Combining photocatalytic collection and degradation of microplastics using self-asymmetric Pac-Man TiO2

Microplastics are a significant environmental threat and the lack of efficient removal techniques further amplifies this crisis. Photocatalytic semiconducting nanoparticles have the potential to degrade micropollutants, among them microplastics. The hydrodynamic effects leading to the propulsion of micromotors can lead to the accumulation of microplastics in close vicinity of the micromotor. Incorporating these different properties into a single photocatalytic micromotor (self-propulsion, phoretic assembly of passive colloids and photocatalytic oxidation of contaminants), we achieve a highly scalable, inherently-asymmetric Pac-Man TiO 2 micromotor with the ability to actively collect and degrade microplastics. The target microplastics are homogeneous polystyrene microspheres (PS) to facilitate the optical degradation measurements. We cross-correlate the degradation with catalytic activity studies and critically evaluate the timescales required for all involved processes

Techniques for Steamflooding improvement

One of the main challenges in developing a process of continuous steam injection is to control the injection profile. Said profile is strongly affected by steam channeling to “thief zones” and the gravitational effect of override, both are characterized by preventing contact of the steam with reservoir zones containing considerable amounts of hydrocarbons thus decreasing the vertical sweep efficiency. These phenomena are favored by some features of the formation such as large thickness and reservoir heterogeneities and may affect the technical and economic feasibility of the project if they are not controlled and / or monitored properly.Several methodologies have been designed to address this problem. Among them are injecting surfactants for the formation of in situ foam, which seeks to reduce the mobility of steam; using thermal gels, for plugging high permeability channels; injection of solvents, used to enhance oil mobility; and water-alternating-steam injection (WASP) for scavenging of both upper and lower zone of the formation. This article collects relevant aspects of the mentioned methods, and a comparison is made in base of the number of applications, incremental production and implementation cost.Keywords: Steamflooding, In Situ Foams, Solvents, High Temperature Gels, Water Alternating Steam.Uno de los principales desafíos en el desarrollo de un proceso de inyección continua de vapor es el control del frente de inyección. Dicho perfil es afectado principalmente por la canalización del vapor por zonas de alta permeabilidad, y el efecto gravitacional de override causado por la diferencia de densidades con los fluidos del yacimiento, los cuales impiden el contacto del vapor con volúmenes considerables de hidrocarburos disminuyendo de esta forma la eficiencia de barrido vertical. Estos fenómenos son favorecidos por algunas características de la formación como los grandes espesores y las heterogeneidades del yacimiento, y de no ser controlados y/o monitoreados correctamente, pueden afectar la viabilidad técnica y económica del proceso.Varias metodologías se han diseñado para hacer frente a esto problemas, entre ellas tenemos la inyección de surfactantes para la formación de espumas in situ, la cual busca reducir la movilidad del vapor; el uso de geles térmicos, para el taponamiento de canales de alta permeabilidad; la inyección de solventes, usado para mejorar la movilidad del aceite; y la inyección de agua alternada con vapor (WASP), para el barrido de la zona tanto superior como inferior de la formación. Este artículo recopila aspectos relevantes de cada una de las técnicas mencionadas, a partir de los cuales es presentada una comparación tomando como criterios la cantidad de aplicaciones, producción incremental y costo de implementación.Palabras clave: Inyección Continua de Vapor, Espumas In Situ, Solventes, Geles Térmicos, Agua Alternada con Vapor

Processi attivati dalla luce per la separazione e la degradazione delle microplastiche comunemente presenti nei sistemi acquatici.

