scholarly journals Coal Fly Ash-based Geopolymer Spheres Coated with Amoxicillin and Nanosilver for Potential Antibacterial Applications

2019 ◽  
Vol 19 (1) ◽  
pp. 25
Author(s):  
Brandon Cyril S. Lira ◽  
Sophia Bianca A. Dellosa ◽  
Casey Irene L. Toh ◽  
Al Patrick A. Quintero ◽  
Andre Leopold S. Nidoy ◽  
...  
Keyword(s):  
Fly Ash ◽  
Coal Fly Ash ◽  
Test Organism ◽  
Embodied Energy ◽  
Sem Images ◽  
E Coli ◽  
Green Materials ◽  
The Matrix ◽  
Disk Diffusion Assay ◽  
Zones Of Inhibition

Geopolymers are emerging “green” materials for its low embodied energy and carbon footprint, and its potential to valorize wastes, such as coal fly ash. It is an inorganic cementitious material formed from the polymerization of aluminosilicates in an activating solution such as that of alkali hydroxides or silicates. Their superior mechanical properties, including heat and fire resistance make them an excellent material for diverse applications. Recent studies have also exploited the tunable open porosity and adsorbing properties of geopolymers. Our work thus explores the potential of porous geopolymer spheres for antibacterial applications. These spheres were synthesized using coal fly ash as the geopolymer precursor and the porous surface is coated with either amoxicillin or silver nanoparticles (AgNPs) adsorbed in the matrix. For the AgNP geopolymer spheres, SEM images show spherical nanostructures when using ascorbic acid as a reducing agent, while spherical, cubical, and wire structures were observed when reduced using NaBH4. Indication from UV-Vis results also suggests the gradual release of both amoxicillin and AgNPs in the solution from the functionalized geopolymer spheres. Using E. Coli as the test organism for a modified disk diffusion assay, both showed zones of inhibition against the bacteria. Further tests on antibacterial application of AgNP geopolymer spheres show their effectiveness to kill at least 95% of the E. coli in a water sample initially containing 105 cfu/mL in just 30 minutes.

scholarly journals Chemical Stability and Leaching Behavior of One-Part Geopolymer from Soil and Coal Fly Ash Mixtures

Minerals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 411 ◽  
Author(s):  
April Tigue ◽  
Roy Malenab ◽  
Jonathan Dungca ◽  
Derrick Yu ◽  
Michael Promentilla
Keyword(s):  
Fly Ash ◽  
Chemical Stability ◽  
Coal Fly Ash ◽  
Embodied Energy ◽  
Synthesis Process ◽  
Attractive Alternative ◽  
Alkali Activation ◽  
Acid Attack ◽  
X Ray ◽  
Stabilized Soil

Aluminosilicate minerals have become an important resource for an emerging sustainable material for construction known as geopolymer. Geopolymer, an alkali-activated material, is becoming an attractive alternative to Portland cement because of its lower carbon footprint and embodied energy. However, the synthesis process requires typically a two-part system for alkali activation wherein the solid geopolymer precursor is mixed with aqueous alkali solutions. These alkali activators are corrosive and may be difficult to handle in the field-scale application. In this study, a one-part geopolymer in which coal fly ash was mixed with solid alkali activators such as sodium hydroxide and sodium silicate to form a powdery cementitious binder was developed. This binder mixed with soil only requires water to form the soil-fly ash (SO-CFA) geopolymer cement, which can be used as stabilized soil for backfill/foundation. This geopolymer product was then evaluated for chemical stability by immersing the material with 5% by weight of sulfuric acid solution for 28 days. Indication suggests that the geopolymer exhibited high resistance against acid attack with an observed increase of unconfined compressive strength even when the immersion time in acidic solution was increased to 56 days. The mineralogical phase, microstructure, and morphology of the material were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), respectively. Results not only confirmed the formation of gypsum due to acid attack but also indicated the dissolution of anorthite and albite that may have caused the microstructure to be composed of sodium aluminosilicate hydrate (N–A–S–H) and calcium (alumino) silicate hydrate (C(–A)–S–H) with poly(ferro-sialate-siloxo) and poly(ferro-sialate-disiloxo) networks. A column leaching test with deionized water was also performed on the soil-fly ash geopolymer to study the leachability of metals in the material. Results showed that arsenic exhibits higher mobility in the geopolymer as compared to that of cadmium, chromium, and lead.

