The Thermodynamics of Heavy Metal Sorption onto Lignocellulosic Biomass

The sorption equilibrium and thermodynamics of Cu(II), Ni(II), Pb(II), and Cd(II) onto grape stalks (GS), a lignocellulosic waste from wine production industries, have been investigated. Different equilibrium models have been assessed to describe the experimental sorption equilibrium profile in the range of 5–60°C. Maximum sorption capacities have been calculated by means of Langmuir equilibrium model and mean free sorption energies through the Dubinin-Radushkevich (D-R) model. Mean free energies suggest that metal sorption takes place mainly through an ion exchange mechanism, except for Pb(II), where an additional contribution connected to a stronger bond might take place. The calculation of thermodynamic parameters, ΔG0, ΔH0 and ΔS0, puts into evidence that the sorption of all the metals onto GS is a spontaneous and exothermic process that occurs with an increase of randomness at the solid/liquid interface

The Chemistry Behind the Use of Agricultural Biomass as Sorbent for Toxic Metal Ions: pH Influence, Binding Groups, and Complexation Equilibria

Waters, because of human activities, are often characterized by different kinds of contamination. In this chapter we will deal with contamination due to toxic metal ions. To purify wastewaters from these pollutants different treatment processes are applied, which include chemical precipitation, chemical oxidation or reduction, electrochemical treatment, membrane filtration, ion exchange, carbon sorption, and coprecipitation/sorption. A number of these processes are extremely expensive and some of them are ineffective at low concentrations. Alternative cost effective technologies based on low cost sorbents are nowadays of great concern in the applied research. These low cost sorbents must be abundant in nature, easily available, and above all they have to fit the worldwide request of recycling. Certain waste products from agricultural operations may become inexpensive sorbents and the potential of some of these wastes for the removal of a number of metal ions has been extensively investigated. The use of these wastes as sorbents fulfills two important scopes for the protection of environment: the reuse of waste materials and the detoxification of wastewaters. The biomass source depends on the agricultural production prevailing in the geographical areas where pollution and subsequent decontamination process take place. The real challenge in the field of biosorption is to identify the chemical mechanism that governs metal uptake by biosorbents. Vegetal biomaterials, constituted principally by lignin, cellulose and by a non-negligible portion of fatty acid as major constituents, can be regarded as natural ion-exchange materials. Furthermore, the functional groups on the biomaterial surface, such as hydroxyl, carbonyl, amino, sulphydryl and carboxylic groups, allow the sorption of metal ions by strong coordination. Therefore, identification of the functional groups can help in shedding light on the mechanism responsible for metal uptake. Also some factors affecting the sorption process such as particle size, pH, metal ion concentration, agitation time, and kinetics must be investigated. The results obtained contribute to the knowledge of the overall process that takes place

La accesibilidad, una clave para la inclusión educativa : Accesibilidad e inclusión educativa

L'escola inclusiva busca oferir la millor resposta a la diversitat i això implica identificar i eliminar els obstacles o barreres que dificulten el procés d'inclusió. Requereix parar atenció contínua al context escolar, especialment, al permanent diàleg i interacció entre aquest context i la diversitat de l'alumnat. L'accessibilitat, en les seves diferents dimensions, física, sensorial, cognitiva i emocional, que aconseguirem implementant els principis del disseny universal, contribuirà a aconseguir la presència, la participació i l'aprenentatge de tot l'alumnat.Inclusive schools seek to provide the best answer to diversity and this involves identifying and removing obstacles or barriers that prevent the inclusion process. It requires continuous attention to the school context, especially to the permanent dialogue and interaction between that context and the diversity of students. Accessibility, in its different dimensions, physical, sensory, cognitive and emotional, which we will achieve by implementing the principles of universal design, will contribute to the presence, participation and learning of all students.La escuela inclusiva busca ofrecer la mejor respuesta a la diversidad y esto implica identificar y eliminar los obstáculos o barreras que dificultan el proceso de inclusión. Requiere prestar atención continua al contexto escolar, en especial, al permanente diálogo e interacción entre ese contexto y la diversidad del alumnado. La accesibilidad en sus distintas dimensiones, física, sensorial, cognitiva y emocional, que conseguiremos implementando los principios del diseño universal, contribuirá a conseguir la presencia, la participación y el aprendizaje de todo el alumnado

La accesibilidad, una clave para la inclusión educativa : Accesibilidad e inclusión educativa

