Materials Science Forum Vols. 743-744

Abstract: The adsorption isotherms and kinetics of nickel ion onto commercial activated carbons were determined and investigated under different temperature and initial pH in solution. The pore size distribution, specific surface area and functional groups of activated carbons were characterized by N₂ adsorption isotherms and Boehm titration. The results showed that the nickel ion adsorption property of activated carbon from precursors including anthracite, long flame coal, lignite and coconut were 4.9, 3.4, 4.1, 5.2mg/g, respectively. There was no obvious correlation with surface area, total volume or surface functional group value. The nickel ion adsorption isotherms and kinetics fitted the Langmuir isotherm and pseudo-second-order model very well. The adsorption was a spontaneous endothermic process, in which the adsorption took place primarily due to the ion-exchange action in low concentration of 50mg/L. On the other hand, the adsorption depended on the physical adsorption when the concentration100mg/L. The nickel ion adsorption capacity was highly affected by solution pH, and the optimum initial pH ranged was from 4 to 7.

Abstract: Ag-doped Bi₂WO₆ photocatalysts were synthesized by hydrothermal method using from Bi (NO)₃·5H₂O, NH₄VO₃, and AgNO₃ and further characterized by X-ray diffraction, Scanning electron microscopy, Energy dispersive X-ray detector (EDS) and UV-Vis diffusion reflectance spectra techniques. The photocatalytic activity of Ag-doped Bi₂WO₆ photocatalysts was evaluated by degrading RhB (10 mg/L) under visible light irradiation (λ > 420 nm). The results showed that in comparison with pure Bi₂WO₆ the photocatalytic activity of Ag-doped composite photocatalysts was improved significantly, and the degradation rate of RhB was increased about 26% when the Ag⁺ dopant concentration was 15%.

Abstract: PPS-based strong acid ion exchange fiber was used to absorb cationic dye basic fuchsin and methyl blue in solution. The experimental results showed that the amount of methylene blue and basic fuchsin absorbed increased respectively with increasing of initial concentration from 100 to 600 mg/L. The adsorption capacity of the fiber was up to 604.81mg/g of basic fuchsin and to 618.94mg/g of methylene blue. The removal rate of the methylene blue reached 99.9% from 100 to 500mg/L, but of basic fuchsin from 100 to 300mg/L. Adsorption kinetic equation for basic fuchsin can be expressed as a pseudo-second-order dynamic process. The fiber is to be perfect prospect for the wastewater treatment because of its high adsorptive capacity and diffusion rate.

Abstract: Ecological colored cellulose material was prepared via UV initiated photografting of acrylic acid/cationic dye system in this study. The colored cellulose material was characterized using scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR). The effects of monomer concentration, photoinitiator amount, dye amount, pH value, grafting time, heating temperature and grafting method on the coloration of cellulose material were discussed. The results showed that the optimum process was as follows: the monomer concentration of 50wt%, photoinitiator amount of 3o.w.m.%, grafting time of 4min, and heating temperature of 70.

Abstract: In this study, kinetics and thermodynamics of sodium alginate/ hydroxyapatite composite adsorption fiber for adsorping Cd () were studied. The morphology and structure were characterized by SEM and IR, and the effects of pH value and bath ratio on Cd () adsorption were discussed. The model of adsorption kinetics and thermodynamics were simulated, and the parameters were calculated. The results showed that the sodium alginate/hydroxyapatite composite adsorption fiber possessed good adsorption ability towards Cd (). The optimum adsorption was found at the pH value of 6-7. High removal percent of more than 90% at low concentration and high concentration of Cd () was obtained at the bath ratio of 1:100 and 1:1000, respectively. The adsorption kinetics and thermodynamics studies showed that the pseudo-second-order model and Freundlich isotherm described the adsorption behaviors well. The thermodynamic parameters indicated that the adsorption of Cd () onto sodium alginate/hydroxyapatite composite adsorption fiber was physical and chemical sorption, endothermic in nature.

