José António Gamelas

University of Coimbra | UC · Department of Chemical Engineering

Cactus cladodes have been emerged as one of the most popular plant-based flocculants. They have been listed as a promising natural alternative to the noxious synthetic flocculants. However, practical application of this bio-flocculant is still hampered by some questions concerning their formulations’ stability, active agents therein and their flocc...

Cellulose nanofibrils (CNFs) are particles with a high aspect ratio. Typically, chemically pre-treated CNFs (containing anionic or cationic charged groups) consist of long fibrils (up to 2 μm) with very low thickness (less than 10 nm). Derived from their high aspect ratio, CNFs form strong hydrogels with high elasticity at low concentrations. Thus,...

Nanocelluloses have gained significant attention in recent years due to their singular properties (good biocompatibility, high optical transparency and mechanical strength, large specific surface area, and good film-forming ability) and wide-ranging applications (paper, food packaging, textiles, electronics, and biomedical). This article is a compr...

Cellulose nanofibrils (CNFs) are materials with high aspect ratio. Typically, TEMPO-oxidised, or cationic CNFs consist of long fibrils (up to 2 μm) with very low thickness (less than 10 nm). Derived from their high aspect ratio, CNFs form strong hydrogels with high elasticity at low concentrations. Thus, CNF suspensions appear as an interesting rhe...

Nanocelluloses have gained significant attention in recent years due to singular properties (good biocompatibility, high optical transparency and mechanical strength, large specific surface area and good film-forming ability) and wide-ranging applications (paper, food packaging, textiles, electronics and biomedical). This article is a comprehensive...

Gas barrier properties are very relevant in composite materials for applications so diverse such as food packaging, electronics, or old document restoration. In the present work, four different types of cellulose nanofibres (CNFs), two types of clay minerals used individually (sepiolite) or combined (sepiolite + kaolinite), and the influence of pH,...

Nanocelluloses have gained increasing attention over the years due to their attractive intrinsic properties, such as high strength and stiffness, high biocompatibility, good film-forming ability, easy surface functionalization, tunable optical properties, etc. With these unique features, nanocelluloses have the potential to be applied in a wide ran...

In sugar production, polyacrylamide-based anionic flocculants are added for juice treatment, the main objective being to remove impurities that affect the quality of the sugar. However, if they remain in the final product, those polymers can present carcinogenic and neurotoxic actions besides contaminating the soils where the waste is discharged. T...

Bacterial nanocellulose (BNC), due to its inherent nanometric scale and strength properties, can be considered as a good candidate to be used in papermaking. This work explored the possibility of using it in the production of fine paper as a wet-end component and for the paper coating. Filler-containing handsheet production was performed with and w...

The dispersion state and the efficiency of the mixture of the different components in a composite film have an important impact on its mechanical and optical properties. In the present work, the impacts of different dispersion treatments on the disaggregation state of fibrous clay particles in water, and on the properties of related cellulose nanof...

The selective extraction and recovery of different lignocellulosic molecules of interest from forestry residues is increasing every day not only to satisfy the needs of driving a society toward more sustainable approaches and materials (rethinking waste as a valuable resource) but also because lignocellulosic molecules have several applications. Fo...

Cellulose nanofibrils (CNFs) are nanomaterials with promising properties to be used in food packaging and printed electronics, thus being logical substitutes to petroleum-based polymers, specifically plastics. CNFs can be combined with other materials, such as clay minerals, to form composites, which are environmentally friendly materials, with acc...

An efficient and eco-friendly process for lignocellulosic biomass fractionation is essential for the production of high value-added bioproducts from biomass. The present work aimed to obtain cellulose-rich materials from the wood of an invasive tree species (Acacia dealbata) using an appropriate choice of ionic liquids (ILs) and deep eutectic solve...

The purpose of this work was the valorization of wood/wastes of two invasive tree species, namely Acacia dealbata and Ailanthus altissima, in the production of polyelectrolytes as high value-added products for a range of applications. Kraft cooking of wood chips followed by the introduction of quaternary ammonium groups into the cellulose backbone...

