Novel hybrid magnetic carbon xerogels for the catalytic wet peroxide oxidation of the antimicrobial agent sulfamethoxazole

The propagation of microcontaminants – such as the antimicrobial agent sulfamethoxazole (SMX) – in urban water cycles has been receiving a great deal of attention from the scientific community, mainly due to major public health concerns about the development of antibiotic resistant bacteria and/or resistance genes. Catalytic wet peroxide oxidation (CWPO) using novel hybrid materials was tested in the degradation of SMX model solutions (500 μg L-1)

Electrochemical oxidation of butyl paraben on boron doped diamond in environmental matrices and comparison with sulfate radical-AOP

The electrochemical oxidation (EO) of butyl paraben (BP) over boron-doped diamond (BDD) anode was studied in this work. Emphasis was put on degradation performance in various actual water matrices, including secondary treated wastewater (WW), bottled water (BW), surface water (SW), ultrapure water (UW), and ultrapure water spiked with humic acid (HA). Experiments were performed utilizing 0.1 M Na2SO4 as the electrolyte. Interestingly, matrix complexity was found to favor BP degradation, i.e. in the order WW ~ BW > SW > UW, thus implying some kind of synergy between the water matrix constituents, the reactive oxygen species (ROS) and the anode surface. The occurrence of chloride in water matrices favors reaction presumably due to the formation of chlorine-based oxidative species, and this can partially offset the need to work at increased current densities in the case of chlorine-free electrolytes. No pH effect in the range 3–8 on degradation was recorded. EO oxidation was also compared with a sulfate radical process using carbon black as activator of sodium persulfate. The matrix effect was, in this case, detrimental (i.e. UW > BW > WW), pinpointing the different behavior of different processes in similar environments

Degradation of propyl paraben by activated persulfate using iron-containing magnetic carbon xerogels: investigation of water matrix and process synergy effects

An advanced oxidation process comprising an iron-containing magnetic carbon xerogel (CX/Fe) and persulfate was tested for the degradation of propyl paraben (PP), a contaminant of emerging concern, in various water matrices. Moreover, the effect of 20 kHz ultrasound or light irradiation on process performance was evaluated. The pseudo-first order degradation rate of PP was found to increase with increasing SPS concentration (25–500 mg/L) and decreasing PP concentration (1690–420 μg/L) and solution pH (9–3). Furthermore, the effect of water matrix on kinetics was detrimental depending on the complexity(i.e., wastewater, river water, bottled water) and the concentration ofmatrix constituents(i.e.,humicacid,chloride,bicarbonate). The simultaneous use of CX/Fe and ultrasound as persulfate activators resulted in a synergistic effect, with the level of synergy (between 35 and 50%) depending on the water matrix.Conversely,couplingCX/FewithsimulatedsolarorUVA irradiation resulted in a cumulative effect in experiments performed in ultrapure water.Part of this work was financially supported by: Project POCI-01-0145-FEDER-006984 - Associate Laboratory LSRELCM funded by FEDER through COMPETE2020—Programa Operacional Competitividade e Internacionalização (POCI)—and by national funds through Fundação para a Ciência e a Tecnologia (FCT). Rui S. Ribeiro acknowledges the FCT individual Ph.D. grant SFRH/BD/ 94177/2013, with financing from FCT and the European Social Fund (through POPH and QREN). Dr. Adrian M.T. Silva acknowledges the FCT Investigator 2013 Programme (IF/01501/2013), with financing from the European Social Fund and the Human Potential Operational Programme.info:eu-repo/semantics/publishedVersio

Environmental sustainability of light-driven processes for wastewater treatment applications

