Environmental pollution is a recognized issue of major concern since a wide range of contaminants has been found in aquatic environment at ngL−1 to μgL−1 levels. In the year 2000, a strategy was ...defined to identify the priority substances concerning aquatic ecosystems, followed by the definition of environmental quality standards (EQS) in 2008. Recently it was launched the Directive 2013/39/EU that updates the water framework policy highlighting the need to develop new water treatment technologies to deal with such problem. This review summarizes the data published in the last decade regarding the application of advanced oxidation processes (AOPs) to treat priority compounds and certain other pollutants defined in this Directive, excluding the inorganic species (cadmium, lead, mercury, nickel and their derivatives).
The Directive 2013/39/EU includes several pesticides (aldrin, dichlorodiphenyltrichloroethane, dicofol, dieldrin, endrin, endosulfan, isodrin, heptachlor, lindane, pentachlorophenol, chlorpyrifos, chlorfenvinphos, dichlorvos, atrazine, simazine, terbutryn, diuron, isoproturon, trifluralin, cypermethrin, alachlor), solvents (dichloromethane, dichloroethane, trichloromethane and carbon tetrachloride), perfluorooctane sulfonic acid and its derivatives (PFOS), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), nonylphenol and octylphenol, as well as the three compounds included in the recommendation for the first watch list of substances (diclofenac, 17-alpha-ethinylestradiol (EE2) and 17-beta-estradiol (E2)). Some particular pesticides (aclonifen, bifenox, cybutryne, quinoxyfen), organotin compounds (tributyltin), dioxins and dioxin-like compounds, brominated diphenylethers, hexabromocyclododecanes and di(2-ethylhexyl)phthalate are also defined in this Directive, but studies dealing with AOPs are missing.
AOPs are recognized tools to destroy recalcitrant compounds or, at least, to transform them into biodegradable species. Diuron (a phenylurea herbicide) and atrazine (from the triazine chemical class) are the most studied pesticides from Directive 2013/39/EU. Fenton-based processes are the most frequently applied to treat priority compounds in water and their efficiency typically increases with the operating temperature as well as under UV or solar light. Heterogeneous photocatalysis is the second most used treatment to destroy pollutants defined in the Directive. Ozone alone promotes the partial oxidation of pollutants, and an increase in the effluent biodegradability, but complete mineralization of pollutants is difficult. To overcome this drawback, ozonation has been combined with heterogeneous catalysts, addition of H2O2, other AOPs (such as photocatalysis) or membrane technologies.
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•AOPs to treat priority compounds listed in the Directive 2013/39/EU are reviewed.•Fenton-based processes, photocatalysis and ozonation are the most frequently applied.•Importance of AOPs to treat recalcitrant compounds is emphasized.
Although there are no legal discharge limits for micropollutants into the environment, some regulations have been published in the last few years. Recently, a watch list of substances for European ...Union-wide monitoring was reported in the Decision 2015/495/EU of 20 March 2015. Besides the substances previously recommended to be included by the Directive 39/2013/EU, namely two pharmaceuticals (diclofenac and the synthetic hormone 17-alpha-ethinylestradiol (EE2)) and a natural hormone (17-beta-estradiol (E2)), the first watch list of 10 substances/groups of substances also refers three macrolide antibiotics (azithromycin, clarithromycin and erythromycin), other natural hormone (estrone (E1)), some pesticides (methiocarb, oxadiazon, imidacloprid, thiacloprid, thiamethoxam, clothianidin, acetamiprid and triallate), a UV filter (2-ethylhexyl-4-methoxycinnamate) and an antioxidant (2,6-di-tert-butyl-4-methylphenol) commonly used as food additive. Since little is known about the removal of most of the substances included in the Decision 2015/495/EU, particularly regarding realistic concentrations in aqueous environmental samples, this review aims to: (i) overview the European policy in the water field; (ii) briefly describe the most commonly used conventional and advanced treatment processes to remove micropollutants; (iii) summarize the relevant data published in the last decade, regarding occurrence and removal in aqueous matrices of the 10 substances/groups of substances that were recently included in the first watch list for European Union monitoring (Decision 2015/495/EU); and (iv) highlight the lack of reports concerning some substances of the watch list, the study of un-spiked aquatic matrices and the assessment of transformation by-products.
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•Decision 2015/495/EU-Watch list of substances for EU-wide monitoring is overviewed.•Removal of these substances in aqueous matrices is reviewed.•Biological, membrane and advanced oxidation processes are applied.•Need to study realistic concentrations/matrices is emphasized.
