Carbon-based materials for water disinfection and heavy metals removal

The presence of heavy metals and/or harmful bacteria in drinking water represents significant risks to human health. This study aimed to develop a low-cost water treatment technology using synthesized nanocomposites with metal nanoparticles supported on activated carbon (AC) for bacteria and heavy metal removal. In addition, the performance of the developed nanomaterials was compared with that of commercial materials - carbon fibers of three different typologies. The chemical and textural properties of all tested materials were characterized. To simulate a technology to be applied in a water outlet point, removal tests were carried out in a continuous system using suspensions of Escherichia coli and/or Staphylococcus aureus, wherein the contact time with the two phases was minimal (1 min). The obtained results revealed that iron and copper oxides supported on AC with a calcination treatment (CuFeO/AC-C) was the nanocomposite with the best performance, achieving a 6 log reduction for both bacteria in the same suspension up to 9 h operation. A mix of bacteria and heavy metals, simulating a real water, was treated with CuFeO/AC-C obtaining a 6 log reduction of bacteria, a Pb2+ removal >99.9% and Cd2+ removal between 97 and 98% over 180 passage times.

Nanofiltration combined with ozone-based processes for the removal of antineoplastic drugs from wastewater effluents

Over the past years, there has been an increasing concern about the occurrence of antineoplastic drugs in water bodies. The incomplete removal of these pharmaceuticals from wastewaters has been confirmed by several scientists, making it urgent to find a reliable technique or a combination of techniques capable to produce clean and safe water. In this work, the combination of nanofiltration and ozone (O3)-based processes (NF + O3, NF + O3/H2O2 and NF + O3/H2O2/UVA) was studied aiming to produce clean water from wastewater treatment plant (WWTP) secondary effluents to be safely discharged into water bodies, reused in daily practices such as aquaculture activities or for recharging aquifers used as abstraction sources for drinking water production. Nanofiltration was performed in a pilot-scale unit and O3-based processes in a continuous-flow column. The peroxone process (O3/H2O2) was considered the most promising technology to be coupled to nanofiltration, all the target pharmaceuticals being removed at an extent higher than 98% from WWTP secondary effluents, with a DOC reduction up to 92%. The applicability of the clean water stream for recharging aquifers used as abstraction sources for drinking water production was supported by a risk assessment approach, regarding the final concentrations of the target pharmaceuticals. Moreover, the toxicity of the nanofiltration retentate, a polluted stream generated from the nanofiltration system, was greatly decreased after the application of the peroxone process, which evidences the positive impact on the environment of implementing a NF + O3/H2O2 process.

Converting carbon black into an efficient and multi-site ORR electrocatalyst: the importance of bottom-up construction parameters

To boost efficient energy transitions, alternatives to expensive and unsustainable noble metal-based electrocatalysts for the oxygen reduction reaction (ORR) are needed. Having this in mind, carbon black - Black Pearls 2000 (BP) was enriched in active nitrogen-containing centers, including single-atom Fe-N sites surrounded by Fe nanoclusters, through a synthesis methodology employing only broadly available precursors. The methodical approach taken to optimize the synthesis conditions highlighted the importance of (1) a proper choice of the Fe precursor; (2) melamine as an N source to limit the formation of magnetite crystals and modulate the charge density nearby the active sites, and glucose to chelate/isolate Fe atoms and thus allow the Fe-N coordination to be established, with a limiting formation of Fe0 clusters; and (3) a careful dosing of the Fe load. The ORR on the optimized electrocatalyst (Fe0.06-N@BP) proceeds mostly through a four-electron pathway, having an onset potential (0.912 V vs. RHE) and limiting current density (4.757 mA cm-2) above those measured on Pt/C (0.882 V and 4.657 mA cm-2, respectively). Moreover, the current density yielded by Fe0.06-N@BP after 24 h at 0.4 V vs. RHE was still above that of Pt/C at t = 0 (4.44 mA cm-2), making it a promising alternative to noble metal-containing electrocatalysts in fuel cells.

Synthesis of monometallic macrostructured catalysts for bromate reduction in a continuous catalytic system

The last few years have seen great leaps in the use of mechano-chemically modified carbon nanotubes in catalysis. While high improvements in catalytic performance have been achieved, the nature of the technique is not compatible with typical strategies for CNT coating of macro-structured catalysts by chemical vapour deposition. Developing macro-structured catalysts is a key step towards the sustainability of multi-phase catalysis and requires a methodology for coating with mechano-chemical modified CNT metallic catalysts. Preparing water-based slurries is not straightforward due to the CNT's hydrophobicity, and the use of organic solvents is unsustainable. A novel methodology for the washcoating of macro-structures with pre-modified monometallic CNT catalysts was assessed. A compromise between surfactant use, post-coating treatment, and the catalyst activity/integrity, was achieved by solubilization of the surfactant in a isopropanol:acetone mixture. The activity of the prepared catalysts was affected by the metallic dispersion, surfactant coverage, and distribution of the palladium throughout the catalytic layer. Palladium centres in the bottommost layers were found to be unavailable for liquid phase reaction. The activity of the catalysts prepared with pre-formed carbon monometallic powders was improved by adopting a coating strategy to maximize the availability of the metallic particles near the surface of the catalytic layer.

Temperature and nitrogen-induced modification of activated carbons for efficient catalytic ozonation of salicylic acid as a model emerging pollutant

The occurrence of emerging pollutants on effluents of wastewater treatment plants makes unfeasible their reutilization and consequently to comply with the sixth goal of 2030 Agenda for sustainable development. Thus, it is extremely important to find ways to remove these pollutants without compromising the quality of reclaimed water. Ozonation has been successfully explored for this purpose, but it still presents limitations towards some oxidant-resistant pollutants. To surpass this, the conversion of ozone (O3) into more reactive species is required, which can be accomplished by using catalysts. Carbon catalysts, such as activated carbons (ACs), represent a more environmentally attractive option than traditional metal-based catalysts, with the advantage of being easily modified to tune their textural and surface properties to the reaction chemistry. In this study, two different sources of ACs were tested in the catalytic ozonation of a frequently detected emerging pollutant: salicylic acid (SalAc). These ACs were submitted to thermal treatment under H2 and functionalization with N precursors, such as melamine and poly(ethyleneimine), to induce changes in the surface properties, especially in the nitrogen content. Although no correlation was found between the N-content and catalytic activity, the thermal treatment under H2 increased the mesopores surface area (Smeso), which reflected in greater catalytic activity. As that, the best-performing AC was the one with the highest Smeso, which revealed also to be resistant to O3 and able to convert O3 into more reactive species, evidenced by the capacity of oxalic acid, a well-known ozone-resistant by-product. The same AC was then submitted to three consecutive reutilization cycles and a more significant activity loss was observed in terms of SalAc degradation rate (⁓ 40%) then total organic carbon removal (⁓ 25%), from the first to the third cycle. This decline in efficiency was ascribed to the presence of by-products adhered to the catalyst surface, which impede its ability to react effectively with O3.

Degradation of p-Nitrophenol by activated persulfate with carbon-based materials

The removal of p-nitrophenol (PNP) from wastewater was evaluated by the activated persulfate process using different materials - carbon xerogels (XG), carbon nanotubes (CNT), and activated carbon (AC) -, and also using such materials doped with nitrogen (XGM, CNTM and ACM). These carbon materials were impregnated with 2 wt.% of iron and tested in the oxidative process to assess the influence of their textural and surface chemical properties. The carbon-based materials' properties influence the efficiencies of the adsorption and oxidative processes; in adsorption, the materials with higher specific surface areas (S_BET), i.e. AC (824 m²/g) and Fe/AC (807 m²/g), have shown to be the most promising (having achieved a PNP removal of about 20%); on the other hand, in the activated persulfate process the carbon or iron-containing carbon materials with the highest mesoporous areas (S_meso) were the preferential ones - XG and Fe/XG, respectively - reaching removals of 47.3% and 75.7% for PNP and 44.9 and 63.3% for TOC, respectively. Moreover, the presence of nitrogen groups on the samples' surface benefits both processes, being found that PNP degradation and mineralization increase with the nitrogen content. The stability of the best materials (XGM and Fe/XGM) was evaluated during four cycles, being noticed that while XGM lost catalytic activity, the Fe/XGM sample remained stable without leaching of iron. The quantification of intermediate compounds formed during persulfate oxidation was performed, and only oxalic acid was detected, in addition to PNP, being that their contribution to the TOC measured was higher than 99%. Experiments carried out in the presence of radical scavengers proved that only the sulfate radical is present under the acidic conditions used. Complete PNP oxidation and TOC removal of ∼96% were reached for the activated persulfate process, proving to be more attractive than the Fenton one.

