Photochemical degradation of persistent organic pollutants (PCDD/FS, PCBS, PBDES, DDTS and HCB) in hexane and fish oil

This study has investigated the photochemical degradation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs) and some organochlorine pesticides, such as hexachlorobenzene (HCB) or dichloro-diphenyl-trichloroethane (DDT) in hexane under UV irradiation at 254 nm. All pollutants were completely degraded after 3.5 h of exposition to the UV light. Moreover, this technique was applied to remove persistent organic pollutants from fish oil, with eliminations of a 34% for PCDD/Fs, 53% for PCBs, 59% for HCB, 67% for PBDEs and 73% for DDTs after 12 h of exposition to the UV light (254 nm). Dioxin-like PCBs increased their concentration after the treatment, probably due to the dehalogenation of other more chlorinated congeners. The fatty acids analysis of the fish oil revealed that the most important ω-3 fatty acids -EPA and DHA-were degraded to 67 and 70% of their initial content respectively. For these reasons elimination of persistent organic pollutants with photochemical treatment has limited applications for oils with food-purposes. However, it still can be a useful technique for decontamination of industrial oils.

Unravelling the performance of UV/H2O2 on the removal of pharmaceuticals in real industrial, hospital, grey and urban wastewaters

This study provides an integrated assessment of UV/H₂O₂ treatment of different real wastewater matrices: two urban wastewater treatment plants (WWTPs) secondary effluents, greywater, hospital, and pharmaceutical industrial effluents. It considers micropollutant removal (up to 30 pharmaceuticals and 13 transformation products at environmental concentrations), energy efficiency and effluent toxicity. The complexity of the wastewater matrix negatively affected the UV fluence in the photo-reactor, scavenged hydroxyl radicals and hindered a proper H₂O₂ utilization thus reducing the treatment efficiency. At the optimal treatment conditions, overall pharmaceuticals removal was the highest for urban WWTPs effluents (69%-86%), followed by greywater (59%), hospital (36%) and industrial (17%) effluents. The ecotoxicity of the treated samples was reduced around one toxicity unit after the UV/H₂O₂ treatment in all cases except in industrial wastewater. The average observed removal in urban wastewater effluents and greywater for photo-susceptible, moderately photo-susceptible, and most photo-resistant compounds was 93%, 73% and 46% including outliers, respectively. The calculated electrical energy per order (E_EO) values were 0.9-1.5 kWh/(m³·order) for urban WWTP effluents and greywater while for hospital and industrial effluents was much higher (7.3-9.1 kWh/(m³·order)).

Life Cycle Assessment of the Separation and Recycling of Fluorinated Gases Using Ionic Liquids in a Circular Economy Framework

The stricter regulation regarding the use of fluorinated gases (F-gases), as a consequence of their high Global Warming Potential (GWP), represents a challenge for the refrigeration industry. The design of alternatives requires the recycling of the low to moderate GWP compounds from current refrigerant blends. However, there is not a developed and standardized technology available to recover them, and once the life cycle of the refrigeration equipment has ended, most gases are incinerated. Fluorinated ionic liquids (FILs) can effectively perform as absorbents to the complex separation of F-gas mixtures. In this work, a methodology based on the COSMO-RS thermodynamic package integrated into an Aspen Plus process simulator was used to evaluate the performance of an FIL to recover difluoromethane (R-32) from the commercial blend R-407F. The environmental sustainability of the recovery process (circular economy scenario) was analyzed with a life cycle assessment (LCA) approach, comparing the obtained results with the conventional R-32 production (benchmark scenario). The results reveal a 30% recovery of 98 wt % R-32 suitable for further reuse with environmental load reduction in the 86-99% range compared to the R-32 production. This study can guide the development of new F-gas recovery technologies to improve the environmental impacts of these compounds from a circular economy perspective.

