1,919 research outputs found
Waste Glass Upcycling Supported by Alkali Activation: An Overview
No full textAlkali-activated materials are gaining much interest due to their outstanding performance, including their great resistance to chemical corrosion, good thermal characteristics, and ability to valorise industrial waste materials. Reusing waste glasses in creating alkali-activated materials appears to be a viable option for more effective solid waste utilisation and lower-cost products. However, very little research has been conducted on the suitability of waste glass as a prime precursor for alkali activation. This study examines the reuse of seven different types of waste glasses in the creation of geopolymeric and cementitious concretes as sustainable building materials, focusing in particular on how using waste glasses as the raw material in alkali-activated materials affects the durability, microstructures, hydration products, and fresh and hardened properties in comparison with using traditional raw materials. The impacts of several vital parameters, including the employment of a chemical activator, gel formation, post-fabrication curing procedures, and the distribution of source materials, are carefully considered. This review will offer insight into an in-depth understanding of the manufacturing and performance in promising applications of alkali-activated waste glass in light of future uses. The current study aims to provide a contemporary review of the chemical and structural properties of glasses and the state of research on the utilisation of waste glasses in the creation of alkali-activated materials
Enhanced methylene blue adsorption by double alkali activation of highly porous glass microspheres prepared from waste glass
No full textThe remediation of water from organic pollutants, such as dyes and related compounds and the reuse of discarded glasses, represents fundamental challenges in highly industrialized countries. Porous glass microspheres have been proposed as efficient adsorbents in wastewater treatment, but their real application is problematic, especially from the perspective of their reuse and recycling. For the first time, the present paper describes the process of preparation and use of highly porous bodies with a specific surface area of nearly 20 m2/g fabricated from alkali activated glass microspheres and applicable for the removal of methylene blue as a model organic dye from wastewater. Alkali activation is applied both as an intermediate step (using 9 M KOH) for the conversion of waste glass into porous microspheres by flame spheroidization process, and as a final step (using 2.5 M NaOH), facilitating low temperature consolidation of the microspheres, and their transformation into porous structures. The experimental adsorption capacity of porous glass microspheres pellet was 122 mg/g. The high correlation coefficient indicates the applicability of Langmuir isotherm adsorption model
Sustainable manufacturing of new construction material from alkali activation of volcanic tuff
No full textThe current climate emergency leads to reduction of virgin raw material extraction and promotes circular economy. In this framework, alkali activation of unemployed fraction of grey tuff, combined with glass waste, provides a range of sustainable construction materials. For the sake of sustainability, tuff powder was subjected to rapid attack (30 min), operated by a 'weak' alkaline solution (3 M NaOH), and then left to dry at low temperature (75 degrees C) for 72 h. The addition of Triton X-100 surfactant was considered to obtain foams starting from slurries with different liquid-to-solid ratio. A thermal treatment was applied to selected samples, at low temperature (700 degrees C). Despite the 'mild' activation conditions, all products survived after immersion in boiling water or acid solution, already in the unfired state, according to the formation of a multiphasic gel. The strength-to density ratio, especially for foams, in both unfired and fired form, compares well with that of already existing construction materials (e.g. it could exceed 5 MPa cm3/g)
Fabrication and environmental applications of glass microspheres: A review
No full textContinuous technological progress is required to improve production efficiency and environmental quality while maintaining economic competitiveness. A non-negligible contribution to some of these goals can be achieved through the production of glass microspheres for a wide range of applications. The fabrication techniques of glass microspheres including flame synthesis, liquid droplet method, dried gel process and electrical arc process are surveyed. The mechanisms of the recent syntheses of porous and hollow glass microspheres are also reviewed. Glass microspheres are a promising substrate for titania coatings which can be used in water purification and self-cleaning systems. Due to their high mechanical strength and low thermal conductivity, they can also be applied in cementitious and insulating products. Glass microspheres can carry hydrogen gas at pressures of up to 150 MPa. In addition, they can enhance the quality of lead-acid batteries by decreasing the critical volume fraction..