Abstract: Ruthenium oxide coated titanium composite powders were prepared by precipitation of ruthenium salt to improve the resistance of titanium to corrosion. The composite powders were characterized by TEM and XPS. The results show that the ruthenium oxide is evenly deposited on the Ti powders. Corrosion test for the composite powders and Ti powders was conducted in 65% sulfuric acid (mass fraction). The composite powders exhibit good corrosion resistance. The corrosion rate decreased from 98.5% to 0.48% through modification. Ru/Ti molar ratio and annealing temperature have a major impact on the corrosion resistance.

Abstract: The corrosion behavior of X52 pipeline steel in H₂S solutions was investigated through immersion corrosion test which was carried out in a high temperature and high pressure autoclave at different temperatures and H₂S concentrations. General corrosion rates were calculated based on the weight loss of samples. The morphology and the chemical composition of the corrosion products were obtained by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The crystal structure of corrosion products was analyzed by X-Ray diffraction patterns (XRD). The corrosion products consisted mainly of the sulfide compounds (mackinawite, cubic ferrous sulfide, troilite and pyrrhotite). The corrosion products included two layers: the inner iron-rich layer and the outer sulfur-rich layer. Under H₂S concentrations of 27g/L, the corrosion rate increased with the increase of temperature up to 90°C and then decreased at 120°C, finaly increased again. The corrosion rate first increased with H₂S concentrations then decreased at 120°C. The structure and stability of the corrosion products due to different corrosion mechanism had a major impact on the corrosion rate. The corrosion resistance of the corrosion products increased as follows: mackinawite < cubic ferrous sulfide < troilite < pyrrhotite.

Abstract: Calcite was synthesized through different drying processes, and characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). By bath experiments, the mechanisms of phosphate removal by synthesizing calcite were investigated. It showed that synthesis calcite had a strong capability to remove phosphate from solution. The adsorption of phosphate mainly depended on the total concentration of phosphate and pH in solution. Magnesium tended to the phosphate adsorption during pH range of 8-13.5; while it inhibited the adsorption at around pH 7. The experimental results suggested that the synthesized calcite with aged process could effectively remove the phosphate from an alkaline aqueous solution.

Abstract: Calcium silicate board has been prepared by press molding from fly-ash based calcium silicate powder with the pulp fiber as the reinforcing fibre. The micro-morphology and crystal structure of the obtained calcium silicate board were analyzed by SEM and XRD. The effects of cement,silica fume and molding pressure on the flexural strength and thermal conductivity of calcium silicate board were investigated. When the molding pressure is 10MPa, samples flexural strength, bulk density and thermal conductivity are 5MPa, 0.7g/cm³ and 0.12 W/m·K respectively. It was found that this kind of calcium silicate powder was complete hydrated and could not be further hydrated even in autoclave curing.

Abstract: The electrochemical behavior of cast X-52 with different Sn content ranging from 0 to 1 wt. % was investigated using the methods of potentiodynamic test, electrochemical impedance spectroscopy (EIS). The immersion tests involved to examine the relationship between Sn addition and corrosion performance of cast X-52. In addition, the morphology and the compositions of surface corrosion products were analyzed using scanning electron microscope (SEM)/ energy dispersive spectroscopy (EDS). Potentiodynamic polarization curves showed that the presence of Sn decreased the corrosion current density. EIS indicated that Sn-containing steels had higher polarization resistances. These results confirmed that Sn played a positive role in reducing corrosion rate in H₂S-containing environment. However, the corrosion resistance decreased with increasing Sn addition. It was proved that Sn improved the corrosion resistance with only a small content and large amount of Sn might lead to an advance of the pit due to occurrence of more acidification. Moreover, a continuous inner O-rich layer adherent to the matrix was found for Sn-addition samples, which lead to a decrease of corrosion rate due to its compact characteristic, compared with porous sulfide formed on the outer surface.