2O2 was electro-activated to produce abundant •OH and form an advanced homogeneous •OH/SO4•– oxidation system via mutual transformation with gradual acidification. Meanwhile, the introduction of oxygen functional groups and defects on the surface of carbon black calcined at 600 °C (CB600) also contributed to the improvement of SMX removal performance, attributing to their enhancing effects on SMX electro-adsorption, PDS electro-activation, and O2 electro-reduction. Thus, side-reactive oxygen reduction played the spontaneous and synergistic oxidation roles in the O2-involved electro-activating PS process, helping to design highly effective advanced oxidation systems in the future.

Degradation of Polystyrene Nanoplastics in UV/NaClO and UV/PMS Systems: Insights into Degradation Efficiency, Mechanism, and Toxicity Evaluation

Nanoplastics have gradually become a concern due to the wide use of plastics. Nanoplastics in aqueous phase can be exposed to users through water supply networks and cannot be efficiently removed by conventional water treatment processes. This work studied the degradation of polystyrene nanoplastics (PS-NP) by two commonly used advanced oxidation systems: UV/NaClO and UV/peroxymonosulfate (PMS). Results showed that almost no turbidity was detected in the PS-NP solution (5.00 mg/L) after treated by both UV/NaClO and UV/PMS for 360 min, suggesting the excellent turbidity removal ability. Yet, scanning electron microscope (SEM) and total organic carbon (TOC) removal tests demonstrated that PS-NP could not be completely degraded by UV/NaClO. The mineralization rate using UV/NaClO was only 7.00% even when the NaClO concentration increased to 5.00 mM, and many PS-NP particles could still be observed in SEM images. By contrast, the mineralization rate reached 63.90% in the UV/PMS system under the identical experimental conditions, and no spherical particles appeared in the SEM results. Density functional theory (DFT) calculations revealed that the different reaction sites and energy barriers of SO4•− and •Cl on PS-NP resulted in the differences in mineralization rates and degradation intermediates. The degradation pathway of PS-NP by UV/NaClO and UV/PMS was proposed accordingly. Additionally, the intermediates toxicity evaluation by a luminescent bacteria test showed that the inhibition rate in the UV/NaClO system (2.97%) was not markedly different from that in the control group without any treatment (1.98%); while that in UV/PMS system increased sharply to 98.19%. This work demonstrated that UV/PMS was more effective in PS-NP degradation than UV/NaClO, and the chemical risks of degradation intermediates were non-negligible.

Coalescence of As(II) with •OH: The pivot for co-processing of As(III) and butyl xanthate

Although water metalloid pollution is widely studied, the effect of the combined pollution of organic matter and metalloids in mining water and, especially, the possible interaction mechanisms between metalloids and flotation reagents, are both poorly understood. Existence of mixed pollution of metalloids and organic compounds tends to cause more serious harm to natural organisms. In this study, a synergistic removal of arsenite (As(III)) and butyl xanthate (Bx) in an advanced oxidation system was reported using biochar-based catalyst loaded with nano-zero-valent iron from an inexpensive iron source (iron slag) to activate peroxodisulfate. The removal efficiencies were improved by 30 % in the co-existence of As(III) and Bx compared to those of the single pollutant. The theoretical calculations, especially frontier molecular orbital theory, revealed the generation of [AsO2-OH]•− by the combination of As(II) with •OH. This [AsO2-OH]•− participated in the oxidative degradation of Bx with high activity and combined with the sulfur falling off Bx after the reaction to form a novel Fe-As-S complex as indicated by X-ray absorption +fine structure analysis. Overall, this study reports the generation of low-valent arsenic active substances of [AsO2-OH]•− and their effect on the removal of organic pollution containing S atoms in advanced oxidation systems under typical mining water conditions with the coexistence of As(III) and expands the understanding and application of traditional free radicals.

The application of the photo-electro-Fenton process in the treatment of wastewater reduces the abundance of genes associated with pathogenicity factors, antibiotic resistance, and metabolism: A metagenomic analysis.

