| Searching for a kind of hydrogen production method which is green environmental protection, economic and effective, portability strong is the focus of research in recent years.Magnesium is rich in resources, low in price, and has high energy density.The extensive use of magnesium alloy result in magnesium scrap recycling become the new problem.The reaction system of Magnesium /water is mild and efficient to generate hydrogen and efficient adsorbing material magnesium hydroxide which has very good application in prospect. Hydrogen production rate of magnesium/water system is closely related to the morphology of magnesium, reaction temperature, concentration of salt brine, catalytic method, and the affecting patterns of these factors were the focus of this analysis and research.This article explores the low for production rate of the magnesium powder, magnesium ribbon, magnesium alloy under different reaction conditions, analyses the influence law of hydrogen production performance. The X-ray powder diffraction(XRD), field emission scanning electron microscopy(FE-SEM) and energy dispersive X-ray spectrometer(EDS) were used to characterize the products, analysis of the characteristics of its morphology evolution law and the formation mechanism of the product.The thermodynamic and kinetic characteristics of adsorbing heavy metal Cd2+ on adsorbent Mg(OH)2 were studied via static adsorption, further study on the heavy metal desorption, adsorbent regeneration and its adsorption performance. The main results were as follows:(1) The hydrogen production rate of magnesium/water system are largely affected by the reaction temperature and salt concentrations, The basic rule is: in the Mg /water system, the hydrogen production rate is proportional to the concentration of brine, when the temperature above 60 ℃ the hydrogen production rate decreased significantly; in the magnesium ribbon /water system, too high or too low brine concentration is not conductive to formation of hydrogen. The hydrogen production rate reached their maximal at room temperature. The difference is mainly due to the complexity of magnesium with large specific surface area can fully contact with the reaction medium and the factors of the formation of the passivating film on the surface of magnesium.(2) The addition of catalysts can effectively improve the hydrogen production rate, with the copper catalyst, the hydrogen production rate of magnesium alloy/water system could to be maximized 61.9ml(min·g)-1, and its Hydrogen production rate was over 93.0%.(3) The products of magnesium hydroxide in the reaction system of magnesium alloy/water system present crystal plate. Chloride concentration has less effect on the crystal thickness.For magnesium powder, the particle size of product decreases with the increase of brine concentration. However, the particle size of magnesium ribbon products decrease with the increase of brine concentration. And for magnesium alloy catalyzed by copper, the particle size of product has a little change when brine concentration changed. The temperature has important influences on the crystal structure and morphology of the crystal, the thickness of crystal thickness increases with temperature, while the particle size decreases with temperature increase, high temperature contribut to form the crystal of regular shape and good dispersivity.(4) The adsorption equilibrium was reached within 30 minutes between the product magnesium hydroxide and Cd(Ⅱ), the temperature has little influence on the adsorption effect, pH neutral removal rate was the highest. The adsorption process can be simulated by Langmuir isotherm which was spontaneous chemical absorption controlled by the liquid film diffusion、surface adsorption and internal diffusion.(5) After adsorption,the magnesium hydroxide with carbon dioxide to produce nesquehonite to strip and enrich the heavy metals. Magnesium Oxide calcined from nesquehonite as adsorbent, the cadmium ion removal rate up to 99.8%. |
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