Lo scopo di questo progetto è stato quello di sviluppare e valutare strategie guidate dalla luce per la separazione e la degradazione delle microplastiche comunemente presenti nei sistemi acquatici. Nella prima parte di questo progetto è stato studiato un processo di degradazione fotocatalitica per la degradazione delle microplastiche di polietilene sotto luce visibile a diverse temperature e pH 3. Un fotocatalizzatore di C,N-TiO2 attivo nel spettro visibile è stato sintetizzato attraverso una procedura di sintesi idrotermale utilizzando il liquido extrapalliale delle cozze Mytilus Edulis come fonte di drogaggio di C e N. Gli esperimenti sono stati condotti in una camera di reazione in cui una lampada LED Visibile da 500 W/m2 irradiava il campione dall'alto. Il ruolo delle specie reattive nella degradazione delle microplastiche in polietilene ad alta densità (HDPE) è stato studiato utilizzando scavengers per OH●, h+, O2●− ed e−. I risultati hanno rivelato che la formazione di OH● libero attraverso i percorsi che coinvolgono il e− fotogenerato gioca un ruolo essenziale nel degrado delle microplastiche. Ulteriori studi sono stati condotti per la degradazione fotocatalitica delle microplastiche di polietilene tereftalato (PET) a temperatura ambiente e pH diversi. In questo caso, un fotocatalizzatore di C,N-TiO2/SiO2 è stato sintetizzato utilizzando il liquido extrapalliale delle cozze Mytilus Edulis e Mytilus Galloprovincialis come fonte di drogaggio di C e N. Entrambi i fotocatalizzatori sono stati completamente caratterizzati e sono state confrontate le loro proprietà e attività fotocatalitica. Gli esperimenti fotocatalitici sono stati condotti in una camera di reazione con irraggiamento di luce visibile, a temperatura ambiente, valutando l'influenza del pH 6 e 8 per 120 ore. I risultati suggeriscono che il processo fotocatalitico ha avviato la degradazione delle microplastiche PET, come è stato confermato da una perdita di massa del 9-16%, dalla diminuzione dell'indice di carbonile estratto dagli spettri FT-IR e dai cambiamenti di cristallinità dei campioni di PET. Il foto-fenton è stato anche valutato per la degradazione delle microplastiche in PE sotto la luce solare. Gli esperimenti sono stati eseguiti in un simulatore solare per 9 ore in 1 L di soluzione a pH 2,8 e 100 mg di microplastiche PE. La degradazione è stata seguita da TOC, SEM e FTIR. Un marcato aumento del TOC è stato ottenuto durante gli esperimenti, suggerendo che i composti del carbonio venivano prodotti come risultato della degradazione. Tuttavia, ciò non può essere dimostrato al SEM poiché la rugosità delle microplastiche PE iniziali limitava l'analisi della morfologia superficiale e, sebbene vi fosse una riduzione di alcune bande caratteristiche del PE negli spettri FT-IR, non vi fu alcun nuovo sviluppo di bande carboniliche, che sono un indicatore di degradazione. L'ultima parte del progetto consisteva nello sviluppo di micromotori fotocatalitici a base di TiO2, che sono in grado di separare e degradare le microplastiche quando irradiate da luce visibile e UV. I micromotori sferici a base di TiO2 sono stati drogati utilizzando il fluido extrapalliale delle cozze Mytilus Galloprovincialis, che erano i campioni caratterizzati e confrontati con i campioni non drogati e il fotocatalizzatore C,N-TiO2 ottenuto attraverso la sintesi idrotermale. L'attività fotocatalitica dei semiconduttori è stata testata per la degradazione delle microplastiche di polistirene sotto la luce UV e visibile. I test sono stati eseguiti con i fotocatalizzatori