The objective of this work was to determine the effect of advanced oxidation systems on the taxonomic and functional diversity of pathogenic microorganisms in the effluent of the wastewater treatment plant in Bogotá - Colombia (“El Salitre” WWTP) by metagenomics analysis. The taxonomic and functional diversity of the microorganisms, before and after oxidation treatment, was determined by Illumina mass sequencing, detecting human pathogenic genera as Pseudomonas (28.0%), Arcobacter (10.0%), Aeromonas (4.0%), Sulfurospirillum (4.0%), Salmonella (3.0%), and Clostridiales (3.0%). Likewise, pathogenicity factors such as antimicrobial resistance genes (ARGs) also were detected in high abundances (∼5% of metagenome reads). In the effluent treated with the photoelectro-Fenton system (for 5, 30, and 60 min), a significant reduction of pathogenicity factors was observed in all cases. ARGs, chemotaxis, quorum sensing, secretion systems, and toxins of pathogenic bacteria (such as Arcobacter, Pseudomonas, Serratia, and Salmonella) were reduced at near-zero log2 values, demonstrating that the photoelectro-Fenton process is a promising alternative to reduce the biological risk associated with this pathogenicity factors.

Investigation of BiVO4-based advanced oxidation system for decomposition of organic compounds and production of reactive sulfate species

Growth of population and expansion of industries lead to increasing contamination of environment with various organic pollutants. If not properly cleaned, wastewater contaminates freshwater resources, aquatic environment and has huge negative impact on ecosystems, quality of drinking water and human health, therefore new and effective purification systems are in demand. In this work bismuth vanadate-based advanced oxidation system (AOS) for the decomposition of organic compounds and production of reactive sulfate species (RSS) was investigated. Pure and Mo-doped BiVO4 coatings were synthesized using sol-gel process. Composition and morphology of coatings were characterized using X-ray diffraction and scanning electron microscopy techniques. Optical properties were analyzed using UV–vis spectrometry. Photoelectrochemical performance was studied using linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopy. It was shown that increase in Mo content affects the morphology of BiVO4 films, reduces charge transfer resistance and enhances the photocurrent in the solutions of sodium borate buffer (with and without glucose) and Na2SO4. Mo-doping of 5–10 at.% leads to 2- to 3-fold increase in photocurrents. Faradaic efficiencies of RSS formation ranged between 70 and 90 % for all samples irrespective of Mo content. All studied coatings demonstrated high stability in long-lasting photoelectrolysis. In addition, effective light-assisted bactericidal performance of the films in deactivation of Gram positive Bacillus sp. bacteria was demonstrated. Advanced oxidation system designed in this work can be applied in sustainable and environmentally friendly water purification systems.

Effects of Film Thickness of ALD-Deposited Al2O3, ZrO2 and HfO2 Nano-Layers on the Corrosion Resistance of Ti(N,O)-Coated Stainless Steel.

The goal of this stydy was to explore the potential of the enhanced corrosion resistance of Ti(N,O) cathodic arc evaporation-coated 304L stainless steel using oxide nano-layers deposited by atomic layer deposition (ALD). In this study, we deposited Al2O3, ZrO2, and HfO2 nanolayers of two different thicknesses by ALD onto Ti(N,O)-coated 304L stainless steel surfaces. XRD, EDS, SEM, surface profilometry, and voltammetry investigations of the anticorrosion properties of the coated samples are reported. The amorphous oxide nanolayers homogeneously deposited on the sample surfaces exhibited lower roughness after corrosion attack compared to the Ti(N,O)-coated stainless steel. The best corrosion resistance was obtained for the thickest oxide layers. All samples coated with thicker oxide nanolayers augmented the corrosion resistance of the Ti(N,O)-coated stainless steel in a saline, acidic, and oxidising environment (0.9% NaCl + 6% H2O2, pH = 4), which is of interest for building corrosion-resistant housings for advanced oxidation systems such as cavitation and plasma-related electrochemical dielectric barrier discharge for breaking down persistent organic pollutants in water.

