Hydrogen storage thermodynamics and dynamics of La-Mg-Ni-based LaMg12-type alloys synthesized by mechanical milling

Nanocrystalline/amorphous LaMg(12)-type alloyNi composites with a nominal composition of LaMg(11)Ni+x wt% Ni(x=100,200) were synthesized by mechanical milling.Effects of Ni content and milling time on the gaseous hydrogen storage thermodynamics and dynamics of alloys were systematically investigated.The hydrogen desorption properties were studied by Sievert apparatus and a differential scanning calorimeter(DSC).Thermodynamic parameters(△H and ΔS) for the hydrogen absorption and desorption of alloys were calculated by Van't Hoff equation.Hydrogen desorption activation energy of alloy hydride was estimated by Arrhenius and Kissinger methods.The increase in Ni content has a slight effect on the thermodynamic properties of alloys,but it significantly enhances the hydrogen absorption and desorption kinetics performance of alloys.Moreover,variation of milling time clearly affects the hydrogen storage properties of alloys.Hydrogen absorption capacity(C(100)~a) and hydrogen absorption saturation ratio(R(10)~a)(a ratio of the hydrogen absorption capacity at 10 min to the saturated hydrogen absorption capacity) have maximum values with milling time varying.But hydrogen desorption ratio(R(20)~d)(a ratio of the hydrogen desorption capacity at 20 min to the saturated hydrogen absorption capacity) always increases with milling time prolonging.Particularly,prolonging milling time from 5 to 60 h makes R(20)~d increase from 10.89% to 16.36% for the x=100 alloy and from 13.93% to 21.68% for the x=200 alloy,respectively.

Research on Adsorption Characteristics of the Helianthus tuberosus Stem s to M ethylene Blue in Water

[Objective] The research aimed to study the adsorption characteristics of the Helianthus tuberosus stems to methylene blue in water. [Method] The optimum condition, adsorption thermodynamic and kinetic characteristics were studied on the methylene blue adsorbed by Helianthus tuberosus stems. [ Result] The equilibrium process was described well by the Langmuir isotherm model. The thermodynamics parameters were enthalpy changes （△H） of -12.147 kJ/mol, Gibb＇S free energy changes （△G） of -25.75 k J/reel, and entropy changes （△S） of 47.21 J/（mol · K）, respectively, at 288 K, indicating that the adsorption thermodynamic of methylene blue adsorbed by helianthus tuberoses stems was a spontaneous and exothermic process. The kinetics of the interactions showed better agreement with the Lagergren second order kinetics. The apparent activation energy （Ea） of adsorption process was 271.7 kJ/mol. [ Conclusion] This study provided the theoretical basis for the development and utilization of low-cost agricultural wastes to remove the hazardous substances in industrial wastewater.