Wood/wastes from invasive tree species Acacia dealbata and Ailanthus altissima were used to produce high-value added nanocellulose. Firstly, bleached pulps were produced from the wood of these tree species after kraft cooking. Afterwards, the resultant pulps were pre-treated by TEMPO-mediated oxidation (Acacia dealbata) or enzymatic hydrolysis (Ail...

The surface properties of two sepiolite samples and one palygorskite sample were compared using inverse gas chromatography (IGC). Samples were previously conditioned at appropriate temperatures for the removal of all zeolitic water. Dispersive (or Lifshitz–van der Waals) component of the surface energy (γsd), specific interactions (−ΔGas) with π el...

Palygorskite is a natural fibrous clay mineral that can be used in several applications, for which colloidal stability in aqueous suspensions is a key point to improve its performance. In this study, methods of magnetic stirring, high-speed shearing, and ultrasonication, as well as different chemical dispersants, combined with these methods, namely...

Modification of cellulosic-rich materials for the production of cellulose-based polyelectrolytes (PELs) can bring several benefits, such as high biodegradability and low or no toxicity, for numerous applications, when compared with the use of traditional, synthetic PELs. Moreover, cellulose-based PELs originating from wood wastes, contribute to the...

To allow the use of fibrous-like clays, as sepiolite, in different applications, their disaggregation and the formation of stable suspensions are crucial steps to enhance their performance significantly, e.g., in cellulose nanofibrils/clay composite formulations, enabling an adequate mixture of the matrix and filler individual components. Three dis...

Abstract: Dye invasion in wastewaters is undeniably one of the crucial environmental concerns in addition to the supplement of toxic synthetic chemical flocculants used for color removal using the conventional coagulation-flocculation process. With the aim to improve the flocculation stage in terms of reagents safety and ensure dyes removal, the pr...

The goal of this study is to find a practicable way to recycle cuttlebone waste in the production of lime. It was studied the behavior of calcium oxide obtained from the calcination of this waste at 900, 1000 and 1100 ºC and, after wet slaking, the produced lime was characterized. All the results were compared to calcium oxide or to hydrated lime o...

The use of nanocelluloses is being conducted for the most diverse applications. Their performance as coating agent has been mainly explored to improve barrier properties, as they emerge as perfect candidate for plastic substitution, but it is also important to explore their potential to improve printing quality. In the present work, the influence o...

The present work intends to study the variations in the rheological properties and aggregation behaviour of TEMPO-oxidised cellulose nanofibrils (CNF) aqueous suspensions, as a function of changes in concentration and systematic changes in the pH, by addition of acids with different anions. It was found that CNF suspensions form strong gels at mass...

Nanocelluloses are being explored and produced at an impressively increasing pace. Due to their good characteristics as reinforcement agent, their application in the most diverse fields has proven to be very beneficial. Their use in papermaking has been investigated in several studies, but the industrial implementation is still in a preliminary sta...

A sensor consisting of an optical fibre with the exposed tip coated with the polyoxometalate salt [(C4H9)4N]4H[PMo10V2O40], specially designed to be insoluble in water, which UV-Vis spectrum changed in contact with formaldehyde, is presented. The sensor limit of detection for formaldehyde was 0.2 mg L-1, and the limit of quantification was 0.6 mg L...

In wastewater treatment, flocculation is a widely used solid/liquid separation technique, which typically employs a charged polymer, a polyelectrolyte (PEL). Polyelectrolytes features, such as charge type, charge density and molecular weight, are essential parameters affecting the mechanism of flocculation and subsequent floc sedimentation. The eff...

Tannin extracts from the bark of Acacia mearnsii and wood of Schinopsis balansae, commonly known as Quebracho, were employed. These were modified at laboratory sale via the Mannich aminomethylation with formaldehyde and dimethylamine hydrochloride. Some reaction conditions were varied, namely the formaldehyde dosage and reaction time, while keeping...