Carbonyl heterocycle modified mesoporous carbon nitride in photocatalytic peroxydisulfate activation for enhanced ciprofloxacin removal: Performance and mechanism

Polymer carbon nitride is considered to be a promising photocatalyst with broad application prospects in water treatment. However, the defects of pristine polymer carbon nitride (PCN), such as small specific surface area, fast photogenerated electron-hole recombination, and low mass transfer efficiency, limit its photocatalytic activity. In this work, by introducing 2-thiouracil into the precursor, a carbonyl heterocycle-containing mesoporous carbon nitride photocatalyst (TCN) was successfully obtained with significantly enhanced peroxydisulfate (PDS) photocatalytic activity. In this study, the modulation mechanism of carbonyl heterocycle introduction on surface electronic structure and the band structure were fully discussed by means of a combination of experiments and theoretical calculations. The carbonyl and vicinal carbon-modified heterocycles dominated the electrons, while the adjacent heptazine ring dominated the holes. The photogenerated electron-hole pair recombination efficiency and the electron transition energy barrier were greatly reduced. According to the findings of density functional theory (DFT) calculations, the introduction of carbonyl and vicinal C modulated the electronic structure of catalyst, enhanced the adsorption of PDS at the carbonyl ortho N site, which promoted the electronic interaction between TCN and PDS molecules. Experiments showed that the free radical pathway and non-radical pathway coexisted in TCN/PDS/Vis system. The reactive oxygen species were mainly derived from PDS molecules. DFT calculations provided a more comprehensive theoretical basis for the experimental results. This study provided a fresh perspective on the rational design of carbon nitride-based catalysts and the reaction mechanism of persulfate advanced oxidation systems.

Two birds with one stone: Cobalt-doping induces to enhanced piezoelectric property and persulfate activation ability of ZnO nanorods for efficient water purification

Piezocatalysis has attracted increasing attention in recent years for environment remediation. However, the efficiency of single piezocatalysis is not high enough because of the low piezo coefficient of most materials, thus limiting the practical application. Herein, we successfully constructed an advanced oxidation system for pollutants degradation by combining piezocatalysis with persulfate (PS) activation on Co doped ZnO nanorods. Theoretical calculations and experimental results revealed that the doped Co not only improves the piezoelectric property of ZnO, but also acts as the activation sites for PS. A non-radical oriented reaction was identified as the main process for pollutants degradation, and the Co-PS complex (Co-S2O8) was confirmed as the main reactive species in the present piezo assisted PS activation system. Moreover, a water flow stimulated reactor was constructed based on self-generated pressure, and the relations between flow field distribution and catalytic efficiency was revealed by computational fluid dynamics (CFD) simulation. This work opens new prospects for the development of piezo-based catalytic systems for efficient water purification by utilizing the kinetic energy of water flow.

Electrochemical-enhanced nanoscale oxygen-vacancy CuFe2O4 to activate persulfate (E/oxygen-vacancy CuFe2O4/PS) for separation of Ebselen from wastewater

ABSTRACT To enhance the catalytic activity of CuFe2O4 on PS, a nanoscale oxygen-vacancy CuFe2O4 was prepared by hydrogenation reduction technique to construct an advanced oxidation system of electrochemical-enhanced nanoscale oxygen-vacancy CuFe2O4-activated persulfate. Using Ebselen (EBS) as a model pollutant, the degradation efficiency, activation mechanism and degradation pathway were studied. The oxygen-vacancy CuFe2O4 was characterized and analysed by FESEM, EDS and XPS. The results show that under the optimal reaction conditions (PS = 0.8 g/L, oxygen-vacancy CuFe2O4 = 0.3 g/L, initial pH = 6.5), the removal rate of 20 mg/L EBS can reach 92% after reaction for 60 min, which proves that the formation of oxygen-vacancy changed the catalytic inertness of CuFe2O4 on PS. It is speculated that in the E/oxygen-vacancy CuFe2O4/PS system, the existence of oxygen holes enhances the electron transfer ability and reducibility of the catalyst, so the oxygen-vacancy CuFe2O4 can efficiently activate PS to degrade EBS. The quenching experiments show that both SO 4 ⋅ − and ⋅ OH are involved in the oxidation reaction as reactive radicals in the system, with SO 4 ⋅ − being the main reactive radical. In addition, both dissolved oxygen (DO) and anions in the solution inhibit the oxidative degradation of EBS by oxygen-vacancy CuFe2O4/PS system. Through GC-MS detection, a possible degradation pathway is proposed.