Exploring the correlations between epi indicators of COVID-19 and the concentration of pharmaceutical compounds in wastewater treatment plants in Northern Portugal

The COVID-19 pandemic caused by the SARS-CoV-2 virus led to changes in the lifestyle and human behaviour, which resulted in different consumption patterns of some classes of pharmaceuticals including curative, symptom-relieving, and psychotropic drugs. The trends in the consumption of these compounds are related to their concentrations in wastewater systems, since incompletely metabolised drugs (or their metabolites back transformed into the parental form) may be detected and quantified by analytical methods. Pharmaceuticals are highly recalcitrant compounds and conventional activated sludge processes implemented in wastewater treatment plants (WWTP) are ineffective at degrading these substances. As a results, these compounds end up in waterways or accumulate in the sludge, being a serious concern given their potential effects on ecosystems and public health. Therefore, it is crucial to evaluate the presence of pharmaceuticals in water and sludge to assist in the search for more effective processes. In this work, eight pharmaceuticals from five therapeutic classes were analysed in wastewater and sludge samples collected in two WWTP located in the Northern Portugal, during the third COVID-19 epidemic wave in Portugal. The two WWTP demonstrated a similar pattern with respect to the concentration levels in that period. However, the drugs loads reaching each WWTP were dissimilar when normalising the concentrations to the inlet flow rate. Acetaminophen (ACET) was the compound detected at highest concentrations in aqueous samples of both WWTP (98. 516 μg L ^- 1 in WWTP2 and 123. 506 μg L ^- 1in WWTP1), indicating that this drug is extensively used without the need of a prescription, known of general public knowledge as an antipyretic and analgesic agent to treat pain and fever. The concentrations determined in the sludge samples were below 1.65 µg g ^- 1 in both WWTP, the highest value being found for azithromycin (AZT). This result may be justified by the physico-chemical characteristics of the compound that favour its adsorption to the sludge surface through ionic interactions. It was not possible to establish a clear relationship between the incidence of COVID-19 cases in the sewer catchment and the concentration of drugs detected in the same period. However, looking at the data obtained, the high incidence of COVID-19 in January 2021 is in line with the high concentration of drugs detected in the aqueous and sludge samples but prediction of drug load from viral load data was unfeasible.

Per- and Poly-Fluoroalkyl Substances in Portuguese Rivers: Spatial-Temporal Monitoring

Eighteen per-and polyfluoroalkyl substances (PFASs) were investigated in surface waters of four river basins in Portugal (Ave, Leça, Antuã, and Cértima) during the dry and wet seasons. All sampling sites showed contamination in at least one of the seasons. In the dry season, perfluorooctanoate acid (PFOA) and perfluoro-octane sulfonate (PFOS), were the most frequent PFASs, while during the wet season these were PFOA and perfluobutane-sulfonic acid (PFBS). Compounds detected at higher concentrations were PFOS (22.6 ng L^-1) and perfluoro-butanoic acid (PFBA) (22.6 ng L^-1) in the dry and wet seasons, respectively. Moreover, the prospective environmental risks of PFASs, detected at higher concentrations, were evaluated based on the Risk Quotient (RQ) classification, which comprises acute and chronic toxicity. The results show that the RQ values of eight out of the nine PFASs were below 0.01, indicating low risk to organisms at different trophic levels in the four rivers in both seasons, wet and dry. Nevertheless, in the specific case of perfluoro-tetradecanoic acid (PFTeA), the RQ values calculated exceeded 1 for fish (96 h) and daphnids (48 h), indicating a high risk for these organisms. Furthermore, the RQ values were higher than 0.1, indicating a medium risk for fish, daphnids and green algae (96 h).

Can aged microplastics be transport vectors for organic micropollutants? - Sorption and phytotoxicity tests

Microplastics have been investigated over the last decade as potential transport vectors for other pollutants. However, the specific role of plastic aging, in which plastics change their characteristics over time when exposed to environmental agents, has been overlooked. Therefore, sorption experiments were herein conducted using virgin and aged (by ozone treatment or rooftop weathering) microplastic particles of LDPE - low-density polyethylene, PET - poly(ethylene terephthalate), or uPVC - unplasticized poly(vinyl chloride). The organic micropollutants (OMPs) selected as sorbates comprise a diversified group of priority substances and contaminants of emerging concern, including pharmaceutical substances (florfenicol, trimethoprim, diclofenac, tramadol, citalopram, venlafaxine) and pesticides (alachlor, clofibric acid, diuron, pentachlorophenol), analyzed at trace concentrations (each ≤100 μg L^-1). Sorption kinetics and equilibrium isotherms were obtained, as well as the confirmation that the aging degree of microplastics plays a major role in their sorption capacities. The results show an increased sorption of several OMPs on aged microplastics when compared to pristine samples, i.e. the sorption capacity increasing from one or two sorbed substances (maximum 3 μg g^-1 per sorbate) up to nine after aging (maximum 10 μg g^-1 per sorbate). The extent of sorption depends on the OMP, polymer and the effectiveness of the aging treatment. The modifications (e.g. in the chemical structure) between virgin and aged microplastics were linked to the increased sorption capacity of certain OMPs, allowing to better understand the different affinities observed. Additionally, phytotoxicity tests were performed to evaluate the mobility of the OMPs sorbed on the microplastics and the potential effects (on germination and early growth) of the combo on two species of plants (Lepidium sativum and Sinapis alba). These tests suggest low or no phytotoxicity effect under the conditions tested but indicate a need for further research on the behavior of microplastics on soil-plant systems.

Gaseous toluene abatement by the heterogeneous Fenton-like process using iron/carbon-coated monolith as catalyst: Proof of concept

The degradation of toluene from a gas stream by the heterogeneous Fenton process was evaluated over a carbon-coated monolith impregnated or not with iron as catalyst in a bubble column reactor (BCR). The carbon-coated monolith support (CM) was prepared by chemical vapor deposition and the catalyst (CM impregnated with iron - herein called CM-Fe) by adsorption. In the screening of processes (absorption, adsorption and reaction), it was shown that the heterogeneous Fenton process catalyzed by CM-Fe presents the best efficiency (toluene transfer (η) = 10 × 10^-3 mol, for 300 mL of liquid solution and 0.69 g of catalyst). Finally, the stability of CM and CM-Fe was evaluated, wherein ten consecutive runs were carried out, the results showing a considerable deactivation of CM during the first five cycles. In contrast, the CM-Fe sample only slightly decreases its activity from the 1st to 2nd cycle (due to a small amount of iron leached from the monolith, 0.7%), remaining stable after that, which is important for applying this technology at the industrial level. This work showed for the first time that the treatment of gaseous effluents containing organic compounds by the Fenton process (which takes place in the liquid phase) using a carbon-coated monolith impregnated with iron is plausible, so the proof of concept was successfully accomplished.

Intensification strategies for cytostatics degradation by ozone-based processes in aqueous phase

Over the past decade there has been an increasing concern on the presence of cytostatics (also known as anticancer drugs) in natural waterbodies. The conventional wastewater treatments seem not to be effective enough to remove them, and therefore new processes must be considered. This work investigates the performance of ozonation (O₃), catalytic ozonation (O₃/Fe²⁺) and peroxone (O₃/H₂O₂) processes, under dark or UV radiation conditions, for the degradation of cytostatics of worldwide concern. The degradation of bicalutamide (a representative of recalcitrant cytostatics) was firstly assessed in batch and then in a tubular column reactor (continuous flow mode runs) using a wastewater treatment plant (WWTP) secondary effluent. Bicalutamide removal ranged between 66 % (O₃) and 98 % (O₃/H₂O₂/UV) in continuous flow mode runs, the peroxone process being the most effective. The performance of these processes was then assessed against a mixture of twelve cytostatics of worldwide concern spiked in the WWTP effluent (25-350 ng/L). After treatment, seven cytostatics were completely removed, whereas the five most recalcitrant ones were eliminated to an extent of 8-92 % in O₃/H₂O₂, and 44-95 % in O₃/H₂O₂/UV. Phytotoxicity tests revealed a noticeable reduction in the effluent toxicity, demonstrating the feasibility of these processes in realistic conditions as tertiary treatment.

