Comparative sorption kinetic studies of phenolic compounds on fly ash and impregnated fly ash

The factors affecting the rate processes involved in the removal of phenolic compounds, e.g. initial phenol concentration, particle size, impregnation of fly ash (IFA), pH and temperature have been studied. The removal rate of phenols varied in the order p-nitrophenol m-nitrophenol > o-nitrophenol > p-cresol > phenol > m-cresol > o-cresol. The process followed first order rate kinetics. The sorption data generally fit the Lagergren equation and the intraparticle diffusion rate equation from which adsorption rate constants, diffusion rate constants and diffusion coefficients were determined. Intraparticle diffusion was found to be the rate-limiting step. These kinetic parameters were compared for various phenols under different conditions using fly ash (FA) and impregnated fly ash (IFA).     

Alkaline hydrothermal zeolites synthesized from high SiO2 and Al2O3 co-disposal fly ash filtrates

A co-disposal reaction was used wherein fly ash (FA) was reacted with acid mine drainage (AMD), to collect filtrates for zeolite synthesis. Raw fly ash as well as fly ash leached with HCl were subjected to the same alkaline hydrothermal zeolite synthesis conditions, as for the co-disposal filtrates, in order to evaluate the zeolitic material obtained. The Si and Al contents of the fly ash (FA) filtrates were used as precursor species for the alkaline hydrothermal conversion of the fly ash filtrates into zeolites. These filtrates were then analysed by XRF spectrometry for quantitative determination of SiO₂ and Al₂O₃. The [SiO₂]/[Al₂O₃] ratio obtained in the filtrates range from 1.4 to 2.5. The [SiO₂]/[Al₂O₃] ratio was used to predict whether the fly ash filtrates could successfully be converted into faujasite zeolitic material by the adopted synthesis procedures. If the [SiO₂]/[Al₂O₃] ratio is higher than 1.5 in the co-disposal filtrates, it favours the formation of faujasite. The zeolite synthesis included an alkaline fusion of the co-disposal filtrates, followed by aging for 8 hours and hydrothermal conversion by crystallisation at 100 °C. Different variables were investigated during the synthesis of zeolite to ascertain their influence on the end product. These variables include adding different amounts of deionised water to the FA-related starting material, using different compositions of FA related starting material and different FA:NaOH ratios in fusing the starting material.     

Industrially viable technique for the preparation of HDPE/fly ash composites at high loading: Thermal,mechanical, and rheological interpretations

This article describes an industrially viable melt blending approach for the preparation of high‐density polyethylene (HDPE)/fly ash composites having high loading of fly ash (FA) (up to 25 wt %). In this approach, solvent was used to enhance the mixing of FA in HDPE matrix. FA coated on the outer surface of HDPE granules using solvent is an economical technique for the incorporation of high loading of FA using conventional twin screw extruder. Herein, the effect of HDPE reinforced with FA on thermal, rheological, and mechanical properties has been investigated. Incorporation of FA in HDPE matrix resulted in higher storage modulus (E′), loss modulus (E″), and complex viscosity (η*) as compared to neat polymer. Tensile and flexural moduli were also found to increase (～47% and ～66%, respectively) with the addition of FA (25 wt %). However, the elongation at break of HDPE reduced as the rigid spherical FA particles do not undergo elongation. The dispersion of FA within the polymer matrix and interaction of FA with HDPE were investigated using scanning electron microscopy. Rheological and mechanical properties of the composites were also correlated with the morphology. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45995.     

Utilization of fly ash for treatment of coal mines wastewater: Solubility controls on major inorganic contaminants

