Robust Photocatalytic MICROSCAFS® with Interconnected Macropores for Sustainable Solar-Driven Water Purification.

Advanced oxidation processes, including photocatalysis, have been proven effective at organic dye degradation. Tailored porous materials with regulated pore size, shape, and morphology offer a sustainable solution to the water pollution problem by acting as support materials to grafted photocatalytic nanoparticles (NPs). This research investigated the influence of pore and particle sizes of photocatalytic MICROSCAFS® on the degradation of methyl orange (MO) in aqueous solution (10 mg/L). Photocatalytic MICROSCAFS® are made of binder-less supported P25 TiO2 NPs within MICROSCAFS®, which are silica-titania microspheres with a controlled size and interconnected macroporosity, synthesized by an adapted sol-gel method that involves a polymerization-induced phase separation process. Photocatalytic experiments were performed both in batch and flow reactors, with this latter one targeting a proof of concept for continuous transformation processes and real-life conditions. Photocatalytic degradation of 87% in 2 h (batch) was achieved, using a calibrated solar light simulator (1 sun) and a photocatalyst/pollutant mass ratio of 23. This study introduces a novel flow kinetic model which provides the modeling and simulation of the photocatalytic MICROSCAFS® performance. A scavenger study was performed, enabling an in-depth mechanistic understanding. Finally, the transformation products resulting from the MO photocatalytic degradation were elucidated by high-resolution mass spectrometry experiments and subjected to an in silico toxicity assessment.

Mechanistic Study of the Formation of Multicomponent Oxide Porous Microspheres (MICROSCAFS®) by Cryo-Scanning Electron Microscopy.

Multicomponent oxide microspheres with interconnected macroporosity (MICROSCAFS®) are new materials with great potential as support materials for photocatalysis, optimized for real life applications and for other uses that are still being explored. They are obtained from an adapted sol-gel process combined with phase separation phenomena that occur within the water droplets of an emulsion. We present here a methodology based on cryogenic scanning electron microscopy (cryo-SEM) that allows, with minimal specimen preparation, the direct and in situ visualization of 'wet' alkoxide-derived microstructures, for the mechanistic study of the complex process of MICROSCAFS® generation. It is simultaneously combined with energy dispersive X-ray spectroscopy (EDS) to visualize phase separation phenomena and study the chemical elemental composition at specific regions of the sample and reaction times.

Multicomponent oxide microspheres with designed macroporosity (MICROSCAFS®): a customized platform for chemicals immobilization.

A novel versatile, easily recoverable, and recyclable material platform is herein presented, consisting of multicomponent oxide microspheres, of silica-titania and silica-titania-hafnia composition, with tailored interconnected macroporosity (MICROSCAFS®). When functionalized or loaded with desired species, they are potential enablers of emerging applications in environmental remediation, among other fields. We combine emulsion templating for the spherical shape of the particles, with an adapted sol-gel technique involving polymerization-induced phase separation by spinodal decomposition. An advantage of our method regards the employed mix of precursors, which prevents the use of specific gelation additives and porogens and allows a high reproducibility of MICROSCAFS®. We present insight into their formation mechanism using cryo-scanning electron microscopy, and a systematic study of the effect of multiple synthesis parameters on the MICROSCAFS® size and porosity. The composition of the silicon precursors has the most significant effect on fine-tuning the pores size, ranging from the nanometer to the micron scale. Mechanical properties are correlated with morphological features. Larger macroporosity (68% open porosity, estimated by X-ray computed tomography) leads to less stiffness, higher elastic recovery, and compressibility values up to 42%. We believe this study creates a base for consistent custom MICROSCAFS® production, with a design for various future applications.

Emulsion Stabilization Strategies for Tailored Isocyanate Microcapsules.