Direct ink writing of three dimensional Ti2AlC porous structures
No full textIn this work, the Direct Ink Writing (DIW)technique was used to produce three-dimensional Ti2AlC ceramic components with high, uniform porosity. Suitable formulations were developed, with appropriate rheological properties for extruding thin filaments through a nozzle with a diameter of 810 μm. The main rheological properties of the inks were investigated to evaluate their behavior and flowability during the printing process. Porous Ti2AlC lattices were fabricated, in selected conditions, with uniform pore size and good interconnectivity, and sintered at 1400 °C in Ar. Total porosity ranged from ∼44 to ∼63 vol%, and the mechanical strength ranged from ∼43 to 83 MPa. The influence of the ink composition and heat-treatment conditions on the phase composition of the 3D porous structures was also evaluated
Baldratia karamae Elsayed and Skuhrava, new species
No full textBaldratia karamae Elsayed and Skuhravá, new species Adult description. Color (freshly emerged individuals): head black, antennae brown, thorax dark brown, wings smoky grey, legs light brown, upper and lower parts of abdomen dark brown, lateral parts red. Body length. 1.8 mm (n= 5) in female when the ovipositor not extended and 1.6 mm (n= 5) in male. Head (Fig. 11): Compound eyes with rounded facets, gap between eyes on vertex about 0-1 times as wide as facet. Palpi one-segmented; labella globular, setose, widely separated. Antenna 2 + 10 –segmented (n= 23), scape conical, pedicel rounded, flagellomeres 1–9 subequal, slightly longer than wide, each with two connected rings of circumfila in both sexes; male terminal flagellomere with circumfila arranged in a network pattern (Fig. 12); female terminal flagellomere (Fig. 13) consisting of the fusion of the three distal flagellomeres. Thorax: Wing (Fig. 14) length about 1.3 mm (n= 5) in male and 1.4 mm (n= 5) in female. Vein R 5 joining C approximately at mid-length; C broken behind the junction point with R 5; Sc and M present; CuA simple. Tarsal claws (Fig. 15) toothed and curved. Empodia shorter than claws. Hind legs of males much longer and thicker than fore- and midlegs of the female. Abdomen, Male: Tergites 1–7 rectangular with posterior row of setae; tergites 3–7 with anterior pair of trichoid sensilla. Tergite 8 about 0.3 times as wide as tergite 7. Sternites rectangular; sternites 1 and 3–5 with posterior row of setae; sternites 2, 6 and 7 with two posterior rows of setae. Genitalia (Fig. 16): Gonostylus about 0.6 times as long as gonocoxite, arched, setulose and setose, apically with blunt tooth. Gonocoxite wide, massive with scattered long setae. Mediobasal lobes small. Cerci fused, notched, setose and setulose, with rounded tips. Hypoproct entire, rounded apically. Aedeagus slender, and rounded at apex, surrounded with wide setulose parameres. Female (Fig. 17): Tergites 2–7 rectangular, with anterior pair of trichoid sensilla and posterior row of setae; tergite 8 about half tergite 7. Sternites rectangular; sternites 3–6 with posterior row of setae; sternites 6 and 7 with 1–2 posterior rows. Ovipositor (Fig. 18): segment 9 anteriorly with dorsal and ventral dark sclerotized patches, posteriorly with some hyaline setae; the two sclerotized rods widened basally. Lateral plate bears ~ 21 straight, hyaline, split setae. Aculeus concave ventrally, with three rows of strong, squamiform, apically hooked setae on the dorsal site. Sclerotized thin spine extends dorsally along the lateral plate. Apical lamella ovoid, densely covered with short setae. Holotype. Female, Egypt, El-Amria district (30 ° 59 '54.00"N, 29 ° 49 '7.00"E), 27.I. 2013, A. K. Elsayed, reared from pustule galls on leaves of Suaeda pruinosa. Paratypes. All from Egypt, Alexandria, and reared by A. K. Elsayed from leaf galls on Suaeda pruinosa. El- Amria district: 2 females, 1 male, 29.I. 2013; 2 females, 30.I. 2013; 1 female, 17.III. 2013; Abo-Talat district: 1 male, 7.III. 2013; 1 female, 27.IV. 2013; 1 female, 30.IV. 2013; Sidi Kreer district: 2 females, 1 male, 4.V. 2013; 1 female, 1 males, 5.V. 2013; 1 female, 1 male, 7.V. 2013; 4 females, 8.V. 2013; 1 female, 2 males, 15.V. 2013. Distribution. Egypt (Sidi Kreer, Abo-Talat, and El-Amria district). Etymology. This species is named in honor of Mrs. Hedaya H. Karam, professor of Economic Entomology at Alexandria University, Egypt. Biology. Larvae of B. karamae develop inside leaves of S. pruinosa (Chenopodiaceae). Attacked leaves do not show any external signs of infestation except for a dark reddish spot, but can be recognized once adults have emerged, leaving behind emergence holes and the protruding