Sunlight-Driven AO7 Degradation with Perovskites (La,Ba)(Fe,Ti)O3 as Heterogeneous Photocatalysts

Perovskites of the (La,Ba)(Fe,Ti)O3 family were prepared, characterized, and utilized as heterogeneous photocatalysts, activated by natural sunlight, for environmental remediation of Acid Orange 7 (AO7) aqueous solutions. Catalysts were prepared by the ceramic (CM) and the complex polymerization (CP) methods and characterized by XRD, SEM, EDS, and band gap energy. It was found that catalytic properties depend on the synthesis method and annealing conditions. In the photocatalytic assays with sunlight, different AO7 initial concentrations and perovskite amounts were tested. During photocatalytic assays, AO7 and degradation products concentrations were followed by HPLC. Only photocatalysis with BaFeO3 -CM and BaTiO3 -CP presented AO7 removals higher than that observed for photolysis. However, photolysis leads to the formation of almost exclusively amino-naphthol and sulfanilic acid, whereas some of the perovskites utilized form lesstoxic compounds as degradation products, such as carboxylic acids (CA). Partial substitution of Ba by La in BaTiO3 -CM does not produce any change in the photocatalytic properties, but the replacement of Ti by Fe in the La0.1Ba0.9TiO3 leads to reduced AO7 removal rate, but with the formation of CAs. The best AO7 removal (92%) was obtained with BaFeO3 -CM (750 mg L−1 ), after 4 h of photocatalytic degradation with solar radiationinfo:eu-repo/semantics/publishedVersio

