Helena Passos

• PhD in Chemical Engineering
• Researcher at University of Aveiro

Poultry is a widely consumed meat worldwide; however, its industrial processing generates a significant amount of feather waste. Since the major component of chicken feathers is keratin (90 wt%), this study focused on using acetate-based ionic liquids (ILs) to fully dissolve chicken feathers and recover keratin, using a sustainable and cost-effecti...

The economic advantages of H2SO4 make it the acid of choice for the hydrometallurgical treatment of waste lithium‐ion batteries (LIBs). However, to facilitate the full dissolution of the higher valency metal oxides present in the cathode black mass, a suitable reducing agent is required. Herein, the application of industrial black liquor (BL) obtai...

Bisphenols, and mostly bisphenol A (BPA), are widely used in many consumer products. Due to their toxicity, BPA presents a noteworthy risk to the environment and human health. Despite these...

Recycling spent lithium-ion batteries is vital to ensure the recovery of added-value resources and minimize environmental impact. Herein, an integrated and efficient process is developed for metal recovery from spent cathode powder combining both leaching and transition metal separation in one step. A hydrophobic deep eutectic solvent (DES) is prop...

The widespread occurrence of metals in water bodies has been fueling the development of platforms for removing and recovering these elements. Biosorption has emerged as a potential tool for metal removal from wastewater. Among the available biosorbents, algae have been highlighted as a sustainable and cost-effective sorbent. Despite the blooming in...

The assessment of waste ecotoxicity (hazardous property HP14 in the European Union) is fundamental for proper waste classification and safe application/disposal. Biotests are relevant for evaluating waste complex matrices, but their efficiency is crucial to encourage their adoption at the industrial level. This work aims at evaluating possibilities...

Environmental protection is a central concern regarding municipal solid waste incineration bottom ash (IBA) management, but the assessment of waste Hazardous Property HP14 (ecotoxicity) is still under debate. Civil engineering applications may be a suitable management strategy. This work aimed at evaluating IBA regarding mechanical behaviour and en...

Valorization of wastes rich in valuable compounds is one of the most relevant topics in biorefinery and circular economy. Kiwifruit industry wastes are a potential source of bioactive compounds, such as phenolic compounds, which, in turn, exhibit many biological activities with potential health benefits. With the aim of developing a green approach...

The poultry-processing industry generates large quantities of waste rich in keratin, a fibrous protein representing around 90 wt % of chicken feathers, which is currently disposed of in landfilling or...

Keratin is a biopolymer with high potential for biomaterials production, being principally investigated in hydrogel and film forms for use in tissue-engineering applications. Aiming to find sustainable solvents and develop...

The use of macroalgae, microalgae and cyanobacteria for metal sorption has been widely reported. Still, there are no studies allowing a direct comparison of the performance of these biomasses, especially while evaluating metal competition. The simultaneous sorption of Co²⁺, Cu²⁺, Ni²⁺ and Zn²⁺ present in a multi-elemental solution by six macroalgae...

Although a theoretically extensive number of hydrophobic eutectic mixtures suitable for solvent extraction are obtainable, to date reported mixtures rely on a limited number of chelating groups, namely phosphine oxide, carboxylic acid, and ketones. Herein, a new family of Type V Deep Eutectic Solvents (DES) based on the polypyridyl ligand 1,10-phen...

Marine-derived food wastes mainly include seafood, fish and feed production resources. From crustaceans, traded annually, 6 to 8 million tonnes of valuable shrimp, lobster and/or crab shells are produced worldwide. In this systemic work, the researchers with complementary technical expertise, covering the fields of chemical engineering design, chem...

This review summarizes and critically addresses the advances achieved on the processing of biomaterials, namely films, scaffolds, and nanoparticles, using ionic liquids as alternative solvents. Biomaterials composed of proteins, polysaccharides, and their blends are here considered. Despite their relevance, the low solubility of these compounds in...