pupal exuviae. Each gall consists of a single chamber in which pupation takes place. The adults were collected from plants from the end of January to the beginning of March, and from the end of April to the middle of October, 2013. Baldratia karamae may have more than two generations per year. Remarks. According to Fedotova (1991 a) the genus Baldratia is divided into five groups on the basis of morphological characters of adults. By reviewing these characters, it was clear that the new species, B. karamae, belongs to the salicorniae Group, which is characterized by the apical lamella positioned at an obtuse angle relative to segment 9, and the lateral plate embraces the entire base of the apical lobe. The salicorniae Group previously contained three species, viz. B. salicorniae, B. suaedifolia, and B. balchanensis (Fedotova 1991 a, 1992). The thin spine of the female ovipositor is longer and thinner in B. suaedifolia, and B. balchanensis than in B. salicorniae. This new species has a long thin spine that does not exceed the base of the aculeus, in contrast to B. balchanensis which has a longer thin spine. Baldratia suaedifolia has a thin spine covered with split setae, while it is bare in B. karamae. Currently only five gall midge species are known to be associated with the host plant Suaeda (Gagné & Jaschhof 2014). Two of them, B. aelleni Möhn, 1969, and B. suaedae Möhn, 1969, were described on the basis of larvae alone (Möhn 1969), and can therefore not be compared to other adults in the genus. Baldratia karamae larvae that develop in leaves of Suaeda pruinosa, differ from the three other species, viz. B. occulta Dorchin, 2001, associated with S. monoica Forssk; B. suaedifolia Fedotova, 1991, associated with Suaeda acuminata (Meyer); and B. terteriani Mamaev & Mirumian, 1990, associated with Suaeda altissima (L.), on the basis published descriptions of these species (Mamaev & Mirumian 1990, Fedotova 1991 a, Dorchin 2001). An unique feature of the B. karamae is the stable number of antennal flagellomeres (2 + 10) in both sexes, in contrast to other species of Baldratia which have a variable number of flagellomeres between the sexes, viz. B. suaedifolia (2 + 12 in female versus 2 + 10 in male), B. occulta (2 + 13-14 in female versus 2 + 12 in male), and B. terteriani (2 + 14 in female versus 2 + 12 in male). The lateral plate of the ovipositor of B. karamae is broad at its base, narrow in the middle and covered with split setae, but B. occulta has a lateral plate which is narrow at the base and bearing 10-15 straight setae, with split setae only on the basal part. The lateral plate of B. terteriani has a small lateral projection at the base that is not present in B. karamae.Published as part of Elsayed, Ayman Khamis, Skuhravá, Marcela, Karam, Hedaya Hamza, Elminshawy, Abdelaziz & Al-Eryan, Mohamed Awad, 2015, New records and new species of gall midges (Diptera: Cecidomyiidae) developing on Chenopodiaceae in Egypt, pp. 105-115 in Zootaxa 3904 (1) on pages 108-110, DOI: 10.11646/zootaxa.3904.1.6, http://zenodo.org/record/23434
Influence of the thermal treatment on the characteristics of porous geopolymers as potential biomaterials
No full textHighly porous sodium geopolymer structures were successfully produced through the chemical direct foaming approach at ambient temperature. The impact of the thermal treatment, as well as the influence of various additions of hydrogen peroxide, as a foaming agent, on the porosity, microstructure and mechanical characteristics of the produced geopolymers was investigated. The evaluation of bioactivity was carried out by assessing the formation of an apatite layer on the samples' surface, using scanning electronic microscopy and inductively coupled plasma spectrometry for the simulated body fluid solution, in which the geopolymer samples were kept up to 28 days. In addition, the biodegradability was estimated through the weight change of the samples and pH-measurements. The results demonstrated that the geopolymer foams, produced using 4.5 vol% H2O2 and heat-treated at 500 °C for 1 h, possessed a high open porosity (71 vol %), excellent compressive strength (3.56 ± 0.27 MPa), and suitable chemical stability. The pH value of SBF solutions, in which these geopolymers were immersed for 28 days, remained close to the physiological one. The in vitro study indicated that the developed geopolymer foams possessed bioactivity, as demonstrated by the formation of apatite particles on their surface after immersion in the simulated body fluid solution for 28 days
Active distribution network modeling for enhancing sustainable power system performance; a case study in Egypt