Assessment of an electrochemical advanced oxidation system for removal of pharmaceutical compounds at the Vaudreuil-Dorion municipal wastewater treatment facility

The Advanced Oxidation System (AOS) is a versatile technology for removal of pharmaceuticals in wastewater.

Inactivation of Escherichia coli and Enterococcus faecalis by sulfate radical and hydroxyl radical using Fe(II) based advanced oxidation systems

Inactivation of Escherichia coli and Enterococcus faecalis by sulfate radical and hydroxyl radical using Fe(II) based advanced oxidation systems

Selective Radical Oxidation of Cyclohexane to Adipic Acid at Electrochemical Interfaces

AbstractDirect conversion of cyclohexane to adipic acid (AA) under mild conditions is an attractive technology in response to the increasing industrial demand of chemical intermediate AA. Exploring advanced free radical oxidation systems is the key to converting cyclohexane in a direct and mild manner. This study demonstrates that electrocatalytic water oxidation can quantitatively generate hydroxyl radicals (⋅OH) to selectively oxidize cyclohexane to AA by a vanadium oxide (VOx)‐platinum (Pt) composite catalyst coupled with persulfate (PS) redox mediator at the electrode/electrolyte interface under ambient temperature and pressure. The three active components of VOx, Pt, and PS can produce different concentrations of ⋅OH radicals alone or in combination, resulting in different AA selectivity and cyclohexane conversion, and the activity increased with the increase of free radical concentration before AA peroxidation. The optimized ternary oxidation system of VOx‐Pt‐PS achieved a cyclohexane conversion of 85 % with 95 % AA selectivity and the corresponding yield was 81 %, better than most traditional oxidation systems. Electrochemical interfaces‐driven radical oxidation provides opportunities to oxidatively convert many other inexpensive hydrocarbons to value‐added chemicals.

Chrome shaving-derived biochar as efficient persulfate activator: Ti-induced charge distribution modulation for 1O2 dominated nonradical process

Efficient degradation of organic contaminants by oxidative radicals remains a challenge due to invalid consumption of radicals and easy generation of secondary halogenated pollutants. In this work, an efficient and recyclable bimetallic biochar (Cr-Ti/BC) was developed through peroxydisulfate (PDS) activation via nonradical pathway for sulfamethoxazole (SMX) degradation. The Cr-Ti/BC exhibited excellent catalytic activity for 99.9 % of SMX removal with a high kobs of 0.13 min−1, and negligible inhibitory effects were observed under various pH condition. The activation mechanisms were (i) metastable reactive intermediates (Cr-Ti/BC-PDS) formation via an interaction between Cr-Ti/BC and PDS on the active defective sites (e.g., OH/COC, COOH, CO, nitric oxides, graphitic N, and pyridinic N), and (ii) 1O2 generation through electron transfer between Cr-Ti/BC-PDS intermediates and dissolved oxygen. The high reusability and strong stability of Cr-Ti/BC also verified the outstanding advantage of the Cr-Ti/BC during practical application. This study not only is the first study the catalytic performance of Cr and Ti co-doped biochar for PDS activation, but also successfully provides a promising strategy to induce a nonradical pathway for PDS activation, which is of great significance for the subsequent method design, and thus paving the path for exploiting advanced oxidation systems in practical application for organic contaminant removal toward polluted site remediation.

A Piezo-Fenton System with Rapid Iron Cycling and Hydrogen Peroxide Self-Supply Driven by Ultrasound.