Organic micropollutants present in drinking water (DW) may cause adverse effects for public health, and so reliable analytical methods are required to detect these pollutants at trace levels in DW. ...This work describes the first green analytical methodology for multi-class determination of 21 pollutants in DW: seven pesticides, an industrial compound, 12 pharmaceuticals, and a metabolite (some included in Directive 2013/39/EU or Decision 2015/495/EU). A solid-phase extraction procedure followed by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (offline SPE–UHPLC–MS/MS) method was optimized using eco-friendly solvents, achieving detection limits below 0.20 ng L
−1
. The validated analytical method was successfully applied to DW samples from different sources (tap, fountain, and well waters) from different locations in the north of Portugal, as well as before and after bench-scale UV and ozonation experiments in spiked tap water samples. Thirteen compounds were detected, many of them not regulated yet, in the following order of frequency: diclofenac > norfluoxetine > atrazine > simazine > warfarin > metoprolol > alachlor > chlorfenvinphos > trimethoprim > clarithromycin ≈ carbamazepine ≈ PFOS > citalopram. Hazard quotients were also estimated for the quantified substances and suggested no adverse effects to humans.
Graphical Abstract
Occurrence and removal of multi-class micropollutants in drinking water, analyzed by an eco-friendly LC–MS/MS method
The basis of recently developed quantitative TG-MS analysis was used for the evaluation of TPD-MS measurements in order to characterize the changes in the surface chemistry of carbon cryogels after ...the oxidation/activation treatment. This methodology was applied to the analysis of partially pyrolysed carbon cryogels (400 °C), which were oxidized/activated in four different ways (phosphoric acid, Fenton like reaction, ammonium persulfate with sulfuric acid and nitric acid with hydrogen peroxide). The quantitative TPD-MS evaluation enables analysis of all the evolved gases during the sample heating (without the calibration of all gases) and distinguishes the carbonization process from the decomposition of the more thermally stable oxygen surface groups (analysis of the effect of oxidation/activation reagents). The activation by H3PO4 results in the hydrolysis and esterification of anhydrides, lactones and phenols and creation of phosphoric acid esters (C-O-P), which decompose into C3-P=O linkages with the CO evolution. All the oxidation treatments had a similar effect on the surface chemistry. The amounts of carboxylic acids and anhydrides increased significantly, while the amount of lactones and phenol groups decreased (oxidized into carbonyls). Application of TG-MS fundamentals to the evaluation of TPD-MS profiles from a wide range of samples allows determining all the gaseous products.
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The oxygen content of activated carbon surface plays a key role on the activity of Au/AC catalysts for the oxidation of glycerol. Oxygen-free supports promote electron mobility, which enhances the ...catalytic performance.
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► The sol immobilization method leads to efficient Au/AC catalysts for glycerol oxidation. ► The activated carbon surface chemistry plays a key role in catalysis by gold. ► Activated carbons with high content of acid groups lead to poor performances. ► Basic activated carbons with a high density of free electrons enhance the activity.
The main goal of this work is the study of the relationship between the surface chemical characteristics of activated carbon and the performance of the respective gold-supported catalysts in the oxidation of glycerol. For that purpose, a set of modified activated carbons with different levels of oxygenated functional groups on the surface, but with no major differences in their textural parameters, was prepared. A strong effect of the activated carbon surface chemistry on the catalytic activity was observed. Gold particles with similar average sizes resulted in different performances, being the surface oxygenated acid groups particularly prejudicial for the catalytic activity. Basic oxygen-free supports characterized by a high density of free π-electrons lead to more active catalysts; the observation was tentatively explained on the basis of a recent proposed mechanism by considering the capability to promote electron mobility. However, the presence of oxygenated groups on the support does not influence significantly the selectivities.
This work provides the first spatial distribution report of micropollutants (MPs) in the entire Portuguese coast, comprising the ocean shore (sea water, SW) and whenever possible the nearest river ...discharging on it (estuarine water, EW). This surface water monitoring programme aimed to assess the spatial distribution of 37 MPs with a wide chemical nature, including some substances prioritized by the European Union Directive 39/2013/EU and contaminants of emerging concern targeted in the Watch List of Decisions 495/2015/EU and 840/2018/EU. The risk quotients were estimated in each sampling point for the detected MPs. High concentrations of diclofenac, tramadol and carbamazepine were determined, the latter with medium to high risk for algae. Some pharmaceuticals and perfluorooctanesulfonic acid (PFOS) were broadly distributed, maybe due to the direct discharge into the sea. Atrazine and alachlor were found in the majority of the samples, with alachlor levels often considered as medium to high risk.