Prospects on coupling UV/H2O2 with activated sludge or a fungal treatment for the removal of pharmaceutically active compounds in real hospital wastewater

Conventional active sludge (AS) process at municipal centralized wastewater treatment facilities may exhibit little pharmaceuticals (PhACs) removal efficiencies when treating hospital wastewater (HWW). Therefore, a dedicated efficient wastewater treatment at the source point is recommended. In this sense, advanced oxidation processes (AOPs) and fungal treatment (FG) have evidenced promising results in degrading PhACs. The coupling of the AOP based on UV/H₂O₂ treatment with biological treatment (AS or FG) treating a real non-sterile HWW, was evaluated in this work. In addition, a coagulation-flocculation pretreatment was applied to improve the efficiency of all approaches. Twenty-two PhACs were detected in raw HWW, which were effectively removed (93-95%) with the combination of any of the biological treatment followed by UV/H₂O₂ treatment. Similar removal results (94%) were obtained when placing UV/H₂O₂ treatment before FG, while a lower removal (83%) was obtained in the combination of UV/H₂O₂ followed by AS. However, the latest was the only treatment combination that achieved a decrease in the toxicity of water. Moreover, deconjugation of conjugated PhACs has been suggested for ofloxacin and lorazepam after AS treatment, and for ketoprofen after fungal treatment. Monitoring of carbamazepine and its transformation products along the treatment allowed to identify the same carbamazepine degradation pathway in UV/H₂O₂ and AS treatments, unlike fungal treatment, which followed another degradation route.

Inactivation kinetics of antibiotic resistant Escherichia coli in secondary wastewater effluents by peracetic and performic acids

While disinfection processes have been central for public health protection, new concerns have been raised with respect to their ability to control the spread of antibiotic resistance in the environment. In this study, we report the inactivation kinetics by peracetic and performic acids of a typical indicator, Escherichia coli and its corresponding antibiotic-resistant subpopulation, in secondary settled wastewater effluent. Performic acid always showed greater inactivation efficiency than peracetic acid, whether or not the indicator was Ampicillin-resistant. Observed inactivation data, fitted with an exposure-based inactivation model, predicted very well the inactivation profile of both total and ampicillin resistant Escherichia coli. Notably, the antibiotic resistance percentage decreased significantly in treated wastewater compared to untreated wastewater thus making the peracid-based disinfection processes beneficial in controlling antibiotic resistance in secondary settled wastewater. Moreover, the minimum inhibitory concentration values remained unchanged. Finally, antibiotic-resistant-specific inactivation kinetics were used to predict the disinfection efficiency in continuous-flow reactors under ideal and non-ideal hydraulics thus providing useful information for future design and operation of disinfection process in antibiotic-resistance controlling mode.

Metoprolol and metoprolol acid degradation in UV/H2O2 treated wastewaters: An integrated screening approach for the identification of hazardous transformation products

Advancements on analytical strategies to determine the chemicals present in treated wastewater are necessary to clearly link their occurrence with the ecotoxicity of such effluents. This study describes the development of an integrated screening approach to determine the highest number of pharmaceutical transformation products (TPs) in a single run. The identification of TPs was based on the comparison of detected features with literature sources, compound prediction tools, in-house libraries and reference standards using high-resolution mass spectrometry (HRMS). This integrated approach allowed a better estimation (in silico) of the ecotoxicological contribution of the individual TPs identified. As a proof of concept, this methodology was applied for identification of the TPs generated from metoprolol and its main human metabolite (metoprolol acid) in pure water, hospital wastewater and industrial wastewater treated by UV/H₂O₂. Twenty-four TPs with potential ecotoxicological implications were identified and their presence was pinpointed as a function of the treated wastewater. An integrated screening approach has been developed using four different screening methodologies in the same run. Additionally, the metabolite MTPA has been considered as a target pollutant in UV/H₂O₂ experiments.

Recycled corrugated wire hose cover as biological carriers for greywater treatment in a sequential batch biofilm reactor

Greywater treatment and reuse can be considered a promising option, in particular in water scarcity affected areas. In this work a waste material, namely recycled corrugated wire hose cover, was applied as an alternative and cheap carrier in a sequencing batch biofilm reactor (SBBR) for greywater treatment. The bioreactor performance was studied in terms of organic matter, nitrogen and micropollutant removal. Four operational stages were investigated: i) inoculation of the carriers; ii) greywater treatment with suspended biomass; iii) synthetic and iv) real greywater treatment with inoculated carriers in the SBBR. The SBBR could treat real greywater showing high removal efficiencies for COD (86.5 ± 5.8%), ammonium (98.4 ± 1.4%) and total nitrogen (71.4 ± 8.2%). The obtained efficiencies were similar to the ones obtained with commercial carriers and to other treatments such as MBBR or MBR. In terms of micropollutants, 7 out of 13 detected micropollutants were highly removed (efficiency higher than 85%) while 5 of them (ofloxacin, metoprolol acid, venlafaxine, iopromide and hydrochlorothiazide) were found to be highly recalcitrant to the treatment.

