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This type of fly ash is difficult to float even at a higher concentration of collector due to less dispersion of the collector molecules on the surface. Emulsification of kerosene in the presence of Sodium Dodecyl Sulfate (SDS) dramatically reduces the size of the kerosene droplets. The results showed that much less collector was required to achieve a good separation of carbon from fly ash when SDS was employed in conjunction with the collector. In this paper, the influence of the concentration of emulsifier on flotation was discussed. The emulsifier concentration of 0.2 kg/t produced the superior performance of LOI of 54.5% and the corresponding CR of 93.1%. The contact angle and attachment efficiency of CFA after pretreatment were found to be increased. The results of XRD and SEM demonstrate that a complete separation of unburned carbon from CFA could be achieved by using the emulsifier. [ABSTRACT FROM AUTHOR]

In this study, a faujasite block with certain compressive strength was successfully fabricated from fly ash based geopolymer via in-situ hydrothermal method. The effects of various factors, such as the SiO 2 /Al 2 O 3 molar ratio of the geopolymer, the concentration of NaOH, crystallization time and crystallization temperature of the hydrothermal curing solution on the structure and morphology of the hydrothermal products were investigated. SEM and XRD results confirmed that these factors played essential roles in controlling the morphology and crystallinity of the hydrothermal products. The optimum faujasite block showed an octahedral shape and sharp edges with good crystallinity. In addition, the BET specific surface area, the total pore volume and the compressive strength of the faujasite block were 136.23 m 2 /g, 0.14 cm 3 /g and 5.14 MPa, respectively. The optimum conditions for the synthesis of faujasite block were SiO 2 /Al 2 O 3 molar ratio of 4.0, NaOH solution concentration of 1.0 mol/L, and 24 h for crystallization at 70 °C. [ABSTRACT FROM AUTHOR]

Geopolymer-TiO2 nanocomposites were prepared by two different techniques, namely the two-step acidification calcination treatment and one-step adding method. The potential photocatalytic activities of geopolymer-TiO2 nanocomposites prepared by the two different methods were tested and compared. Nanocomposites prepared via the one-step process showed better photocatalytic activity. The amount of TiO2 particles loaded on the surface of the foaming materials was investigated by XRD and SEM-Mapping. By comparing with the sample obtained from two-step treatment, the TiO2 particles were distributed uniformly on the surface of the foaming materials for the sample obtained from the one-step method in this study. Results showed that the specific surface area of the geopolymer-TiO2 prepared by the one-step treatment process (28.67 m2/g) was significantly lower than the two-step acidification calcination process (215.04 m2/g), while the photocatalytic efficiency with methylene blue trihydrate (MB) was better. This is due to the more stable structure of geopolymer-TiO2 nanocomposites, the better dispersion and more loading of TiO2 particles on the foaming materials surfaces, leading to the enhanced photocatalytic activity. [ABSTRACT FROM AUTHOR]

The efficiency of the flotation of the fine unburned carbon from coal fly ash (CFA) is closely dependent on the dispersion of the collector on the carbon surface. In this work, we carried out the froth flotation tests of CFA using four different surfactants: Sodium Dodecyl Sulfate (SDS), Sodium Dodecyl Benzene Sulfonate (SDBS), Tween-80 (TW) and Triton X-100 (TX), to investigate the effect of surfactants on forth flotation. The surfactants were mixed with the collector kerosene at given ratios to produce the emulsions, and they were employed as promoters to increase the hydrophobicity of unburned carbon. The flotation results showed a strong relationship between the loss on ignition (LOI) and the type of the surfactants used. Flotation combustible recovery (CR) of 79.58% and LOI of 54.43% were obtained when TX was used as promoter. The removal mechanism was discussed according to the kinetic theory and surface-chemistry theory. The results of surface tension and zeta potential demonstrate that the tail length of the surfactants can affect the adsorption of kerosene significantly. Besides, the scanning electron microscopy energy dispersive spectroscopy (SEM-EDS) data indicate that the recovery of unburned carbon using TX as a synergist is apparently efficient, and reveal the microstructure of the unburned carbon and the gangue materials in CFA. [ABSTRACT FROM AUTHOR]

Abstract In this work, zeolite P1 is synthesized from fluidized bed fly ash (FA) via a solvent-free process. The formation of zeolite P1 is investigated as a function of crystallization reaction time. The solid mixture of FA and Na 2 SiO 3 ·9H 2 O with a mole ratio of Na:Al:Si = 1.5:1:1.7 can be converted to zeolite P1 at 80 °C for 24–96 h. XRF, XRD, SEM/EDS, FTIR, TG/DSC and BET techniques are used to test the properties of resultant zeolite products. The efficiencies of the resultant zeolite for ammonium adsorption are evaluated on factors including solution pH, NH 4 + ions concentration, temperature and adsorption time. The kinetic data and adsorption equilibrium data fit satisfactory with the Ho's pseudo-second-order kinetic model and Langmuir model. The maximum ammonium adsorption capacity of zeolite P1 (22.9 mg/g) can be reached within 40 min at optimal pH of 6. The adsorption performance is higher than many of the natural zeolites and closely similar to the zeolites synthesized from fly ash through the conventional hydrothermal route. Our study not only provides new insights into the preparation of zeolite from fly ash, but also reveal that the zeolite P1 synthesized through solvent-free route is a promising material for ammonium removal. Graphical abstract Image Highlights • Zeolite P1 was synthesized from fly ash via a sustainable solvent-free route. • The fusion of impurities in the raw fly ash is difficult in the trace water system. • The adsorption performance is comparable to those synthesized by hydrothermal route. • Zeolite P1 was efficient in ammonium removal. [ABSTRACT FROM AUTHOR]

We present a process of fabricating water floatable and permeable geopolymer block from industrial by-product fly ash. By adding oleic acid and H 2 O 2 solution during the geopolymer manufacture process, a foamed geopolymer block with highly interconnected pores can be manufactured. The compressive strength of those foamed geopolymer block are 0.55±0.08 MPa at dry density of 0.37 g/cm 3 , and its permeability to water coefficient is 0.35 cm/s and the BET surface area is 67.62 m 2 /g. In addition, the porous geopolymer block possesses a high adsorption capacity for methylene blue, 50.7±0.7 mg/g, and shows the potential of being employed as low cost replacement for zeolites in applications such as waste water treatment at high mass transport rate. [ABSTRACT FROM AUTHOR]

This work aims to evaluate the efficiencies of fly ash, fly ash-based geopolymer and faujasite block, which is transformed from geopolymer, as sorbents for lead (Pb) from aqueous solutions. Comparative experiments were performed to examine the mineralogical features of the fly ash, geopolymer and faujasite block and their adsorption capacities. Equilibrium isotherms and thermodynamic parameters were obtained through systematic investigation of parameters including pH, initial Pb concentration, temperature and contact time. The adsorption kinetics of geopolymer and faujasite block fit well to the pseudo-second-order kinetic model, while the adsorption of fly ash fit to the pseudo-first-order kinetic model. The adsorption equilibrium data of fly ash, geopolymer and faujasite can be expressed using Langmuir model. The maximum adsorption capacities of fly ash, geopolymer and faujasite block at pH = 3 were determined to be 49.8, 118.6 and 143.3 mg/g, respectively. Through this study we demonstrate that both geopolymer and faujasite can effectively remove Pb from wastewater. Most importantly, we prove that geopolymer has the same adsorption mechanisms as faujasite or similar zeolite materials. This finding suggests geopolymer technology being an energy-saving, low cost and environmentally friendly process in adsorbent manufacturing. [ABSTRACT FROM AUTHOR]