Explore the vast range of titles available.

Carbamazepine and diclofenac are two examples of drugs with widespread geographical and environmental media proliferation that are poorly removed by traditional wastewater treatment processes. Advanced oxidation processes (AOPs) have been proposed as alternative methods to remove these compounds in solution. AOPs are based on a wide class of powerful technologies, including UV radiation, ozone, hydrogen peroxide, Fenton process, catalytic wet peroxide oxidation, heterogeneous photocatalysis, electrochemical oxidation and their combinations, sonolysis, and microwaves applicable to both water and wastewater. Moreover, processes rely on the production of oxidizing radicals (•OH and others) in a solution to decompose present pollutants. Water radiolysis-based processes, which are an alternative to the former, involve the use of concentrated energy (beams of accelerated electrons or γ-rays) to split water molecules, generating strong oxidants and reductants (radicals) at the same time. In this paper, the degradation of carbamazepine and diclofenac by means of all these processes is discussed and compared. Energy and byproduct generation issues are also addressed.

Over the last years, the photo-Fenton process has been established as an effective, green alternative to chemical disinfection of waters and wastewaters. Microorganisms’ inactivation is the latest success story in the application of this process at near-neutral pH, albeit without clearly elucidated inactivation mechanisms. In this review, the main pathways of the combined photo-Fenton process against the most frequent pathogen models ( Escherichia coli for bacteria and MS2 bacteriophage for viruses) are analyzed. Firstly, the action of solar light is described and the specific inactivation mechanisms in bacteria (internal photo-Fenton) and viruses (genome damage) are presented. The contribution of the external pathways due to the potential presence of organic matter in generating reactive oxygen species (ROS) and their effects on microorganism inactivation are discussed. Afterwards, the effects of the gradual addition of Fe and H 2 O 2 are assessed and the differences among bacterial and viral inactivation are highlighted. As a final step, the simultaneous addition of both reagents induces the photo-Fenton in the bulk, focusing on the differences induced by the homogeneous or heterogeneous fraction of the process and the variation among the two respective targets. This work exploits the accumulated evidence on the mechanisms of bacterial inactivation and the scarce ones towards viral targets, aiming to bridge this knowledge gap and make possible the further application of the photo-Fenton process in the field of water/wastewater treatment.

Prednisolone is a widely prescribed synthetic glucocorticoid and stated to be toxic to a number of non-target aquatic organisms. Its extensive consumption generates environmental concern due to its detection in wastewater samples at concentrations ranged from ng/L to μg/L that requests the application of suitable degradation processes. Regarding the actual treatment options, advanced oxidation processes (AOPs) are presented as a viable alternative. In this work, the comparison in terms of pollutant removal and energetic efficiencies, between different AOPs such as Fenton (F), photo-Fenton (UV/F), photolysis (UV), and hydrogen peroxide/photolysis (UV/H 2 O 2 ), was carried out. Light diode emission (LED) was the selected source to provide the UV radiation. The UV/F process revealed the best performance, reaching high levels of both degradation and mineralization with low energy consumption. Its optimization was conducted and the operational parameters were iron and H 2 O 2 concentrations and the working volume. Using the response surface methodology with the Box-Behnken design, the effect of independent variables and their interactions on the process response were effectively evaluated. Different responses were analyzed taking into account the prednisolone removal (TOC and drug abatements) and the energy consumptions associated. The obtained model showed an improvement of the UV/F process when treating smaller volumes and when adding high concentrations of H 2 O 2 and Fe 2+ . The validation of this model was successfully carried out, having only 5% of discrepancy between the model and the experimental results. Finally, the performance of the process when having a real wastewater matrix was also tested, achieving complete mineralization and detoxification after 8 h. In addition, prednisolone degradation products were identified. Finally, the obtained low energy permitted to confirm the viability of the process.

The importance of seawater treatment in order to avoid microbiological pollution related to aquaculture or ballast water management has increased during the last few years. Bacterial indicators used for the evaluation of different disinfection treatments are usually related with both waste and drinking water, these standards are not usual microorganisms found in seawater. Thus, it is thought necessary to study the behavior of different marine-specific organisms in regard to improve the disinfection processes in seawater. In this study, three different bacteria have been selected among major groups of bacterial community from marine waters: two water-associated, Roseobacter sp. and Pseudomonas litoralis , and one sediment-associated, Kocuria rhizophila . A kinetic inactivation model together with a post-treatment growth tendency has been obtained after the application of UV-C and UV/H 2 O 2 processes. According to the first kinetic rate constant, different responses were obtained for the different bacterial groups. Once the treatment was applied, modeling of growth curves revealed high recover within the first 3 days after treatment, even when UV/H 2 O 2 was applied. This study introduces a sensitivity index, in which results show different levels of resistance for both treatments, being Roseobacter sp. the most sensitive bacteria, followed by P. litoralis and K. rhizophila .