Cyanobacteria are indicated as organisms that can possibly support Mars colonization, contributing to the production of oxygen and other commodities therein. In this general context, the aim of this work was to evaluate the ability of three species of cyanobacteria (Anabaena cylindrica, Nostoc muscorum, and Arthrospira platensis) and a green microa...

The factors influencing metal partition in acidic aqueous biphasic systems (AcABS) containing phosphonium-based ILs are still poorly explored. To assess their influence the effect of the IL counter anion, acid and its concentration, and temperature, were systematically evaluated on the extraction of four transition metals (Cu(II), Co(II), Ni(II), a...

Marine-derived food wastes mainly include seafood, fish and feed production resources. From crustaceans, traded annually, 6 to 8 million tonnes of valuable shrimp, lobster and/or crab shells are produced worldwide. In this systemic work, the researchers with complementary technical expertise, covering the fields of chemical engineering design, chem...

Bio-based ionic liquids (ILs) are being increasingly sought after, as they are more sustainable and eco-friendly. Purines are the most widely distributed, naturally occurring N-heterocycles, but their low water-solubility limits their application. In this work, four purines (theobromine, theophylline, xanthine, and uric acid) were combined with the...

An acidic aqueous biphasic system (AcABS) presenting a desired and reversible phase transition with HNO3 concentration and temperature was developed herein as an integrated platform for metal separation. The simple, economical, and fully incinerable (C,H,O,N) AcABS composed of tetrabutylammonium nitrate ([N4444][NO3])+HNO3+H2O was characterized and...

Zwitterionic compounds (ZIs) have been attracting much attention due to their properties. Unlike ionic liquids - constituted by separated ions - the ZI structures with their cations and anions covalently bonded exhibit added complexity and diversity, suggesting that their ecotoxicological behavior should probably not be extrapolated from those of i...

By using amino acids as anions, ten chiral ionic liquids (CILs) composed of tetrabutylammonium or cholinium as cations were synthesized by neutralization reactions and further characterized by assessing their optical rotation, thermophysical properties (melting and decomposition temperatures, density, viscosity and refractive index) and ecotoxicity...

In this work, the aqueous phase diagram for the mixture of the hydrophilic tributyltetradecyl phosphonium ([P44414]Cl) ionic liquid with acetic acid (CH3COOH) is determined, and the temperature dependency of the biphasic region established. Molecular dynamic simulations of the [P44414]Cl + CH3COOH + H2O system indicate that the occurrence of a clos...

The use of hydrophilic zwitterionic compounds (ZI) to act as phase forming components of aqueous biphasic systems (ABS) has been attracting increased interest. Although previous works studied the phase behavior of ZI, there is still a lack of knowledge on the partition behavior of compounds in ZI-based ABS. This work reports a study on the influenc...

The continued electrification of society and the related growing demand for rechargeable batteries requires in turn the elaboration of efficient and sustainable recycling strategies for their recovery and valorization. An important separation relevant to Nickel Metal Hydride (NiMH) and Lithium-Ion battery recycling is the inter-transition elements...

Aqueous two-phase systems (ATPS) have been proposed as platforms for the purification of biomolecules, and the application of adjuvants to tune the properties of ATPS phases and their ability to extract and separate biological products investigated. This work addresses, for the first time, the use of acetonitrile (ACN) as adjuvant in ATPS composed...

The temperature responsive solubility of ionic liquids with ‘bulky’ polar regions, such as tributyltetradecyl phosphonium chloride [P44414]Cl, in acidic aqueous solutions, is elucidated through a combined experimental and computational approach. The temperature effect in the acidic aqueous biphasic system HCl/[P44414]Cl/H2O was characterised in the...

An acidic aqueous biphasic system (AcABS), in which the inorganic salt component of a traditional aqueous biphasic system (ABS) is replaced by the inorganic acid inherently present in typical hydrometallurgical leachate solution, is shown to selectively separate cobalt from nickel, a separation relevant to the recycling of nickel metal hydride (NiM...