We report on the stabilization of an oil-in-water (O/W) emulsion to, combined with interfacial polymerization, produce core-shell polyurea microcapsules (MCs) containing isophorone diisocyanate (IPDI). These will act as crosslinkers for mono-component adhesives. The emulsion stabilization was evaluated using three types of stabilizers, a polysaccharide (gum arabic) emulsifier, a silicone surfactant (Dabco®DC193), a rheology modifier (polyvinyl alcohol), and their combinations. Emulsion sedimentation studies, optical microscopy observation, and scanning electron microscopy enabled us to assess the emulsions stability and droplet size distribution and correlate them to the MCs morphology. Fourier transform infrared spectroscopy and thermogravimetric analysis revealed the MCs composition and enabled us to evaluate the encapsulation yield. All stabilizers, except DC193, led to spherical, loose, and core-shelled MCs. The rheology modifier, which increases the continuous phase viscosity, reduces the emulsion droplets sedimentation, keeping their size constant during the MCs' synthesis. This allowed us to obtain good quality MCs, with a smaller average diameter, of approximately 40.9 µm mode, a narrower size distribution and 46 wt% of encapsulated IPDI. We show the importance of the emulsion stability to tune the MCs morphology, size, and size distribution, which are critical for improved homogeneity and performance when used, e.g., in natural and synthetic adhesive formulations industry.

Effect of polymer type on the properties of polypropylene composites with high loads of spent coffee grounds.

The main focus of this work is to study the processability and characteristics of highly loaded spent coffee grounds (SCG) thermoplastic polymer composites, for sustainable applications. SCG powder was characterized in terms of size distribution, moisture, morphology and thermal stability. Polymer/SCG composites were prepared by extrusion compounding. Polypropylene (PP) homopolymer and copolymer were used as the polymeric matrix. Upon compounding by extrusion composites were injection moulded and characterized for its physical, morphological and mechanical properties in order to determine the effect of polymer type and filler content. Morphological characteristics of the composites were investigated using optical microscopy and SEM analysis. The results for PP homopolymer showed little deterioration of the mechanical properties when using the highest SCG load. In the case of PP homopolymer, the greatest variations occurred when increasing from 0 to 20 %. With higher SCG loads, the measured properties changed little. PP copolymer showed a more continuous pattern of properties decay with increasing SCG load, especially for tensile strength, elongation at break and impact strength. Regarding PP copolymer, with maximum SCG load, the tensile strength decreased from 26.8 GPa (neat PP) to 10.8 GPa, the elongation at break showed a drop of more than 95 %, while the Young's modulus increased from 800 MPa to 1160 MPa. This research work has shown that SCG can be used as fillers in the preparation of environmentally friendly composites with SCG load up to 60 wt% thus contributing to the reuse of waste generated by the coffee industry.

Is the COVID-19 pandemic accelerating the platformisation of the urban economy?

This paper shows that, while the pandemic lockdown decelerated everyday life, it has also potentiated further acceleration of the platformisation of urban economic sectors. We show this through an empirical qualitative study of the restaurant sector in Lisbon, in which we found that: (i) the digitalisation of three management tasks during the COVID-19 lockdown - namely marketing, customer relationship management, and delivery tasks - was the trigger for the acceleration of the platformisation of the restaurant sector in Lisbon and (ii) restaurant firms had different departure points in terms of the use of digital technologies - which are linked to their location within the city - and these led to different rhythms in the platformisation of restaurants. We conclude that, as the lockdown measures led to a deceleration of social and economic activities, they also promoted further acceleration of economic change, especially under the logic of the platform economy. Additionally, we show that firms unable to engage with digital platforms have been trying to mimic online dynamics through the implementation of non-platformised digital processes, which leads us to consider that the effects of the process of platformisation extend beyond the platform itself.

Macroporosity Control by Phase Separation in Sol-Gel Derived Monoliths and Microspheres.

Macroporous and hierarchically macro/mesoporous materials (mostly monoliths and microspheres) have attracted much attention for a variety of applications, such as supporting or enabling materials in chromatography, energy storage and conversion, catalysis, biomedical devices, drug delivery systems, and environmental remediation. A well-succeeded method to obtain these tailored porous materials relies on the sol-gel technique, combined with phase separation by spinodal decomposition, and involves as well emulsification as a soft template, in the case of the synthesis of porous microspheres. Significant advancements have been witnessed, in terms of synthesis methodologies optimized either for the use of alkoxides or metal-salts and material design, including the grafting or immobilization of a specific species (or nanoparticles) to enable the most recent trends in technological applications, such as photocatalysis. In this context, the evolution, in terms of material composition and synthesis strategies, is discussed in a concerted fashion in this review, with the goal of inspiring new improvements and breakthroughs in the framework of porous materials.

Porous Silica Microspheres with Immobilized Titania Nanoparticles for In-Flow Solar-Driven Purification of Wastewater.