Modification of cellulosic-rich materials such as Eucalyptus wood waste and production of cellulose-based polyelectrolytes (PELs) presents several advantages for a variety of applications, when compared to the utilization of synthetic PELs, due to the nature, availability, high biodegradability and low or no toxicity of cellulosic materials. Moreov...

Scaffolds are of paramount importance in tissue engineering, providing support for cell attachment and allowing proliferation or differentiation, and production of extracellular matrix. Their surface properties are of major interest since in great part, they determine the biological response to the scaffold. In the present work, three chitosan‐base...

The present work aimed at valorizing marine bivalve shells. First, clam, mussel, edible cockle, wedge, razor, oyster, dog cockle and scallop shells wastes were thoroughly characterised for their mineralogical, chemical and thermal properties. Then, the materials were calcined at 1000 °C, milled and sieved to lower than 0.250 mm. The obtained calciu...

Wood-based polyelectrolytes, produced from renewable and biodegradable sources, can be considered as more environmentally friendly flocculation agents for the wastewater treatment compared to the traditional synthetic flocculants. The aim of this study was to produce new natural-based polyelectrolytes (bio-PELs), water-soluble, cationic cellulose-b...

Nanocelluloses have been increasingly used in composites since their reduced size, high aspect ratio and stiffness confer great strength to the materials. In papermaking, it has been proved that harsh and expensive chemical pre-treatments to generate nanofibrils, such as TEMPO-mediated oxidation, are not the most favourable and therefore the use of...

Biopolymers-based composites are, in general, environmentally friendly materials, which can be obtained from renewable sources. Some of them can also present promising properties to be used in food packaging and electronic devices, being thus logical substitutes to petroleum-based polymers, specifically plastics. Cellulose nanofibrils (CNF) obtaine...

The papermaking industry competitiveness has been exponentially increasing. In order to improve the paper properties, processes have to be optimized in such a way that new horizons, such as the synthesis of new materials, are in sight. The present paper deals with the production of cellulose nanofibrils (CNF) from bleached Eucalyptus kraft pulp by...

In order to close the water cycle in pulp mills with condensates instead of fresh water, the malodorous/hazardous volatile compounds and colored substances have to be removed by appropriate efficient methods. In the present work, the condensate from the evaporation of black liquor (BL) from a kraft mill was purified by a batch adsorptive process by...

The wastewater generated from many industries contains suspended and dissolved solids, including organic and inorganic particles, metals and other impurities. Direct flocculation is regularly used to neutralize the charge of the colloidal particles and bridge the destabilized particles together to form flocs, in a cost and time-effective way. This...

Eggshells wastes are produced in huge amounts worldwide. The recycling or valorization of this waste, which otherwise is usually disposed in landfills, represents an opportunity within a circular economy perspective. In the present work, the potential of chicken eggshell waste to produce calcitic lime was explored. After collection from an industry...

The surface of a thermomechanical pulp (TMP), containing 26 wt% of lignin, was modified by silanization with trichloromethylsilane (TCMS) via chemical vapor deposition, and thoroughly analyzed for its physicochemical properties by inverse gas chromatography (attenuated total reflection-Fourier transform infrared spectroscopy and X-ray photoelectron...

Bark tannin extract from Acacia mearnsii (Mimosa ME) was modified at laboratory and pilot plant scales via the Mannich condensation reaction using formaldehyde and dimethylamine hydrochloride. Several conditions were varied during the modification procedure (heating rate, formaldehyde dosage, and Mannich solution activation time) to evaluate their...

The main objective of this work was to investigate the possibility of producing new polyelectrolytes (flocculants) synthesized using health-friendly ingredients. A well-known copolymer used in water treatment, poly(acrylamide-co-2-(acryloyloxy)ethyltrimethyl ammonium chloride), was prepared by inverse-emulsion polymerization using new alternative o...

Olive oil production involves a significant annual release of industrial olive oil mill effluent (OME) to the environment. These discharges bring serious environmental problems since they are extremely hazardous for the aquatic environment due to their organic matter and high turbidity levels. The present study comprises the development of new, hyd...

