Many industrial applications need supporting or shaping powdery zeolites. Since geopolymers can be considered the amorphous counterpart or precursors of crystalline zeolites, it is possible to ...promote zeolite crystallization inside the geopolymeric matrix by tuning pH, temperature and time of the geopolymerization reaction. In this paper, combining zeolite crystallization with a foaming process initiated by silicon, a multifunctional self-supporting zeolitic material has been obtained with pores ranging from the micro to the macro range. Geopolymerization and crystallization have been realized simultaneously curing the samples at specific temperature and humidity conditions. Every specimen obtained at curing time higher than two days, regardless relative humidity and silicon content, contained zeolite A LTA and X FAU as the only crystalline phases. Finally, the porosity generated by the foaming process promotes the zeolite nucleation mainly on the surfaces of the pores, whereas the struts remain amorphous.
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•Geopolymerization, crystallization and foaming have been realized simultaneously using mild operating condition.•The presence of geopolymeric backbone supports and shapes zeolitic powder.•Co-crystallization of LTA and FAU zeolites has been obtained tailoring the synthesis parameters.
In this paper fly ash based geopolymer mortars have been prepared and their thermal behavior evaluated in order to assess the suitability of fly ash based alkali-activated binders for thermal energy ...storage in solar thermal plants. Different parameters, such as binder/aggregate ratio, percentage of fly ash replaced by slag, temperature and curing time, have been changed and optimized using the Design Of Experiments (DOE) approach. In order to estimate the thermal cycling stability of geopolymeric mortars at elevated temperatures, mechanical strength and weight loss of each sample subjected to different thermal cycles in the temperature range 150–550 °C were evaluated. Finally, thermal conductivity of some of the mixtures, selected on basis of the thermal stability test results, have been measured.
Fly ash based geopolymeric mortars remained stable after each thermal treatment and specimens treated at elevated temperatures retained acceptable compressive strength. The thermal stability was preserved also after repeated thermal cycles, proving that fly ash based geopolymers are suitable materials for thermal energy storage concretes.
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•Fly ash based geopolymer mortars were proposed for thermal energy storage application.•Geopolymerization process parameters were optimized using DOE approach.•The thermal stability of the mortars was evaluated after repeated thermal cycles.•Fly ash based geopolymer mortars showed good thermal stability at elevated temperatures.
In this work, the design of a monolithic softener obtained by geopolymer gel conversion is proposed. The softener used consists in a geopolymeric macroporous matrix functionalized by the ...co-crystallization of zeolite A and X in mixture. The dual nature of the proposed material promotes a softening process based on the synergistic effect of cation exchange and alkaline precipitation. A softening capacity of 90% and 54% for Ca
and Mg
respectively was attained in 24 h. In fact, the softener reported a Cation Exchange Capacity (CEC) value of 4.43 meq g
. Technical features such as density, porosity and mechanical resistance were also measured. The use of this monolithic softener can improve performance and sustainability of hardness removal from tap water, reducing the production of sludge and adding the possibility to partially regenerate or reuse it.
•We prepared Sr-, Zn- and Cd-exchanged zeolitic materials as water vapor adsorbents.•Water vapor adsorption isotherms at different temperatures were collected.•Water vapor adsorption isotherms were ...modeled by means of the Dubinin equation.•The isosteric heat of water vapor adsorption was successfully estimated.•The specific heat storage density of the adsorbents was successfully calculated.
