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)

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

Metal-organic frameworks (MOFs) as novel adsorbents for alternative fuel gas storage - A short review

In this study, recent research papers have been studied, significant factors regarding metal-organic frameworks (MOFs) such as chemistry, crystalline structure, design, production process simplicity, yield optimization, as well as gas adsorption-delivery mechanisms and performance are discussed, and the potential for increased applicability is analyzed in view of a broader implementation of this class of materials as efficient new adsorbents for compressed hydrogen and natural gas storage. Indeed, a zero-carbon emission future, aimed at addressing the crucial problem of global warming and climate change, demands the use of sustainable and clean energy sources. In this context, hydrogen and natural gas are increasingly gaining attention, particularly as promising alternative vehicle fuels. In order to achieve truly sustainable transportation, however, these gases should not only be produced but also stored before their final consumption. Nevertheless, both hydrogen (H2) and natural gas (mainly CH4) possess volumetric energy densities much lower than that of gasoline, which poses a significant challenge regarding the storage of compressed gas in alternative vehicle fuel cells. For overcoming this barrier, an increase in onboard gas storage capacity is needed, in order to attain a driving range equivalent to that of conventional vehicles. One option for increasing the energy density is the gas storage onto a solid surface by physical adsorption through weak van der Waals interactions. MOFs, being considered solid materials for this purpose in recent years, are noteworthy because of their favorable adsorption properties, especially due to their high specific surface, pore volume, and gas affinity adsorption sites, as well as their appropriately tunable chemical composition and microstructure. Indeed, numerous MOFs, composed of a network of metal cations and clusters bridged by organic ligands, and synthesized by different methods ranging from conventional solvothermal synthesis to alternative processing techniques with reduced organic solvent utilization, are reported in literature. Many of them are currently being considered for increasing the hydrogen/natural gas storage capacities, either in relatively moderate-pressure onboard adsorbent-based fuel tanks or in high-pressure compressors at fuel delivery station infrastructures

A ferrous oxalate mediated photo-Fenton system: Toward an increased biodegradability of indigo dyed wastewaters

This study assessed the applicability of a ferrous oxalate mediated photo-Fenton pretreatment for indigo-dyed wastewaters as to produce a biodegradable enough effluent, likely of being derived to conventional biological processes. The photochemical treatment was performed with ferrous oxalate and hydrogen peroxide in a Compound Parabolic Concentrator (CPC) under batch operation conditions. The reaction was studied at natural pH conditions (5–6) with indigo concentrations in the range of 6.67–33.33 mg L−1, using a fixed oxalate-to-iron mass ratio (C2O42−/Fe2+ = 35) and assessing the system's biodegradability at low (257 mg L−1) and high (1280 mg L−1) H2O2 concentrations. In order to seek the optimal conditions for the treatment of indigo dyed wastewaters, an experimental design consisting in a statistical surface response approach was carried out. This analysis revealed that the best removal efficiencies for Total Organic Carbon (TOC) were obtained for low peroxide doses. In general it was observed that after 20 kJ L−1, almost every treated effluent increased its biodegradability from a BOD5/COD value of 0.4. This increase in the biodegradability was confirmed by the presence of short chain carboxylic acids as intermediate products and by the mineralization of organic nitrogen into nitrate. Finally, an overall decrease in the LC50 for Artemia salina indicated a successful detoxification of the effluent

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

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

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