The piezo-Fenton system has attracted attention not only because it can enhance the Fenton reaction activity by mechanical energy input, but also because it is expected to realize a class of stimuli-responsive advanced oxidation systems by regulating energy input and hydrogen peroxide self-supply, thus greatly enriching the application possibilities of Fenton chemistry. In this work, a series of Fe-doped g-C3 N4 (g-C3 N4 -Fe) as a piezo-Fenton system were synthesized where the iron stably immobilized through Fe-N interaction. The piezo-induced electrons generate on g-C3 N4 matrix support the conversion of Fe(III) to Fe(II) and promote rate-limiting step of Fenton reaction. With the optimal Fe loading, g-C3 N4 -0.5Fe can achieve methylene blue (MB) degradation under ultrasonic treatment with first-order kinetic rate constants of 75×10-3 min-1 . Most importantly, the g-C3 N4 -Fe can maintain good catalytic activity in a wide pH range (pH=2.0∼9.0) and be cyclic used without iron leaching to solution (<0.001 μg ⋅ L-1 ), overcoming the disadvantage of traditional Fe-based Fenton catalysts that can only be applied under acidic conditions and prone to secondary pollution. In addition, g-C3 N4 -0.5Fe also exhibits antibacterial properties of Escherichia coli and Staphylococcus aureus under ultrasound. Hydroxyl radicals mainly contribute to the degradation of MB and the sterilization process. Our work is an attempt to clarify the role of g-C3 N4 -Fe in the conversion of mechanical energy to ROS and provide inspirations for the piezo-Fenton system design.

Degradation of petroleum hydrocarbons in oil-based drilling cuttings by a zero-valent iron Fenton-like advanced oxidation system

Oil-based drilling cuttings (OBDCs) containing large amounts of petroleum hydrocarbons generated from shale gas extraction constitute hazardous waste. In this study, the commonalities and differences of three systems, Fe0/peroxymonosulfate (PMS), Fe0/peroxydisulfate (PDS), and Fe0/H2O2, for treating OBDCs have been compared. The results show that oxidant initial concentration, Fe0 dosage, and reaction time are significantly positively correlated with the oil removal efficiency within certain ranges. Moreover, the initial pH is more critical in the Fe0/H2O2 and Fe0/PMS systems than in the Fe0/PDS system, with the oil removal efficiency being better under acidic conditions. FTIR and GC-MS analyses have shown that all three systems are effective in the removal of straight-chain alkanes, and the degradation ability decreases in the order Fe0/H2O2 > Fe0/PMS > Fe0/PDS. By characterizing the morphology, elemental composition, and crystal composition of OBDC before and after treatments, it showed that Fe0 was corroded and produced Fe2+, which benefited the formation of hydroxyl and sulfate radicals by reacting with oxidants (H2O2/PMS/PDS) and was responsible for the degradation of petroleum hydrocarbons of OBDCs. This study may provide theoretical support for the development and optimization of a technology for rendering OBDCs harmless.

Excess sludge biochar facilitates persulfate activation for highly efficient tetracycline removal.

This study proposed a novel advanced oxidation system to treat metal and antibiotic pollution in water simultaneously. Meanwhile, the enhancement effect of absorbed metal pollution on the activation of persulfate in the system was also investigated. As the most widely used and polluting material, tetracycline (TC) and metal Fe were used as the pollutant models. In this study, a carbonaceous material (BC) was prepared from excess sludge and then combined with the persulfate system (Fe/BC/PS). It was found that the best biochar was obtained when the pyrolysis temperature reached 500 °C (BC500), with the specific surface area of 39.712 m2/g. Combining it with 300 mg/L PS, the removal rate of 120 mg/L TC reached 70.6%. Moreover, the sludge biochar itself possessed numerous reaction sites and good defective structure, which provided a perfect reaction site for the variable metals absorbed by BC. They accelerated electron conduction greatly, which led to the activation of PS very active and generating far more active radicals than normal. In addition, it also proposed the rational pathway and potential mechanism of TC degradation based on the degradation intermediates. This study has a high reference value for resource utilization of sewage sludge and antibiotics removal from water.

Efficient degradation of bisphenol A by the UV-enhanced nano zero-valent iron-activated hydrogen peroxide advanced oxidation system

