Inês Portugal

Biomass‐Based Polyols through Oxypropylation Reaction

Biomass residues are a potential renewable source for the sustainable production of chemicals, materials, fuels, and energy embodying the so-called biorefinery concept. In this context, agro-forestry and agro-food industry by-products have attracted considerable interest of researchers in academia and industry as a renewable source of polymeric materials. The research developed to date on the valorization of biomass residues by converting them into polyols through oxypropylation is the subject of this review. These bio-based polyols exhibit properties similar to their petrochemical counterparts and, as such, can be used with economical advantage in the production of polyurethanes. The operating conditions of the oxypropylation reaction depend on the biomass and on the desired polyol properties. The discussion of their influence and the economic viability of the process are also presented.

New polyoxometalate-functionalized cellulosic fibre/silica hybrids for environmental applications

Cellulosic fibre/silica hybrid materials functionalized with Keggin-type polyoxometalates ([PV2Mo10O40]5−, [PVMo11O40]4−, ([PMo12O40]3− or [PW12O40]3−) were prepared by a sol–gel method at room temperature. The novel materials are composed of ca. 56 wt% of polysaccharides, ca. 37 wt% of propylamine-modified silica, 2 wt% of polyoxometalate, and 5% of hydration water. The silica network of these hybrids exhibits relatively high degree of condensation being distributed mainly on the surface of the cellulosic fibres as a dense film. The functionalization of silica with polyoxometalates via electrostatic interactions with protonated propylamino groups of modified silica was unambiguously confirmed. Despite their high silica content cellulose/silica hybrids retained basic cellulosic pulp properties—supramolecular and fibrous structure, porosity, relatively low density, etc. The novel bio-based material functionalized with 2% of [PVMo11O40]4− shows particularly high activity towards the oxidation of volatile organic compounds (VOCs) present in urban air thus anticipating future environmental applications.

Inorganic Membranes for Hydrogen Separation

Hydrogen, one of the most promising energy carriers for the future, is currently produced mainly by natural gas reforming or coal gasification, where mixtures containing H2, CO2 and contaminants like CO, H2S and CH4 are obtained. Among other methods, membrane technology has received special attention due to its potential efficiency for hydrogen separation, simplicity of operation, low energy consumption, and because it is environmentally friendly. For this application, the inorganic membranes can be essentially divided into five main families: metallic and proton conducting (dense phases), and silica, zeolite and carbon molecular sieve (porous solids). Over the past 20 years, palladium-based membranes have been the most studied and implemented at industrial level; however, recent advances in other membrane types have received a great deal of attention. This article critically reviews more than 520 publications, highlighting the latest research developments on inorganic membranes for the recovery and purification of hydrogen, with emphasis on their structural characteristics, synthesis, commercial application, drawbacks and challenges. Furthermore, a large compilation of data is provided in Supplementary Material divided according to membrane type.

Influence of Polyphosphoric Acid on the Consistency and Composition of Formulated Bitumen: Standard Characterization and NMR Insights

Over the recent years, bitumen modification with polymers, acids, or mineral fillers has gained relevance to adjust its performance properties. This work reports the use of polyphosphoric acid (PPA) for the modification of formulated bitumen. With this objective, an in-depth literature review on PPA modification was firstly performed. Subsequently, five individual refinery components were selected for the preparation of bitumen blends, namely, asphaltic residue, vacuum residue, and three lube oils extracts. Seven binary/ternary bitumen blends were prepared and then treated with PPA. Afterwards, the five components and the unmodified and PPA-modified bitumen were characterized by standard methods (penetration, softening point, and penetration index), SARA analysis, elemental analysis, and (31)P and (1)H nuclear magnetic resonance (NMR) spectroscopy. The results evidenced higher asphaltenes and lower saturates/resins contents in PPA-modified bitumen. The NMR data suggest that the paraffinic chains became longer, the content of condensed aromatics increased, more substituted aromatic structures appeared, and α-hydrogen in aromatic structures diminished. These findings disclosed the improved consistency and oxidation stability of PPA-modified bitumen blends.