Removal of Natural Organic Matter of Artificial Lake by Modified Fly Ash

2013 ◽  
Vol 690-693 ◽  
pp. 1020-1023
Author(s):  
Chang Nian Wu ◽  
Li Wang ◽  
Qi Ling ◽  
Yu Chao Tang ◽  
Jian Huang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Fly Ash ◽  
Natural Organic Matter ◽  
Low Cost ◽  
Coal Fly Ash ◽  
Kinetic Studies ◽  
Artificial Lake ◽  
Sem Images ◽  
Sulfuric Acid Treatment ◽  
Surface Areas

Coal fly ash (CFA) modified by sulfuric acid treatment was used as a low-cost adsorbent for removing natural organic matter (NOM) in an artificial lake. The specific surface areas and SEM images of modified coal fly ash (MCFA) and CFA were observed. Two equilibrium models were compared to evaluate NOM removal process with a better fitting using the Freundlich model. Kinetic studies were also carried out to fit the experimental data. The pseudo second-order provided the highest coefficients of determination.

scholarly journals Layer-by-Layer Assembly and Photocatalytic Activity of Titania Nanosheets on Coal Fly Ash Microspheres

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Xing Cui ◽  
Jianwen Shi ◽  
Zhilong Ye ◽  
Zhaoji Zhang ◽  
Bin Xu ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Fly Ash ◽  
Coal Fly Ash ◽  
Layer By Layer ◽  
X Ray Diffraction ◽  
Sem Images ◽  
Visible Absorption ◽  
Layer By Layer Assembly ◽  
Decoloration Rate ◽  
Layer Assembly

In order to address the problem with titania distribution and recovery, series of Ti0.91O2/CFA photocatalysts (Ti0.91O2/CFA-n,n=2,4,6,and8) were fabricated by assembling Ti0.91O2nanosheets on coal fly ash (CFA) microspheres via the layer-by-layer assembly (LBLA) process and characterized by scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), N2-sorption, and ultraviolet-visible absorption (UV-vis) techniques. The SEM images and UV-vis spectra illustrated that Ti0.91O2nanosheets were immobilized successfully on the CFA by the LBLA approach and changed the characteristics of CFA noticeably. The photocatalytic activity of Ti0.91O2/CFA was evaluated by the photodegradation of methylene blue (MB) under UV irradiation. The results demonstrated that Ti0.91O2/CFA-6 showed the best photocatalytic activity among the series of Ti0.91O2/CFA irradiated for 60 min, with a decoloration rate above 43%. After photocatalysis, the Ti0.91O2/CFA could be easily separated and recycled from aqueous solution and Ti0.91O2nanosheets were still anchored on the CFA.

Embodied energy as key parameter for sustainable materials selection: The case of reusing coal fly ash for removing anionic surfactants

2017 ◽  
Vol 141 ◽  
pp. 230-236 ◽  
Author(s):  
Alessandra Zanoletti ◽  
Stefania Federici ◽  
Laura Borgese ◽  
Paolo Bergese ◽  
Matteo Ferroni ◽  
...  
Keyword(s):  
Fly Ash ◽  
Anionic Surfactants ◽  
Coal Fly Ash ◽  
Embodied Energy ◽  
Materials Selection ◽  
Sustainable Materials ◽  
Key Parameter

Characterization of Coal Fly Ash for Use in Synthesis of Zeolites

2018 ◽  
Vol 930 ◽  
pp. 578-583
Author(s):  
Augusto César Cavalcanti Gomes ◽  
Andrea de Vasconcelos Ferraz ◽  
Lucimar Pacheco Gomes da Rocha
Keyword(s):  
Fly Ash ◽  
Coal Fly Ash ◽  
Coal Ash ◽  
X Ray Diffraction ◽  
X Ray ◽  
Inorganic Oxides ◽  
Chemical Treatments ◽  
Xrf Scanning ◽  
The Matrix ◽  
Physical And Chemical

Due to the large quantity of fly ash produced during the combustion of coal, it has become necessary to give greater applicability to this residue of low commercial value. The residue contains inorganic oxides which can act on the crystalline structure of zeolites, namely silicon and aluminum oxide. The coal ash was submitted to physical and chemical treatments with the aim of potentiating the silicon and aluminum extraction from the residue. The pure ash and the treated ashes were characterized by: X-ray fluorescence (XRF), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transformation infrared spectroscopy (FTIR). By means of the carried out characterizations it was observed that the treatments were effective for the extraction of aluminosilicates from the matrix. The treatments did not affect the morphology, the crystalline phases and neither the chemical composition of the ashes. Seeing this, the coal ash and its treatments showed to be a precursor for the synthesis of zeolites.