This paper reports the characterization of Sr-, Zn- and Cd-exchanged zeolitic materials as water vapor adsorbents, in order to evaluate the influence of the extraframework species on their adsorption properties. Both synthetic and natural substrates are taken into account. Water vapor adsorption isotherms on each ion-exchanged sample have been obtained at 298, 318, 338, and 358K and have then been modeled using the Dubinin-Astakhov equation. Focusing on the possible implementation of such adsorbents in thermodynamic cycles, an estimation of their specific heat storage densities has been expressed. Results revealed that adsorbents of natural origin are not suitable for a valid employment in thermodynamic cycles, while FAU-type zeolite X samples exchanged with Sr2+ or divalent transition metal ions (i.e., Zn2+ or Cd2+) show a significant potential as heat storage media. The same trend of the specific heat storage density with the cationic content of the adsorbent can be identified for both series of synthetic and naturally originating materials (i.e., Zn>Sr>Cd>Na), confirming how ion exchange allows effective tuning of zeolitic substrates when employed in thermodynamic cycles based on the reversible adsorption of water vapor.
Nowadays the study of the potential applications of multifunctional materials for environmental remediation is one of the main goals of the materials engineering. Multifunctional porous materials, ...MPMs, incorporate, all in once, different and multiple functionalities that make them suitable for several uses and can satisfy many purposes at the same time. Multifunctional diatomite-based foams with a hierarchical porosity, already produced and characterized to be applied in building as well as aerospace sectors, are proposed as adsorbents for inorganic and organic pollutants removal from wastewaters. Then, the effect of the addition of different carbonaceous nanofillers (graphite, graphene and graphene oxide) on the water purification efficiency of the adsorbent was evaluated. Firstly, pristine MPM showed the best performance in adsorbing Indigo Carmine due to its intrinsic chemism and hierarchical porosity (at macro-, micro- and nano-level), but it is not the best with respect to the Cd2+ adsorption, if compared with the nanocomposites. Among the nanocomposite products, both graphene- and graphene oxide-MPM samples showed a significantly improved adsorption capacity towards Cd2+. This behavior is due to the synergistic effect of the finer morphology, higher available foam surface, and the highly exfoliated fillers, graphene and graphene oxide, which permit a better dispersion into the matrix.
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•Novel sustainable absorber multifunctional porous materials-MPMs with a hierarchical porosity.•Nanocomposite MPM-absorbers with Graphite, Graphene and Graphene Oxide were obtained.•Heavy metal, Cd2+ and anionic dyes absorption ability of MPM nanocomposite was studied.
► Cs+ and Sr2+ were jointly removed by two different zeolitic materials. ► The matrix encloses Cs-selective phillipsite-rich tuff and Sr-selective zeolite A. ► Cs+ and Sr2+ were safely entrapped in ...crystalline-amorphous matrix obtained at 1200°C.
A solidification–stabilization procedure aiming at immobilizing Cs+ and Sr2+, two of the radioactive species more frequently present in nuclear power plant wastewaters, was successfully tested. Both cations were simultaneously exchanged by a blend of two zeolites, a phillipsite-rich tuff, selective for Cs+, and a synthetic zeolite Linde-type A, selective for Sr2+. The contaminated material was then heat treated up to 1200°C with the result of safely immobilizing both cations, as demonstrated by leaching estimation with three different procedures. X-ray studies of the single cation-loaded zeolites or mixture of them helped to interpret the immobilization mechanism, involving cation trapping in chemically stable crystalline/amorphous matrices formed as a result of firing.
The WHO informal consultation was held to promote the revision of WHO guidelines on evaluation of similar biotherapeutic products (SBPs) adopted by the Expert Committee on Biological Standardization ...(ECBS) in 2009. It was agreed in the past consultations that the evaluation principles in the guidelines are still valid, but a review was recommended to provide more clarity and case-by-case flexibility. The opportunity was therefore taken to review the experience and identify areas where the current guidance could be more permissive without compromising its basic principles, and where additional explanation could be provided regarding the possibility of reducing the amount of data needed for regulatory approval. The meeting participants applauded the leading role taken by the WHO in providing a much-needed streamlined approach for development and evaluation of SBPs which will provide efficient and cost-effective product development and increase patient access to treatments. It was recognized that the principles as currently described in the draft WHO guidelines are based on sound science and experience gained over the last fifteen years of biosimilar approvals. However, since these guidelines when finalised will constitute the global standard for biosimilar evaluation and assist national regulatory authorities in establishing revised guidance and regulatory practice in this complex area, it was felt that further revision and clarity on certain perspectives in specific areas was necessary to dispel uncertainties arising in the current revised version. This report describes the principles in the draft guidelines, including topics discussed and consensus reached.