Degradation of malachite green by a pulsed light/H2O2 process

Pulsed light (PL) is a type of photonic technology characterized by intense short light pulses that enhance the speed of photochemical reactions, and which might be useful as light source in advanced oxidation processes. This work aimed to test PL as light source for the degradation of the dye malachite green (MG) by combining PL with H₂O₂. To this end, the effect of dye and H₂O₂ concentrations and pH on the degradation rate of MG was studied and a degradation pathway was proposed. Dye degradation followed a pseudo-first order kinetics; it increased with low initial dye concentration, high H₂O₂ concentration and low pH. Complete decolourization was achieved after 35 light pulses (75 J/cm²), with a degradation rate of 0.0710 cm²/J. The degradation was initiated by the attack of hydroxyl radicals to the central carbon of MG generating 4-(dimethylamino)benzophenone (DLBP) followed by the addition of hydroxyl radicals to the non-amino aromatic ring of DLBP and the demethylation of the amino group. Results indicate that PL technology has potential to be implemented to decrease the environmental impact of dyeing industries.

Use of by-products from integrated steel plants as catalysts for the removal of trichloroethylene from groundwater

The removal of tricholoroethylene (TCE) has been investigated in this work through the Fenton-like process using different catalytic materials obtained from metallic by-products of the steel industry. These materials are the slag produced during the transformation of molten pig iron produced in a blast furnace into liquid steel (SLD), the dry particles (or dust) obtained from the bag filters installed in the coking installations to minimize diffuse emissions (POCA) and the dry particles obtained from the liquid sludge from the scrubber (LHA). This study aims to explore the potential of these materials for being used as permeable catalytic barriers to treat groundwater polluted with trichloroethylene (TCE). The wastes used as catalysts were chemically and physically characterized to determine their composition and porosity. The results of this study point out that among the different catalysts used LHA showed the highest catalytic activity to degrade TCE using hydrogen peroxide. Moreover, LHA was the most efficient catalyst using hydrogen peroxide due to its higher stoichiometric efficiency. It is thus concluded that LHA has a high potential to be combined with hydrogen peroxide in permeable catalytic barriers to remove organic compounds from groundwater.

Influencing factors on the removal of pharmaceuticals from water with micro-grain activated carbon

The removal efficiency of 6 micro-grain AC (μGAC) was examined for 23 selected pharmaceutical compounds, usually found at trace level in municipal wastewater treatment plant (WWTP) effluents. Two different sets of experiments were carried out using distilled water and a real WWTP secondary effluent in order to understand the adsorption mechanisms of pharmaceuticals, including the role of the presence of background organic matter. Physical and chemical properties of μGACs and target pollutants were checked for their potential to predict the pharmaceutical removal. Textural properties of μGACs, and especially the mesopore volume, seemed to play the most important role during the adsorption without background organic matter whereas the chemistry of the μGACs, such as the presence of surface oxygen groups and the point of zero charge, could have more influence in the experiments with WWTP effluent water. Positively charged molecules are better adsorbed due to the influence of the background organic matter and the presence of oxygenated groups in the surface of the μGACs. The UV₂₅₄ removal correlated well with the pharmaceutical removal and it is confirmed as an indicator to control the performance of pharmaceuticals adsorption with μGACs in tertiary treatment.