Degradation of Toluene from Gas Streams by Heterogeneous Fenton Oxidation in a Slurry Bubble Reactor with Activated Carbon-Based Catalysts

A novel approach for the treatment of volatile organic compounds from gaseous streams was developed. In order to accomplish this, a semi-batch bubble reactor was used, aiming to assess the toluene (selected as model compound) degradation from gaseous streams via heterogeneous Fenton oxidation. Activated carbon-based catalysts-metal-free or iron-impregnated-with different textural and chemical surface properties were used for the first time as catalysts, in order to degrade gaseous toluene using such technology. Complementary characterization techniques, such as nitrogen adsorption at -196 °C, elemental analysis, pH at the point of zero charge (pH_PZC), inductively coupled plasma optical emission spectrometry (ICP-OES) and transmission electron microscopy (TEM), were used. The materials' chemical surface properties, particularly the presence of N-surface groups, were herein found to play an important role in toluene adsorption and catalytic performance. The maximum amount of toluene transferred, 6.39 × 10^-3 mol, was achieved using melamine-doped activated carbon (N-doped material) that was impregnated with iron (sample herein called ACM-Fe). This iron-based catalyst was found to be quite stable during three reutilization cycles.

Antibiotics removal from aquaculture effluents by ozonation: chemical and toxicity descriptors

Antibiotics are often applied in aquaculture to prevent fish diseases. These substances can cause disturbances on receiving waters, when not properly eliminated from the aquaculture effluents. In this work, ozone (O₃) was investigated as a possible oxidizing agent to remove fishery antibiotics from aquaculture effluents: florfenicol (FF), oxytetracycline (OTC), sulfadimethoxine (SDM), sulfamethoxazole (SMX), and trimethoprim (TMP). Batch experiments were performed using ultrapure water and aquaculture effluents spiked with a mixture of target antibiotics at relatively high concentrations (10 mg L^-1 each). OTC, SMX and TMP were fully removed (< 30 min) regardless of the tested conditions, mainly by O₃ direct attack. In contrast, FF was partially removed in 30 min (∼ 10 and 60%, in aquaculture effluents and ultrapure water, respectively), but only in the presence of hydroxyl radicals (HO^•), the FF concentrations reaching levels below the detection limits in ultrapure water after 60 min. In the case of SDM, its degradation was highly influenced by the selected water matrix, but with removals always higher than 68%. In continuous-flow experiments applying more environmentally relevant antibiotic concentrations (100 ng L^-1 each) and low O₃ doses (1.5 mg L^-1), ozonation highly removed (> 98%) all tested antibiotics from aquaculture effluents with a hydraulic retention time (HRT) of 10 min, except FF (68%). Although by-products were detected in treated samples, zebrafish (Danio rerio) embryotoxicity tests did not show a toxicity increase by applying this ozonation treatment. Ozonation is thus a possible solution to remove antibiotics from aquaculture effluents. Still, full-scale studies in aquaculture farms are needed, and generation of HO^• may be favoured to readily oxidize the FF antibiotic.

Advanced oxidation technologies and constructed wetlands in aquaculture farms: What do we know so far about micropollutant removal?

Aquaculture is the fastest growing animal food-producing sector. Water is the central resource for aquaculture, and it is essential that its quality be preserved. Micropollutants (MPs) can reach aquaculture through anthropogenic addition or inlet water, and may cause harmful effects such as endocrine disruption and antibiotic resistance, adversely affecting the fish species being farmed. Furthermore, the discharge of aquaculture effluents into the environment may contribute to the deterioration of water courses. In this sense, the implementation of environmentally responsible measures in aquaculture farms is imperative for the protection of ecosystems and human health. The European Commission (EC) has recently launched a guiding document promoting ecological aquaculture practices; however, options for water treatment are still lacking. Conventional processes are not designed to deal with MPs; this review article consolidates relevant information on the application of advanced oxidation technologies (AOTs) and constructed wetlands (CWs) as potential strategies in this regard. Although 161 studies on the application of AOTs or CWs in aquaculture have already been published, only 34 focused on MPs (28 on AOTs and 6 on CWs), whereas the others reported the removal of contaminants such as bacteria, organic matter, solids and inorganic ions. No study coupling both treatments has been reported to date for the removal of MPs from aquaculture waters. AOTs and CWs are prospective alternatives for the treatment of aquacultural aqueous matrices. However, the type of aquaculture activity and the specifications of these available technologies should be considered while selecting the most suitable treatment option.

Selecting the most environmentally friendly oxidant for UVC degradation of micropollutants in urban wastewater by assessing life cycle impacts: Hydrogen peroxide, peroxymonosulfate or persulfate?

The quality of water bodies has been decreasing over time. Urban wastewater treatment plants (UWWTPs) are key players to avoid that potentially toxic micropollutants reach the environment, and advanced treatment processes are being applied to address this issue. However, several variables have to be taken into account, particularly environmental sustainability. The aim of this study is to assess the life cycle impacts of combining UVC with different oxidants - hydrogen peroxide (H₂O₂), peroxymonosulfate (PMS) and persulfate (PS) -, considering different concentrations (0.05, 0.20 and 0.50 mM) and UVC dosages of 42, 63 and 170 J/L, corresponding to UV contact times of 4, 7 and 18 s in a specific industrial equipment. UVC/PMS was the worst performing process (despite being able to achieve removals similar to UVC/H₂O₂), followed by UVC/PS. Both would only be preferred relatively to H₂O₂ if much lower concentrations of PMS or PS could be used to achieve the same removal of micropollutants (10 times lower was not enough). Additionally, PMS and PS production contributes more to the environmental footprint than the electricity use, unlike H₂O₂. Therefore even if considering lower treatment times when using sulfate-based oxidants, these will still be more impactful than using H₂O₂ at the studied conditions. Based on both avoided and generated impacts, H₂O₂ is the best option environmentally. In this case, the environmental impacts are more affected by an increase in treatment time rather than by an increase in the H₂O₂ concentration. It is thus best to opt for a higher concentration and the lowest treatment time possible for a significant ecotoxicity reduction. Electricity is a relevant parameter in all cases and its impact can be reduced in nearly all endpoint categories by opting for cleaner energy sources.

Overgrowth control of potentially hazardous bacteria during storage of ozone treated wastewater through natural competition

Improving the chemical and biological quality of treated wastewater is particularly important in world regions under water stress. In these regions, reutilization of wastewater is seen as an alternative to reduce water demand, particularly for agriculture irrigation. In a reuse scenario, the treated wastewater must have enough quality to avoid chemical and biological contamination of the receiving environment. Ozonation is among the technologies available to efficiently remove organic micropollutants and disinfect secondary effluents, being implemented in full-scale urban wastewater treatment plants worldwide. However, previous studies demonstrated that storage of ozone treated wastewater promoted the overgrowth of potentially harmful bacteria, putting at risk its reutilization, given for instance the possibility of contaminating the food-chain. Therefore, this study was designed to assess the potential beneficial role of inoculation of ozone treated wastewater with a diverse bacterial community during storage, for the control of the overgrowth of potentially hazardous bacteria, through bacterial competition. To achieve this goal, ozone treated wastewater (TWW) was diluted with river water (RW) in the same proportion, and the resulting bacterial community (RW+TWW) was compared to that of undiluted TWW over 7 days storage. As hypothesized, in contrast to TWW, where dominance of Beta- and Gammaproteobacteria, namely Pseudomonas spp. and Acinetobacter spp., was observed upon storage for 7 days, the bacterial communities of the diluted samples (RW+TWW) were diverse, resembling those of RW. Moreover, given the high abundance of antibiotic resistance genes in RW, the concentration of these genes in RW+TWW did not differ from that of the non-ozonated controls (WW, RW and RW+WW) over the storage period. These results highlight the necessity of finding a suitable pristine diverse bacterial community to be used in the future to compete with bacteria surviving ozonation, to prevent reactivation of undesirable bacteria during storage of treated wastewater.