Methamphetamine (MET) is one of the most used illicit drugs in Europe and is recognized as one of the Emerging Organic Micropollutants. It is discharged into the sewerage system from different sources and then enters the wastewater treatment plants. The present study aimed at providing a better knowledge of the fate of MET through the wastewater treatment plants. The study addressed two different issues: (1) optimization of the analytical methods for MET determination in both liquid and sludge phases, focusing on the effects of potentially interfering substances and (2) investigation on the behaviour of MET in the biological treatment process, with specific concern for the biomass activity at different drug concentrations. Results of the study on issue 1 highlighted that the applied analytical method for MET determination (UPLC–MS/MS) is affected by the main components of wastewater for about 9–23%, which is comparable with the uncertainties of the method (about ± 28%). The method showed also to be repeatable and reliable (recovery > 75%; repeatability < 10–15%; bias uncertainty < 30%), and relatively easy-to-use. Therefore, it can be considered suitable for measurements on routine base in the WWTPs. Batch tests conducted to address issue 2 showed total removal of 84, 90, and 96% at 50, 100, and 200 ng/L initial MET concentration, respectively, for a contact time of 6 h. The removal process was mainly ascribed to the biological activity of both heterotrophic and autotrophic bacteria. The pseudo first-order kinetic model provided the best fitting of the experimental data of the overall biological processes at all the tested concentrations. Furthermore, the respirometric tests showed that MET does not induce any inhibition. Adsorption of MET on activated sludge was always very low.

The mineralization of bio-recalcitrant humic acids (HAs) by a solar photo-Fenton (SPF) process was investigated in aqueous system, in order to understand its abatement in real high-HA content matrices, such as sanitary landfill leachates. SPF reactions were performed in tubular photoreactors with CPCs at lab-scale (simulated solar light) and pilot-scale (natural sunlight). Considering the experimental conditions selected for this work, the formation of insoluble HA-Fe 3+ complexes was observed. Thus, to avoid HA precipitation, oxalic acid (Ox) was added, since Fe 3+ -Ox complexes present a higher stability constant. The effect of different process variables on the performance of SPF reaction mediated by ferrioxalate complexes (SPFF) was assessed with excess of H 2 O 2 (50–250 mg L −1 ), at lab-scale: (i) pH (2.8–4.0); (ii) initial iron concentration (20–60 mg Fe 3+ L −1 ); (iii) iron-oxalate molar ratio (Fe 3+ -Ox of 1:3 and 1:6); (iv) temperature (20–40 °C); (v) UV irradiance (21–58 W UV  m −2 ); and (vi) commercial-HA concentration (50–200 mg C L −1 ). At the best lab conditions (40 mg Fe 3+ L −1 , pH 2.8, 30 °C, 1.6 Fe 3+ -Ox molar ratio, 41 W UV m −2 ), commercial HAs’ mineralization profile was also compared with HAs extracted from a sanitary landfill leachate, achieving 88 and 91% of dissolved organic carbon removal, respectively, after 3-h irradiation (8.7 kJ UV  L −1 ). Both reactions followed the same trend, although a 2.1-fold increase in the reaction rate was observed for the leachate-HA experiment, due to its lower humification degree. At pilot-scale, under natural sunlight, 95% HA mineralization was obtained, consuming 42 mM of H 2 O 2 and 5.9 kJ UV  L −1 of accumulated UV energy. However, a pre-oxidation during 2.8 kJ UV  L −1 (12 mM H 2 O 2 ) was enough to obtain a biodegradability index of 89%, showing the strong feasibility to couple the SPFF process to a downstream biological oxidation, with low chemicals and energetic demands. Graphical abstract ᅟ

Polycyclic aromatic hydrocarbons (PAHs) are on the list of priority pollutants to be eliminated from the environment due to their carcinogenic and mutagenic action, chemical stability, and resistance to biodegradation. The aim of this study was to evaluate the degradation of fluorene, a well-known PAH, in aqueous solutions (0.03 and 0.08 mg L −1 ), by means of a solar-driven conventional (PF) and modified photo-Fenton mediated by ferrioxalate complexes (PFF). Photolysis was also employed for comparison purposes. PF reaction was evaluated at different pH values (2.8, 3.5, and 4.0) and iron concentrations (2, 5, 10, and 20 mg L −1 ). On the other hand, PFF studies were conducted at mild pH conditions (4.0, 5.0, and 6.0) and iron content of 2 mg L −1 , keeping initial iron/oxalate molar ratio at 1:3. In both PF and PFF, the initial hydrogen peroxide/iron molar ratio was maintained at 5. In the presence of methanol as cosolvent for fluorene dissolution, the PF reaction was hampered and no consumption of H 2 O 2 was observed during the reaction carried out at constant pH (2.8). This led to low degradation rates, similar to those achieved by photolysis. Under the same pH but using acetonitrile as cosolvent for fluorene dissolution, fluorene degradation was found to be proportional to the iron content used in the PF experiments. On the other hand, at an invariable iron concentration of 5 mg Fe 2+ L −1 , the increase in pH was accompanied by a decrease in the molar fraction of the most photoactive iron complex (FeOH 2+ ) and ferric hydroxides precipitation, leading to a reduction in the fluorene degradation rate. With regard to the PFF tests, similar fluorene degradation performance was achieved at pH 4 and 5, while at pH 6 iron precipitation became relevant and the degradation rate was slightly slower. PFF has shown to be more efficient than the PF under the same pH (4) and iron concentration (2 mg L −1 ). Moreover, even at near neutral pH (6), fluorine degradation was shown to be feasible by using ferrioxalate complexes.