Preparation, characterization and environmental applications of SnO2-Sb2Ox films

O sucesso do tratamento eletroquímico de águas residuais depende de um grande número de fatores; em particular, da natureza do material do elétrodo, que influencia fortemente a eficiência do processo. Os materiais de elétrodo são claramente um dos parâmetros mais importantes na otimização dos processos eletroquímicos. A opção por um determinado material de elétrodo é feita em função da sua zona útil de potencial na solução a utilizar. Esta zona de potenciais está limitada por diversos fatores, como a estabilidade estrutural, mecânica, química e eletroquímica do material de elétrodo, a formação na sua superfície de uma camada de uma substância isoladora (passivação), a decomposição do eletrólito suporte, etc. A durabilidade do elétrodo nas condições de trabalho, assim como o seu custo, são igualmente parâmetros a ter em conta. O material de elétrodo ideal para a degradação de poluentes orgânicos deve exibir alta atividade para a oxidação e baixa atividade perante as reações secundárias (por exemplo, evolução de oxigénio). Este trabalho consistiu na preparação de filmes de SnO2-SbOx que sejam estrutural, química, mecânica e electroquimicamente estáveis; estes materiais devem ainda ter tempos de vida útil prolongados, de modo a que possam vir a ser utilizados exaustivamente na degradação de contaminantes, reduzindo assim o seu custo. Ao longo deste trabalho, foram preparados diferentes filmes de óxidos mistos de estanho e antimónio. Um dos métodos utilizado foi a eletrodeposição em camadas alternadas de estanho e antimónio sobre um substrato. Foram testadas deposições diretas sobre o substrato de titânio ou sobre uma camada intermédia de platina ou de cobre. Estas deposições intermédias têm como objetivo otimizar o tempo de vida útil do filme de óxidos. De seguida, e com o objetivo de obter filmes mais finos e uniformes, testou-se a eletrodeposição simultânea de Sn e Sb, tendo utilizado substratos idênticos: Ti; Ti/Pt; Ti/Cu. Deste modo, foram preparadas vários materiais de elétrodos com base em filmes de óxidos de estanho e antimónio, usando os dois métodos de eletrodeposição diferentes e com diferentes camadas intermédias. Para todos os materiais preparados foi realizada a caracterização estrutural, morfológica e eletroquímica do elétrodo, recorrendo-se a várias técnicas, como difração de raios X, microscopia eletrónica de varrimento e voltametria cíclica. Com estes filmes de óxidos, após a caracterização usual, foi efetuado um estudo sobre a reação de evolução de oxigénio, tendo-se determinado a energia de ativação aparente da oxidação da água em cada um dos diferentes materiais. Conclui-se ainda que o fator de rugosidade influencia profundamente a reação de evolução de oxigénio, pois o material com fator de rugosidade superior apresenta menor energia de ativação aparente para a evolução do oxigénio. Os materiais preparados sobre substratos contendo uma camada intermédia de cobre mostraram ter apetência para a evolução do oxigénio, não podendo contudo ser usados na degradação de poluentes orgânicos, pois este processo requer potenciais mais elevados, onde se dá a oxidação do cobre e a desativação do elétrodo. O elétrodo Ti/Pt/SnO2-Sb que apresentava boas características para ser utilizado em eletro-oxidação, foi utilizado na degradação de soluções de 100 mg L-1 de diclofenac, tendo-se obtido remoções de carga poluente de cerca de 50% ao fim de 6 h de ensaio. Para além disso, o material manteve-se e com resultados reprodutíveis ao fim de 200 h de ensaios. O material que ao longo de todos os estudos já descritos mostrou apresentar uma maior estabilidade mecânica, química e eletroquímica, o Ti/Pt/SnO2-Sb2O4, foi usado na degradação de lixiviados de aterros sanitários, que são efluentes com cargas orgânicas e inorgânicas muito elevadas. Este material foi ainda usado em amostras de efluentes simulados contendo ácido húmico e sais inorgânicos. Embora os resultados obtidos para este material em termos de remoção de carga orgânica sejam, em geral, ligeiramente inferiores aos obtidos com outros materiais de ânodo, como o diamante dopado com boro (BDD) e o Ti/Pt/PbO2, os elétrodos de Ti/Pt/SnO2-Sb2O4 provaram ser uma excelente alternativa àqueles dois materiais. Em particular, para a remoção de azoto total verifica-se que o ânodo Ti/Pt/SnO2-Sb2O4 é mais eficiente do que o ânodo de BDD.In this work, SnO2-SbOx films were prepared over different substrates and utilizing different electrodeposition techniques for the deposition of the tin and antimony layers over the substrates, namely alternate and simultaneous depositions. All the mixed oxides prepared were structural, morphological and electrochemically characterized by, respectively, X-ray diffraction, scanning electron microscopy and cyclic voltammetry. To obtain thinner and uniform films, Sn-Sb oxide materials were prepared using the simultaneous and alternate deposition of the metals over several different substrates, namely Ti; Ti/Pt; Ti/Cu. All these materials were fully characterized and used in a thermodynamic study to find the material most suitable for oxygen evolution. It was observed that: Materials roughness depends mainly on the substrates roughness, being Ti/Pt/SnO2-Sb the material with higher roughness; Oxides grown on Ti/Cu substrate presented the lowest potential for oxygen evolution, particularly the material prepared by simultaneous electrodeposition of Sn and Sb; The roughness deeply influences the oxygen evolution potential. Ti/Pt/SnO2-Sb material, prepared by simultaneous Sn Sb electrodepositions, was utilized in a degradation study, using as model pollutant diclofenac. It was observed a good degradation rate of the diclofenac, with the electrode material presenting good mechanical, chemical and electrochemical stabilities. From all the prepared materials, the Ti/Pt/SnO2-Sb2O4 was the anode that presented more stability towards anodic oxidation, as well as the highest lifetime. For this reason, it was chosen to be used in the degradation of very complex real effluents, sanitary landfill leachates, and in the degradation of humic acid. Results were compared with other anode materials, boron-doped diamond (BDD) and Ti/Pt/PbO2. Ti/Pt/SnO2-Sb2O4 electrodes proved to be an excellent alternative to the other materials, although they were not so efficient in the removal of the organic matter. On the other hand, they were more efficient than BDD in the removal of the total nitrogen. The exhaustive utilization of the Ti/Pt/SnO2-Sb2O4 anode, even with sanitary landfill leachates at 700 A m-2, has been showing that it is an excellent option to other electrode materials. However, the use of the platinization step increases its price and an alternative solution should be further attempted

Treatment of aqueous solutions of oxytetracycline by different electrochemical approaches: anodic oxidation, pressurized electro-Fenton and oxidation by electrogenerated active chlorine

The tetracycline group (TCs) includes the most common antibiotics for treatment of both human and animal infections. TCs are resistant to biological degradation; hence, conventional wastewater treatments are unable to remove these contaminants. Here, the utilization of different electrochemical processes, such as electro-Fenton (EF), direct anodic oxidation (AO) and indirect oxidation by electrogenerated active chlorine (EAC), for the treatment of aqueous solutions of oxytetracycline (OTC), which is one of the TCs, was studied. The effect of various operating conditions was evaluated to optimize the selected processes. EAC gave the fastest abatement of OTC, but the lowest removal of TOC and formation of chlorate. However, the utilization of carbon felt cathodes allowed the formation of chlorate to be reduced. AO gave the highest TOC removals, but it required the use of an expensive anode, as BDD, and high cell potentials. EF performed with pressurized-air (5–10 bar) presented intermediate removals of OTC and TOC with respect to AO and EAC and consumed the least energy

Study of the atenolol degradation using a Nb/BDD electrode in a filter-press reactor

