An evaluation of coal fly ash as an adsorbent for the removal of methylene blue from aqueous solutions: kinetic and thermodynamic studies

Abstract

In this study the effect of the dose and particle size of the adsorbent, initial dye concentration, initial pH, contact time and temperature were investigated for the removal of by means of fly ash (FA) methylene blue (MB) from an aqueous solution. The FA dose was found to be 2.0?g and the under 270 mesh sized particles were found to be effective particles for adsorption. The adsorption process reached its maximum value at 0.5?mg/L dye concentration and attained equilibrium within 10?minutes. The adsorption isotherm was found to follow the Langmuir model. The estimated adsorption free energy (ΔG^o), enthalpy change (ΔH^o), and entropy change (ΔS^o) for the adsorption process were ?37.77?kJ mol^?1, ?13.44?kJ mol^?1 and 122 J mol^?1 K^?1 respectively at 298 K. The maximum adsorption capacity is 0,12?mg g^?1 at 298 K and 0,07?mg g^?1 at 398 K. The adsorption process was exothermic, feasible and spontaneous. The positive value of ΔS^o shows the affinity of FA for MB while the low value of ΔG^o suggests a physical adsorption process.     

粉煤灰物化性质对单质汞吸附性能的影响

在固定床实验台上考察了三种不同来源粉煤灰对单质汞的吸附性能,采用X射线荧光光谱仪、X射线光电子能谱仪、激光粒度分析仪、扫描电子显微镜等对不同粉煤灰的物化性质进行了表征,并探讨了物化性质对汞吸附性能的影响。结果表明,粉煤灰对汞的吸附包括物理吸附和化学吸附;粉煤灰中未燃尽碳是影响粉煤灰汞吸附性能的重要因素之一,其中,表面C元素与Ti、Si等元素(M)相互作用形成的"C-M"化学键促进了单质汞的氧化,同时粉煤灰中含有的无机化合物Fe₂O₃等也对单质汞的氧化有促进作用;增大比表面积和减小孔径,及适中的颗粒粒径均有利于提高粉煤灰单质汞吸附性能。     

Synthesis and properties of organo-fly ash/polyaniline with core/shell structure based on emulsion polymerization

Organo-fly ash(OFA) was prepared with pretreated fly ash(FA) and hexadecyltrimethyl ammonium bromide (HDTMAB),and the composites composed of OFA and polyaniline were obtained by emulsion polymerization at different OFA weight ratios(2.0 wt%,5.0 wt%,10.0 wt%,15.0 wt%and 20.0 wt%) in the presence of dodecylbenzenesulfonic acid as dopant and emulsifier.A polymerization procedure was supposed.The electrical conductivities of the composites were tested by the four-probe technique.The chemical structure and crystallinity of the composites were confirmed by FT-IR and X-ray diffraction,respectively.Morphologies of FA,OFA and the composites were observed by SEM.The element analysis was performed by energy dispersive spectrometry.The thermal stability of the composites was analyzed by TGA.The results showed that the electrical conductivity of the composites decreased with increasing the feed weight ratio of OFA,and the lowest value was 0.62 S/cm.HDTMAB and PAn were just adsorbed on the surface of FA and OFA,respectively according to the physical adsorption without destroying the crystalline structure of FA or OFA.The surface became smoother after organification of FA by using HDTMAB,and its content on FA surfaces was about 26.9 wt%.The core/shell structure of the composite was observed by SEM analysis.The composites showed a higher thermal stability than pure PAn by introduction of OFA into this polymerization system,the heat stability of PAn was increased by decreasing 31.8 wt%of weight loss after introducing 20 wt%of OFA.     

不同灰成分的低熔点煤灰熔融性调控机理研究

通过灰熔点较低且接近的两种煤与灰熔点较高的天池煤混配,结果表明,在含铁类矿物质较低的小屯煤与天池煤的混煤中,混煤灰熔点随天池煤混入比例的增加而提高,含铁类矿物质较高的宁鲁原煤与天池煤的混煤灰熔点随天池煤混入比例的增加没有明显变化。通过XRD分析配煤中矿物质的转变过程,结果表明,宁鲁原煤灰中含有的钙铁类矿物质(如赤铁矿、硬石膏)抑制了莫来石的生成,缺少作为骨架支撑作用的高熔点莫来石,煤灰的熔点得不到显著提高。最后将配煤在沉降炉中进行实验模拟电站锅炉的结渣过程,并使用SEM分析灰渣的微观形貌,发现与宁鲁原煤相比,小屯与天池煤的混煤更能显著改善结渣特性。     

Three component one-pot synthesis of novel pyrimidino thiazolidin-4-ones catalyzed by activated fly ash

Abstract

2-Phenyl-3-(4,6-diarylpyrimidin-2-yl) thiazolidin-4-ones, 12–22, were synthesized with good yields in a short reaction time by the “one-pot” multicomponent reaction of the appropriate 2-amino-4,6-diarylpyrimidines, benzaldehyde, and thioglycolic acid under microwave irradiation in the presence of activated fly ash catalyst. The characterization of these compounds was confirmed by melting point, elemental analysis, MS, FT-IR, and one-dimensional NMR (¹H and ¹³C) spectroscopic data.     

煤灰在高温下的流变特性研究

为了研究煤灰在高温下的流变特性,以陕西神木煤、内蒙纳林沟煤、宁夏羊肠湾煤和山东南屯煤四种煤灰为样品,利用高温旋转黏度计,研究了高温下煤灰渣黏度和剪切应力随剪切速率的变化。实验结果表明,当实验温度高于煤灰的液相线温度时,其流型表现为牛顿流体;当温度低于液相线温度时,其流型逐渐由牛顿流体转变为非牛顿流体。其中,陕西神木煤和宁夏羊肠湾煤的煤灰样品在高温下表现为剪切增稠,随着温度的降低,由牛顿流体转变为屈服涨塑性流体;内蒙纳林沟煤和山东南屯煤的煤灰样品在高温下表现为剪切变稀,随着温度的降低,由牛顿流体转变为屈服假塑性流体。另外,随着温度的降低,由于液态煤灰中晶体的不断析出,使屈服应力逐渐增大,降低了煤灰的流动性。     

Effects of a new modifier on the water-resistance of magnesite cement tiles

The magnesium oxychloride composite is an inorganic cementitious material with high bending and compression strength in air characteristics. However its strength decreases significantly after immersion in water. The preparing process of a new magnesite cement tile using nano rice husk ashes and a complex water-resistance agent as modifiers was described in the paper. The effects of low-temperature rice husk ashes (RHAs) and the complex water-resistance agent constituted with phosphoric acid, calcium superphosphate, wooden calcium and styrene-acrylic emulsion on the water-resistance of magnesite materials were mainly studied. The samples properties were characterized by XRD, SEM, BET, a laser particle size analyzer and bending test. The experiments show that the proportional addition of nano RHAs markedly increases the water-resistance of magnesite materials without reducing the bending strength and promotes the softening coefficient from 0.29 to 0.78, while the softening coefficient reaches up to 0.97 combined with the use of complex water-resistance agent. The new magnesite cement tiles prepared were not scumming, not warping, and not contracting at room temperature for 360 d.     

The Determination by Neutron Activation Analysis of Selected Elements in Cigarettes

Abstract

Neutron activation analysis was used for the determination of Na, Al, CI, K, Ca, Sc, Mn, Cu, Br, and La in the tobacco, mainstream smoke condensate, paper, and dropped ash of the Kentucky Reference Cigarette (IRI). The procedure requires no sample transfers prior to activation and no radiochemical separations before counting.