Acid mine drainage (AMD) has been reacted with coal fly ash in a 24 h equilibration time using 1:3 and 1:1.5 FA:AMD ratios by weight to produce neutral and alkaline process waters. The capacity of the fly ash to remove the major inorganic contaminants was examined. The elemental concentration trends with time for the two ratios were used to discern which elements have solubility control in the neutralization process. The geochemical computer code PHREEQC and WATEQ4 database was used for geochemical modeling of the process water. The resulting solid residues (SR) were analyzed by X-ray diffraction (XRD), and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDX) in an attempt to detect the minerals phases controlling the inorganic contaminants concentration in solution. The relative quantities of soluble bases (CaO, MgO) in fly ash and hydrolyzable constituents in AMD dictated whether the final solution at a given contact time will have a dominant acidic or basic character. Concentration of Fe, Al, B were observed to be controlled by mineral solubility for the entire reaction time while mineral solubility control for Ca, Na, Mg, Si and Mn concentrations developed after the initial rapid dissolution. Initial concentration was controlled by precipitation of gypsum and adsorption on iron-oxy-hydroxides at pH > 5.5. Increase of pH in solution with contact time caused the removal of the metal ions mainly by precipitation, co-precipitation and adsorption. Fe was mainly removed as Fe(OH)_3(a), goethite, Al as basaluminite, boehmite and alunite at pH 5.28-6.95 and as gibbsite and diaspore at pH 5.53-9.12. Cu and Zn were removed by adsorption onto the precipitating iron(oxy)-hydroxides and aluminum (oxy)-hydroxides. Si is released by dissolution of SiO_2(a) at pH < 5. Na was removed as Na-jarosite at pH 3.96-6.95 and Ca as gypsum and anhydrite. The treatment of AMD with fly ash was observed to be site-specific, i.e., the effectiveness of the treatment process will depend on the quality of the fly ash and the AMD. The product water meets the DWAF water quality limits for domestic use and irrigation at pH > 8 except for species Na, B, Mg, Ca, Sr and Ba which remain in solution. In addition B, Mg, Sr, Mo and Ba are released from dissolution of fly ash and will be of concern in the proposed treatment process.     

不同品质粉煤灰在砂浆中减水效应及强度规律的研究

选取甘肃地区4种不同品质的粉煤灰,研究各粉煤灰的减水率和同流动度条件下砂浆的强度.结果表明:粉煤灰的品质对砂浆的减水效果和强度有较大的影响,品质较优的FA1、FA2减水效应、各龄期砂浆强度均高于品质较劣的FK3、FA4.粉煤灰水泥砂浆抗压强度与粉煤灰减水率两者之间具有负线性相关.粉煤灰减水效果越好,其与强度的线性关联度...     

Fabrication of High Performance Fly Ash/Mica/Poly(ether-ether-ketone) Hybrid Composites

This paper deals with the preparation and characterization of poly(ether-ether-ketone) (PEEK) fly ash mica hybrid composites containing filler 5:15, 10:10 and 15:5 fly ash mica combinations loading. The performances and properties of the resulting 20 wt% loading of fly ash mica/PEEK hybrid composites were examined. The resulting hybrid composites of 20 wt% fly ash and mica with varying combinations exhibit the optimum improvement of mechanical properties and dielectric strength. MDSC showed the decrease in the crystallization temperature (Tc) with varying combinations of fly ash and mica. The morphology of fly ash/mica/PEEK hybrid composites was studied by SEM.     

UV固化水性聚氨酯/粉煤灰复合材料的制备及其涂膜性能的研究

将微米级的粉煤灰(FA)用于可紫外光固化水性聚氨酯的改性,以改善水性聚氨酯的耐水性能。首先用KH-550对粉煤灰进行表面改性,再通过偶联剂中—NH2基团与异佛尔酮二异氰酸酯(IPDI)的反应制得表面带有—NCO基团的改性粉煤灰。原位反应制备可紫外光固化的WPU/FA复合材料,复合体系中粉煤灰的掺杂量达到5%。利用扫描电子显微镜(SEM)观察了粉煤灰颗粒及复合物薄膜的表面形态,测试结果证明这种回收利用的无机粒子能够改善水性聚氨酯材料的耐水性能和机械性能,其耐热性能也有明显的提升。     

Quantification of the degree of reaction of fly ash

The quantification of the fly ash (FA) in FA blended cements is an important parameter to understand the effect of the fly ash on the hydration of OPC and on the microstructural development. The FA reaction in two different blended OPC-FA systems was studied using a selective dissolution technique based on EDTA/NaOH, diluted NaOH solution, the portlandite content and by backscattered electron image analysis.The amount of FA determined by selective dissolution using EDTA/NaOH is found to be associated with a significant possible error as different assumptions lead to large differences in the estimate of FA reacted. In addition, at longer hydration times, the reaction of the FA is underestimated by this method due to the presence of non-dissolved hydrates and MgO rich particles. The dissolution of FA in diluted NaOH solution agreed during the first days well with the dissolution as observed by image analysis. At 28 days and longer, the formation of hydrates in the diluted solutions leads to an underestimation. Image analysis appears to give consistent results and to be most reliable technique studied.     