scholarly journals Characterization of Bacterial Cellulose-Based Wound Dressing in Different Order Impregnation of Chitosan and Collagen

Biomolecules ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1511
Author(s):  
Khatarina Meldawati Pasaribu ◽  
Saharman Gea ◽  
Syafruddin Ilyas ◽  
Tamrin Tamrin ◽  
Izabela Radecka
Keyword(s):  
Bacterial Cellulose ◽  
Wound Dressing ◽  
Antibacterial Properties ◽  
Tissue Growth ◽  
Hydroxyl Group ◽  
Sem Images ◽  
E Coli ◽  
Zones Of Inhibition ◽  
Collagen Molecules

Bacterial cellulose (BC), chitosan (Chi), and collagen (Col) are known as biopolymers which have met some properties that are required as wound dressing. This study focused on investigating the fabrication of BC-based wound dressing with chitosan and collagen, since chitosan has red blood cells binding and anti-bacterial properties, while collagen can support cell and tissue growth for skin wounds. The BC-based wound dressing was prepared by impregnating BC fibers in the chitosan and/or collagen solution for 24 h. FTIR was used to confirm the intermolecular interaction of amine and hydroxyl group of chitosan and/or collagen in BC-based wound dressing. Furthermore, the XRD diffractogram of the wound dressing show broader peaks at 14.2°, 16.6°, and 22.4° due to the presence of chitosan and collagen molecules in BC fibers. These results were then supported by SEM images which confirmed that chitosan and collagen were well penetrated into BC fibers. TGA curves revealed that BC/Chi/Col has better thermal properties based on the Tmax compare to BC/Col/Chi. Feasibility of the mats to be applied as wound dressing was also supported by other tests, i.e., water content, porosity, and hemocompatibility, which indicates that the wound dressing is classified as nonhemolytic materials. However, BC/Col/Chi was considered a more potential wound dressing to be applied compared to BC/Chi/Col since it has larger pores and showed better antibacterial properties (larger zones of inhibition) against S. aureus and E. coli via disk diffusion tests.

scholarly journals The Behaviour of Rare Earth Elements from South African Coal Fly Ash during Enrichment Processes: Wet, Magnetic Separation and Zeolitisation

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 950
Author(s):  
Mero-Lee Ursula Cornelius ◽  
Alechine Emmanuel Ameh ◽  
Chuks Paul Eze ◽  
Olanrewaju Fatoba ◽  
Asel Sartbaeva ◽  
...  
Keyword(s):  
Rare Earth ◽  
Fly Ash ◽  
Rare Earth Elements ◽  
South African ◽  
Magnetic Separation ◽  
Coal Fly Ash ◽  
Clean Energy ◽  
Separation Process ◽  
Matrix Elements ◽  
The Matrix

Rare earth elements (REEs) are essential raw materials in a variety of industries including clean energy technologies such as electric vehicles and wind turbines. This places an ever-increasing demand on global rare earth element production. Coal fly ash (CFA) possesses appreciable levels of REEs. CFA, a waste by-product of coal combustion, is therefore a readily available source of REEs that does not require mining. CFA valorisation to zeolites has been achieved via various synthesis pathways. This study aimed to evaluate one such pathway by monitoring how REEs partition during CFA processing by the wet, magnetic separation process and zeolitisation. South African CFA was subjected to wet, magnetic separation and subsequent zeolitisation of the nonmagnetic fraction (NMF); solid products were characterised by XRD, SEM, XRF and LA-ICP-MS. The wet, magnetic separation process resulted in the partitioning of a specific set of transition metals (such as Fe, Mn, Cr, V, Ni, Zn, Cu, Co and Mo) into the magnetic fraction (MF) of CFA, while REEs partitioned into the NMF with a total REE content of 530.2 ppm; thus, the matrix elements of CFA were extracted with ease. Zeolitisation resulted in a solid zeolite product (hydroxysodalite) with a total REE content of 537.6 ppm. The process of zeolitisation also resulted in the selective enrichment of Ce (259.1 ppm) into the solid zeolite product (hydroxysodalite), while other REEs were largely partitioned into the liquid phase. CFA valorisation by wet, magnetic separation and zeolitisation therefore allowed for the partitioning of REEs into various extraction products while recovering the matrix elements of CFA such as Fe, Si and Al. The findings of this study highlight the geopolitical importance of REEs in terms of the development of alternative processes for REE recovery from waste and alternative sources, which may potentially give countries that employ and develop the technology a key advantage in the production of REEs for the global market.