Aging assessment of microplastics (LDPE, PET and uPVC) under urban environment stressors

The changes in the chemical structure, surface morphology and crystallinity are reported for three different polymers (LDPE, PET and uPVC) in microplastic form, after being artificially exposed to different aging agents that can affect microplastics in urban environments: ozone, UV-C, and solar radiation. In parallel to the laboratory experiments, the microplastics were exposed to real weathering conditions for three-months in a building rooftop located in the city of Porto (Portugal). By analysing the (virgin and aged) microplastic samples periodically through ATR-FTIR spectroscopy and estimating the Carbonyl Index, it was possible to sketch the aging degree evolution through time and identify the most aggressive agents for each polymer regarding the changes in their chemical structure. SEM and XRD measurements allowed to complement the ATR-FTIR results, giving a more complete picture of the effects of each treatment on each polymer and suggesting that ATR-FTIR measurements are not sufficient to correctly evaluate the aging degree of microplastics. The changes observed in the microplastic particles studied support the theory that microplastics in the environment undergo aging and change their characteristics through time, potentially affecting their behavior and intensifying their impacts.

Ozonation of cytostatic drugs in aqueous phase

As the number of cancer patients increases, so does the consumption of cytostatic drugs, which are commonly used in chemotherapy. These compounds are already ubiquitous in wastewater treatment plant (WWTP) effluents and natural water streams, revealing the urgent need for efficient technologies for their removal from the aqueous phase. This work presents the elimination of five cytostatics of concern, found in Portuguese WWTP effluents: bicalutamide (BICA), capecitabine (CAP), cyclophosphamide (CYC), ifosfamide (IFO) and mycophenolic acid (MPA), using non-catalytic ozonation. Experiments were performed starting from trace-level concentrations (1 μM) for all cytostatics at neutral pH (pH: 7.3 ± 0.1) and room temperature (23 ± 1 °C), employing different ozone dosages. Under the studied conditions, CAP and MPA were quickly eliminated by direct ozonation, whereas BICA, CYC and IFO were more slowly degraded, as they undergo a breakdown via hydroxyl radicals generation (HO) exclusively. Increasing the O₃ dosage from 1 to 3 mg_O3/mg_DOC, CAP, MPA and IFO were completely removed, and BICA and CYC were converted more than 90% after 180 min. The presence of both inorganic ions and organic matter in real water matrices (river water, WWTP secondary effluent) did not affect the removal of CAP and MPA. Nonetheless, there was an inefficient and very fast O₃ consumption that resulted in only around 30% elimination of BICA, CYC and IFO, even if the reaction time is extended.

Solar Light-Induced Methylene Blue Removal over TiO2/AC Composites and Photocatalytic Regeneration

TiO₂-containing photocatalysts, which combine TiO₂ with carbon-based materials, are promising materials for wastewater treatment due to synergistic photodegradation and adsorption phenomena. In this work, TiO₂/AC composites were produced by the in situ immobilization of TiO₂ nanoparticles over activated carbon (AC) derived from spent coffee grains, using different TiO₂/AC proportions. The TiO₂/AC composites were tested as adsorbents (dark) and as photocatalysts in a combined adsorption+photocatalytic process (solar irradiation) for methylene blue (MB) removal from ultrapure water, and from a secondary effluent (SecEf) of an urban wastewater treatment plant. All the materials were characterized by XRD (X-ray powder diffraction), N₂ adsorption–desorption isotherms at −196 °C, SEM (scanning electron microscopy), UV-Vis diffuse reflectance, FTIR (Fourier-transform infrared spectroscopy), TPD (temperature programmed desorption), XPS (X-ray photoelectron spectroscopy) and TGA (thermogravimetric analysis). The TiAC60 (60% C) composite presented the lowest band gap (1.84 eV), while, for TiAC29 (29% C), the value was close to that of bare TiO₂ (3.18 vs. 3.17 eV). Regardless of the material, the solar irradiation improved the percentage of MB discolouration when compared to adsorption in dark conditions. In the case of simultaneous adsorption+photocatalytic assays performed in ultrapure water, TiAC29 presented the fastest MB removal. Nevertheless, both TiAC29 and TiAC60 led to excellent MB removal percentages (96.1–98.1%). UV-induced photoregeneration was a promising strategy to recover the adsorption capacity of the materials, especially for TiAC60 and AC (>95%). When the assays were performed in SecEf, all the materials promoted discolouration percentages close to those obtained in ultrapure water. The bulk water parameters revealed that TiAC60 allowed the removal of a higher amount of MB, associated with the overall improvement of the SecEf quality.

Rethinking water treatment targets: Bacteria regrowth under unprovable conditions

Ozonation is among the currently used technologies to remove chemical and biological contaminants from secondary treated urban wastewater (UWW). Despite its effectiveness on the abatement of organic micropollutants (OMPs) and disinfection, previous studies have shown that regrow of bacteria may occur upon storage of the ozonated UWW. This reactivation has been attributed to the high content of assimilable organic carbon after treatment. In order to investigate if ozonation by-products are the main biological regrowth drivers in stored ozonated UWW, the ozonation surviving cells were resuspended in sterile bottled mineral water (MW), simulating a pristine oligotrophic environment. After 7 days storage, organisms such as Acinetobacter, Methylobacterium, Cupriavidus, Massilia, Acidovorax and Pseudomonas were dominant in both ozonated UWW and pristine MW, demonstrating that bacterial regrowth is not strictly related to the eventual presence of ozonation by-products, but instead with the ability of the surviving cells to cope with nutrient-poor environments. The resistome of UWW before and after ozonation was analysed by metagenomic techniques. Draft metagenome assembled genomes (dMAGs), recovered from both ozonated UWW and after cell resuspension in MW, harboured genes conferring resistance to diverse antibiotics classes. Some of these antibiotic resistance genes (ARGs) were located in the vicinity of mobile genetic elements, suggesting their potential to be mobilized. Among these, dMAGs affiliated to taxa with high relative abundance in stored water, such as P. aeruginosa and Acinetobacter spp., harboured ARGs conferring resistance to 12 and 4 families of antibiotics, respectively, including those encoding carbapenem hydrolysing oxacillinases. The results herein obtained point out that the design and development of new wastewater treatment technologies should include measures to attenuate the imbalance of the bacterial communities promoted by storage of the final treated wastewater, even when applying processes with high mineralization rates.

Carbon xerogels combined with nanotubes as solid-phase extraction sorbent to determine metaflumizone and seven other surface and drinking water micropollutants

Carbon xerogels (CXs) were synthesized by polycondensation of resorcinol and formaldehyde, followed by thermal annealing, and subjected to hydrothermal oxidation. Solid-phase extraction (SPE) cartridges were filled with CXs and tested for extraction of metaflumizone and other seven environmental micropollutants (acetamiprid, atrazine, isoproturon, methiocarb, carbamazepine, diclofenac, and perfluorooctanesulfonic acid) before chromatographic analysis. The recoveries obtained with the pristine CX were low for most analytes, except for metaflumizone (69 ± 5%). Moreover, it was concluded that the adsorption/desorption process of the micropollutants performed better on CXs with a less acidic surface (i.e., pristine CX). Thus, cartridges were prepared with pristine CX and multi-walled carbon nanotubes (MWCNTs) in a multi-layer configuration. This reusable cartridge was able to simultaneously extract the eight micropollutants and was used to validate an analytical methodology based on SPE followed by ultra-high performance liquid chromatography-tandem mass spectrometry. A widespread occurrence of 6/8 target compounds was observed in surface water collected in rivers supplying three drinking water treatment plants and in the resulting drinking water at the endpoint of each distribution system. Therefore, the first study employing CXs and MWCNTs as sorbent in multi-layer SPE cartridges is herein reported as a proof of concept for determination of multi-class water micropollutants.

