| With the development of power industry,coal fly ash production increased yearby year. Coal fly ash pollution has been a serious threat for the environment andhuman health. Therefore, disposal of coal fly ash attracts the attention of scholars'home and abroad. Furthermore, zeolization will not only solve the environmentalproblems but also have a profitable potential, which has been a critical aspect ofprotecting the environment. Seawater and large quantities of brine produced duringthe desalination contain a variety of cations zeolite synthesized required.Comprehensive utilization of seawater and brine cannot only reduce environmentpollution but also save energy, improve economic efficiency.The main objective of the present research is to develop a chemical synthesisprocess to produce useful materials from the coal fly ash. A novel method for thesynthesis of zeolite was developed. The synthesis was carried out by hydrothermalactivation after alkali fusion, and coal fly ash was used as raw material with seawaterof different salinities. Seawater salinity was varied from32to88for zeolitecrystallization during the hydrothermal process. The structure and properties of theproducts were determined by instrumental analysis and chemical methods. Thesynthesized zeolite was characterized using various techniques such as X-raydiffraction, scanning electron microscopy, Fourier transform infrared spectroscopy,and N2adsorption–desorption measurements, etc. In addition, the impact of seawatersalinity on the mineral composition, crystallization, and chemical composition, andtransformation yield, capacity of cation exchange and specific surface area of thezeolites were investigated and compared.The synthesis was carried out by hydrothermal activation after alkali fusion at550℃,and coalfly ash w as used as raw m aterialw ith seaw ater of differentsalinities.Furthermore, zeolite can be synthesized from coal fly ash with a wide range ofseawater salinities. Experimental results show that the seawater salinity plays an important role on zeolite synthesis with coal fly ash during hydrothermal treatment.XRD spectra and SEM photographs show that the synthesized zeolite was a mixtureof NaX zeolite and hydroxysodalite; seawater salinity affected more thecrystallization of zeolites than the type and chemical composition of zeolites. As theseawater salinity raised from32to88, the degree of crystallinity of hydroxy-sodaliteincreased, while that of NaX zeolite decreased. Seawater enhanced thehydroxysodalite formation better than the conventional way using distilled water.SEM/EDS analysis showed that the zeolite surface roughness, mainly from silicon,aluminum, oxygen and potassium and other elements. The synthesized zeolites havebeen tested for their cation exchange capacity with262.40to388.59mmol/100g,which increasing of nearly500times compared to the coal fly ash with the cationexchange capacity of7.96mmol/100g. The zeolites have high surface area are therange from148.56to225.84m2/g, average pore sizes of range from4.40to7.07nm,and the average pore volume of range from0.1635to0.3994ml/g.Therefore,compared with the coal fly ash, synthetic zeolite greatly enhanced the performance.The yield of coal-fly-ash transformed zeolite elevated gradually with the salinityincrease, reaching48%–62%in transformation rate. The yield increased by theseawater because that the Na and other impurities in the seawater. The applicationshows that the zeolites synthesized with seawater salinity of32to42are better thanthat form with distilled water. When the seawater salinity was76to88, the highsalinity caused the aggregation of synthetic zeolite.In this paper, we study the adsorption characteristics of methylene blue dye onthe synthesized zeolite. The effects of different factors such as reaction time,temperature, pH, initial dye concentration on adsorption capacity were investigated.The adsorption mechanism of methylene blue on the zeolites was discussed.Equilibrium data have been analyzed using Langmuir and Freundlich isotherms, andthe results were found to be well represented by the Langmuir isotherm equation.Adsorption data were fitted to both Lagergren first-order and pseudo-second-orderkinetic models and the data were found to follow pseudo-second-order kinetics.This study illustrates the mechanism of synthetic zeolite from coal fly ash usingseawater as solvent, which deepen expounded the theory of using coal fly ash tosynthesize zeolite. The zeolites synthesized adopting two different methods(traditionaldistilled water as the solvent and seawater as solvent) were characterized andcompared in details(structure, properties and application of indicators). It is show that large-scale application of synthetic zeolite will not cause harm to the environmentby comparing the chemical composition of the synthetic zeolite. Comparison ofspecific surface area, pore size, pore volume and cation exchange capacity of thesynthetic zeolite shows that the performance of synthetic zeolite and the application ofindicators has a good potential for industrial applications value.In this study, we provide a new way of fly ash and sea water utilization. It notonly can save distilled water, improve the yield of zeolite, modified zeoliteperformance, but also can handle wastewater, waste control by waste. Therefore,application of seawater for zeolite synthesis shall be promising with great economicand ecological benefits.
|
PDF Full Text Request