Properties of a ternary calcium sulfoaluminate–calcium sulfate–fly ash cement

In this paper, cement combinations based on calcium sulfoaluminate cement (CSAC) were developed and the effect of fly ash and the hemihydrate form of calcium sulfate on the properties of the systems was studied. Fly ash (FA), anhydrite (ANH), flue-gas desulfurization gypsum (FGDG) and plaster gypsum (PL) were used to develop appropriate CSAC/calcium sulfate and CSAC/calcium sulfate/addition systems, the hydration of which was studied. Tested properties of cements were the compressive strength and the setting times. The results suggest that the use of fly ash in the presence of anhydrite accelerates the formation of a strong ettringite-rich matrix that firmly accommodated unreacted fly ash particles, both synergistically contributing to a dense microstructure. At a given sulfate content, the use of anhydrite was shown to be favourable in terms of the setting times, heat patterns and strength development compared to the hemihydrate-based formulations.     

Chemical modification of coal fly ash for the removal of phosphate from aqueous solution

This study investigated the chemical modifications of coal fly ash treated with HCl and NaOH. Sorption behavior of phosphate from water solution on treated fly ash was examined. Results showed that the HCl-treated fly ash (TFA-HCl) had a greater specific surface area (SSA) than the NaOH-treated fly ash (TFA-NaOH) and untreated fly ash (FA). The XRF, XRD patterns, and SEM images revealed the decreased CaO content in the TFA-HCl and observed the presence of NaP1 and sodalite zeolites in the TFA-NaOH. The P sorption capacity of all studied fly ashes increased with increasing initial P concentration and mechanisms of P sorption were influenced by the equilibrium pH. Maximum phosphate immobilization capacity obtained from Langmuir model was in the following manner, TFA-NaOH > FA > TFA-HCl (57.14, 23.20, and 6.90 mg P g⁻¹, respectively). The decreased CaO content and acidic pH in the TFA-HCl were responsible for the lowest capacity of phosphate immobilization, because of unfavorable condition for calcium phosphate precipitation. In contrast, due to alkaline condition and relatively high calcium content, the precipitation of calcium phosphate was a key mechanism for phosphate removal in the FA and TFA-NaOH. The TFA-NaOH had a greatest phosphate immobilization, due to high CaO content and an increased SSA after the conversion of fly ash to zeolite. Both Langmuir and Freundlich models were good fitted for the TFA-NaOH, while was only Langmuir model for the FA and Freundlich model for the TFA-HCl. Results suggested that treating fly ash with alkaline solution was a promising way to enhance phosphate immobilization.     

Characteristics of the ultrafine component of fly ash

Post-production processing of fly ash (FA) is an important issue for its use in concrete. Given (i) the need for environmental protection, (ii) the measures being applied on coal-fired power stations to reduce acidic gas emissions and (iii) the effect these have had on fly ash quality, there is a need to consider efficient post-production processing to enhance fly ash characteristics. This is particularly important for fly ash used as a cement in concrete production, since the additional residual carbon content and decreased fineness significantly affect its quality. This paper details the material characteristics of an ultrafine, low-lime fly ash (UF-FA), produced, in this case, by processing a coarse FA (referred to as parent FA) from a bituminous coal-fired power station via air-cyclonic separation. The UF-FA is shown to have much improved material characteristics compared to the parent FA in terms of morphology, mineralogy and chemical composition. Further results are presented on the effect of UF-FA on the properties of cementitious systems. Improved consistence and compressive strengths of combined Portland cement (PC) and UF-FA mortars were observed, whilst enhanced PC hydration and a high degree of FA reactivity were concluded from heat of hydration measurements and calcium hydroxide contents of pastes.     

Influence of additive contents on the properties of SiC ceramic membranes and their performance in oil-water separation

The high processing cost is the key challenge for the economic industrial use of SiC membrane The aim of this research was to fabricate mullite bonded porous SiC ceramic membrane at low temperature from novel combinations of fly ash and alumina (FA) in weight ratio 44.5:55.5 as sintering additives. The influences of FA and pore former content on the porosity, morphology, crystalline phase composition, mechanical performance, permeability properties were investigated. The membrane prepared at 1300°C using 20 wt% FA showed pure water permeability 3690 Lm⁻²h⁻¹bar⁻¹ and exhibited high oil removal efficiency of ∼ 98% from the synthetic oil-water emulsion having oil concentration of 1000 mg/L. The corrosion behaviour of silicon carbide membrane in the strong acid and alkali solution and its mechanism were investigated. The utilization of fly ash successfully reduced the raw material cost and sintering temperature and the use of alumina reduced the amount of oxidation of SiC as well as increased the amount of mullite bond phase which resulted excellent mechanical strength to the final ceramics.     