L'escola inclusiva busca oferir la millor resposta a la diversitat i això implica identificar i eliminar els obstacles o barreres que dificulten el procés d'inclusió. Requereix parar atenció contínua al context escolar, especialment, al permanent diàleg i interacció entre aquest context i la diversitat de l'alumnat. L'accessibilitat, en les seves diferents dimensions, física, sensorial, cognitiva i emocional, que aconseguirem implementant els principis del disseny universal, contribuirà a aconseguir la presència, la participació i l'aprenentatge de tot l'alumnat.Inclusive schools seek to provide the best answer to diversity and this involves identifying and removing obstacles or barriers that prevent the inclusion process. It requires continuous attention to the school context, especially to the permanent dialogue and interaction between that context and the diversity of students. Accessibility, in its different dimensions, physical, sensory, cognitive and emotional, which we will achieve by implementing the principles of universal design, will contribute to the presence, participation and learning of all students.La escuela inclusiva busca ofrecer la mejor respuesta a la diversidad y esto implica identificar y eliminar los obstáculos o barreras que dificultan el proceso de inclusión. Requiere prestar atención continua al contexto escolar, en especial, al permanente diálogo e interacción entre ese contexto y la diversidad del alumnado. La accesibilidad en sus distintas dimensiones, física, sensorial, cognitiva y emocional, que conseguiremos implementando los principios del diseño universal, contribuirá a conseguir la presencia, la participación y el aprendizaje de todo el alumnado

Valorisation of Lignocellulosic Biomass Wastes for the Removal of Metal Ions from Aqueous Streams: A Review

Heavy metal pollution derived from anthropogenic activities is a relevant environmental threat nowadays due to their toxic nature, persistence and accumulation potential in the food chain. A wide variety of lignocellulosic-based biomaterials have been thoroughly assessed by the scientific community as sorbents for the removal of metals from aqueous streams. This kind of biomaterials, mainly constituted by lignin and cellulose, bear functional groups such as alcohol, ketone and carboxylates that provide active sorption points for the effective removal of heavy metals. The role of lignin in the sorption process is especially relevant, since this substance provides polyhydroxy and polyphenol functional groups—especially effective in the coordination of metals—and that provide ion exchange functionality to the material. Depending on their nature, these materials can be used either in their raw form or chemically modified form so as to enhance their sorption capacity and/or to achieve improved mechanical and mass transfer properties

Measurement of the Teamwork and Networking Competencies in Innovative Contexts

[EN] The aim of our research is to develop a questionnaire that allows a valid and reliable self-assessment of two soft competencies: Teamwork (TW) and Networking (NW), for professionals at organizations or job applicants. In this paper, focus will be set on the filtering of a bank of possible items, and the confirmation that the items finally selected: a) Represent one or several conceptual dimensions within TW or NW b) Show an agreement between independent evaluators to analyze the overlap between items and dimensions: in our case, to be able to classify the items into their adequate dimension c) Check that the set of items selected in agreement among evaluators represents all the sub-dimensions of the construct to be assessed We will use the bank of TW and NW items identified by previous research (itemsA) (Lukes & Stephan, 2017, Pérez Peñalver et al., 2018), which was classified and carried out within the European Project FINCODA (itemsB) (Marin-Garcia, 2018). With itemsA and B, we will try to sort out items into their corresponding categories. To identify the items with the best content validity, we will use the raw agreement and Content Validity Ratio (CVR) measures (Lawshe, 1975, Tristan-Lopez, 2008), the intercoder agreement measures (Marin-Garcia et al., 2008a; Marin -Garcia et al., 2016b) and Krippendorff's Alpha (Friese, 2018; Krippendorff, 2018; Krippendorff et al., 2016).Marín García, JA.; Martínez Villaescusa, MI.; Aznar Más, L. (2020). Measurement of the Teamwork and Networking Competencies in Innovative Contexts. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/156434OC