Elimination study of the chemotherapy drug tamoxifen by different advanced oxidation processes: Transformation products and toxicity assessment

Tamoxifen is a chemotherapy drug considered as recalcitrant contaminant (with low biodegradability in conventional activated sludge wastewater treatment), bioaccumulative, ubiquitous, and potentially hazardous for the environment. This work studies the removal of Tamoxifen from water by advanced oxidation processes, paying special attention to the formation of transformation products (TPs) and to the evolution of toxicity (using the Microtox^® bioassay) during the oxidation processes. Five types of treatments were evaluated combining different technologies based on ozone, hydrogen peroxide and UV radiation: i) O₃, ii) O₃/UV, iii) O₃/H₂O₂ (peroxone), iv) UV and v) UV/H₂O₂. Complete removal of tamoxifen was achieved after 30 min for all the treatments carried out with O₃ while a residual concentration (about 10% of initial one) was observed in the treatments based on UV and UV/H₂O₂ after 4 h of reaction. Eight TPs were tentatively identified and one (non-ionizable molecule) was suspected to be present by using ultra high performance liquid chromatography coupled to high resolution mass spectrometry. An increase of toxicity was observed during all the oxidation processes. In the case of ozone-based treatments that increase was attributed to the presence of some of the TPs identified, whereas in the case of UV-based treatments there was no clear correlation between toxicity and the identified TPs.

Degradation pathways of aniline in aqueous solutions during electro-oxidation with BDD electrodes and UV/H2O2 treatment

In this work, it has been studied the mineralization of aniline, a toxic substance of low biodegradability typically found in many industrial wastewaters, through electro-oxidation using boron doped diamond (BDD) electrodes and photo-oxidation (UV photolysis and UV/H₂O₂ treatments). It was observed that in electro-oxidation and UV/H₂O₂, it was feasible to reach aniline mineralizations higher than 85%. Two different degradation routes have been observed during the aniline oxidation in these two treatments. The first route was the mineralization pathway, in which aniline was oxidized to CO₂, water and nitrate. The second route was the polyaniline pathway in which polyanilines of high molecular weight are formed. The intermediate compounds involved in both degradation routes are different depending on the treatment used. In the electro-oxidation, denitrification processes were also observed. From an economical point of view, electro-oxidation of aniline using BDD electrodes is more interesting than UV/H₂O₂ due it has an 87% lower operational cost. So, electro-oxidation using BDD electrodes seems to be a more suitable technique for the mineralization of wastewater containing aniline than UV or H₂O₂ based technologies.

A key parameter on the adsorption of diluted aniline solutions with activated carbons: The surface oxygen content

A total of 11 different commercial activated carbons (AC) with well characterized textural properties and oxygen surface content were tested as adsorbents for the removal of aniline as a target water pollutant. The maximum adsorption capacity of aniline for the studied AC was from 138.9 to 257.9 mg g(-1) at 296.15 K and it was observed to be strongly related to the textural properties of the AC, mainly with the BET surface area and the micropore volume. It was not observed any influence of the oxygen surface content of the AC on the maximum adsorption capacity. However, it was found that at low aniline aqueous concentration, the presence of oxygen surface groups plays a dominant role during the adsorption. A high concentration of oxygen surface groups, mainly carboxylic and phenolic groups, decreases the aniline adsorption regardless of the surface area of the AC.

UV/H2O2degradation of the antidepressants venlafaxine and O-desmethylvenlafaxine: Elucidation of their transformation pathway and environmental fate

The aim of the present work is to investigate the removal and transformation of the antidepressants venlafaxine (VFX) and its main metabolite O-desmethylvenlafaxine (DVFX) upon advanced oxidation with UV/H2O2 under lab conditions. High-resolution mass spectrometry (HRMS) analyses were carried out by means of ultra-high pressure liquid chromatography (UHPLC)-linear ion trap high resolution Orbitrap instrument (LTQ-Orbitrap-MS) in order to elucidate the different transformation products (TPs) generated. The depletion of both VFX and DVFX was very significant, with the 99.9% of both compounds eliminated after 5 and 30 min of reaction, respectively. Eleven TPs for VFX and six for DVFX were detected and their molecular structures elucidated by means of MS(2) and MS(3) scans, and the corresponding degradation pathways were proposed. The combined ecotoxicity at different treatment times was evaluated by means of bioluminescence inhibition assays with the marine bacteria Vibrio fischeri. Results showed an increase in the ecotoxicity during the UV/H2O2 experiment, especially at those reaction times where the total abundance of TPs was higher.