A new method for the quantification of acetaldehyde in a water matrix, namely commercial ciders, was developed using solid phase micro-extraction (SPME) followed by detection with a coated acoustic wave sensor. The sensitive coating was a polyoxometalate salt specially synthesised for this application, a compound tailored to be insoluble in water....

Natural-based polyelectrolytes (PELs), with all the advantages coming from being produced from renewable and biodegradable sources, are a potential solution for the removal of dyes from wastewater. In this work, surplus Eucalyptus bleached cellulose fibres from a paper mill were modified to increase the charge and solubility of cellulose. First, re...

Two functionalized xylans, namely a carboxymethyl xylan (CMX) and a 2-dodecenyl succinic anhydride-modified xylan (X-2-DSA) were, i) synthesized from beechwood xylan (BX) and characterized for their structural properties, thermal behaviour and molar mass and, ii) used in the production of paper/xylan laminates for food packaging. Films prepared fro...

In the present study, the surface chemistry of fibres from different sources (groundwood, cotton linters, eucalyptus sulphate and a mixture of pine sulphate and spruce sulphate) was initially assessed via inverse gas chromatography. Significant differences were revealed among the four fibre types, especially between groundwood and the other three w...

In this work, cellulose nanofibrils (CNF) were produced from a Eucalyptus globulus bleached kraft pulp by TEMPO-mediated oxidation and mechanical homogenisation, and their effects in papermaking, namely filler flocculation and retention, dry and wet-web strength and structural properties, were studied in detail. Cellulose nanofibrils possessing 0.6...

In this work, the successful derivatization of a beechwood xylan (BX) by carboxymethylation and hydroxypropylation was achieved aimed to produce bio-based films. Carboxymethyl xylan (CMX) and hydroxypropyl xylan (HPX) with a substitution degree of 0.3 and 1.1, respectively, as determined by ¹H NMR, were synthesised. The xylan's characterization by...

Cellulose fibres were first functionalized on the surface by silanization with trichloromethylsilane in an optimized gas-solid reaction and the occurrence of the reaction assessed by ATR-FTIR. Then, changes in the physicochemical surface properties of the material were thoroughly assessed by using inverse gas chromatography (IGC) and X-ray photoele...

Catalytic efficiency of tetrabutylammonium salts of sandwich tungstophosphates B‐α‐[M4(H2O)2(PW9O34)2]ⁿ⁻, M = CoII, MnII, FeIII, was studied in the oxidation of (R)-(+)-limonene, geraniol, linalool, linalyl acetate, carveol, and cis-cyclooctene with hydrogen peroxide, in acetonitrile. Oxidation of (R)-(+)-limonene gave limonene-1,2-diol as main pro...

Mineral fillers have been widely used in papermaking, especially in printing and writing papers, since they add positively to sheet formation, brightness, opacity and printability besides lowering furnish cost. The main drawback of incorporating inorganic fillers in paper is, however, the decrease in the fibre-to-fibre bonding, which disturbs the p...

Cellulosic wastes from paper mills or other wood wastes from various industries are becoming one of the most promising alternative sources of chemicals for further modification. One of the potential added values is the production of natural based polyelectrolytes (PEL) with all the advantages that come from their renewable and biodegradable source,...

High concentrations of 5-hydroxymethylfurfural (HMF) in honey provide an indication of overheating under inappropriate storage conditions or aging. Conventional methods for determining HMF are cumbersome and require expensive equipment or hazardous reagents. Hence the aim of this study was to propose a new analytical tool for HMF determination in h...

Xylan (the most common hemicellulose in wood and annual plants) and xylan derivatives have a very wide field of uses for which physico-chemical surface properties play an important role (e.g. in composites or barrier materials). In the present work, for the first time, inverse gas chromatography (at infinite dilution conditions) was used to assess...

The results of the papermaking tests performed in paper sheets produced in a pilot paper machine using Eucalyptus globulus bleached kraft fibres and a new filler of silica-modified PCC obtained by the sol-gel method are presented. This new filler proved already to be advantageous at lab scale and its performance is now evaluated at a pilot scale. I...

