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 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.

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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 realization of some composite materials that allow the best removal of H2S from syngas was the main objective of this work. Thus, the optimization of the technological parameters for obtaining composites based on Zn-Ti was achieved. The paper studies the influence of calcination temperature on the characteristics of the binary ZnO-TiO2 system used to synthesize a composite material with suitable properties to be used subsequently for syngas treatment. The mineralogical and structural analyzes showed that starting with the calcination temperature of 700 °C the material synthetized is composed mainly of zinc orthotitanate which possess the corresponding characteristics to be finally used in the treatment of the syngas for its desulfurization. At this calcination temperature the material has a compact structure most likely due to sintering of the formed titanates. These composites have a texture that places them rather in the category of non-porous materials, the pore volume and their surface area obviously decreasing as the calcination temperature increases. A maximum sulfur removal degree of about 97% was obtained by using a composite synthetized at a temperature of 700 °C (ZT-700).