An NMR Spectroscopic Investigation of Aluminosilicate Gel in Alkali-Activated Fly Ash in a CO₂-Rich Environment.
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ABSTRACT:
SUBMITTER: Park SM
PROVIDER: S-EPMC5503083 | biostudies-other | 2016 Apr
REPOSITORIES: biostudies-other
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Project description:An incredible amount of joss fly ash is produced from the burning of Chinese holy joss paper; thus, an excellent method of recycling joss fly ash waste to extract aluminosilicate nanocomposites is explored. The present research aims to introduce a novel method to recycle joss fly ash through a simple and straightforward experimental procedure involving acidic and alkaline treatments. The synthesized aluminosilicate nanocomposite was characterized to justify its structural and physiochemical characteristics. A morphological analysis was performed with field-emission transmission electron microscopy, and scanning electron microscopy revealed the size of the aluminosilicate nanocomposite to be ~25 nm, while also confirming a uniformly spherical-shaped nanostructure. The elemental composition was measured by energy dispersive spectroscopy and revealed the Si to Al ratio to be 13.24 to 7.96, showing the high purity of the extracted nanocomposite. The roughness and particle distribution were analyzed using atomic force microscopy and a zeta analysis. X-ray diffraction patterns showed a synthesis of faceted and cubic aluminosilicate crystals in the nanocomposites. The presence of silica and aluminum was further proven by X-ray photoelectron spectroscopy, and the functional groups were recognized through Fourier transform infrared spectroscopy. The thermal capacity of the nanocomposite was examined by a thermogravimetric analysis. In addition, the research suggested the promising application of aluminosilicate nanocomposites as drug carriers. The above was justified by an enzyme-linked apta-sorbent assay, which claimed that the limit of the aptasensing aluminosilicate-conjugated ampicillin was two-fold higher than that in the absence of the nanocomposite. The drug delivery property was further justified through an antibacterial analysis against Escherichia coli (gram-negative) and Bacillus subtilis (gram-positive).
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Project description:The environmental impacts related to Portland cement production in terms of energy consumption, the massive use of natural resources and CO2 emissions have led to the search for alternative cementitious materials. Among these materials, alkali-activated cements based on fly ash (FA) have been considered for concrete production with greater sustainability. In the present article, the chemical durability properties (resistance to sulphates, chloride permeability, and resistance to carbonation) of a hybrid alkali-activated concrete based on fly ash-ordinary Portland cement (FA/OPC) with proportions of 80%/20% were evaluated. It is noted that the FA was a low-quality pozzolan with a high unburned carbon content (20.67%). The results indicated that FA/OPC concrete had good durability with respect to the OPC concrete, with 95% less expansion in the presence of sodium sulphate and a 2% strength loss at 1100 days, compared with the 56% strength loss of the OPC concrete. In addition, FA/OPC showed lower chloride permeability. On the contrary, the FA/OPC was more susceptible to carbonation. However, the residual compressive strength was 23 MPa at 360 days of CO2 exposure. Based on the results, FA/OPC, using this type of FA, can be used as a replacement for OPC in the presence of these aggressive agents in the service environment.
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Project description:The present study investigates the retention mechanisms of cesium and strontium for alkali-activated cements. Retention mechanisms such as adsorption and precipitation were examined in light of chemical interactions. Batch adsorption experiments and multi-technical characterizations by using X-ray diffraction, zeta potential measurements, and the N₂ gas adsorption/desorption methods were conducted for this purpose. Strontium was found to crystalize in alkali-activated cements, while no cesium-bearing crystalline phases were detected. The adsorption kinetics of alkali-activated cements having relatively high adsorption capacities were compatible with pseudo-second-order kinetic model, thereby suggesting that it is governed by complex multistep adsorption. The results provide new insight, demonstrating that characteristics of aluminosilicate gel with a highly negatively charged surface and high micropore surface area facilitated more effective immobilization of cesium and strontium in comparison with calcium silicate hydrates.
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Project description:Sugarcane bagasse fly ash, a residual product resulting from the incineration of biomass to generate power and steam, is rich in SiO2. Sodium silicate is a fundamental material for synthesizing highly porous silica-based adsorbents to serve circular practices. Aflatoxin B1 (AFB1), a significant contaminant in animal feeds, necessitates the integration of adsorbents, crucial for reducing aflatoxin concentrations during the digestive process of animals. This research aimed to synthesize aluminosilicate and zinc silicate derived from sodium silicate based on sugarcane bagasse fly ash, each characterized by a varied molar ratio of aluminum (Al) to silicon (Si) and zinc (Zn) to silicon (Si), respectively. The primary focus of this study was to evaluate their respective capacities for adsorbing AFB1. It was revealed that aluminosilicate exhibited notably superior AFB1 adsorption capabilities compared to zinc silicate and silica. Furthermore, the adsorption efficacy increased with higher molar ratios of Al:Si for aluminosilicate and Zn:Si for zinc silicate. The N2 confirmed AFB1 adsorption within the pores of the adsorbent. In particular, the aluminosilicate variant with a molar ratio of 0.08 (Al:Si) showcased the most substantial AFB1 adsorption capacity, registering at 88.25% after an in vitro intestinal phase. The adsorption ability is directly correlated with the presence of surface acidic sites and negatively charged surfaces. Notably, the kinetics of the adsorption process were best elucidated through the application of the pseudo-second-order model, effectively describing the behavior of both aluminosilicate and zinc silicate in adsorbing AFB1.
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