This paper addresses the removal of four aromatic hydrocarbons typically found in petrochemical wastewater: benzene ( B ), toluene ( T ), o-xylene ( X ), and naphthalene ( N ), by microwave-assisted catalytic wet peroxide oxidation (MW-CWPO) using activated carbon (AC) as catalyst. Under the studied conditions, complete pollutant elimination ( B , 1.28 mM; T , 1.09 mM; X , 0.94 mM; and N , 0.78 mM) was achieved, with more than 90% TOC removal after only 15-min reaction time, working at 120 °C, pH 0  = 3, AC at 1 g L −1 , and H 2 O 2 at the stoichiometric dose. Furthermore, in the case of toluene, naphthalene, and xylene, the hydroxylation and breakdown of the ring is very rapid and toxic intermediates were not detected. The process follows two steps: (i) pollutant adsorption onto AC followed by (ii) adsorbed compounds oxidation. Thus, MW-CWPO with AC as catalyst appears a promising way for a fast and effective process for B , T , X , and N removal in aqueous phase.

Magnetite (Fe 3 O 4 ), a core-shell material (SiO 2 @Fe 3 O 4 ), and reduced graphene oxide-Fe 3 O 4 (referred as rGO-MN) were used as supports of a specific highly active TiO 2 photocatalyst. Thermal treatments at 200 or 450 °C, different atmospheres (air or N 2 ), and TiO 2 :support weight ratios (1.0, 1.5, or 2.0) were investigated. X-ray diffractograms revealed that magnetite is not oxidized to hematite when the core-shell SiO 2 @Fe 3 O 4 material—or a N 2 atmosphere (instead of air) in the thermal treatment—was employed to prepare the TiO 2 -based catalysts (the magnetic properties being preserved). The materials treated with N 2 were first tested for degradation of imazalil (a well-known fungicide) in deionized water. The best compromise between the photocatalytic activity, magnetic separation, and Fe leached (1.61 mg L −1 , i.e., below the threshold for water reuse in irrigation) was found for the magnetic catalyst prepared with SiO 2 @Fe 3 O 4 , an intermediate TiO 2 :support ratio (1.5), and treated at 200 °C under N 2 atmosphere (i.e., SiO 2 @Fe 3 O 4 -EST-1.5-200-N 2 ). This material was then tested for the treatment of imazalil in a synthetic wastewater, SW (with a chemical composition simulating an effluent resulting from fruit postharvest activity). This SW has a pH of 4.2 and the experiments were carried out at this natural pH 0 and at neutral conditions (keeping pH at 7 along the reaction). The magnetic catalyst was more active than bare TiO 2 for the treatment of imazalil in SW at natural pH. Since Fe leaching was observed (3.53 mg L −1 ), added H 2 O 2 enhanced both imazalil degradation and mineralization. Conveniently, these catalysts can be readily recovered by using a conventional magnetic field, as demonstrated over three consecutive recycling runs. Graphical abstract % Imazalil conversion using different magnetic catalysts and comparison with bare TiO 2

Semiconductors based on Fe/Nb oxides can present both solar sensitivity and high catalytic activity. However, there is still a lack regarding the comparison between different routes to produce Fe/Nb-based solar photocatalysts and the evaluation of the impact of the synthesis operating conditions on the material properties. In this work, Fe/Nb 2 O 5 ratio, type of precipitating agent, presence/absence of washing stage, and temperature of calcination were verified to be the most relevant parameters in the synthesis by the co-precipitation method. These factors led to remarkable differences in the properties and performance of the photocatalysts produced by each distinct synthesis route. Composition, iron species present in the materials, crystallinity characteristics, and pH of the catalysts were affected, leading to different photocatalytic activities under UV-Vis light. Due to their characteristics, the synthesized materials are potential photocatalysts for application in solar processes. Graphical abstract ᅟ