Feasibility of using magnetic nanoparticles in water disinfection

Disinfection is a crucial step during the water treatment process due to the significant risks of water contamination with human and animal excreta. The development of innovative disinfection technologies that can be applied at water point of use, avoiding contamination problems in water distribution systems and reservoirs, are needed. Thus, the present work aimed at assessing the disinfection efficiency of iron oxide magnetic nanoparticles (MNPs) modified with different compounds, such as carbon nanotubes, copper and silver, in water solutions contaminated with bacteria. Kinetic and influence of nanoparticles concentration experiments, performed with Escherichia coli, allowed to define the optimal reaction conditions to apply in batch experiments (1 min of contact time and 50 mg/mL of MNPs). During these experiments, CuFeO/CNT, C-FeO@CVD750 and 5% Ag/FeO were selected as the most efficient presenting log reduction values of 2.99, 1.50 and 2.11, respectively; however, experiments performed with Staphylococcus aureus suspension and a mixed bacterial suspension (E. coli + S. aureus) allowed to observe a slight decrease in nanomaterials efficiency, which was more evident for C-FeO@CVD750 and 5% Ag/FeO materials achieving efficiencies of 94 and 83% (corresponding log reductions of 1.26 and 0.77, respectively). CuFeO/CNT nanoparticles proved to be the most efficient material for both bacteria removal presenting an efficiency of 99% (corresponding log reduction of 1.99) for the mixed bacterial suspension. These nanoparticles proved to have great stability over successive experiments, and the low leaching values of the metals present in their composition after reaction proved the resistance and efficiency of these magnetic nanoparticles.

A life cycle assessment of solar-based treatments (H2O2, TiO2 photocatalysis, circumneutral photo-Fenton) for the removal of organic micropollutants

Micropollutants have been linked to freshwater and human toxicity. Their occurrence in water bodies arises from different causes, including the discharge of effluents from conventional urban wastewater treatment plants, which are not designed for their removal. The addition of an advanced treatment process for this purpose will allow a toxicity reduction; however, such will also imply further resources and energy use resulting in other environmental impacts. Energy use is a particularly relevant hotspot of the environmental impacts associated with advanced treatments; therefore, solar-based treatments have great potential in this field. The present study assessed the environmental impacts via life cycle assessment (LCA) of five solar-based treatments - solar photolysis (with and without H₂O₂), photocatalysis using TiO₂ (with and without H₂O₂) and circumneutral photo-Fenton - using a pilot-scale compound parabolic collector photoreactor to select the most suitable option for the removal of micropollutants (carbamazepine, diclofenac and sulfamethoxazole; 5 μg/L) from a secondary-treated wastewater. The ranking of solar treatments per highest generated impacts is, overall, as follows: circumneutral photo-Fenton > TiO₂-P25/H₂O₂ > TiO₂-P25 > solar/H₂O₂ > solar. While solar photolysis uses fewer resources and energy, thus generating lower environmental impacts, the common incomplete mineralization of the parent micropollutants implies that toxicity reduction cannot be guaranteed in this case. Aiming for a balance between ecotoxicity reduction and the impacts caused by the application of each technology, the solar TiO₂-P25 treatment, which was here investigated by LCA for the first time to remove organic micropollutants from secondary-treated urban wastewater, appears to be the most suitable option at the studied conditions (and when TiO₂ is reused at least 5 times). One of the environmental downfalls of the assessed treatments is the energy required to produce the chemicals, and so the importance of minimizing external energy use during the application of advanced treatment processes is reinforced.

Detoxification of Ciprofloxacin in an Anaerobic Bioprocess Supplemented with Magnetic Carbon Nanotubes: Contribution of Adsorption and Biodegradation Mechanisms

In anaerobic bioreactors, the electrons produced during the oxidation of organic matter can potentially be used for the biological reduction of pharmaceuticals in wastewaters. Common electron transfer limitations benefit from the acceleration of reactions through utilization of redox mediators (RM). This work explores the potential of carbon nanomaterials (CNM) as RM on the anaerobic removal of ciprofloxacin (CIP). Pristine and tailored carbon nanotubes (CNT) were first tested for chemical reduction of CIP, and pristine CNT was found as the best material, so it was further utilized in biological anaerobic assays with anaerobic granular sludge (GS). In addition, magnetic CNT were prepared and also tested in biological assays, as they are easier to be recovered and reused. In biological tests with CNM, approximately 99% CIP removal was achieved, and the reaction rates increased ≈1.5-fold relatively to the control without CNM. In these experiments, CIP adsorption onto GS and CNM was above 90%. Despite, after applying three successive cycles of CIP addition, the catalytic properties of magnetic CNT were maintained while adsorption decreased to 29 ± 3.2%, as the result of CNM overload by CIP. The results suggest the combined occurrence of different mechanisms for CIP removal: adsorption on GS and/or CNM, and biological reduction or oxidation, which can be accelerated by the presence of CNM. After biological treatment with CNM, toxicity towards Vibrio fischeri was evaluated, resulting in ≈ 46% detoxification of CIP solution, showing the advantages of combining biological treatment with CNM for CIP removal.

Tailoring Carbon Nanotubes to Enhance their Efficiency as Electron Shuttle on the Biological Removal of Acid Orange 10 Under Anaerobic Conditions

Anaerobic treatments have been described for the biodegradation of pollutants. However, the reactions proceed slowly due to the recalcitrant nature of these compounds. Carbon nanomaterials (CNM) intermediate in, and favor, the electron transfer, accelerating the anaerobic reduction of pollutants, which act as final electron acceptors. In the present work, different carbon nanotubes (CNT) with modified surface chemistry, namely CNT oxidized with HNO₃ (CNT_HNO₃) and CNT doped with nitrogen in a ball milling process (CNT_N_MB) were prepared using commercial CNT as a starting material. The new CNM were tested as redox mediators (RM), 0.1 g L^-1, in the biological reduction of the azo dye, Acid Orange 10 (AO10), with an anaerobic granular sludge, over 48 h of reaction. Methane production was also assessed to verify the microorganism's activity and the CNM's effect on the methanogenic activity. An improvement in the biological removal of AO10 occurred with all CNM (above 90%), when compared with the control without CNM (only 32.4 ± 0.3%). The best results were obtained with CNT_N_MB, which achieved 98.2 ± 0.1% biological AO10 removal, and an 11-fold reduction rate increase. In order to confer magnetic properties to the CNM, tailored CNT were impregnated with 2% of iron-samples: CNT@2%Fe, CNT@2%Fe_N_MB, and CNT@2%Fe_HNO₃. The better performance of the CNT doped with nitrogen was confirmed with CNT@2%Fe_N_MB, and the magnetic character facilitated its recovery after treatment, and did not affect its good catalytic properties. No dye removal was observed in the abiotic assays, so the removal was not due to adsorption on the CNM. Furthermore, the microorganism's viability was maintained during the assay and methane production was not affected by the presence of the CNM. Despite the toxic character of the aromatic amines formed, detoxification was observed after the biological process with thermally treated CNT.

Microplastics in the environment: A DPSIR analysis with focus on the responses

This review organizes key information about microplastic pollution through a DPSIR (driving forces, pressures, states, impacts and responses) analysis, namely the current knowledge on the sources of microplastics in the environment, the abundance, mobility and fate of microplastics distributed across the different environmental compartments, as well as their socio-economic and environmental impacts. The available or developing upstream and downstream responses to the microplastic pollution are also reviewed as part of the DPSIR analysis. These include the regulatory and policy instruments, environmental education campaigns, product design, the development of biodegradable plastics, environmental cleanups, waste management, drinking water and wastewater treatment plants, and other treatment technologies and processes. Whenever possible, the current trends and discerning gaps in the research conducted so far by the scientific community are identified, giving some clues to what is going to be the future research on this topic and into new lines of research.

Selective formic acid dehydrogenation at low temperature over a RuO2/COF pre-catalyst synthesized on the gram scale

Selective formic acid dehydrogenation over an efficient RuO₂/COF pre-catalyst with good dispersion of the active metal and large N-content on the COF support.

The role of surface properties in CO2 methanation over carbon-supported Ni catalysts and their promotion by Fe

CO₂ methanation over activated carbon-supported Ni catalysts with enhanced surface chemistry properties and their improved performance by Fe promotion.