[EN] The present paper deals with the atenolol (ATL) degradation by advanced anodic oxidation using a boron-doped diamond anode supported on niobium (Nb/BDD). Cyclic voltammetry performed on this electrode revealed that it presents a high quality (diamond-sp3/sp2-carbon ratio), high potential for OER and that ATL can be oxidized directly and/or indirectly by the electrogenerated oxidants, such as hydroxyl radicals, persulfate ions and sulfate radicals. Electrolysis experiments demonstrated that ATL degradation and mineralization follow a mixed (first and zero) order kinetics depending on the applied current density. At high applied current densities, the amount of OH radicals is very high and the overall reaction is limited by the transport of ATL (pseudo first-order kinetics) whereas for low applied current densities, the rate of OH radicals generation at the anode is slower than the rate of arrival of ATL molecules (pseudo-zero order kinetics). Estimated values of kzero and kfirst based on the assumption of pseudo-zero or pseudo-first order kinetics were carried oud as a function of the supporting electrolyte concentration, indicating that both parameters increased with its concentration due the higher production of sulfate reactive species that play an important role in degradation. Finally, MCE increased with the decrease of current density, due to the lower amount of OH present in solution, since this species could be rapidly wasted in parasitic reactions; and the increase of sulfate concentration due to the more efficient production of persulfate.The authors thank the financial support from the Ministerio de Economía y Competitividad (Spain) under projects CTQ2015-65202-C2-1-R and RTI2018-101341-B-C21, co-financed with FEDER funds. The authors thank to FAPERGS, CAPES, FINEP and CNPQ.Heberle, ANA.; García Gabaldón, M.; Ortega, EM.; Bernardes, AM.; Pérez-Herranz, V. (2019). Study of the atenolol degradation using a Nb/BDD electrode in a filter-press reactor. Chemosphere. 236:1-8. https://doi.org/10.1016/j.chemosphere.2019.07.049S1823

Diclofenac Photodegradation Under Visible Light With (La,Ba)(Fe,Ti)O3 Perovskites

Perovskites BaTiO3 and BaFeO3 were prepared by the ceramic and complex polymerization methods and the substituted perovskites La0.2Ba0.8TiO3, BaFe0.8Ti0.2O3, and BaFe0.6Ti0.4O3 were prepared by the ceramic method. All of them were used as photocatalytic material for the degradation of the pharmaceutical diclofenac under visible light. The best diclofenac degradation results were obtained with the substituted perovskite La0.2Ba0.8TiO3 (46%), prepared by the ceramic method, and with the nonsubstituted perovskite BaFeO3 (43%), prepared by the complex polymerization method. Keywords: visible light, perovskites, photocatalysis, (La,Ba)(Fe,Ti)O3, diclofena

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

Avaliação toxicológica de lixiviados de aterro sanitário tratados usando o crustáceo de água doce Daphnia magna.

Os resíduos sólidos urbanos, gerados em grande escala pela sociedade moderna, precisam de ser corretamente descartados por forma a mitigar o seu impacto ambiental e na saúde pública. Estes resíduos são normalmente depositados em aterros sanitários, e, consequentemente, são gerados lixiviados altamente tóxicos que precisam de ser tratados. Este trabalho tem como objetivo avaliar a eficácia de diferentes tratamentos eletroquímicos na redução da toxicidade de um concentrado de lixiviado de aterro sanitário. O concentrado de lixiviado, resultante da aplicação de um processo de osmose inversa, foi tratado por processos eletroquímicos combinados, eletrocoagulação (EC) seguida de eletro-Fenton (EF) com diferentes intensidades de corrente e com diferentes concentrações iniciais de ferro. A eficácia do tratamento na diminuição da toxicidade foi avaliada através de ensaios de toxicidade aguda com o organismo modelo Daphnia magna. Os resultados obtidos mostraram que os ensaios de EF realizados à densidade de corrente mais alta (200 A m-2) e com uma concentração de Fe inferior (60 mg L-1) permitiram uma diminuição da toxicidade inicial de 61,305 unidades tóxicas (UTs) para 33,195 UTs, correspondente a uma redução da toxicidade de cerca de 46

Phytoremediation as a Sustainable Alternative for Organic Matter Removal From Slaughterhouse Wastewater Pretreated by Immediate One-Step Lime Precipitation