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•38 micropollutants were investigated along the Portuguese coast.•Atrazine was the most frequently detected compound in both estuarine and sea water.•Pharmaceuticals were found more often near highly urbanized areas.•PFOS, EHMC and pesticides were largely spread.•Only norfluoxetine, imidacloprid and methiocarb were never detected.
•Potentiation of 5-FU was carried out with Y and LTL zeolites.•5-FU release from the zeolites was explained by the Weibull model.•DDS efficacy was evaluated in vitro models of colorectal ...carcinoma.•Significant potentiation of the 5-FU effect on the cell viability by the DDS.•Immunofluorescence studies provided evidence for zeolite-cell internalization.
The studies of potentiation of 5-fluorouracil (5-FU), a traditional drug used in the treatment of several cancers, including colorectal (CRC), were carried out with zeolites Faujasite in the sodium form, with different particle sizes (NaY, 700nm and nanoNaY, 150nm) and Linde type L in the potassium form (LTL) with a particle size of 80nm. 5-FU was loaded into zeolites by liquid-phase adsorption. Characterization by spectroscopic techniques (FTIR, 1H NMR and 13C and 27Al solid-state MAS NMR), chemical analysis, thermal analysis (TGA), nitrogen adsorption isotherms and scanning electron microscopy (SEM), demonstrated the successful loading of 5-FU into the zeolite hosts. In vitro drug release studies (PBS buffer pH 7.4, 37°C) revealed the release of 80–90% of 5-FU in the first 10min. To ascertain the drug release kinetics, the release profiles were fitted to zero-order, first-order, Higuchi, Hixson–Crowell, Korsmeyer–Peppas and Weibull kinetic models. The in vitro dissolution from the drug delivery systems (DDS) was explained by the Weibull model. The DDS efficacy was evaluated using two human colorectal carcinoma cell lines, HCT-15 and RKO. Unloaded zeolites presented no toxicity to both cancer cells, while all DDS allowed an important potentiation of the 5-FU effect on the cell viability. Immunofluorescence studies provided evidence for zeolite-cell internalization.
A remarkable high selectivity to dihydroxyacetone combined with a high activity is obtained in the glycerol oxidation over Au/MWCNT catalysts, particularly if the sol immobilization technique is used ...for the impregnation of gold. Display omitted
► Gold-sol immobilization leads to the most efficient Au/MWCNT catalyst for glycerol oxidation. ► Au/MWCNT catalysts favor the oxidation toward dihydroxyacetone (DIHA). ► High DIHA selectivities (about 60%) are related with the wide mesopores of MWCNTs. ► Acidification of the mixture obtained after reaction allows DIHA stabilization.
Gold nanoparticles were supported on multi-walled carbon nanotubes (MWCNTs) by different methods and tested in the selective oxidation of glycerol under basic conditions, with the main purpose of evaluating the effect of the preparation technique on the activity and selectivity. The catalytic performances largely depended on the gold crystallite size. The sol immobilization method was the most suitable technique to prepare gold supported on carbon nanotubes. The use of MWCNTs as support for Au nanoparticles resulted in the oxidation of the secondary hydroxyl group, and therefore, a remarkable high dihydroxyacetone selectivity of about 60% is obtained independently of the preparation method used. A possible explanation based on the peculiar characteristics of the support is proposed. It was also concluded that dihydroxyacetone in the final mixture can be stabilized by lowering the pH to about 3.
Multi-walled carbon nanotubes (MWCNTs) with different surface chemical properties were prepared by oxidative treatments with HNO
3, H
2O
2 and O
2 to introduce oxygen-containing surface groups and by ...thermal treatments for their selective removal. The texture and surface chemistry of the MWCNTs were characterized by nitrogen adsorption, temperature programmed desorption (TPD) and pH at the point of zero charge. A deconvolution procedure of the TPD spectra was used to quantify the oxygenated surface groups. These materials were used as catalysts for ozone decomposition, and for the ozonation of oxalic and oxamic acids. Generally, all these catalytic processes are favoured by carbon nanotubes with low acidic character. MWCNTs were shown to exhibit higher activity for the ozonation of oxalic and oxamic acids, compared to activated carbon. Successive experimental runs of oxalic acid removal carried out with a selected MWCNT sample show that the catalyst suffers some deactivation as a result of the introduction of oxygenated groups on the surface. Therefore, the effect of the surface chemistry is mainly observed for the fresh catalysts.
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