Quenchers in advanced oxidation technologies for analysis of micropollutants by liquid chromatography coupled to mass spectrometry: Sodium sulphite or catalase?

This work aimed to investigate the possible effect of 2 quenchers commonly used in H₂O₂-based advanced oxidation technologies (AOTs), i.e. catalase and sodium sulphite (Na₂SO₃), on the analytical signal of 3 detectors coupled to liquid chromatography (LC): tandem mass spectrometry (LC-MS/MS), fluorescence detection (LC-FD) and LC-diode array detection (LC-DAD). The observation of analytical interferences for a group of compounds when studying the removal by continuous mode UV/H₂O₂ of 26 micropollutants (MPs) from a spiked surface water (SW), for which the residual H₂O₂ in the samples was quenched by Na₂SO₃, triggered the need of understanding these effects and thus catalase was used as comparative quencher. From the 26 MPs having a wide range of polarity and pK_a, those monitored after electrospray ionization (ESI) under positive ionization (PI) mode and presenting a pK_a higher than 5.9 revealed a great signal suppression, but only when using Na₂SO₃ as H₂O₂ quencher. In this sense, we further explored this effect by selecting 2 MPs, metoprolol and diclofenac, which had respectively signal suppression and no interference in the LC-MS/MS response. These MPs were analysed before and after addition of H₂O₂ and catalase or Na₂SO₃ in reaction vials, using: (i) different detectors coupled to LC, namely LC-MS/MS with ESI under PI and negative ionization (NI) modes, LC-FD and LC-DAD; (ii) different environmental matrices (SW, drinking water, wastewater) and ultrapure water; and (iii) different magnitude levels (0.1-10 mg L^-1). The results demonstrated a remarkable signal suppression in LC-MS/MS analyses under PI mode for those compounds with pK_a higher than 5.9, confirming the interfering effect of H₂O₂/Na₂SO₃. To the best of our knowledge, the analytical interference in the LC-MS/MS analysis, after adding Na₂SO₃ to quench H₂O₂ in AOTs experiments was never reported before and the results presented herein support the recommendation to use catalase instead of Na₂SO₃ as quencher in AOTs studies.

Continuous ozonation of urban wastewater: Removal of antibiotics, antibiotic-resistant Escherichia coli and antibiotic resistance genes and phytotoxicity

This work evaluated the removal of a mixture of eight antibiotics (i.e. ampicillin (AMP), azithromycin (AZM), erythromycin (ERY), clarithromycin (CLA), ofloxacin (OFL), sulfamethoxazole (SMX), trimethoprim (TMP) and tetracycline (TC)) from urban wastewater, by ozonation operated in continuous mode at different hydraulic retention times (HRTs) (i.e. 10, 20, 40 and 60 min) and specific ozone doses (i.e. 0.125, 0.25, 0.50 and 0.75 gO₃ gDOC^{- 1}). As expected, the efficiency of ozonation was highly ozone dose- and contact time-dependent. The removal of the parent compounds of the selected antibiotics to levels below their detection limits was achieved with HRT of 40 min and specific ozone dose of 0.125 gO₃ gDOC^{- 1}. The effect of ozonation was also investigated at a microbiological and genomic level, by studying the efficiency of the process with respect to the inactivation of Escherichia coli and antibiotic-resistant E. coli, as well as to the reduction of the abundance of selected antibiotic resistance genes (ARGs). The inactivation of total cultivable E. coli was achieved under the experimental conditions of HRT 40 min and 0.25 gO₃ gDOC^-1, at which all antibiotic compounds were already degraded. The regrowth examinations revealed that higher ozone concentrations were required for the permanent inactivation of E. coli below the Limit of Quantification (<LOQ = 0.01 CFU mL^{- 1}). Also, the abundance of the examined ARGs (intl1, aadA1, dfrA1, qacEΔ1 and sul1) was found to decrease with increasing HRT and ozone dose. Despite the fact that the mildest operating parameters were able to eliminate the parent compounds of the tested antibiotics in wastewater effluents, it was clearly demonstrated in this study that higher ozone doses were required in order to confer permanent damage and/or death and prevent potential post-treatment re-growth of both total bacteria and ARB, and to reduce the abundance of ARGs below the LOQ. Interestingly, the mineralization of wastewater, in terms of Dissolved Organic Carbon (DOC) removal, was found to be significantly low even when the higher ozone doses were applied, leading to an increased phytotoxicity towards various plant species. The findings of this study clearly underline the importance of properly optimising the ozonation process (e.g. specific ozone dose and contact time) taking into consideration both the bacterial species and associated ARGs, as well as the wastewater physicochemical properties (e.g. DOC), in order to mitigate the spread of ARB&ARGs, as well as to reduce the potential phytotoxicity.

Monitoring of the 17 EU Watch List contaminants of emerging concern in the Ave and the Sousa Rivers

The occurrence of micropollutants in the environment is a matter of high concern. Some regulations have been published in the last years and a Watch List of contaminants of emerging concern (CECs) for European Union monitoring of surface water was launched in the Decision 2015/495, including three estrogens (estrone, E1; 17-β-estradiol, E2; and 17-α-ethinylestradiol, EE2), four pharmaceuticals (diclofenac and the macrolide antibiotics azithromycin, clarithromycin and erythromycin), an anti-oxidant (2,6-ditert-butyl-4-methylphenol, BHT), an UV filter (2-ethylhexyl 4-methoxycinnamate, EHMC), some pesticides (methiocarb and the neonicotinoids imidacloprid, thiacloprid, thiamethoxam, clothianidin and acetamiprid) and two herbicides (oxadiazon and triallate). This study provides the first spatial and seasonal monitoring campaign in the Ave and the Sousa Rivers for the all set of the 17 Watch List CECs (not reported yet for any country), in order to assess their occurrence, distribution, frequency and risk assessment. It also highlights the need of extend the study to other regions and environmental matrices to investigate the occurrence and possible sources of contamination of CECs, aiming to give insights for decision makers to define mitigation strategies for a more sustainable water policy.

Spatial and seasonal occurrence of micropollutants in four Portuguese rivers and a case study for fluorescence excitation-emission matrices

The European Union (EU) has recommended the monitoring of specific priority substances (PSs, Directive 2013/39) and some contaminants of emerging concern (CECs, Decision 2015/495) in surface waterbodies. The present study provides spatial distributions and temporal variations of a wide range of multi-class PSs and CECs in four stressed rivers in Portugal (Ave, Leça, Antuã, and Cértima). Thirteen micropollutants were found in all four rivers, including the priority pesticide isoproturon (up to 92 ng L^-1), various pharmaceuticals (up to 396 ng L^-1), and the UV-filter 2-ethyl-hexyl-4-methoxycinnamate (EHMC, up to 562 ng L^-1) identified in Decision 2015/495. The industrial priority compound perfluorooctanesulfonic acid (PFOS) was found in three rivers (Antuã, Cértima, and Leça) below the method quantification limit, together with four pharmaceuticals not included in these EU guidelines. The already banned priority pesticide atrazine was detected in Ave, Antuã, and Leça (up to 41 ng L^-1) and simazine in Cértima and Leça (up to 26 ng L^-1). Acetamiprid and imidacloprid (included in Decision 2015/495) were only detected during the dry season in the Ave. Leça river was selected as a waterbody case study for assessment of fluorescence excitation-emission matrices (EEMs). These results matched the spatial distribution trend of micropollutants along the river, with stronger fluorescence response and higher concentrations being found downstream of industrial areas and urban wastewater treatment plants (WWTPs). Moreover, the fluorescence signature of surface water collected downstream of an urban WWTP aligned very well with that obtained for the respective WWTP effluent. Thus, actions are needed to preserve a good environmental status of these stressed European waterbodies.