The physicochemical surface properties of precipitated calcium carbonate (PCC) modified with silica by sol-gel method were evaluated using inverse gas chromatography and compared to those of the original PCC. The modification of the surface of PCC crystals by a dense film of silica provided a slight decrease of the dispersive component of the surfa...

The ability to increase the filler content of paper without significantly sacrificing its mechanical strength is of high interest for papermakers. In this work, three samples of ground calcium carbonate (GCC), differing in size and in brightness, modified with silica via the sol-gel method, were used as fillers in papermaking. Handsheets were produ...

Cellulose/silica hybrid material produced by a sol-gel method from cellulosic fibres and silica precursors (tetraethoxysilane and 3-aminopropyltriethoxysilane) was functionalized with α-[SiW9O37RuIII3(H2O)xCl3-x](10-x)- (Ru-POM), and thoroughly characterised by 13C and 29Si solid state NMR, FTIR spectroscopy, UV-vis reflectance spectroscopy, X-ray...

The surface modification of papermaking fillers with compounds that promote a better bonding with the cellulosic fibres is nowadays one of the strategies used to increase the filler content in paper without sacrificing the mechanical properties. In this study precipitated calcium carbonate (PCC) was surface coated with poly(diallyldimethylammonium)...

Composites of nanocellulose with layered silicates have recently emerged as a new type of composite materials offering superior strength, as well as thermal and gas barrier properties. These organic-inorganic hybrid composites with a nacre-like structure can be obtained from renewable resources and are environmentally friendly. They can potentially...

The adhesion and surface properties of nanocelluloses are an important issue to consider when using this material for composites production, in food packaging or coatings, as well as for determining the influence of added functional groups. In the present work, the surface properties of two nanofibrillated celluloses obtained by mild 2,2,6,6-tetram...

The morphological properties of cellulose nanofibrils obtained from eucalyptus pulp fibres were assessed. Two samples were produced with the same chemical treatment (NaClO/NaBr/TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) oxidation), but distinct mechanical treatment intensities during homogenization. It was shown that the nanofibrils produ...

The present work aimed characterizing in a systematic way the surface of metakaolinitic materials produced by calcination of a kaolinitic clay at different temperatures and to study the effect of grinding on the surface properties of metakaolinitic materials. Using X-ray photoelectron spectroscopy, it was found for all materials a Si/Al atomic rati...

One way of increasing the filler content in paper without sacrificing the mechanical properties is based on the modification of the filler surface with compounds that promote a better bonding with the cellulosic fibres. In this context, sodium alginate was deposited at the surface of precipitated calcium carbonate (PCC) as a first layer and alterna...

The increase of filler content in paper without significantly sacrificing the paper mechanical resistances is of high interest for papermakers. In this work, precipitated calcium carbonate (PCC) modified with silica was used as filler for papermaking. Handsheets based on a eucalyptus kraft pulp furnish with different amounts of the modified filler,...

The present study reports the development of a new generation of bio-based nanocomposite proton exchange membranes based on bacterial cellulose (BC) and poly(4-styrene sulfonic acid) (PSSA), produced by in situ free radical polymerization of sodium 4-styrene sulfonate using poly(ethylene glycol) diacrylate (PEGDA) as cross-linker, followed by conve...

New hybrid materials of precipitated calcium carbonate (PCC) and cellulose esters (cellulose acetate and cellulose acetate butyrate) were prepared aiming to obtain new modified fillers for papermaking. A novel simple procedure based on the mixing of an aqueous suspension of PCC with an organic solution of the cellulose derivative, followed by the a...

The physicochemical surface properties of cellulose and lignocellulosic materials are of major importance in the context of the production of composites, in papermaking, and textile area. These properties can be evaluated by using inverse gas chromatography (IGC), a particularly suitable technique for the characterization of the surface properties...

One by-product of the brewing process is a waste containing spent grains (barley malt and maize grits). In the brewing process, this cake is composed mainly of organic matter containing high fiber content, provided by the separation of suspended particles through wort filtration. The study presented here was carried out to assess if the spent brewe...