Advanced oxidation of the antibiotic sulfapyridine by UV/H₂O₂: Characterization of its transformation products and ecotoxicological implications

The aim of the present work is to investigate, under lab-scale conditions, the removal and transformation of the antibiotic sulfapyridine (SPY) upon advanced oxidation with UV/H2O2. High resolution mass spectrometry (HRMS) analyses by means of an ultra-high pressure liquid chromatography (UHPLC)-linear ion trap high resolution Orbitrap instrument (LTQ-Orbitrap-MS) were carried out in order to elucidate the different transformation products (TPs) generated. The abatement (>99%) of the antibiotic was only achieved after 180 min, highlighting its resilience to elimination and its potential persistence in the environment A total of 10 TPs for SPY were detected and their molecular structures elucidated by means of MS(2) and MS(3) scans. Finally, the combined ecotoxicity at different treatment times was evaluated by means of bioluminescence inhibition assays with the marine bacteria Vibrio fischeri.

Assessment of the effect of UV and chlorination in the transformation of fragrances in aqueous samples

The removal and transformation of 15 common fragrance allergens and two polycyclic musks in water samples were studied using UV irradiation and chlorination treatments. The monitoring of the reaction was carried out by a HS-SPME method coupled to GC-MS analysis. Different behaviours were observed depending on the compound and the treatment applied. Elimination experiments showed that all target compounds were affected by at least one of the two treatments. A total of 15 UV transformation products were detected and chemical structures were proposed for five of them. In the chlorination experiments, only galaxolide and benzyl cinnamate transformation products were observed.

Regeneration of siloxane-exhausted activated carbon by advanced oxidation processes

In the context of the biogas upgrading, siloxane exhausted activated carbons need to be regenerated in order to avoid them becoming a residue. In this work, two commercial activate carbons which were proved to be efficient in the removal of octamethylcyclotetrasiloxane (D4) from biogas, have been regenerated through advanced oxidation processes using both O3 and H2O2. After the treatment with O3, the activated carbon recovered up to 40% of the original adsorption capacity while by the oxidation with H2O2 the regeneration efficiency achieved was up to 45%. In order to enhance the H2O2 oxidation, activated carbon was amended with iron. In this case, the regeneration efficiency increased up to 92%.

Optimizing chemical conditioning for odour removal of undigested sewage sludge in drying processes

Emission of odours during the thermal drying in sludge handling processes is one of the main sources of odour problems in wastewater treatment plants. The objective of this work was to assess the use of the response surface methodology as a technique to optimize the chemical conditioning process of undigested sewage sludges, in order to improve the dewaterability, and to reduce the odour emissions during the thermal drying of the sludge. Synergistic effects between inorganic conditioners (iron chloride and calcium oxide) were observed in terms of sulphur emissions and odour reduction. The developed quadratic models indicated that optimizing the conditioners dosage is possible to increase a 70% the dewaterability, reducing a 50% and 54% the emission of odour and volatile sulphur compounds respectively. The optimization of the conditioning process was validated experimentally.

Deciphering the electron transfer mechanisms for biogas upgrading to biomethane within a mixed culture biocathode

This study describes the electron transfer mechanism of a BES fed with the effluent from water scrubbing to improve biogas upgrading.

Integration of advanced oxidation processes at mild conditions in wet scrubbers for odourous sulphur compounds treatment

The effectiveness of different advanced oxidation processes on the treatment of a multicomponent aqueous solution containing ethyl mercaptan, dimethyl sulphide and dimethyl disulphide (0.5 mg L(-1) of each sulphur compound) was investigated with the objective to assess which one is the most suitable treatment to be coupled in wet scrubbers used in odour treatment facilities. UV/H2O2, Fenton, photo-Fenton and ozone treatments were tested at mild conditions and the oxidation efficiency obtained was compared. The oxidation tests were carried out in magnetically stirred cylindrical quartz reactors using the same molar concentration of oxidants (hydrogen peroxide or ozone). The results show that ozone and photo-Fenton are the most efficient treatments, achieving up to 95% of sulphur compounds oxidation and a mineralisation degree around 70% in 10 min. Furthermore, the total costs of the treatments taking into account the capital and operational costs were also estimated for a comparative purpose. The economic analysis revealed that the Fenton treatment is the most economical option to be integrated in a wet scrubber to remove volatile organic sulphur compounds, as long as there are no space constraints to install the required reactor volume. In the case of reactor volume limitation or retrofitting complexities, the ozone and photo-Fenton treatments should be considered as viable alternatives.