In this study, slaughterhouse wastewater previously treated by immediate one-step lime precipitation was treated using a vertical flow constructed wetland (VFCW). A VFCW pilot scale planted with Vetiveria zizanioides in light expanded clay aggregates was used to study the influence of the organic load applied (3 to 212 g m−2 d−1) and the bed depth of the VFCW (0.35 and 0.70 m) on the organic matter removal (COD). Two VFCWs operated in parallel under continuous flow, and a hydraulic load of around 80 L m−2 d−1 was used. The results indicated that an increase in the organic load decreased COD removal efficiency. The bed depth of the VFCW had a significant influence on the removal of organic matter, with greater removal at high bed depths. For organic loads applied up to 9.5 g m−2 d−1, COD removal efficiencies of 71.4 ± 4.0% and 85.2 ± 3.4% were observed for lower and higher VFCW bed depth, respectively, which met the requirements for water reuse for irrigation. Throughout the tests, Vetiveria zizanioides did not show signs of toxicity, and its growth was substantial. Keywords: slaughterhouse wastewater, vertical flow constructed wetlands, Vetiveria zizanioides, organic matter removal, immediate one-step lime precipitatio

Electrochemical Fenton-based treatment of tetracaine in synthetic and urban wastewater using active and non-active anodes

The electrochemical degradation of tetracaine hydrochloride has been studied in urban wastewater. Treatments in simulated matrix with similar ionic composition as well as in 0.050 M Na2SO4 were comparatively performed. The cell contained an air-diffusion cathode for H2O2 electrogeneration and an anode selected among active Pt, IrO2-based and RuO2-based materials and non-active boron-doped diamond (BDD). Electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF) were comparatively assessed at pH 3.0 and constant current density. The pharmaceutical and its byproducts were oxidized by ¿OH formed from water oxidation at the anode surface and in the bulk from Fenton's reaction, which occurred upon addition of 0.50 mM Fe2+ in all media, along with active chlorine originated from the anodic oxidation of Cl- contained in the simulated matrix and urban wastewater. The PEF process was the most powerful treatment regardless of the electrolyte composition, owing to the additional photolysis of intermediates by UVA radiation. The use of BDD led to greater mineralization compared to other anodes, being feasible the total removal of all organics from urban wastewater by PEF at long electrolysis time. Chlorinated products were largely recalcitrant when Pt, IrO2-based or RuO2-based anodes were used, whereas they were effectively destroyed by BDD(¿OH). Tetracaine decay always obeyed a pseudo-first-order kinetics, being slightly faster with the RuO2-based anode in Cl- media because of the higher amounts of active chlorine produced. Total nitrogen and concentrations of NH4+, NO3-, ClO3-, ClO4- and active chlorine were determined to clarify the behavior of the different electrodes in PEF. Eight intermediates were identified by GC-MS and fumaric and oxalic acids were quantified as final carboxylic acids by ion-exclusion HPLC, allowing the proposal of a plausible reaction sequence for tetracaine mineralization by PEF in Cl--containing medium

Combining chemical with biological oxidation for efficient treatment of chloronitrobenzene in groundwater

2019 Fall.Includes bibliographical references.Chloronitrobenzene (CNB) is a chloronitroaromatic compound widely used in the synthetic production of pharmaceuticals, pesticides, dyes, lumber preservatives, and many other industrial products. CNB has been recognized as a toxic organic contaminant to humans and is recalcitrant to microbial biodegradation in anoxic environments. When receptors are threatened by CNB-contaminated groundwater, regulators may demand immediate remedial approaches, such as advanced oxidation processes (AOPs). While AOPs are effective for the removal of many organic contaminants from water, these techniques are often costly, especially when complete mineralization is the goal. In this study, it was hypothesized that chemical oxidation for the primary purpose of ring cleavage followed by biological oxidation of the generated intermediates is more cost-effective than relying on AOPs only for complete mineralization. Electrochemical oxidation via hydroxyl radicals was chosen as model AOP and performed at various applied potentials and for different treatment durations. Liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC/QToF-MS) revealed that the aromatic ring in CNB is rapidly hydroxylated and cleaved to form dicarboxylic products including muconic acid, succinic acid, malic acid, and maleic acid. Further electrochemical oxidation of these dicarboxylates was slower by about two orders of magnitude. To evaluate the universal biodegradability of the generated intermediates, the electrochemically oxidized samples of CNB were then exposed to a microbial culture enriched from a rhizosphere soil. Results showed that the dicarboxylic ring opening products biodegraded under anoxic conditions within 7 days while aromatic species including CNB, chloronitrophenol, chlorohydroquinone and dihydroxybenzoquinone persisted over 28 days of biological treatment. A comprehensive cost analysis considering both capital costs (electrodes) and operational costs (electric energy) revealed that the most efficient treatment strategy is to apply electrochemical oxidation at a low applied potential around 6 V until complete cleavage of the aromatic ring is achieved. Beyond that, advanced oxidation of the readily biodegradable ring cleavage products becomes uneconomical. Consequently, the coupling of chemical oxidation for persistent parent compounds with biodegradation of transformation intermediates is an efficient approach for the treatment of groundwater contaminated with CNB and likely other aromatic contaminants