This study reports the modification of the paper surface by the application of different chemicals and its effect on the paper structural and surface properties and inkjet print quality parameters. 3-(N,N-dimethylmyristylammonio)propanesulphonate and hexadecyltrimethylammonium bromide, as zwitterionic and cationic surfactants, respectively, and a c...

Kraft pulps at the kappa number level of 15 obtained from Acer saccharum (sugar maple) and Eucalyptus globulus prepared with and without hot water extraction (HWE) were analyzed by inverse gas chromatography (IGC) and X-ray photoelectron spectroscopy (XPS). In the case of A. saccharum pulps, the dispersive component of the surface energy (gamma(d)(...

Silica-coated precipitated calcium carbonate (PCC) prepared by a sol–gel method in a previous study, was used, for the first time, as filler for papermaking. Three samples of modified PCC, containing 11, 21, and 29 wt % of silica, were prepared. The handsheets produced with a eucalyptus kraft pulp furnish containing the new PCC-based materials show...

In this work, Ailanthus altissima (tree-of-heaven) wood was analyzed for its chemical, morphological and papermaking properties. The A. altissima wood was cooked under kraft conditions using different active alkali charges and then handsheets were produced with the pulps having a kappa number of 16. Based on structural, strength and optical data it...

Redox reactions of Keggin-type polyoxometalates (POM), [PVxMo12−xO40](3+x)− (x = 1, 2), have been studied for the first time employing an array of potentiometric chemical sensors. Variations in the concentrations of vanadyl ions (VO2+) during the redox reactions of POMs were followed in the real-time. Differences in the vanadyl concentration profil...

This work was a comprehensive study of the properties of extracted Eucalyptus globulus kraft pulps. Five levels of hot water extraction were performed, each followed by kraft cooking to three different kappa numbers. As extraction took place, the hemicelluloses content of the kraft pulps was reduced from 21%-22% to 3%-4% and, conversely, the cellul...

Lignin is one of the major components of plants constituting up to 30% by weight and 40% by energy of the lignocellulosic biomass. The lignin oxidation reactions are very important not only in the context of traditional pulp-and-paper industry (lignin is oxidised/removed from wood in order to produce bleached pulp for the papermaking), but also wit...

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%...

This study focus on the modification of the particles of precipitated calcium carbonate (PCC) with silica formed in situ by sol–gel method. The new materials were characterized by several spectroscopic, analytical and microscopic techniques. A dense film of highly branched silica was formed at the surface of the scalenohedral PCC crystals. The amou...

Novel ruthenium multi-substituted polyoxometalate compounds of general formulae K6Na[SiW9O37RuIII4(H2O)3Cl3]·nH2O (α- and β-SiW9O34 isomers) were synthesised via the reactions of the trilacunary Keggin α- and β-[SiW9O34]10− anions with RuCl3 in aqueous solution. Characterisation was performed by analytical, spectroscopic, magnetic, and electrochemi...

The effect of paper surface sizing on Inkjet pigment penetration was evaluated by studying four different paper samples: one taken as reference, without surface sizing (paper RP), one surface sized with cationic starch (RPS1), one with a mixture of cationic starch and poly(styrene-co-maleic anhydride) (RPS2), and one with a mixture of cationic star...

The synergistic effect between polyoxometalates (POMs), namely K(5)[SiW(11)V(V)O(40)]·11H(2)O and H(5)[PMo(10)V(V) (2)O(40)]·13H(2)O and laccase from ascomycete Myceliophthora thermophila has been employed for the first time in oxidative polymerization of catechol. Such a laccase-mediator system allowed the formation of a relatively high molecular...

Oxidation of the manganese-substituted polyoxometalate [SiW(11)Mn(II)(H(2)O)O(39)](6-) (SiW(11)Mn(II)) to [SiW(11)Mn(III)(H(2)O)O(39)](5-) (SiW(11)Mn(III)), one of the most selective polyoxometalates for the kraft pulp delignification, by versatile peroxidase (VP) was studied. First, SiW(11)Mn(II) was demonstrated to be quickly oxidized by VP at ro...