Nanostructured cobalt materials have recently attracted considerable attention due to their potential applications in high-density data storage, magnetic separation and heterogeneous catalysts. The size as well as the morphology at the nano scale strongly influences the physical and chemical properties of cobalt nano materials. In this study, cobalt nano particles synthesized by a a polyol process, which is a liquid-phase reduction method, were investigated. Cobalt hydroxide (Co(OH)2), as an intermediate reaction product, was synthesized by the reaction between cobalt sulphate heptahydrate (CoSO4·7H2O) used as a precursor and sodium hydroxide (NaOH) dissolved in DI water. As-synthesized Co(OH)2 was washed and filtered several times with DI water, because intermediate reaction products had not only Co(OH)2 but also sodium sulphate (Na2SO4), as an impurity. Then the cobalt powder was synthesized by diethylene glycol (DEG), as a reduction agent, with various temperatures and times. Polyvinylpyrrolidone (PVP), as a capping agent, was also added to control agglomeration and dispersion of the cobalt nano particles. The optimized synthesis condition was achieved at 220˚C for 4 hours with 0.6 of the PVP/Co(OH)2 molar ratio. Consequently, it was confirmed that the synthesized nano sized cobalt particles had a face centered cubic (fcc) structure and with a size range of 100-200 nm.

The influence of sulfate on the selective catalytic reduction of on the Ag/ catalyst was studied when was used as a reducing agent. Various preparation methods influenced differently on the activity. Among the methods, cogelation precipitation gave best activity. When sulfates were formed on the surfaces of samples prepared by impregnated and deposition precipitation, activity was enhanced as long as suitable forming condition is satisfied. The major sulfate formed in Ag/ catalyst was the aluminum sulfate and it seems that this sulfate acted as a promoter. When Mg was added to the Ag/ catalyst it promoted activity at high temperature. Intentionally added sulfate also enhanced activity, when their amount was confined less than 3 wt%.

Concentrations of sulfate and δ-values of sulfate, (δ^34SO_4)_pw, dissolved in pore waters were measured from the sediment cores of the two different marine environments: deep northeast Pacific (ST-1) and coastal Kyunggi Bay of Yellow Sea (ST-2). Sulfate concentration in pore waters decreases with depth at both cores, reflecting sulfate reduction in the sediment columms. However, much higher gradient of pore water sulfate at ST-2 than ST-1 indicates more rapid sulfate reduction at ST-2 because of high sedimentation rate at the coastal area compared to the deep-sea. The measured 6-values, (δ^34SO_4)_pw, follow extremely well the predicted trend of the Rayleigh fractionation equation. The range of 26.7‰ to 61.3‰ at the coastal core ST-2 is not so great as that of 32.4‰ to 97.8‰ at the deep-sea core ST-1. Despite greater gradient of pore water sulfate at ST-2, the δ-values become lower than those of the deepsea core ST-1. This inverse relation between the S-values and the gradients of pore water sulfate could be explained by the combination of the two subsequent factors: the kinetic effect by which the residual pore water sulfate becomes progressively enriched with respect to the heavy isotope of ^34S as sulfate reduction proceeds, and the intrinsic formulation effect of the Rayleigh fractionation equation in which the greater becomes the fractionation factor, the more diminished values of (δ^34SO_4)_pw are predicted.