In this paper, inorganic silica microspheres with interconnected macroporosity are tested as a platform for designing robust and efficient photocatalytic systems for a continuous flow reactor, enabling a low cost and straightforward purification of wastewater through solar-driven photocatalysis. The photocatalytically active microspheres are prepared by wet impregnation of porous silica scaffolds with Trizma-functionalized anatase titania (TiO2) nanoparticles (NPs). NPs loading of 22 wt% is obtained in the form of a thin and well-attached layer, covering the external surface of the microspheres as well as the internal surface of the pores. The TiO2 loading leads to an increase of the specific surface area by 26%, without impacting the typically interconnected macroporosity (≈60%) of the microspheres, which is essential for an efficient flow of the pollutant solution during the photocatalytic tests. These are carried out in a liquid medium for the decomposition of methyl orange and paracetamol. In addition to photocatalytic activity under continuous flow, the microspheres offer the advantage that they can be easily removed from the reaction medium, which is an appealing aspect for industrial applications. In this work, the typical issues of TiO2 NPs photocatalysts are circumvented, without the need for elaborate chemistries, and for low availability and expensive raw materials.

Polycaprolactone microcapsules containing citric acid and naringin for plant growth and sustainable agriculture: physico-chemical properties and release behavior.

Plant growth promoting rhizobacteria (PGPR) is an alternative to chemical fertilizers for sustainable, environment friendly agriculture. There is a need to develop strategies to potentiate the interaction between rhizobacteria and plants. Flavonoids and organic acids (components of root exudates) play specific beneficial roles as carbon sources and signal molecules in the plant - rhizobacteria interactions. The goal of this work is to encapsulate signal molecules, namely citric acid and naringin, an organic acid and a flavonoid, respectively, by a biodegradable polymer, polycaprolactone (PCL), in order to maintain the stability and activity of those signal molecules and enable their slow or controlled release over a selected period of time, according to the needs of the plants. This approach is expected to potentiate food crops, namely peanut crop, in adverse environmental conditions (water deficit), by promoting the beneficial interaction between the peanut plant (A. hypogaea) and rhizobacteria. The microcapsules (MCs) are obtained by an emulsion process combined with solvent evaporation technique and are characterized by scanning electron microscopy, thermogravimetry and Fourier transformed infrared spectroscopy. The kinetics of in vitro release of encapsulated molecules, in a period where the uptake of the compound in plants can occur, is studied. The encapsulation synthesis parameters that lead to the best encapsulation process yield and efficiency, as well as to the best final performance in terms of release, are identified. The effect of pH and molecular weight of PCL is found to mediate the release properties of the molecules for different types of soil. PCL 45000 Mw dissolved at 16% in dichloromethane leads to an encapsulation efficiency of 75% and the resulting MCs containing naringin exhibit a slow release profile for 30 days, unmodified by pH, enabling their use in soils of different characteristics. This research makes possible the manufacturing of smart materials for sustainable agriculture practices.

Isophorone Diisocyanate (IPDI) Microencapsulation for Mono-Component Adhesives: Effect of the Active H and NCO Sources.

Polyurea/polyurethane (PUa/PU) shell microcapsules (MCs), containing high loadings of isophorone diisocyanate (IPDI) in the core, were developed to enable the production of mono-component, eco-friendly and safer adhesive formulations for the footwear industry. IPDI microencapsulation was obtained via oil⁻in⁻water (O/W) microemulsion combined with interfacial polymerization. A methylene diphenyl diisocyanate (MDI) compound (a commercial blend of monomeric and polymeric species), with higher reactivity than IPDI and low viscosity, was added to the O phase to competitively contribute to the shell formation, improving its quality. Four different active H sources were tested, aimed at achieving a high encapsulation yield. The successful encapsulation of IPDI was confirmed by Fourier transformed infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), while the MCs' morphology and size distribution were assessed by scanning electron microscopy (SEM). The incorporation of a multifunctional isocyanate silane in the O phase, as "latent" active H source, led to the formation of impermeable PUa/PU-silica hybrid shell MCs with more than 60 wt.% of pure encapsulated IPDI. A proof-of-concept study shows high peeling strength and a structural type of failure of the adhesive joint, revealing an effective IPDI release. These new engineered MCs are found to be promising crosslinkers for mono-component adhesives for high demanding applications.