A review on environmental monitoring of water organic pollutants identified by EU guidelines

The contamination of fresh water is a global concern. The huge impact of natural and anthropogenic organic substances that are constantly released into the environment, demands a better knowledge of the chemical status of Earth's surface water. Water quality monitoring studies have been performed targeting different substances and/or classes of substances, in different regions of the world, using different types of sampling strategies and campaigns. This review article aims to gather the available dispersed information regarding the occurrence of priority substances (PSs) and contaminants of emerging concern (CECs) that must be monitored in Europe in surface water, according to the European Union Directive 2013/39/EU and the Watch List of Decision 2015/495/EU, respectively. Other specific organic pollutants not considered in these EU documents as substances of high concern, but with reported elevated frequency of detection at high concentrations, are also discussed. The search comprised worldwide publications from 2012, considering at least one of the following criteria: 4 sampling campaigns per year, wet and dry seasons, temporal and/or spatial monitoring of surface (river, estuarine, lake and/or coastal waters) and ground waters. The highest concentrations were found for: (i) the PSs atrazine, alachlor, trifluralin, heptachlor, hexachlorocyclohexane, polycyclic aromatic hydrocarbons and di(2-ethylhexyl)phthalate; (ii) the CECs azithromycin, clarithromycin, erythromycin, diclofenac, 17α-ethinylestradiol, imidacloprid and 2-ethylhexyl 4-methoxycinnamate; and (iii) other unregulated organic compounds (caffeine, naproxen, metolachlor, estriol, dimethoate, terbuthylazine, acetaminophen, ibuprofen, trimethoprim, ciprofloxacin, ketoprofen, atenolol, Bisphenol A, metoprolol, carbofuran, malathion, sulfamethoxazole, carbamazepine and ofloxacin). Most frequent substances as well as those found at highest concentrations in different seasons and regions, together with available risk assessment data, may be useful to identify possible future PS candidates.

A "Nanopore Lithography" Strategy for Synthesizing Hierarchically Micro/Mesoporous Carbons from ZIF-8/Graphene Oxide Hybrids for Electrochemical Energy Storage

Porous carbons derived from metal-organic frameworks (MOFs) are promising materials for a number of energy- and environment-related applications, but their almost exclusively microporous texture can be an obstacle to their performance in practical uses. Here, we introduce a novel strategy for the generation of very uniform mesoporosity in a prototypical MOF, namely, zeolitic imidazolate framework-8 (ZIF-8). The process, referred to as "nanopore lithography", makes use of graphene oxide (GO) nanosheets enclosing ZIF-8 particles as masks or templates for the transfer of mesoporous texture to the latter. Upon controlled carbonization and activation, nanopores created in the GO envelope serve as selective entry points for localized etching of carbonized ZIF-8, so that such nanopores are replicated in the MOF-derived carbonaceous structure. The resulting porous carbons are dominated by uniform mesopores ∼3-4 nm in width and possess specific surface areas of ∼1300-1400 m² g^-1. Furthermore, we investigate and discuss the specific experimental conditions that afford the mesopore-templating action of the GO nanosheets. Electrochemical characterization revealed an improved capacitance as well as a faster, more reversible charge/discharge kinetics for the ZIF-8-derived porous carbons obtained through nanopore lithography, relative to those for their counterparts with standard activation (no GO templating), thus indicating the potential practical advantage of the present approach in capacitive energy storage applications.

Electrochemical Exfoliation of Graphite in Aqueous Sodium Halide Electrolytes toward Low Oxygen Content Graphene for Energy and Environmental Applications

Graphene and graphene-based materials have shown great promise in many technological applications, but their large-scale production and processing by simple and cost-effective means still constitute significant issues in the path of their widespread implementation. Here, we investigate a straightforward method for the preparation of a ready-to-use and low oxygen content graphene material that is based on electrochemical (anodic) delamination of graphite in aqueous medium with sodium halides as the electrolyte. Contrary to previous conflicting reports on the ability of halide anions to act as efficient exfoliating electrolytes in electrochemical graphene exfoliation, we show that proper choice of both graphite electrode (e.g., graphite foil) and sodium halide concentration readily leads to the generation of large quantities of single-/few-layer graphene nanosheets possessing a degree of oxidation (O/C ratio down to ∼0.06) lower than that typical of anodically exfoliated graphenes obtained with commonly used electrolytes. The halide anions are thought to play a role in mitigating the oxidation of the graphene lattice during exfoliation, which is also discussed and rationalized. The as-exfoliated graphene materials exhibited a three-dimensional morphology that was suitable for their practical use without the need to resort to any kind of postproduction processing. When tested as dye adsorbents, they outperformed many previously reported graphene-based materials (e.g., they adsorbed ∼920 mg g^-1 for methyl orange) and were useful sorbents for oils and nonpolar organic solvents. Supercapacitor cells assembled directly from the as-exfoliated products delivered energy and power density values (up to 15.3 Wh kg^-1 and 3220 W kg^-1, respectively) competitive with those of many other graphene-based devices but with the additional advantage of extreme simplicity of preparation.

Photocatalytic ozonation of aniline with TiO2-carbon composite materials

The photocatalytic ozonation of aniline (ANL) aqueous solutions was carried out in the presence of neat titanium dioxide (TiO₂), multi-walled carbon nanotubes (MWCNT) and a composite of TiO₂ and MWCNT. Independent tests for catalytic ozonation and photocatalysis were also carried out in order to explore the potential occurrence of a synergetic effect. Photocatalytic and catalytic ozonation carried out with an ozone dose of 50 g m^-3 converted ANL in 15 min. Photocatalysis using P25, commercial TiO₂, and an 80:20 (w/w) composite of P25 and MWCNT also led to total ANL conversion, but at longer reaction times. Removal of TOC was higher than 70% for all photocatalytic ozonation systems at 1 h of reaction. With the exception of neat MWCNT, photocatalytic ozonation in the presence of the selected samples led to nearly complete mineralization after 3 h of reaction. Photocatalytic ozonation completely removed oxalic acid (OXA) formed during ANL degradation. The concentration of oxamic acid (OMA, other ANL degradation by-product more refractory than OXA) generally increased with time, and in the photocatalytic ozonation with P25 based materials its concentration decreased earlier. The presence of nitrates and ammonium was confirmed during ANL degradation by all tested treatments, with the exception of the cation in TiO₂ catalysed reactions.

Effect of cobalt loading on the solid state properties and ethyl acetate oxidation performance of cobalt-cerium mixed oxides

Cobalt-cerium mixed oxides were prepared by the wet impregnation method and evaluated for volatile organic compounds (VOCs) abatement, using ethyl acetate (EtAc) as model molecule. The impact of Co content on the physicochemical characteristics of catalysts and EtAc conversion was investigated. The materials were characterized by various techniques, including N₂ adsorption at -196°C, scanning electron microscopy (SEM), X-ray diffraction (XRD), H₂-temperature programmed reduction (H₂-TPR) and X-ray photoelectron spectroscopy (XPS) to reveal the structure-activity relationship. The obtained results showed the superiority of mixed oxides compared to bare CeO₂ and Co₃O₄, demonstrating a synergistic effect. The optimum oxidation performance was achieved with the sample containing 20wt.% Co (Co/Ce atomic ratio of ca. 0.75), in which complete conversion of EtAc was attained at 260°C. In contrast, temperatures above 300°C were required to achieve 100% conversion over the single oxides. Notably, a strong relationship between both the: (i) relative population, and (ii) facile reduction of lattice oxygen with the ethyl acetate oxidation activity was found, highlighting the key role of loosely bound oxygen species on VOCs oxidation. A synergistic Co-Ce interaction can be accounted for the enhanced reducibility of mixed oxides, linked with the increased mobility of lattice oxygen.

Ozonation and UV254nm radiation for the removal of microorganisms and antibiotic resistance genes from urban wastewater

Conventional wastewater treatment has a limited capacity to reduce antibiotic resistant bacteria and genes (ARB&ARG). Tertiary treatment processes are promising solutions, although the transitory inactivation of bacteria may select ARB&ARG. This study aimed at assessing the potential of ozonation and UV_254nm radiation to inactivate cultivable fungal and bacterial populations, and the selected genes 16S rRNA (common to all bacteria), intI1 (common in Gram-negative bacteria) and the ARG vanA, bla_TEM, sul1 and qnrS. The abundance of the different microbiological parameters per volume of wastewater was reduced by ∼2 log units for cultivable fungi and 16S rRNA and intI1 genes, by∼3-4 log units, for total heterotrophs, enterobacteria and enterococci, and to values close or below the limits of quantification for ARG, for both processes, after a contact time of 30min. Yet, most of the cultivable populations, the 16S rRNA and intI1 genes as well as the ARG, except qnrS after ozonation, reached pre-treatment levels after 3days storage, suggesting a transitory rather than permanent microbial inactivation. Noticeably, normalization per 16S rRNA gene evidenced an increase of the ARG and intI1 prevalence, mainly after UV_254nm treatment. The results suggest that these tertiary treatments may be selecting for ARB&ARG populations.