Biogas upgrading: optimal activated carbon properties for siloxane removal

A total of 12 commercial activated carbons (ACs) have been tested for the removal of octamethylcyclotetrasiloxane (D4) in dynamic adsorption experiments using different carrier gases and D4 concentrations. Characterization of the ACs included several physical and chemical techniques. The D4 adsorption capacities were strongly related with the textural development of the ACs. Results showed that the optimum adsorbent for D4 is a wood-based chemically activated carbon, which rendered an adsorption capacity of 1732 ± 93 mg g(-1) using 1000 ppm (v/v) of D4 with dry N2 as the carrier gas. When the concentration of D4 was lowered to typical values found in biogas, the adsorption capacity was halved. The presence of major biogas compounds (i.e., CH4 and CO2) and humidity further reduced the D4 adsorption capacity. The polymerization of D4 over the surface of all ACs was found to be relevant after prolonged contact times. The extent of this phenomenon, which may negatively affect the thermal regeneration of the AC, correlated reasonably well with the presence of phenolic and carboxylic groups on the carbon surfaces.

Robust iron coordination complexes with N-based neutral ligands as efficient Fenton-like catalysts at neutral pH

The homogeneous Fenton-like oxidation of organic substrates in water with hydrogen peroxide, catalyzed by six different metal coordination complexes with N-based neutral ligands, was studied at ambient conditions and initial pH 7, employing hydrogen peroxide as the terminal oxidant. At low catalyst concentration, the catalytic oxidative depletion of toluene achieved by selected catalysts was much more efficient than that obtained by the Fenton reagent at pH 3. The influence of pH, the water matrix and the catalyst/hydrogen peroxide concentration were investigated for the oxidation of toluene employing [FeCl2(bpmcn)] (1, bpmcn = N,N'-bis(2-pyridylmethyl)-N,N'-dimethyl-trans-1,2-diaminocyclohexane), the most efficient catalyst of the series. Moreover, the evolution of catalysts [FeCl2(bpmcn)] (1) and [Fe(OTf)2(Pytacn)] (3, Pytacn = 1-(2-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane, OTf = trifluoromethanesulfonate anion) during the course of the reaction was also studied by electrospray ionization mass spectrometry (ESI-MS). The oxidation products derived from toluene oxidation were also analyzed. A plausible mechanism of toluene degradation using [FeCl2(bpmcn)] (1) and [Fe(OTf)2(Pytacn)] (3) as catalysts was proposed, which involves the coexistence of a metal-based path, analogous to that operating in organic media where substrate oxidation is executed by an iron(V)-oxo-hydroxo species, in parallel to a Fenton-type process where hydroxyl radicals are formed.

Adsorption of volatile sulphur compounds onto modified activated carbons: effect of oxygen functional groups

The effect of physical and chemical properties of activated carbon (AC) on the adsorption of ethyl mercaptan, dimethyl sulphide and dimethyl disulphide was investigated by treating a commercial AC with nitric acid and ozone. The chemical properties of ACs were characterised by temperature programme desorption and X-ray photoelectron spectroscopy. AC treated with nitric acid presented a larger amount of oxygen functional groups than materials oxidised with ozone. This enrichment allowed a significant improvement on adsorption capacities for ethyl mercaptan and dimethyl sulphide but not for dimethyl disulphide. In order to gain a deeper knowledge on the effect of the surface chemistry of AC on the adsorption of volatile sulphur compounds, the quantum-chemical COSMO-RS method was used to simulate the interactions between AC surface groups and the studied volatile sulphur compounds. In agreement with experimental data, this model predicted a greater affinity of dimethyl disulphide towards AC, unaffected by the incorporation of oxygen functional groups in the surface. Moreover, the model pointed out to an increase of the adsorption capacity of AC by the incorporation of hydroxyl functional groups in the case of ethyl mercaptan and dimethyl sulphide due to the hydrogen bond interactions.