A comparative analysis is presented of light-driven advanced oxidation processes in terms of environmental sustainability. Photochemical oxidation has proven a viable option for treating emerging and priority pollutants at laboratory scale. Nevertheless, as a nascent technology, photocatalysis is yet to be widely applied at large-scale water treatment plants. This paper presents a powerful tool that should enable stakeholders to develop sustainable, large-scale, photocatalytic treatment plants by providing knowledge of environmental sustainability and hotspots (where technological flaws have high environmental impact) and understanding as to how process sustainability can be improved through scenario analyses. The following processes were examined: natural and simulated solar photolysis, solar photo-Fenton without hydrogen peroxide addition (solar/Fe), solar photo-Fenton (solar/Fe/H2O2), photolysis under UV-A irradiation (UV-A), titania-mediated photocatalysis (UV-A/TiO2), photolysis under UV-C irradiation (UV-C), and UV-C treatment with hydrogen peroxide addition (UV-C/H2O2). Actual life cycle inventory data were collected at bench scale, and the environmental performances estimated by means of life cycle assessment. Effective removal of 1 μg of 17α-ethynylestradiol per liter of wastewater, a commonly occurring micropollutant and endocrine disrupting chemical, was used as the functional unit. Solar photolysis exhibited an environmental footprint about 23 times higher than solar/Fe. Solar/Fe/H2O2 minimized the environmental footprint. Being energy intensive, simulated solar irradiation had a much higher (∼5-fold) environmental footprint than natural solar light. UV photolysis exhibited low environmental impact, with UV-C found to be about 3 times more environmentally friendly than UV-A photolysis. Addition of TiO2 to UV-A and H2O2 to UV-C caused their total environmental impacts to decrease by about 97% and 88%, implying that UV-A/TiO2 was better than UV-C/H2O2. In terms of total environmental footprint, the advanced oxidation processes descend in the following order: solar photolysis > UV-A > UV-C > solar/Fe > UV-A/TiO2 > UV-C/H2O2 > solar/Fe/H2O2. The environmental sustainability of all processes was directly proportional to treatment efficiency but inversely proportional to treatment time (due to the large energy input per unit time). Although reagent use (i.e. titania, iron, and hydrogen peroxide) was not associated with high environmental impact, its addition greatly improved process efficiency as well as environmental sustainability. For all examined light-driven processes, the main environmental hotspot was electricity consumption. Introduction of renewable energy sources could reduce the environmental footprint of oxidation processes by up to 87.5%

Activation of sodium persulfate by magnetic carbon xerogels (CX/CoFe) for the oxidation of bisphenol A: Process variables effects, matrix effects and reaction pathways

An advanced oxidation process comprising sodium persulfate (SPS) and a novel magnetic carbon xerogel was tested for the degradation of bisphenol A (BPA), a model endocrine-disrupting compound. The catalyst, consisting of interconnected carbon microspheres with embedded iron and cobalt microparticles, was capable of activating persulfate to form sulfate and hydroxyl radicals at ambient conditions. The pseudo-first order degradation rate of BPA in ultrapure water (UPW) was found to increase with (i) increasing catalyst (25–75 mg/L) and SPS (31–250 mg/L) concentrations, (ii) decreasing BPA concentration (285–14,200 μg/L), and (iii) changing pH from alkaline to acidic values (9–3). Besides UPW, tests were conducted in drinking water, treated wastewater, groundwater and surface water; interestingly, the rate in UPW was always lower than in any other matrix containing several organic and inorganic constituents. The effect of natural organic matter (in the form of humic acids) and alcohols was detrimental to BPA degradation owing to the scavenging of radicals. Conversely, chlorides at concentrations greater than 50 mg/L had a positive effect due to the formation and subsequent participation of chlorine-containing radicals. Liquid chromatography time-of-flight mass spectrometry was employed to identify major transformation by-products (TBPs) of BPA degradation in the absence and presence of chlorides; in the latter case, several chlorinated TBPs were detected confirming the role of Cl-related radicals. Based on TBPs, main reaction pathways are proposed.Z. Frontistis would like to thank the Greek State Scholarships Foundation (IKY) for the financial support of this research through the “IKY Fellowships of Excellence for Postgraduate Studies in Greece e Siemens Programme” in the framework of the Hellenic Republic e Siemens Settlement Agreement. Part of this work was financially supported by: Project POCI-01- 0145-FEDER-006984 - Associate Laboratory LSRE-LCM funded by FEDER through COMPETE2020 e Programa Operacional Competitividade e Internacionalizaç~ao (POCI) - and by national funds through FCT - Fundaçaeo para a Ciencia e a Tecnologia. R.S. Ribeiro acknowledges the FCT individual Ph.D. grant SFRH/BD/94177/2013, with financing from FCT and the European Social Fund (through POPH and QREN). A.M.T. Silva acknowledges the FCT Investigator 2013 Programme (IF/01501/2013), with financing from the European Social Fund and the Human Potential Operational Programme.Z. Frontistis would like to thank the Greek State Scholarships Foundation (IKY) for the financial support of this research through the “IKY Fellowships of Excellence for Postgraduate Studies in Greece e Siemens Programme” in the framework of the Hellenic Republic e Siemens Settlement Agreement. Part of this work was financially supported by: Project POCI-01- 0145-FEDER-006984 - Associate Laboratory LSRE-LCM funded by FEDER through COMPETE2020 e Programa Operacional Competitividade e Internacionalizaç~ao (POCI) - and by national funds through FCT - Fundaçaeo para a Ciencia e a Tecnologia. R.S. Ribeiro acknowledges the FCT individual Ph.D. grant SFRH/BD/94177/2013, with financing from FCT and the European Social Fund (through POPH and QREN). A.M.T. Silva acknowledges the FCT Investigator 2013 Programme (IF/01501/2013), with financing from the European Social Fund and the Human Potential Operational Programme.info:eu-repo/semantics/publishedVersio