e le microplastiche in film e in dispersione. I risultati del SEM indicano che il micromotore TiO2 drogato ha un'attività fotocatalitica migliorata rispetto al campione non drogato e al fotocatalizzatore C,N-TiO2.The purpose of this project was to develop and evaluate light-driven strategies for the separation and degradation of microplastics commonly present in aquatic systems. In the first part of this project, a photocatalytic degradation process was studied for the degradation of polyethylene microplastics under visible light at different temperatures and pH. A visible active C,N-TiO2 was synthesized through a hydrothermal synthesis procedure using the extrapallial fluid of Mytilus Edulis mussels as the C and N doping source. The experiments were carried out in a reaction chamber in which a 500 W/m2 Visible LED lamp was irradiating the sample from the top. The reactive species’ role in the degradation of high-density polyethylene (HDPE) microplastics was studied using OH●, h+, O2●− and e− scavengers. The results revealed that the formation of free OH● through the pathways involving the photogenerated e− plays an essential role in the MPs’ degradation. Further studies were carried out for the photocatalytic degradation of polyethylene terephthalate (PET) microplastics at ambient temperature and different pH. In this case, a C,N-TiO2/SiO2 was synthesized using the extrapallial fluid of Mytilus Edulis and Mytilus Galloprovincialis mussels as the C and N doping source. Both photocatalysts were completely characterized and their properties and photocatalytic activity were compared. The photocatalytic experiments were also carried out in a reaction chamber with Visible light irradiation, at room temperature, evaluating the influence of pH 6 and 8 for 120 hours. Results suggest that the photocatalytic process initiated the degradation of PET microplastics, as was confirmed by a 9-16% mass loss, the decreasing of carbonyl index extracted from FT-IR spectra, and the changes of crystallinity of PET samples. Photo-fenton was also evaluated for the degradation of PE microplastics under solar light. The experiments were performed in a solar simulator for 9 h in 1 L of pH 2.8 solution and 100 mg of PE microplastics. The degradation was followed by TOC, SEM and FTIR. A marked increase in TOC was obtained throughout the experiments, suggesting that carbon compounds were being produced as a result of degradation. However, this could not be proved by SEM as the rugosity of initial PE microplastics limited the analysis of the surface morphology, and even though there was a reduction of some characteristic bands of PE in the FT-IR spectra, there was no new development of carbonyl bands, which are an indicator of degradation. The last part of the project was developing TiO2-based photocatalytic micromotors, that can separate and degrade microplastics when irradiated by visible and UV light. Spherical TiO2-based micromotors were doped using the extrapallial fluid of Mytilus Galloprovincialis mussels, which were the characterized and compared to the undoped samples and the C,N-TiO2 photocatalyst obtained through the hydrothermal synthesis. The photocatalytic activity of the semiconductors was tested for the degradation of polystyrene microplastics under UV and visible light. The tests were performed with the photocatalysts and microplastics in a film and in dispersion. SEM results indicate that the doped TiO2 micromotor has an improved photocatalytic activity compared to the undoped sample and the C,N-TiO2 photocatalyst

