scholarly journals Hybrid Geopolymeric Foams for the Removal of Metallic Ions from Aqueous Waste Solutions

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4091 ◽  
Author(s):  
Giuseppina Roviello ◽  
Elena Chianese ◽  
Claudio Ferone ◽  
Laura Ricciotti ◽  
Valentina Roviello ◽  
...  

For the first time, hybrid organic–inorganic geopolymeric foams were successfully used as monolithic adsorbents for the removal of metallic ions pollutants from wastewaters. The foams were realized by the in situ foaming of a hybrid geopolymer obtained by a reaction of metakaolin and polysiloxane oligomers under strong alkaline conditions and then cured at room temperature. In this way, porous materials with densities ranging from 0.4 to 0.7 g/cm3 and showing good mechanical properties were produced. With the aim of producing self-standing monolithic adsorbents for the removal of metallic ions pollutants from wastewaters, these porous hybrid geopolymers were subjected to a washing pretreatment with ultrapure water, dried, and then used for absorption tests by dipping them into an aqueous solution with an initial concentration of 20 ppm of Pb2+, Cd2+, Cu2+, and Zn2+ ions. Preliminary results indicated that all the tested materials are effective in the adsorption of the tested metal ions and do not release the removed metal ions upon sinking in ultrapure water, even for a very long time. Interestingly, compressive strength tests performed before and after the washing treatments show that the foamed samples remain intact and maintain their physical–mechanical characteristics, suggesting that these kinds of materials are promising candidates for the production of self-standing, monolithic adsorbent substrates that can be easily collected when exhausted, which is a major advantage in comparison with the use of powdered adsorbents. Moreover, since these materials can be obtained by a simple and versatile experimental procedure, they could be easily shaped or directly foamed into precast molds to be used in packed beds as membranes.

Molecules ◽  
2020 ◽  
Vol 25 (11) ◽  
pp. 2533
Author(s):  
Nuno Araújo ◽  
Manuela Corrêa-Silva ◽  
Tiago Miranda ◽  
António Topa Gomes ◽  
Fernando Castro ◽  
...  

The influence of suction on the mechanical behaviour of unsaturated chemically stabilised soils is still mostly unknown and unquantified. This is also motivated by the difficulties associated with the experimental procedure required to fully characterise the unsaturated response of the soil, including its direct influence on traditional strength tests. The present paper presents the soil water retention curves obtained for a Portuguese soil before and after being stabilised with Portland cement (OPC) and an alkali-activated cement (AAC). Saturated undrained triaxial tests were also performed for the same curing conditions (0, 28, and 90 days). Previous attempts to characterise the retention curve of soils stabilised with AAC are unknown, and the results showed that the pore volume structure is already formed after 28 days, prior to the full development of the gel matrix responsible for the strength increase between 28 and 90 days. The curve changed after stabilisation, and with each binder, as the OPC presented a higher air-entry value and a narrower suction range compared to the AAC solution. The significant differences between the curves obtained from each binder suggest the future development of a methodology to assess the quality of the AAC stabilisation.


RSC Advances ◽  
2016 ◽  
Vol 6 (53) ◽  
pp. 48145-48154 ◽  
Author(s):  
Youjun He ◽  
Meishan Pei ◽  
Ni Xue ◽  
Luyan Wang ◽  
Wenjuan Guo

A sodium polyacrylate–bentonite material (PAANa–Bent), as an adsorbent for heavy metal ions, is synthesized for the first time using in situ polymerization.


The Analyst ◽  
2014 ◽  
Vol 139 (12) ◽  
pp. 2998-3001 ◽  
Author(s):  
Juan Tang ◽  
Minghua Lu ◽  
Dianping Tang

A target-initiated proximity ligation assay protocol with DNAzyme formation was for the first time designed for ultrasensitive impedimetric monitoring of heavy metal ions (silver ions were used in this case) by coupling with an enzymatic biocatalytic precipitation technique.


