A novel hydrogel composite based on gellan gum and graphene oxide (GG/GO) was synthesized, characterized and tested for sorption capacity in this work. The microstructural, thermogravimetric and spectroscopic analysis confirmed the formation of the GG/GO composite. Comparative batch sorption experiments revealed a sorption capacity of the GG/GO composite for Zn (II) ions of approximately 2.3 higher than that of pure GG. The GG/GO composite exhibits a maximum sorption capacity of 272.57 mg/g at a pH of Zn (II) initial solution of 6. Generally, the sorption capacity of the sorbents is approximately 1.5 higher in slightly acidic conditions (pH 6) comparative with that for strong acidic conditions (pH 3). The sorption isotherms revealed that the sorption followed a monolayer/homogenous behavior. The sorption kinetic data were well fitted by the pseudo-second-order kinetic model, and were consistent with those derived from sorption isotherms. The intraparticle diffusion was considered to be the rate-determining step. Two main sorption mechanisms for Zn (II) were identified namely, ion exchange at low pH values, and both ion exchange and chemisorption in weekly acidic conditions.
The paper presents the optimization results of coating by welding technology of the sealing surfaces of a rod-valve and seat assembly by using finite element programs. The assemblies - rod, valve and seat - are used for closing or opening track heat from heating systems used in power plants. The heat is given by steam that is found at a pressure of 400-450 atm and a temperature range of approximately 500°C. These values determine the use of materials of steels grades that are thermo resistant, alloyed with Cr and Mo, and work surfaces are coated with materials out of stellite grades (Co). To optimize parameters of the welding system and decrease heat loss, by conduction and convection, there were used programs of finite element to simulate the propagation of heat gradient acording to the parameters of welding regime.
The article presents a study on the influence of chemical composition on the hardness and microstructural properties in case of crushing hammers used in stone quarries that can be refurbishment by welding, using different types of filler material. In this research paper it is analyzed the effect that chemical composition of the filler material exerts on the microstructure of the loading area, the dilution effects at the welding interfaces level and the modification of the microhardness. Three types of filler material with different chemical composition have been used in order to choose the optimal version that ensures the best performance in operation.
Abstract.The present work is takes in consideration the experimental study of the influence of some morphological fields regarding the development of the complex technological forms. The goal that we have set in this paper was to bring in new points of view on technology morphologies arising in technological processes, whose goal is to generate surfaces.The development of the technological shapes could be controlled and oriented from the quality and quantity point of view, by using the morphological fields.. We refer here in particular to complex forms, not the Euclidean upon which adequate studies have been done already. Among the illustrations of the experimental parameters of forming events, electrochemical deposit is regarded as a paradigm for theoretical studies of diffusion limited aggregation. In fact, by changing the concentration of metal ions, the cathodic potential and the morphological field you can explore different morphologies, such as: dense radial aggregates, dendridic patterns and fractal aggregates. This topic has been treated and shown in the paper. The box-counting algorithm was used in calculating the fractal dimension of the deposited agregates.
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