A sustainable and flexible approach for the extraction and separation of rhenium and molybdate species based on a polymeric aqueous two-phase system (ATPS) is proposed in which the high metal content in concentrated copper effluents is directly used as the driver of phase demixing. The partition coefficient and selectivity of Re, Mo, and Cu are stu...

Deep eutectic solvents (DES) are an emerging type of green solvents that have been used in aqueous two-phase systems (ATPS). However, its application in ATPS can present some limitations, due to the non-stoichiometric partition between the two aqueous phases of the hydrogen-bond acceptor (HBA) and the hydrogen-bond donor (HBD) that compose the DES....

Waste electrical and electronic equipment (WEEE) is the fastest growing type of waste globally and is an important challenge due to its heterogeneity, intrinsic toxicity and potential environmental impact. However, WEEE also represents an important secondary source of critical and valuable elements and must be viewed as a resource within the contex...

Ionic-liquid-based aqueous biphasic systems (IL-based ABS) have demonstrated exceptional performance in bioseparation processes. However, IL-based ABS are of limited interest for metal extraction as most metals are not stable in their neutral or alkaline pH conditions. In the quest for better extraction systems for metals, the development of IL-bas...

Aqueous biphasic systems (ABS) composed of ionic liquids (ILs) and conventional salts have been largely investigated and successfully used in separation processes, for which the determination of the corresponding ternary phase diagrams is a previous requirement. However, due the large number of ILs that can be prepared and their high structural ver...

Ionic liquid-based acidic aqueous biphasic systems (AcABS) represent a promising alternative to solvent extraction process for the recovery of critical metals in which the substitution of the inorganic salt by an acid allows for the ‘one pot’ approach to the leaching and separation of metals. However, a more fundamental understanding of AcABS forma...

In the past decade it has been demonstrated the remarkable potential of ionic-liquid-based aqueous biphasic systems (IL-based ABS) to extract and purify a large range of valued-added biocompounds. However, the transposal of lab-experiments to an industrial scale has been precluded by a poor understanding of the molecular-level mechanisms ruling the...

Thermoreversible aqueous biphasic systems (ABS) composed of ammonium-based zwitterions (ZIs) and polymers are here disclosed to act as integrated bioreaction-separation processes. The biocatalytic reaction involving laccase occurs in homogeneous media, after which small changes in temperature induce the formation of two phases and the complete sepa...

Novel aqueous multiphase systems (MuPS) formed by quaternary mixtures composed of cholinium-based ionic liquids (ILs), polymers, inorganic salts and water are here reported. The influence of several ILs was studied, demonstrating that a triple salting-out is a required phenomenon to prepare MuPS. The respective phase diagrams and "tie-surfaces" wer...

Novel aqueous multiphase systems (MuPS) formed by quaternary mixtures composed of cholinium-based ionic liquids (ILs), polymers, inorganic salts and water are here reported. The influence of several ILs was studied, demonstrating that a triple salting-out is a required phenomenon to prepare MuPS. The respective phase diagrams and "tie-surfaces" wer...

The use of deep eutectic solvents (DES) as phase forming components of aqueous biphasic systems (ABS) has been proposed, however, it was shown that when dissolved in aqueous solutions, the DES complexes are destroyed and a nonstoichiometric partition of the hydrogen-bond acceptor (HBA) and the hydrogen-bond donor (HBD) between the phases of the ABS...

The ability of water-soluble ammonium-based zwitterions (ZIs) to form aqueous biphasic systems (ABS) in presence of salts aqueous solutions is here disclosed. These systems are thermoreversible at temperatures close to room temperature and further allow the design of their thermal behavior, from an upper critical solution temperature (UCST) to a lo...

Human activities are responsible for the release of innumerous substances into the aquatic environment. Some of these substances can be used as pollution tracers to identify contamination sources and to prioritize monitoring and remediation actions. Thus, their identification and quantification is of high priority. However, due to their presence in...