Environmentally Benign Supercritical Fluid Extraction

Abstract Supercritical fluid extraction (SFE), and in particular supercritical carbon dioxide (SC-CO2) extraction, is an environmental-friendly high-pressure extraction technology alternative to conventional solid–liquid extraction. The use of SC-CO2 can provide valuable industrial advantages such as intensification and simplification of the processes, with consequent savings on chemicals, utilities and processing time. Moreover, it may preserve the natural character of the products and even act as enhancer of composition and properties such as antioxidant activity, shelf life, cooking time, etc. Prospective novel applications are expected to emerge at industrial scale in the coming years, extending the valences and scope of SFE and SC-CO2 to novel fields. These topics are addressed in this chapter.

High Pressure Laminates with Antimicrobial Properties

High-pressure laminates (HPLs) are durable, resistant to environmental effects and good cost-benefit decorative surface composite materials with special properties tailored to meet market demand. In the present work, polyhexamethylene biguanide (PHMB) was incorporated for the first time into melamine-formaldehyde resin (MF) matrix on the outer layer of HPLs to provide them antimicrobial properties. Chemical binding of PHMB to resin matrix was detected on the surface of produced HPLs by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Antimicrobial evaluation tests were carried out on the ensuing HPLs doped with PHMB against gram-positive Listeria innocua and gram-negative Escherichia coli bacteria. The results revealed that laminates prepared with 1.0 wt % PHMB in MF resin were bacteriostatic (i.e., inhibited the growth of microorganisms), whereas those prepared with 2.4 wt % PHMB in MF resin exhibited bactericidal activity (i.e., inactivated the inoculated microorganisms). The results herein reported disclose a promising strategy for the production of HPLs with antimicrobial activity without affecting basic intrinsic quality parameters of composite material.

Inorganic Ion Exchangers for Cesium Removal from Radioactive Wastewater

Ion exchange is a proven process for radioactive wastewater decontamination, where inorganic sorbents are ideal due to their thermal, chemical and radiation stability. This review focuses on the removal of Cs+ by inorganic exchangers, viz. zeolites, titanosilicates, hexacyanoferrates metal oxides and hydrous metal oxides, bentonite/clays and the key family of ammonium phosphomolybdates (AMPs). The design of new selective composites is also addressed focusing on those based on AMPs, hexacyanoferrates and titanosilicates/zeolites. Future inorganic Cs+ exchangers will encompass promising solids, like lanthanide silicates, sodium titanates and metal sulfides. The sensing ability derived from the photoluminescence properties of lanthanide silicates and the efficiency of layered gallium-antimony-sulfide materials in acidic and basic solutions disclose considerable potential for real applications. The ion exchange systems are discussed in terms of sorbent capacity and selectivity (with competitors), pH, temperature and solution salinity. The microscopic features of the exchangers and the associated mechanisms (e.g., pore size, counterions radii, dehydration energy of the ions, coordination environments in the solid exchanger, and site accessibility) are always used for interpreting the ion exchange behavior. On the whole, more than 250 publications were reviewed and a large compilation of data is provided in Supplemental Material.

Emerging technologies for the recovery of valuable compounds from coffee processing by-products

Abstract Spent coffee grounds (SCG) and coffee silverskins (CSS) are two high-volume industrial by-products rich in valuable components, such as alkaloids, diterpenic, and phenolic compounds, triglycerides (oils), and polysaccharides. Their recovery yield and purity are highly dependent on the selected extraction method and operating conditions. This chapter discusses recent advances on the following separation technologies: solid–liquid extraction (SLE) using conventional solvents and ionic liquids, supercritical fluid extraction (SFE), subcritical water extraction, ultrasound assisted extraction, and microwave assisted extraction. SLE and SFE are the most mature approaches for the extraction of coffee by-products, although promising results have been reported for the other technologies. Solvents like ionic liquids (ILs) and deep eutectic solvents are expected to play an important role in the near future, along with other approaches, such as pervaporation, nanofiltration, sorption (adsorption and ion exchange), hydrothermal liquefaction, pulsed electric fields extraction, and products synthesis under the scope of nanotechnology. Overall, these methods produce oils/extracts rich in phenolic compounds exhibiting valuable antioxidant activity levels, with encouraging extraction yields. The optimization of both operating conditions and unit’s arrangement is crucial to ensure their technological and economic viability. Currently, a considerable number of scientific studies and patents demonstrate or claim their use for various applications, including dermatological formulations, pest control formulations, growth enhancer substrates for bacterial cultures, biodiesel production, among others.