Photocatalytic collection and degradation of microplastics by self-asymmetric Pac-Man TiO2

Microplastics are a significant environmental threat as they are not regularly monitored or removed and the lack of efficient removal techniques further amplifies this crisis. In this direction and many other environmental remediation processes, photocatalytic micro/nanomotors hold vast potential to remove and degrade micropollutants. Unifying the different properties of a photocatalytic micromotor (self-propulsion, phoretic assembly with passive colloids and photocatalytic oxidation of contaminants), we present highly scale-able, inherently-asymmetric Pac-Man TiO2 particles that can actively collect and degrade polystyrene microplastics

Técnicas para el mejoramiento de la inyección continua de vapor

One of the main challenges in developing a process of continuous steam injection is to control the injection profile. Said profile is strongly affected by steam channeling to “thief zones” and the gravitational effect of override, both are characterized by preventing contact of the steam with reservoir zones containing considerable amounts of hydrocarbons thus decreasing the vertical sweep efficiency. These phenomena are favored by some features of the formation such as large thickness and reservoir heterogeneities and may affect the technical and economic feasibility of the project if they are not controlled and / or monitored properly.Several methodologies have been designed to address this problem. Among them are injecting surfactants for the formation of in situ foam, which seeks to reduce the mobility of steam; using thermal gels, for plugging high permeability channels; injection of solvents, used to enhance oil mobility; and water-alternating-steam injection (WASP) for scavenging of both upper and lower zone of the formation. This article collects relevant aspects of the mentioned methods, and a comparison is made in base of the number of applications, incremental production and implementation cost.Keywords: Steamflooding, In Situ Foams, Solvents, High Temperature Gels, Water Alternating Steam.Uno de los principales desafíos en el desarrollo de un proceso de inyección continua de vapor es el control del frente de inyección. Dicho perfil es afectado principalmente por la canalización del vapor por zonas de alta permeabilidad, y el efecto gravitacional de override causado por la diferencia de densidades con los fluidos del yacimiento, los cuales impiden el contacto del vapor con volúmenes considerables de hidrocarburos disminuyendo de esta forma la eficiencia de barrido vertical. Estos fenómenos son favorecidos por algunas características de la formación como los grandes espesores y las heterogeneidades del yacimiento, y de no ser controlados y/o monitoreados correctamente, pueden afectar la viabilidad técnica y económica del proceso.Varias metodologías se han diseñado para hacer frente a esto problemas, entre ellas tenemos la inyección de surfactantes para la formación de espumas in situ, la cual busca reducir la movilidad del vapor; el uso de geles térmicos, para el taponamiento de canales de alta permeabilidad; la inyección de solventes, usado para mejorar la movilidad del aceite; y la inyección de agua alternada con vapor (WASP), para el barrido de la zona tanto superior como inferior de la formación. Este artículo recopila aspectos relevantes de cada una de las técnicas mencionadas, a partir de los cuales es presentada una comparación tomando como criterios la cantidad de aplicaciones, producción incremental y costo de implementación.Palabras clave: Inyección Continua de Vapor, Espumas In Situ, Solventes, Geles Térmicos, Agua Alternada con Vapor

The Role of the Reactive Species Involved in the Photocatalytic Degradation of HDPE Microplastics Using C,N-TiO2 Powders

Microplastics (MPs) are distributed in a wide range of aquatic and terrestrial ecosystems throughout the planet. They are known to adsorb hazardous substances and can transfer them across the trophic web. To eliminate MPs pollution in an environmentally friendly process, we propose using a photocatalytic process that can easily be implemented in wastewater treatment plants (WWTPs). As photocatalysis involves the formation of reactive species such as holes (h+), electrons (e−), hydroxyl (OH●), and superoxide ion (O2●−) radicals, it is imperative to determine the role of those species in the degradation process to design an effective photocatalytic system. However, for MPs, this information is limited in the literature. Therefore, we present such reactive species’ role in the degradation of high-density polyethylene (HDPE) MPs using C,N-TiO2. Tert-butanol, isopropyl alcohol (IPA), Tiron, and Cu(NO3)2 were confirmed as adequate OH●, h+, O2●− and e− scavengers. These results revealed for the first time that the formation of free OH● through the pathways involving the photogenerated e− plays an essential role in the MPs’ degradation. Furthermore, the degradation behaviors observed when h+ and O2●− were removed from the reaction system suggest that these species can also perform the initiating step of degradation

Low environmental impact remediation of microplastics: Visible-light photocatalytic degradation of PET microplastics using bio-inspired C,N-TiO2/SiO2 photocatalysts

: Microplastics (MPs) are plastic particles with sizes between 1 μm and 5 mm with a ubiquitous presence in aquatic ecosystems. MPs harm marine life and can cause severe health problems for humans. Advanced oxidation processes (AOPs) that involve the in-situ generation of highly oxidant hydroxyl radicals can be an alternative to fight MPs pollution. Of all the AOPs, photocatalysis has been proven a clean technology to overcome microplastic pollution. This work proposes novel C,N-TiO2/SiO2 photocatalysts with proper visible-active properties to degrade polyethylene terephthalate (PET) MPs. Photocatalysis was performed in an aqueous medium and at room temperature, evaluating the influence of two pH values (pH 6 and 8). The results demonstrated that the degradation of the PET MPs by C,N-TiO2/SiO2 semiconductors is possible, achieving mass losses between 9.35 and 16.22 %