Coupling anammox and advanced oxidation-based technologies for mature landfill leachate treatment

The aim of this study was to evaluate the suitability to couple anammox process with advanced oxidation processes (AOPs) to treat mature landfill leachate with high nitrogen and non-biodegradable organic matter concentrations (2309±96 mg N-TN L(-1) and 6200±566 mg COD L(-1)). The combination of a partial nitiration-anammox system coupled with two AOP-based technologies (coagulation/flocculation+ozonation and photo-Fenton) was assessed in terms of nitrogen and carbon removal. Total nitrogen removal efficiency within a range of 87-89% was obtained with both configurations without the need of any external carbon source. The COD removal efficiencies attained were 91% with coagulation/flocculation+ozonation and 98% with photo-Fenton. Applying the biological treatment prior to advanced oxidation processes-based technologies reduced the quantity of needed reagents giving attaining higher removal efficiencies. From a basic economical point of view and taking into account the results of this study, the combination of partial nitritation-anammox system with photo-Fenton treatment was more favorable than with coagulation/flocculation+ozonation treatment.

Hydrophobic Fe-zeolites for removal of MTBE from water by combination of adsorption and oxidation

Several zeolites were evaluated as adsorbents for the removal of MTBE from water in a screening process. It was observed that the SiO2/Al2O3 molar ratio is a decisive factor for the adsorption properties, at least in the case of ZSM5 zeolites. ZSM5 zeolites with SiO2/Al2O3 ratios >200 were found to provide the best sorption properties for MTBE. To design a combined sorption/reaction method, regeneration of the loaded zeolites by selected advanced oxidation processes (AOP) was studied: (1) Fenton treatment using H2O2 with dissolved iron salts and (2) heterogeneous Fenton-like oxidation with Fe immobilized on the zeolites. The first was ineffective in regenerating loaded zeolites. However, heterogeneous catalysis using Fe species immobilized on the zeolite by liquid ion exchange was markedly more effective. Although these hydrophobic zeolites have a low ion exchange capacity, resulting in iron loadings of ≤ 0.09 wt %, it was possible to obtain sufficiently active catalysts. Hydrophobic Fe-zeolites can therefore be regarded as promising materials for the removal of MTBE from water, since they allow the combination of efficient adsorption and oxidative degradation of MTBE by H2O2. In contrast to the homogeneous catalysis by dissolved iron ions, these heterogeneous catalysts work at near-neutral pH and can be easily reused. Fe-zeolites as adsorbents/catalysts showed a good stability in both batch and column experiments.

H2O2-based oxidation processes for the regeneration of activated carbons saturated with volatile organic compounds of different polarity

This study reports the sequential regeneration treatment of activated carbons (ACs) saturated with volatile organic compounds (VOCs) of different polarity using H(2)O(2) as oxidizing agent. In this process, VOCs were adsorbed onto the AC and further oxidized by H(2)O(2). A commercial AC was selected and saturated with three different VOCs: two non-polar and hydrophobic VOCs, toluene and limonene, and one polar and hydrophilic VOC, methyl ethyl ketone (MEK). The saturated AC was regenerated with H(2)O(2), and the Fenton reagent for comparison. It was found that regeneration efficiencies obtained with the H(2)O(2) treatment were equal to or even higher than those obtained with the Fenton treatment. The fate of the pre-adsorbed VOCs, once the regeneration process is completed was studied. It was found that this regeneration treatment is limited for non-polar VOCs such as toluene and limonene, as they tend to remain adsorbed onto the ACs after regeneration treatment. Contrarily, MEK tend to be transferred to the bulk phase and react with the generated oxidant species.