2017 ◽  
Vol 7 (2) ◽  
pp. 339
Author(s):  
Plácido Lizancos

Introducción: Galicia es uno de los territorios del Estado Español que ha presentando tradicionalmente una de sus mayores tasas migratorias.Conseguir levantar una casa propia, moderna y funcional, que ofreciera unas condiciones de habitabilidad mejores a las de la vivienda tradicional ha sido uno de los motivos que han provocado las migraciones que en el último siglo se han registrado en Galicia, por lo que el proyecto arquitectónico suele formar parte del propio proyecto migratorio de las familias.Como no podía ser de otra manera, la casa que levantan las gentes emigradas presenta unas características que la diferencian de las de los otros ciudadanos. Siendo la ruptura respecto a la vivienda tradicional la característica que aparentemente la hace diferente, esto ha impactado en la opinión pública y en la profesional. En este artículo se recogen los resultados de una investigación que analiza el proceso de creación de la casa del emigrado, identificando de entre las partes de ese proceso aquellas que ocasionan el referido impacto y proponiendo maneras de gestionarlo.Método: el proyecto de investigación se ha planteado como una búsqueda estrictamente arquitectónica, sustentado en un sistemático trabajo de campo en el que se localizan y estudian in situ las referidas edificaciones. El abordaje del estudio de la casa contemporánea del emigrante es la primera vez -hasta donde llega nuestro conocimiento- que se realiza en Galicia aun siendo una materia a la que ya se han aproximado antropólogos, sociólogos y economistas que han dejado constancia de sus investigaciones en una amplísima bibliografía.Nuestro trabajo comprende el levantamiento gráfico de los edificios y la entrevista a sus usuarios. Con los materiales obtenidos se reproducen “en laboratorio” para su análisis las circunstancias de cada caso de estudio que es completado con la lectura atenta de la bibliografía existente.El ámbito territorial de nuestro trabajo se circunscribe a Galicia, si bien se ha reconocido que los emigrantes en general han levantado construcciones que le son propias en muchos otros lugares del mundo. El ámbito territorial definido presenta rasgos culturales, económicos y políticos homogéneos.  Resultados: Se ha conseguido entender el proceso que siguen las personas emigradas para alzar su casa, identificándose este con la autogestión. Se trata de un proceso no formal, ideado por las propias personas emigradas ya que les resulta adecuado pues les permite mantener el control de la obra aun viviendo a caballo entre dos países y eludir el crédito hipotecario comercial al que no podrían acceder debido a su destierro. Esto nos ha permitido entender uno de los aspectos físicos de la casa del emigrado que más impacto causa: su proceso de ejecución dilatado en el tiempo, detenido muchas veces en pasos intermedios, aparentando abandono.Discusión o Conclusión: Una vez identificado el proceso por el que se construye esta tipología se indaga en la forma en que éste es interpretado por las personas ajenas al asunto de la casa del emigrante.Como resultado final se proponen directrices que podrían ser incorporadas a las políticas públicas a los efectos de empoderar a los migrantes cuando alzan con sus propias manos y sus recursos la casa soñada y a la opinión pública en la gestión del vasto parque inmobiliario alzado por los emigrantes. Introduction: Galicia is one of the Spanish territories showing larger migratory taxes. Building your own house, modern and functional, provided with much better habitat conditions than the traditional house has been one of the reasons that fuelled this past century the Galician migratory movements. Therefore, a migratory project usually comes together with an architectonic one.The house that has been built by migrated people enjoys characteristics different from other people’s houses and from vernacular ones. All this stuff has shocked public and professional opinion.On this paper, we collect the outcomes of a research that analyses the emigrant’s house creation process. We identify within that process the dimensions that are responsible of such an impact and we propose how to manage it.Method: Research strategy has been based on an all-country field survey, looking for case studies. This is the very first time –as far as we know- that this house has been studied from the architectonic point of view although it has been on the sociologist, anthropologist and economist researchers that have produced diverse outcomes.We sketch up many buildings and interviewed users. With all this stuff, we reproduced a model “at the laboratory” to analyse the circumstances behind the buildings.The area of study is Galicia; even though we know migrants that have already built characteristic houses all over the world. The area we studied shows a cultural, economic and social homogeneous shape.Results: We have been able to identify and understand the process of self-management used by Galician migrants to implement their homes. It was an unformal process, designed by migrated people on their own as it suited to them and allowed them to build a house when living among two different countries and to escape from a commercial mortgage, stuff they couldn’t afford because of living away from their motherland. This has addressed us to understand why construction procedure delays for a very long time, even offering the idea that worksite has been left unfinished.Discussion or Conclusion: Once we identified the process followed to build this home, we look for the way it is understood by people out of the migratory world.As an outcome, we propose guidelines to be included on public policies to empower migrants when building a personal home by their own and to help public opinion on the management of the huge housing stock that was once built by migrants.


Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3976 ◽  
Author(s):  
Matjaž Finšgar ◽  
David Majer ◽  
Uroš Maver ◽  
Tina Maver

In this work, unmodified screen-printed electrode (bare SPE) and Sb-film modified SPE (SbFSPE) sensors were employed for the analysis of trace amounts of Pb(II) in non-deaerated water solutions. The modified electrode was performed in situ in 0.5 mg/L Sb(III) and 0.01 M HCl. The methodology was validated for an accumulation potential of –1.1 V vs. Ag/AgCl and an accumulation time of 60 s. A comparative analysis of bare SPE and SbFSPE showed that the detection and quantification limits decrease for the bare SPE. The method with the bare SPE showed a linear response in the 69.8–368.4 µg/L concentration range, whereas linearity for the SbFSPE was in the 24.0–319.1 µg/L concentration range. This work also reports the reason why the multiple standard addition method instead of a linear calibration curve for Pb(II) analysis should be employed. Furthermore, the analytical method employing SbFSPE was found to be more accurate and precise compared to the use of bare SPE when sensors were employed for the first time, however this performance changed significantly when these sensors were reused in the same manner. Furthermore, electrochemical impedance spectroscopy was used for the first time to analyse the electrochemical response of sensors after being used for multiple successive analyses. Surface characterisation before and after multiple successive uses of bare SPE and SbFSPE sensors, with atomic force microscopy and field emission scanning electron microscopy, showed sensor degradation. The interference effect of Cd(II), Zn(II), As(III), Fe(II), Na(I), K(I), Ca(II), Mg(II), NO3–, Bi(III), Cu(II), Sn(II), and Hg(II) on the Pb(II) stripping signal was also studied. Finally, the application of SbFSPE was tested on a real water sample (from a local river), which showed high precision (RSD = 8.1%, n = 5) and accurate results.


Holzforschung ◽  
1999 ◽  
Vol 53 (5) ◽  
pp. 474-480 ◽  
Author(s):  
Annica Berglund ◽  
Harald Brelid ◽  
Anders Rindby ◽  
Per Engström

Summary The possibility of using synchrotron radiation microbeam X-ray fluorescence (μ -XRF) for the determination of the morphological distribution of inorganic elements in wood has been investigated. A number of samples were analyzed and some of the results are presented in this paper. The new application of the method showed good results and it was concluded that the technique is useful for specific in situ metal ion analysis of wood. One of its special advantages is that it is a non-destructive method, which may allow analysis of the same sample before and after a chemical treatment. This study shows the natural distribution of a selection of metal ions in wood. Some differences in the distribution and amount of certain metals could also be observed in a sample that had been subjected to treatment with an EDTA-solution.


Author(s):  
Matjaž Finšgar ◽  
David Majer ◽  
Uroš Maver ◽  
Tina Maver

In this work, unmodified screen-printed electrode (bare SPE) and Sb-film modified SPE (SbFSPE) sensors were employed for the analysis of trace amounts of Pb(II) in non-deaerated water solutions. The modified electrode was performed in situ in 0.5 mg/L Sb(III) and 0.01 M HCl. The methodology was validated for an accumulation potential of –1.1 V vs. Ag/AgCl and an accumulation time of 60 s. A comparative analysis of bare SPE and SbFSPE showed that the detection and quantification limits decrease for the bare SPE. The method with the bare SPE showed a linear response in the 69.8–368.4 µg/L concentration range, whereas linearity for the SbFSPE was in the 24.0–319.1 µg/L concentration range. This work also reports the reason why the multiple standard addition method instead of a linear calibration curve for Pb(II) analysis should be employed. Furthermore, the analytical method employing SbFSPE was found to be more accurate and precise compared to the use of bare SPE when sensors were employed for the first time, however this performance changed significantly when these sensors were reused in the same manner. Furthermore, electrochemical impedance spectroscopy was used for the first time to analyse the electrochemical response of sensors after being used for multiple successive analyses. Surface characterisation before and after multiple successive uses of bare SPE and SbFSPE sensors, with atomic force microscopy and field emission scanning electron microscopy, showed sensor degradation. The interference effect of Cd(II), Zn(II), As(III), Fe(II), Na(I), K(I), Ca(II), Mg(II), NO3– Bi(III), Cu(II), Sn(II), and Hg(II) on the Pb(II) stripping signal was also studied. Finally, the application of SbFSPE was tested on a real water sample (from a local river), which showed high precision (RSD = 8.1%, n = 5) and accurate results.