Perspectives on carbon materials as powerful catalysts in continuous anaerobic bioreactors

The catalytic effect of commercial microporous activated carbon (AC) and macroporous carbon nanotubes (CNT) is investigated in reductive bioreactions in continuous high rate anaerobic reactors, using the azo dye Acid Orange 10 (AO10) as model compound as electron acceptor and a mixture of VFA as electron donor. Size and concentration of carbon materials (CM) and hydraulic retention time (HRT) are assessed. CM increased the biological reduction rate of AO10, resulting in significantly higher colour removal, as compared to the control reactors. The highest efficiency, 98%, was achieved with a CNT diameter (d) lower than 0.25 mm, at a CNT concentration of 0.12 g per g of volatile solids (VS), a HRT of 10 h and resulted in a chemical oxygen demand (COD) removal of 85%. Reducing the HRT to 5 h, colour and COD removal in CM-mediated bioreactors were above 90% and 80%, respectively. In the control reactor, thought similar COD removal was achieved, AO10 decolourisation was just approximately 20%, demonstrating the ability of CM to significantly accelerate the reduction reactions in continuous bioreactors. AO10 reduction to the correspondent aromatic amines was proved by high performance liquid chromatography (HPLC). Colour decrease in the reactor treating a real effluent with CNT was the double comparatively to the reactor operated without CNT. The presence of AC in the reactor did not affect the microbial diversity, as compared to the control reactor, evidencing that the efficient reduction of AO10 was mainly due to AC rather than attributed to changes in the composition of the microbial communities.

Photocatalytic ozonation of urban wastewater and surface water using immobilized TiO2 with LEDs: Micropollutants, antibiotic resistance genes and estrogenic activity

Photocatalytic ozonation was employed for the first time in continuous mode with TiO2-coated glass Raschig rings and light emitting diodes (LEDs) to treat urban wastewater as well as surface water collected from the supply area of a drinking water treatment plant (DWTP). Different levels of contamination and types of contaminants were considered in this work, including chemical priority substances (PSs) and contaminants of emerging concern (CECs), as well as potential human opportunistic antibiotic resistant bacteria and their genes (ARB&ARG). Photocatalytic ozonation was more effective than single ozonation (or even than TiO2 catalytic ozonation) in the degradation of typical reaction by-products (such as oxalic acid), and more effective than photocatalysis to remove the parent micropollutants determined in urban wastewater. In fact, only fluoxetine, clarithromycin, erythromycin and 17-alpha-ethinylestradiol (EE2) were detected after photocatalytic ozonation, by using solid-phase extraction (SPE) pre-concentration and LC-MS/MS analysis. In surface water, this treatment allowed the removal of all determined micropollutants to levels below the limit of detection (0.01-0.20 ng L(-1)). The efficiency of this process was then assessed based on the capacity to remove different groups of cultivable microorganisms and housekeeping (16S rRNA) and antibiotic resistance or related genes (intI1, blaTEM, qnrS, sul1). Photocatalytic ozonation was observed to efficiently remove microorganisms and ARGs. Although after storage total heterotrophic and ARB (to ciprofloxacin, gentamicin, meropenem), fungi, and the genes 16S rRNA and intI1, increased to values close to the pre-treatment levels, the ARGs (blaTEM, qnrS and sul1) were reduced to levels below/close to the quantification limit even after 3-days storage of treated surface water or wastewater. Yeast estrogen screen (YES), thiazolyl blue tetrazolium reduction (MTT) and lactate dehydrogenase (LDH) assays were also performed before and after photocatalytic ozonation to evaluate the potential estrogenic activity, the cellular metabolic activity and the cell viability. Compounds with estrogenic effects and significant differences concerning cell viability were not observed in any case. A slight cytotoxicity was only detected for Caco-2 and hCMEC/D3 cell lines after treatment of the urban wastewater, but not for L929 fibroblasts.

Fast mineralization and detoxification of amoxicillin and diclofenac by photocatalytic ozonation and application to an urban wastewater

The degradation of two organic pollutants (amoxicillin and diclofenac) in 0.1 mM aqueous solutions was studied by using advanced oxidation processes, namely ozonation, photolysis, photolytic ozonation, photocatalysis and photocatalytic ozonation. Diclofenac was degraded quickly under direct photolysis by artificial light (medium-pressure vapor arc, λ(exc) > 300 nm), while amoxicillin remained very stable. In the presence of ozone, regardless of the type of process, complete degradation of both organic pollutants was observed in less than 20 min. Photolysis or ozonation on their own led to modest values of total organic carbon (TOC) removal (<6% or 41%, respectively in 180 min), while for photocatalysis (no ozone present) a significant fraction of nonoxidizable compounds remained in the treated water (∼15% after 180 min). In the case of photolytic ozonation, the kinetics of TOC removal was slow. In contrast, a relatively fast and complete mineralization of amoxicillin and diclofenac (30 and 120 min, respectively) was achieved when applying the photocatalytic ozonation process. The absence of toxicity of the treated waters was confirmed by growth inhibition assays using two different microorganisms, Escherichia coli and Staphylococcus aureus. Photocatalytic ozonation was also applied to an urban wastewater spiked with both amoxicillin and diclofenac. The parent pollutants were easily oxidized, but the TOC removal was only as much as 68%, mainly due to the persistent presence of oxamic acid in the treated sample. The same treatment allowed the effective degradation of a wide group of micropollutants (pesticides, pharmaceuticals, hormones and an industrial compound) detected in non-spiked urban wastewater.

Removal of oxalic acid, oxamic acid and aniline by a combined photolysis and ozonation process

Aniline (ANL), an aromatic amine, oxalic acid (OXA) and oxamic acid (OMA), short-chain carboxylic acids, were chosen as model organic pollutants for testing the combined effect of neat photolysis and ozonation in the treatment of aqueous effluents. In order to better understand the results, single ozonation and neat photolysis were also carried out. OXA has a high refractory character relatively to single ozonation and neat photolysis only accounted for 26% conversion of OXA after 2 h of reaction. On the other hand, OXA complete degradation was observed in less than an hour when ozone and light were used simultaneously. Despite OMA, a compound never studied before by a combined ozonation and photolysis treatment, being highly refractory to oxidation, more than 50% was removed by photo-ozonation after 3 h of reaction. In the case of ANL, both single ozonation and photo-ozonation resulted in 100% removal in a short reaction period due to the high reactivity of ozone to attack this type of molecules; however, only the combined method leads to efficient mineralization (89%) after 3 h of reaction. A significant synergetic effect was observed in the degradation of the selected contaminants by the simultaneous use of ozone and light, since the mineralization rate of combined method is higher than the sum of the mineralization rates of the individual treatments. The promising results observed in the degradation of the selected contaminants are paving the way to the application of photo-ozonation in the treatment of wastewater containing this type of pollutants.

Process design for wastewater treatment: catalytic ozonation of organic pollutants

Emerging micropollutants have been recently the target of interest for their potential harmful effects in the environment and their resistance to conventional water treatments. Catalytic ozonation is an advanced oxidation process consisting of the formation of highly reactive radicals from the decomposition of ozone promoted by a catalyst. Nanocarbon materials have been shown to be effective catalysts for this process, either in powder form or grown on the surface of a monolithic structure. In this work, carbon nanofibers grown on the surface of a cordierite honeycomb monolith are tested as catalyst for the ozonation of five selected micropollutants: atrazine (ATZ), bezafibrate, erythromycin, metolachlor, and nonylphenol. The process is tested both in laboratorial and real conditions. Later on, ATZ was selected as a target pollutant to further investigate the role of the catalytic material. It is shown that the inclusion of a catalyst improves the mineralization degree compared to single ozonation.