Although highly relevant to a priori select adequate solvents for a given application, the determination of the hydrogen-bond acidity or proton donor ability of aqueous solutions of ionic liquids is a difficult task due to the poor solubility of the commonly used probes in aqueous media. In this work, we demonstrate the applicability of the pyridin...

Due to their unique properties, in recent years, ionic liquids (ILs) have been largely investigated in the field of analytical chemistry. Particularly during the last sixteen years, they have been successfully applied in the chromatographic and electrophoretic analysis of value-added compounds extracted from biomass. Considering the growing interes...

Among different classes of ionic liquids (ILs), those with cyano-based anions have been of special interest due to their low viscosity and enhanced solvation ability for a large variety of compounds. Experimental results from this work reveal that the solubility of glucose in some of these ionic liquids may be higher than in water - a well-known so...

Deep eutectic solvents (DES) have emerged in the past few years as a new class of solvents with promising applications in several fields. In the present work, the application of DES (formed by binary mixtures of cholinium chloride and carboxylic acids or urea) as phase-forming components of aqueous biphasic systems (ABS) is investigated. The mechan...

The ability to induce reversible phase transitions between homogeneous solutions and biphasic liquid-liquid systems, at pre-defined and suitable operating temperatures, is of crucial relevance in the design of separation processes. Ionic-liquid-based aqueous biphasic systems (IL-based ABS) have demonstrated superior performance as alternative extra...

Aiming at the development of self-buffering and benign extraction/separation processes, this work reports a novel class of aqueous biphasic systems (ABS) composed of ionic liquids (ILs) and organic biological buffers (Good's buffers, GBs). A large array of ILs and GBs was investigated, revealing than only the more hydrophobic and fluorinated ILs ar...

Ionic-liquid-based aqueous biphasic systems (IL-based ABS) have been largely investigated as promising extraction and purification routes. In this context, the determination of their phase diagrams and the physical properties of the coexisting phases are of high relevance when envisaging their large-scale applications. Low viscosities improve mass...

Ethinylestradiol (EE2) is a synthetic hormone that has been recognized as one of the most prominent endocrine disruptors found in the aqueous environment. Nevertheless, the low content of EE2 in wastewater makes its identification/quantification unfeasible – a major drawback for the evaluation of its persistence and environmental impact. In this co...

In the past few years, the number of studies regarding the application of ionic liquids (ILs) as alternative solvents to extract value-added compounds from biomass has been growing. Based on an extended compilation and analysis of the data hitherto reported, the main objective of this review is to provide an overview on the use of ILs and their mix...

The industrial application of ionic liquids (ILs) requires the knowledge of their physical properties and phase behavior. This work addresses the experimental determination of the vapor-liquid equilibria (VLE) of binary systems composed of water + imidazolium-based ILs. The ILs under consideration are 1-butyl-3-methylimidazolium trifluoromethanesul...

Ionic liquids (ILs) with improved hydrogen-bonding acceptor abilities, such as acetate-based compounds, have shown great potential for CO2 capture and biomass dissolution. In this context, the knowledge of the thermophysical properties of acetate-based fluids is essential for the design and scale-up of related processes. However, at this stage, ace...

Bisphenol A is a human endocrine disruptor. Its normally low levels in biological fluids make it difficult to detect via conventional techniques. This work demonstrates the complete extraction of bisphenol A, and its possible concentration up to 100-fold in a single-step procedure, using ionic-liquid-based aqueous biphasic systems. Bisphenol A (BPA...

Albeit ionic-liquid-based aqueous biphasic systems (ABS) have been largely explored as liquid–liquid extractive approaches for a large array of (bio)molecules, the application of biodegradable and nontoxic salts as phase constituents of these systems has been seldom investigated. In this work 15 ionic liquids were evaluated toward their ability to...