Author(s):  
Alberto Colella ◽  
Addolorata De Chiaro ◽  
Vincenzo Lettera

The aim of the present work was to develop an innovative and environmentally friendly process for wood fiber dyeing and to produce 3-dimensionally fully colored medium-density fiberboard (MDF). The potential of laccase-catalyzed polymerization of selected precursors to form dyes useful in fiberboard manufacturing, a technique used for the first time in this field, was demonstrated. Some of the 7 aromatic compounds tested yielded colored products after laccase treatment under both acid and alkaline conditions, and a good variety of colors was attained by using mixtures of two different monomers. To demonstrate the coloration and design potential of laccase conversion of aromatic compounds, MDFs were enzymatically dyed using an in situ one-step laccase-catalyzed coloration process, and the results were compared against commercial MDFs obtained by using organic coloring agents. Important advantages over conventional processing methods include good color fastness and, in some cases, new hydrophobic properties, allowing designers and woodworkers to explore the beauty of textures and the use of simpler and milder processing conditions that eliminate harsh chemical use and reduce energy consumption.


1996 ◽  
Vol 74 (2) ◽  
pp. 232-237 ◽  
Author(s):  
J. Bouchard ◽  
C. Maine ◽  
R.M. Berry ◽  
D.S. Argyropoulos

Dimethyldioxirane (DMD) is a cyclic peroxide made by oxidizing acetone with peroxymonosulfate (PMS) in water buffered at pH 7.5 using sodium bicarbonate. It has been shown that DMD generation can be achieved in situ within a pulp suspension allowing very selective TCF bleaching of kraft pulp. This process involves simultaneous generation of DMD, reaction of PMS and DMD with residual lignin, and spontaneous decomposition of both oxidants. The first part of this work is a kinetics study of the decomposition of PMS and DMD as a function of pH under conditions similar to those for in situ bleaching. The effect of chelation as well as the effect of transition metal ions on decomposition rate was also investigated. DMD is very sensitive to pH and its half-life is very short under alkaline conditions. The presence of any transition metal ion that can be involved in a one-electron transfer is detrimental to DMD stability. However, fast reaction of DMD with pulp almost counteracts the effect of metal ions. Key words: bleaching, peroxymonosulphate, dimethyldioxirane, metal ions, kinetics, decomposition, kraft pulp.


2012 ◽  
Vol 124 (1) ◽  
pp. 20 ◽  
Author(s):  
Richard H. Loyn

Vertebrate fauna respond actively to individual fires by movement before and after the event, as well as by mortality and reproduction at the population level. They rely very much on mechanisms for avoiding fire fronts and ex situ recolonisation of burnt and regenerating habitat, as well as in situ survival. This sets them apart from most plant species and the more sedentary examples of invertebrate fauna. Rates of recolonisation after fire events depend on habitat development, and this includes both structure and floristic aspects of the vegetation, and also on accessibility of refuge habitat. Strategies for conserving vertebrate fauna need to take a broad landscape perspective to ensure that fire regimes are designed so that species can survive particular fire events in the broad landscape, and have potential to recolonise habitat as it becomes suitable over time. Long-unburnt vegetation provides important habitat for some species and should be valued accordingly. Long time-frames may be needed for some structural elements to develop after severe fires. Hence it is necessary to think big in managing habitat for vertebrate fauna, at both spatial and temporal scales. A conceptual model is offered for doing this, and a research program is described which aims to provide the detail necessary to make appropriate settings in policy and management frameworks.


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