粉煤灰和矿渣微粉在水泥基材料中的复合效应研究

通过测定不同龄期的水泥净浆、砂浆和混凝土的力学强度以及水泥净浆的抗模拟酸雨侵蚀性能，探讨了在矿物掺合料总量为胶凝材料总量的40％时，单掺粉煤灰、单掺矿渣微粉以及粉煤灰与矿渣微粉双掺对水泥基材料性能的影响。试验结果表明：在本试验条件下，与基准试件相比，矿物掺合料的掺入可以显著改善水泥基材料的工作性能，但是在一定程度上会导致其力学性能的降低；同时双掺可以发挥出明显的“叠加效应”，但是“超叠加效应”不显著.     

活性炭对医疗垃圾焚烧飞灰水泥固化的影响

对医疗垃圾焚烧飞灰(FA)及其灼烧灰(IFA)进行水泥固化实验研究,考察了飞灰中活性炭对水泥固化体凝结时间、抗压强度、重金属浸出毒性等的影响. 结果表明,掺60% FA的水泥固化体终凝时间长达63 h,超出48 h的限值,相同IFA配比下水泥固化体终凝时间低于该值; 掺40%和60% FA的水泥固化体7 d的抗压强分别仅为0.187和0.16 MPa,低于0.2 MPa的标准,但2种IFA配比下水泥固化体的抗压强度均达标;掺40%和60% FA的水泥固化体中Pb的渗沥浓度分别为5.634和6.032 mg/L,均超过5 mg/L的限值,而掺60% IFA的水泥固化体Pb渗沥浓度超过限值. 结果证实医疗垃圾焚烧飞灰中活性炭是导致水泥固化体凝结时间延长、抗压强度降低、重金属渗沥浓度升高的主要原因.     

Colour control in fly ash as a combined function of particle size and chemical composition

This paper presents the results of an investigation on the combined effect of particle size and chemical composition on the colour of fly ash - a property that determines whether fly ash polymer composites can be engineered to have very light appearance satisfying the need for a wide range of commodity applications, particularly in the building material and computer housing industry. Four fly ash samples were collected from Tarong power plant Queensland, Australia, namely fly ash from first hopper (T59), classified fly ash from first hopper (T60), grinded and then classified fly ash from first hopper (T63) and fly ash from fourth hopper (T64). It was found that the particle size of T64 is smaller but still in the same order as T63. Colour measurement and chemical composition analysis of the different FA samples showed that there is a correlation between the particle size, chemical composition and colour of the fly ash. This information could be effectively used in fly ash recycling industry.     

改性粉煤灰填充废胶粉复合材料研究

以废胶粉（URP）为基体相,粉煤灰（FA）为增强相,烷偶联剂为相容性制备了粉煤灰/废胶粉复合材料。研究了废胶粉和粉煤灰的最佳用量和偶联剂的用量,混合方式和最佳的硫化条件。通过扫描电镜（SEM）和红外光谱（FT-IR）分析了粉煤灰/废胶粉试样的结构和形貌。结果表明：用Si-69对粉煤灰的改性效果好于KH-550。废胶粉最佳用量为100份,粉煤灰40份,Si-69 1.0份。最佳的初混方式为热混,偶联剂先与粉煤灰混合,而后再与废胶粉混合。最佳硫化条件为：温度160℃,压力8MPa,时间25 min。Si-69/FA/URP比KH-550/FA/URP的相容性要好。硅烷偶联剂中的Si—OH和粉煤灰表面的—OH发生脱水缩合,形成了Si—O键;偶联剂的有机端和废胶粉形成了C—H键,从而改善了FA/URP复合材料相容性和力学性能。     

Effects of fly ash on the properties of environmentally friendly dam concrete

The utilization of a solid waste – fly ash (FA) in the construction of concrete dams was investigated in this paper, which contained its effects on the strength, shrinkage and expansion strain of dam concrete with and without 8% of a novel MgO-bearing expansive agent. The results are shown a relationship between the content of fly ash replacing cement and the above properties of dam concrete.The compressive strengths of dam concrete with 50% fly ash in 90 d are higher than that of dam concrete with 30% fly ash or without fly ash slightly. Fly ash may decrease the deformation of dam concrete in that with 50% fly ash, and the shrinkage and expansive strain was reduced significantly – about 33% and 40% less than that of the specimens without fly ash respectively.     