•WHO guidelines serve as a basis for the development of national regulatory framework for biosimilars.•Revision of guidelines is to provide more flexibility and clarification on data required for regulatory approval.•Revised guidelines would contribute to improving consistency on regulatory decision and patient access to treatments.
In this work, a chromium-based metal organic framework (Cr-MOF) was synthesized, characterized and tested for the adsorption of a model highly ozone-depleting anaesthetic (sevoflurane). Adsorption ...isotherms were measured at different temperatures e.g., 283, 298, 313 and 328 K on both Cr-MOF and a conventionally used reference adsorbent. At the temperatures used in this study, the Cr-based MOF showed a significantly higher sevoflurane (selected anaesthetic) equilibrium adsorption capacity compared to the reference sample, although adsorption on the selected MOF did not take place on all active sites (i.e., it did not expose its coordinatively unsaturated sites). Moreover, sevoflurane adsorption on Cr-MOF was found to be fully reversible in the 283-328 K temperature range, and the adsorbent was fully regenerated by vacuum treatment at ambient temperature. The semiempirical Sips model was successfully used to fit sevoflurane adsorption data, substantially confirming the phenomenological aspects of the process inferable from the experimental results.
Objectives This study assessed the health effects of occupational acrylamide exposure using hemoglobin (Hb) adducts as biomarkers of internal dose.Methods Two hundred and ten tunnel workers exposed ...for about 2 months to a chemical-grouting agent containing acrylamide and N-methylolacrylamide underwent a health examination. Blood samples were drawn for the analysis of Hb adducts of acrylamide. Fifty workers claiming recently developed or deteriorated symptoms of the peripheral nervous system (PNS) were referred to a neurophysiological examination. Workers with Hb-adduct levels exceeding 0.3 nmol/g globin attended follow-up examinations 6, 12, and 18 months after exposure cessation.Results Forty-seven workers had Hb-adduct levels within the normal background range (0.02-0.07 nmol/g globin), while the remaining 163 had increased levels up to a maximum of 17.7 nmol/g globin. Clear-cut doseresponse associations were found between the Hb-adduct levels and PNS symptoms. Thirty-nine percent of those with Hb-adduct levels exceeding 1 nmol/g globin experienced tingling or numbness in their hands or feet. A no-observed adverse effect level of 0.51 nmol/g globin was estimated for numbness or tingling in the feet or legs. For 23 workers there was strong evidence of PNS impairment due to occupational exposure to acrylamide. All but two had recovered 18 months after the cessation of exposure.Conclusions Occupational exposure to a grouting agent containing acrylamide resulted in PNS symptoms and signs. The use of Hb adducts of acrylamide as a biomarker of internal dose revealed strong dose-response associations. The PNS symptoms were, however, generally mild, and in almost all cases they were reversible.
The ion-exchange properties of a synthetic hydrosodalite (Na-hS) have been investigated by kinetic and thermodynamic analysis of exchange reactions of the original sodium form for lithium, potassium ...and calcium forms. Kinetic curves, modelled by a Langmuir-type equation, revealed that exchange rate for lithium and for potassium are of the same order, whereas they are two order faster than for calcium. Thermodynamic analysis of the cation exchange isotherms pointed out that sodalite is selective for sodium over the other three cationic forms examined, which is consistent with the preference exhibited by the sodalite type for sodium environments, either in natural or in laboratory crystallization. Na/Li and Na/Ca exchanges are incomplete, whereas unexpectedly Na/K exchange turns out to be complete, even though K
+
dimension exceeds the width of the access window to sodalite cages. The obtained results have been discussed in terms of Eisenman–Sherry theory, pointing out agreements and discrepancies.
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