No full textThe remarkable growth of distributed generation (DG) penetration inside electrical power systems turns the familiar passive distribution networks (PDNs) into active distribution networks (ADNs). Based on the backward/forward sweep method (BFS), a new power-flow algorithm was developed in this paper. The algorithm is flexible to handle the bidirectional flow of power that characterizes the modern ADNs. Models of the commonly used distribution network components were integrated with the developed algorithm to form a comprehensive tool. This tool is valid for modeling either balanced or unbalanced ADNs with an unlimited number of nodes or laterals. The integrated models involve modeling of distribution lines, losses inside distribution transformers, automatic voltage regulators (AVRs), DG units, shunt capacitor banks (SCBs) and different load models. To verify its validity, the presented algorithm was first applied to the unbalanced IEEE 37-node standard feeder in both passive and active states. Moreover, the algorithm was then applied to a balanced 22 kV real distribution network as a case study. The selected network is located in a remote area in the western desert of Upper Egypt, far away from the Egyptian unified national grid. Accordingly, the paper examines the current and future situation of the Egyptian electricity market. Comparison studies between the performance of the proposed ADNs and the classical PDNs are discussed. Simulation results are presented to demonstrate the effectiveness of the proposed ADNs in preserving the network assets, improving the system performance and minimizing the power losses
Additive manufacturing of inorganic components using a geopolymer and binder jetting
No full textA large volume binder jetting printer was employed to fabricate prism-shaped geopolymer components. A two parts system was used, comprising: 1) a highly alkaline solution, which was jetted on a powder bed containing aggregates (sand particles), and 2) a reactive solid component (pure metakaolin or metakaolin plus fast setting cement), present in the powder bed. In order to be able to generate appropriate, defect-free powder layers and suitably discharge the powders from the hopper feeding the layer forming system, a granulation approach was employed. The jetted alkaline solution effectively reacted with the metakaolin powders present in the granules, forming a geopolymer. Printed geopolymer parts, fabricated with the addition of 30 wt% metakaolin, possessed a compressive strength of ~20 MPa, even with ~30 vol% of residual porosity, and no significant variation in the compressive strength was observed after leaving the printed parts submerged in water for 1 week
Cold Consolidation of Pharmaceutical Waste Glass Powders Through Alkali Activation and Binder Jet 3D Printing
No full textThe recent COVID-19 emergency has led to an impressive increase in the production of pharmaceutical vials. This has led to a parallel increase in the amounts of waste glass; manufacturers typically recover material from faulty containers by crushing, giving origin to an unrecyclable fraction. Coarse fragments are effectively reused as feedstock for glass melting; on the contrary, fine powders (<100 microns), contaminated by metal and ceramic particles due to the same crushing operations, are landfilled. Landfilling is also suggested for pharmaceutical containers after medical use. This study aims at proposing new opportunities for the recycling of fine glass particles, according to recent findings concerning alkali activation of pharmaceutical glass, combined with novel processing, i.e., binder jetting printing. It has already been shown that pharmaceutical glass, immersed in low-molarity alkaline solution (not exceeding 2.5 M NaOH), undergoes surface dissolution and hydration; cold consolidation is later achieved, upon drying at 40–60 °C, by a condensation reaction occurring at hydrated layers of adjacent particles. Binder jetting printing does not realize a full liquid immersion of the glass powders, as the attacking solution is selectively sprayed on a powder bed. Here, we discuss the tuning of key parameters, such as the molarity of the attacking solution (from 2.5 to 10 M) and the granulometry of the waste glass, to obtain stable printed blocks. In particular, the stability depends on the formation of bridges between adjacent particles consisting of strong T-O bonds (Si-O-Si, Al-O-Si, B-O-Si), while degradation products (concentrating Na ions) remain as a secondary phase, solubilized by immersion in boiling water. Such stability is achieved by operating at 5 M NaOH
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