Bisphenol A (BPA) in a water environment has hazardous and is difficult to degrade under natural conditions. In this study, the UV-nZVI-H2O2 system was constructed to efficiently degrade BPA. The results show that the removal rate and mineralization rate of BPA were 85.03 % and 21.31 %, respectively, under the conditions of initial pH = 3, UV = 10 W, [nZVI] = 0.05 g/L, [H2O2] = 0.06 mmol/L, [BPA] = 40 mg/L and t = 60 min. This is mainly attributed to the synergistic effect among UV, nZVI and H2O2. The dominant reactive oxygen species in the UV-nZVI-H2O2 system was HO•, and the yield of HO• was up to 333.81 μmol/L, which was much higher than that of other systems in the controlled experiment. In addition, the system can efficiently remove a variety of aromatic and refractory organic matter (e.g., ibuprofen (IBU) and ciprofloxacin (CIP)). The reaction intermediates were identified, and it was speculated that the possible degradation pathways of BPA were mainly HO• attack on the electron-rich benzene ring in the BPA molecule and attack on the C–C bond connected between isopropyl and the benzene ring. The possible degradation pathways of IBU include decarboxylation, hydroxylation addition and single bond breaking. The possible degradation pathway of CIP is the loop opening of the piperazine ring and quinolone ring of CIP after continuous oxidation of HO•. The reaction mechanism of this system is a homogeneous and heterogeneous Fenton reaction and adsorption and precipitation of BPA by iron-based oxides.

Effectiveness and degradation pathways of bisphenol A (BPA) initiated by hydroxyl radicals and sulfate radicals in water: Initial reaction sites based on DFT prediction

Bisphenol A (BPA), one of the widely known endocrine-disrupting chemicals, can be effectively degraded by advanced oxidation processes in water because of the powerful reactive oxygen species. In this study, Fenton, UV/Fenton, and metal ion/peroxymonosulfate (PMS) processes were compared to investigate BPA degradation efficiency and pathways initiated by hydroxyl radicals and sulfate radicals. In contrast to the Fenton system, which only degraded 60% of BPA within 15 min, the UV/Fenton system could degrade greater than 80% of BPA, because more hydroxyl radicals (•OH) were generated under the reduction of Fe3+ to Fe2+. The optimized parameters of the UV/Fenton system were as follows: 8 μmol/L of Fe2+, 80 μmol/L of H2O2, and a pH value of 3.0. As for the metal ion/PMS system, the BPA degradation efficiency was closely associated with the applied metal ions, and the order was as follows: Co2+/PMS (∼100%) > Fe2+/PMS (∼80%) > Cu2+/PMS (∼79%). The degradation pathways of BPA were theoretically interpreted through density functional theory prediction and degradation products during various processes. Two major initial reaction sites (4C and 6C) for •OH initiated using the UV/Fenton system and one initial reaction site (4C) for sulfate radicals (SO4•−) using the metal ion/PMS system were recognized for BPA degradation processes. The degradation products by •OH showed a larger average molecular weight than those by SO4•−. These studies are instructive for the application of different advanced oxidation systems in the treatment process of BPA in wastewater.

Life Cycle Assessment of UV-C based treatment systems for the removal of compounds of emerging concern from urban wastewater

In the last decades particular attention is being paid to the efficient and effective removal of compounds of emerging concern (CECs) present in wastewater before their eventual reuse or disposal. Several technologies have been developed for the degradation of CECs in aqueous matrix, in this regard advanced oxidation processes (AOPs) represent a nascent technological solution developed on a laboratory scale with applications on a prototype scale. The experimental evidences have shown that AOPs processes can oxidize numerous organic compounds in a much faster and more efficient way than that of the most common disinfection processes. The most common AOPs processes are those that involve the use of H2O2/UV, O3/UV, H2O2/O3, H2O2/O3/UV, Fenton and photo-Fenton. The aim of this work is to illustrate the results of a comparative LCA study of a laboratory scale UV-C photoreactor for the tertiary treatment of urban wastewater of three treatment systems (UV-C, UV-C + H2O2 e UV-C + TiO2). In particular, the specific objective is to evaluate, from an environmental point of view, an innovative advanced oxidation system based on nanostructures TiO2 immobilized on a stainless steel mesh. Compared to the UV-C photolysis reference system, the addition of hydrogen peroxide reduces the total environmental impact of the system by almost 75 %, while the use of the stainless-steel mesh coated by the nanostructures titanium dioxide reduces the UV-C environmental impact by 30 %. These results are due to the lower energy consumption of these last treatments compared to photolysis alone. The main impacts of the three systems are related to the electric power consumption of the centrifugal pump (63–64 %) and of the UV-C lamp (32–33 %). The LCA applied to these systems has shown that TiO2 assisted photocatalysis is not yet advantageous from an environmental point of view and that, therefore, the efficiency of the system needs to be improved.