Critical evaluation of the 2D-CSIA scheme for distinguishing fuel oxygenate degradation reaction mechanisms

Although the uniform initial hydroxylation of methyl tert-butyl ether (MTBE) and other oxygenates during aerobic biodegradation has already been proven by molecular tools, variations in carbon and hydrogen enrichment factors (ε(C) and ε(H)) have still been associated with different reaction mechanisms (McKelvie et al. Environ. Sci. Technol. 2009, 43, 2793-2799). Here, we present new laboratory-derived ε(C) and ε(H) data on the initial degradation mechanisms of MTBE, ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME) by chemical oxidation (permanganate, Fenton reagents), acid hydrolysis, and aerobic bacteria cultures (species of Aquincola, Methylibium, Gordonia, Mycobacterium, Pseudomonas, and Rhodococcus). Plotting of Δδ(2)H/ Δδ(13)C data from chemical oxidation and hydrolysis of ethers resulted in slopes (Λ values) of 22 ± 4 and between 6 and 12, respectively. With A. tertiaricarbonis L108, R. zopfii IFP 2005, and Gordonia sp. IFP 2009, ε(C) was low (<|-1|‰) and ε(H) was insignificant. Fractionation obtained with P. putida GPo1 was similar to acid hydrolysis and M. austroafricanum JOB5 and R. ruber DSM 7511 displayed Λ values previously only ascribed to anaerobic attack. The fractionation patterns rather correlate with the employment of different P450, AlkB, and other monooxygenases, likely catalyzing ether hydroxylation via different transition states. Our data questions the value of 2D-CSIA for a simple distinguishing of oxygenate biotransformation mechanisms, therefore caution and complementary tools are needed for proper interpretation of groundwater plumes at field sites.

Study of fuel oxygenates solubility in aqueous media as a function of temperature and tert-butyl alcohol concentration

Methyl tert-butyl ether (MTBE) is the most widely used oxygenate in gasoline blending and has become one of the world's most widespread groundwater and surface water pollutants. Alternative oxygenates to MTBE, namely ethyl tert-butyl ether (ETBE), tert-amyl ether (TAME) and diisopropyl ether (DIPE) have been hardly studied yet. The solubility of these chemicals is a key thermodynamic information for the assessment of the fate and transport of these pollutants. This work reports experimental data of water solubility at the range from 278.15 to 313.15K and atmospheric pressure of ethers used in fuels (MTBE, ETBE, TAME and DIPE) due to the strong influence of temperature on its trend. From the experimental data, temperature dependent polynomials were fitted, thermodynamic parameters were calculated and theoretical models were used for prediction. Finally, the tert-butyl alcohol (TBA) influence in the solubility of MTBE and ETBE in aqueous media was studied.

New short aliphatic chain ionic liquids: synthesis, physical properties, and catalytic activity in aldol condensations

This paper reports on the synthesis of new short aliphatic chain ionic liquids and the study of the temperature dependence of density, ultrasonic velocities, and ionic conductivity in the range of 278.15-338.15 K. Fourier transform infrared spectra establishes their simple ionic salt structure. Because of their polarity, the ionic liquids are able to dissolve polar solvents and inorganic salts, all of them showing high tolerance in hydroxylic media. The observed temperature trend of the studied properties points out the special packing of these ionic liquids, as well as the strong influence of the steric hindrance among linear aliphatic residues enclosed in anions and cations. One of them showed a very high melting temperature. A collection of slightly basic ionic liquids were used to test their catalytic activity in several aldol condensation reactions of some carbonyl compounds. The best conversions and selectivities were obtained using single ionic liquids, with no synergetic effects being observed when different concentrations of mixed ionic liquids were used as catalysts. In any case, the ionic liquid can also easily be recycled from reaction media, suggesting a promising method of process design for this kind of reaction.

Measuring and modelling experimental densities and ultrasonic velocities of aromatic and halogenated environmental pollutants

The potential environmental impact of aromatic and halogenated chemicals from the petrochemical and steel industry is of growning concern. The present paper deals with the modelling and experimental determination of density and speed of sound at the range 278.15-323.15 of six aromatic and halogenated compounds (Benzene, Toluene, Ethylbenzene, Fluorobenzene, 2-Fluorotoluene and Chlorobenzene). Fitting equations were applied to the data in order to correlate for later computer based design. The estimation of the studied properties was made by the application of different theoretical procedures. The Mchaweh-Nasrifar-Moshfeghian model (MNM), an equation of state based on the generalized van der Waals theory which combines the Staverman-Guggenheim combinatorial term of lattice statistics with an attractive lattice gas expression and the Free Length Theory showed a good response at the studied conditions.