Solar Photocatalytic Degradation of Bisphenol A on Immobilized ZnO or TiO2

The removal of bisphenol A (BPA) under simulated solar irradiation and in the presence of either TiO2 or ZnO catalysts immobilized onto glass plates was investigated. The effect of various operating conditions on degradation was assessed including the amount of the immobilized catalyst (36.1–150.7 mg/cm2 for TiO2 and 0.5–6.8 mg/cm2 for ZnO), initial BPA concentration (50–200 μg/L), treatment time (up to 90 min), water matrix (wastewater, drinking water, and pure water), the addition of H2O2 (25–100 mg/L), and the presence of other endocrine disruptors in the reaction mixture. Specifically, it was observed that increasing the amount of immobilized catalyst increases BPA conversion and so does the addition of H2O2 up to 100 mg/L. Moreover, BPA degradation follows first-order reaction kinetics indicating that the final removal is not practically affected by the initial BPA concentration. Degradation in wastewater is slower than that in pure water up to five times, implying the scavenging behavior of effluent’s constituents against hydroxyl radicals. Finally, the presence of other endocrine disruptors, such as 17α-ethynylestradiol, spiked in the reaction mixture at low concentrations usually found in environmental samples (i.e., 100 μg/L), neither affects BPA degradation nor alters its kinetics to a considerable extent

PHOTOCATALYTIC DEGRADATION OF 4-TERT-BUTYLPHENOL USING SOLAR LIGHT RESPONSIVE AG2CO3

In this work, Ag2CO3 was prepared via a solution-based method and was further characterized by XRD, Raman spectroscopy, SEM/EDS analysis, and UV-VIS spectroscopy. SEM results revealed the formation of micro-sized particles with a rectangular shape. The photocatalytic activity of the catalyst was evaluated in the degradation of 4-tert-butylphenol (4-t-BP) under simulated solar light irradiation. The effects of 4-t-BP initial concentration (2.5–10 ppm), catalyst dosage (100–300 mg/L), different types of lamp sources, and water matrix were investigated. Complete 4-t-BP (5 ppm) degradation was achieved after 60 min by Ag2CO3 (200 mg/L). The effect of anions such as CO32−, HCO3−, NO3−, and Cl- in the concentration range of 100–300 mg/L was also studied. CO32− promoted the photocatalytic degradation process, while HCO3− and NO3− exhibited an inhibition effect, which was marked with increasing HCO3− and NO3− concentrations. The presence of Cl− at the concentration of 100 mg/L increased 4-t-BP degradation, but higher concentrations inhibited the photocatalytic reaction. Cyclic experiments showed that the catalyst practically retained its catalytic activity toward 4-t-BP degradation after three successive experimental runs. Keywords: 4-tert-butylphenol; degradation; heterogeneous photocatalysis; solar ligh

Emerging advanced oxidation processes for the elimination of micro-pollutants

Emerging advanced oxidation processes for the elimination of micro-pollutant