Trace elements (Mn,Cr, Pb,Se, Zn,Cd and Hg) in emissions from a pulverized coal boiler

The concentrations of seven trace elements (Mn, Cr, Pb, Se, Zn, Cd, Hg) in raw coal, bottom ash and fly ash were measured quantitatively in a 220 tons/h pulverized coal boiler. Factors affecting distribution of trace elements were investigated, including fly ash diameter, furnace temperature, oxygen concentration and trace elements' characteristics. Modified enrichment factors show more directly element enrichment in combustion products. The studied elements may be classified into three groups according to their emission features: Group 1: Hg, which is very volatile. Group 2: Pb, Zn, Cd, which are partially volatile. Group 3: Mn, which is hardly volatile. Se may be located between groups 1 and 2. Cr has properties of both Groups 1 and 3. The smaller the diameter of fly ash, the higher is the relative enrichment of trace elements (except Mn). Fly ash shows different adsorption mechanisms of trace elements and the volatilization of trace elements rises with furnace temperature. Relative enrichments of trace elements (except Mn and Cr) in fly ash are larger than that in bottom ash. Low oxygen concentration will not always improve the volatilization of trace elements. Pb forms chloride more easily than Cd during coal combustion.     

Melt rheological studies of polypropylene filled with coconut water treated and untreated fly ash

The melt rheology of polypropylene (PP) filled with fly ash (FA) before and after treatment with coconut water (CW) was studied for different concentration of the filler. The fly ash after coconut water treatment clearly showed additional peaks in the infrared (IR) spectra corresponding to the hydroxyl and carbonyl groups indicating good adsorption of CW on FA. The X‐ray diffraction of melt compounded PP filled with CW‐treated (CWT) FA showed large reduction of the main silica peak of FA and considerable broadening of Mullite and hematite peaks suggesting formation of fine particles by this treatment. Scanning electron microscopy (SEM) confirmed the drastic reduction of particle size in these composites. The melt rheological studies for these composites indicated considerable increase in viscosity at low filler loading for CW treated FA. The concentration dependence of melt viscosity did not follow any of the theoretical equations suggested in literature. Although, the behavior was similar to nanoparticle‐filled polymers, there were some differences especially above the critical concentration of 4.5% by volume. The frequency dependence of storage and loss modulus indicated crossover point clearly, which was greatly affected by CW treatment. The Cole–Cole plots of real and imaginary part of melt viscosity brought out the broad distribution of relaxation time for the CW treated FA. The CW treated FA melt compounded with PP gave rise to nanocomposites with uniform dispersion. However, above 4.5% by volume, there appears to be agglomerate formation along with a thin interfacial layer, which assists the melt flow even at high filler loading. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43900.     

Size fraction characterization of highly-calcareous fly ash

The chemical and mineralogical composition of lignite fly ash (FA) varies as a function of the prevalent conditions in both the processes of power production and lignite mining. The differentiation of the qualitative and quantitative composition of the highly-calcareous lignite fly ash, as a function of its particle size distribution, is verified in this paper. According to the results of the conducted research, a fine-grained fraction of considerable amount presents properties that obstruct the sustainable exploitation of calcareous lignite fly ash in cement industry applications. On the other hand, the same grain fraction (because of its hydraulic properties) can be utilized in other sort of applications, based on different criteria, i.e. in road constructions. The coarse-grained fraction (which reflects a low proportion to the total fly ash output) presents the same undesired characteristics as well. Rather, the intermediate grain fraction (75-150 μm) presents the highly desirable properties when fly ash is utilized as a pozzolanic additive. In addition, the mechanism of the formation of the intermediate grain fraction strongly prevents the factors that cause the variation of fly ash-quality. It is therefore the optimum part of the whole amount of lignite FA, to be utilized as additive in cement manufacturing. The outcomes of this paper will hopefully contribute towards the crucial goal of the expansion of the utilization of calcareous lignite fly ash by proposing a more effective way of using this material, basically by taking advantage of its fundamental chemical and mineralogical properties.