Micromechanical Behavior and Micromorphology of Single PVA Fiber Pullout

2018 ◽  
Vol 768 ◽  
pp. 331-335 ◽  
Author(s):  
Bo Chen ◽  
Li Ping Guo ◽  
Ya Nan Yang ◽  
Zheng Kai Chen
Keyword(s):  
Fly Ash ◽  
Testing Machine ◽  
Fiber Surface ◽  
Fiber Pullout ◽  
Sem Images ◽  
Tensile Testing Machine ◽  
Cement Ratio ◽  
Water To Cement Ratio ◽  
The Matrix ◽  
Pva Fiber

To evaluate the suitability of domestic polyvinyl alcohol (PVA) fiber for preparing high ductility cementitious composites (HDCC), single PVA fiber pullout tests were conducted. The tests were carried out with four matrices having a water-to-cement ratio of 0.25 or 0.30, and fly ash replacement level 60% or 80%. The micromechanical behavior of single PVA fiber pullout from the matrix was monitored using a fiber tensile testing machine. Micromorphology of the pulled fiber was subsequently investigated using scanning electron microscopy (SEM). The results indicated that the slip-hardening coefficient is greater than zero and that the fiber therefore meets the micromechanical requirements for preparing HDCC. The chemical bonding energy and frictional bond strength were determined to decrease with the increasing fly ash content and/or water-to--cement ratio. SEM images indicate a significant number hydration products attached to the fiber surface, associated with an increase friction force during fiber pullout. After the pullout test, a complete tunnel containing fiber fragments was observed in the matrix, indicative of matrix cutting.

scholarly journals Complete Extraction of Amorphous Aluminosilicate from Coal Fly Ash by Alkali Leaching under Atmospheric Pressure

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1684
Author(s):  
Andrei Shoppert ◽  
Dmitry Valeev ◽  
Irina Loginova ◽  
Leonid Chaikin
Keyword(s):  
Fly Ash ◽  
Inductively Coupled Plasma ◽  
Coal Fly Ash ◽  
Optical Emission ◽  
Product Layer ◽  
Emission Spectrometry ◽  
Sem Images ◽  
X Ray ◽  
Before And After ◽  
Shrinking Core

One of the potential sources of alumina and mesoporous silica is the coal-fired thermal plants waste known as the coal fly ash (CFA). The studies of the alumina extraction from CFA are often focused on the preliminary desilication, but the efficiency of the alkali desilication is low due to formation of the desilication product—Na6[Al6Si6O24]·Na2X (DSP). This research is focused on the possibility of CFA desilication without formation of DSP using a leaching process with higher liquid to solid ratios (L/S) and alkali concentrations. The experimental data were analyzed using an artificial neural network (ANN) machine learning method and a shrinking core model (SCM). The investigation of the CFA morphology, chemical and phase composition before and after leaching were carried out by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), inductively coupled plasma optical emission spectrometry (ICP-OES) and X-ray diffraction (XRD). The present work shows that it is possible to avoid formation of DSP if using the L/S ratio >20 and concentration of Na2O—400 g/L during CFA leaching. The kinetics analysis by SCM showed that the process is limited by the surface chemical reaction at T <100 °C, and by diffusion through the product layer at T >100 °C, respectively. The SEM images of the solid residue after NaOH leaching under conditions that prevent the DSP formation show mullite particles with an acicular structure.

Coal fly ash industrial waste recycling for fabrication of mullite-whisker-structured porous ceramic membrane supports

RSC Advances ◽  
2015 ◽  
Vol 5 (15) ◽  
pp. 11163-11174 ◽  
Author(s):  
Li Zhu ◽  
Yingchao Dong ◽  
Lingling Li ◽  
Jing Liu ◽  
Sheng-Jie You
Keyword(s):  
Fly Ash ◽  
Industrial Waste ◽  
Ceramic Membrane ◽  
Coal Fly Ash ◽  
Porous Ceramic ◽  
Waste Recycling ◽  
Sem Images ◽  
Porous Ceramic Membrane

SEM images of mullite membrane support (a) without addition, (b) with addition of AlF3, (c) with addition of MoO3 and (d) with addition of AlF3 and MoO3.

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