Nickel removal from exhausted electroplatting baths by using vegetable wastes

During the last years our research group has been studying the use of industrial vegetable wastes as grape stalks and exhausted coffee to remove metals ions such as Ni(II), Cu(II), Pb(II), Zn(II), Cd(II) or Cr(VI) and Cr(III) in aqueous solution from the point of view to use these wastes as biosorbents in a low cost alternative to activated carbon for wastewater treatment. The optimal experimental conditions for the removal of each of these metal ions in synthetic solutions by using both biosorbents were determined in previous studies . In this work, the performance of grape stalks and exhausted coffee for the removal of nickel ions from an exhausted electroplating bath of a metal finishing industry from Barcelona (Spain) has been investigated. Batch and column experiments were carried out at room temperature by using grape stalk wastes (particle size 0.8-1.0 mm), meanwhile in the case of exhausted coffee, two different particle size ranges were used, 0.25-0.50 mm and 0.50-1.00 mm for batch and column experiments, respectively. Kinetics and equilibrium studies were carried out in batch mode to determine the equilibrium contact time and to obtain the sorption capacity of sorbents. The data in both studies have been treated by using different models. Column experiments were designed to establish the optimal condition for the treatment of the industrial wastewater. The experiments were performed in packed bed up flow columns of different internal diameter and bed depth in order to predict the transport and sorption parameters. In all column experiments the flow rate was around 11 mL h-1. From perspective of process modelling, the dynamic behavior was described in terms of breakthrough curves. The bed depth service time (BDST), Thomas and Yoon Nelson models were used to analyze the experimental data and to determine model parameters. Batch results show that about 1hour was the time needed to reach equilibrium when using grape stalks and around 15 h when using exhausted coffee. In the case of exhausted coffee, the pH solution decreased during the sorption process from initial pH 5,5 to lower pH than the corresponding pHpzc (point zero charge). To avoid this, pH solution was controlled to a constant pH 5,5 and the equilibrium were achieved in 1h. Kinetic data of both sorption processes fit pseudo-second order model, indicating that chemisorption could be rate limiting in the sorption step. Equilibrium data of nickel sorption onto grape stalks and exhausted coffee fit adequately Langmuir model, indicating monolayer coverage. Results showed that maximum sorption capacity of grape stalks (4,8 10-2 mmol/g; 2,84 mg/g) is slightly higher than exhausted coffee (2,9 10-2 mmol/g; 1,70 mg/g). The maximum nickel sorption capacity of both sorbents was reduced to 50% compared to maximum sorption capacity determined using synthetic Ni(II) solutions. Thus, grape stalks and exhausted coffee performance for the removal of Ni(II) from the studied industrial wastewater are negatively affected by the presence of other compounds in the industrial wastewater. In column experiments, the best results were obtained by using 2.8 cm internal diameter columns and bed depth 6 cm and 8 cm for grape stalks and exhausted coffee, respectively. Breakthrough curves were successfully modelled by the proposed columns models. The results obtained demonstrated that grape stalks sorption capacity was higher than exhausted coffee but this one presented a higher sorption rate.Postprint (published version

Valorització de residus vegetals procedents de processos industrials com a biosorbents per a l'eliminació d'ions metàl•lics d'afluents aquosos

L’objectiu d’aquest projecte és la valorització de residus vegetals procedents de processos industrials, com són el pinyol d’oliva, rapa del raïm, suro, marro de cafè, etc.,com a biosorbents per a l’eliminació de diferents ions metàl·lics, crom, arsènic, plom, cadmi, coure, níquel, etc., d’afluents aquosos.Peer Reviewe

Green synthesis of Ag nanoparticles using grape stalk waste extract for the modification of screen-printed electrodes

The chemical synthesis of silver nanoparticles (Ag-NPs) by using an environmentally friendly methodology for their preparation is presented. Thus, considering that plants possess components that can act as reducing agents and stabilizers in nanoparticles' production, the synthesis of Ag-NPs by using an extract aqueous solution of grape stalk waste as a reducing and capping agent is studied. First, the total polyphenols and reducing sugars contained in the produced extracts at different conditions are characterized. After that, Ag-NPs are synthesized regarding the interaction of Ag ions (from silver nitrate) and the grape stalk extract. The effect of temperature, contact time, extract/metal solution volume ratio and pH solution in the synthesis of metal nanoparticles are also studied. Different sets of nanoparticle samples are characterized by means of Electron Microscopy coupled with Energy Dispersive X-Ray for qualitative chemical identification. Ag-NPs with an average diameter of 27.7 ± 0.6 nm are selected to proof their suitability for sensing purposes. Finally, screen-printed electrodes modified with Ag-NPs are tested for the simultaneous stripping voltammetric determination of Pb(II) and Cd(II). Results indicate good reproducibility, sensitivity and limits of detection around 2.7 µg L−1 for both metal ions