Split-flow Taylor dispersion technique for diffusivity and concentration measurements of hydrazine in aqueous solution

Abstract

A sensitive continuous-flow monitoring method is developed for the determination of the diffusion coefficient and concentration of hydrazine in an aqueous solution. The effect of pH on the diffusion coefficient of hydrazine in water was studied at room temperature using the developed split-flow Taylor dispersion technique. The hydrazine calibration curve was linear in the range of 10−1000 ppb and the limit of quantification was 10 ppb. The results showed that the diffusion coefficient of hydrazine does not change significantly over the pH range of 4.01−8.27 but increases in alkaline media of pH greater than 8.27. This method can be used for accurate determination of hydrazine concentration in aqueous flow systems.

Effects of grain-size distribution and hysteresis on soil-water characteristic curve (SWCC)

“…The unsaturated permeability function of soil is often estimated using the SWCC and the saturated water coefficient of permeability (Wessolek et al, 1994;Leong and Rahardjo, 1997a;Børgesen and Schaap, 2005;Fodor et al, 2011). The volume change and aqueous diffusion of unsaturated soils are related to the SWCC (Fredlund and Morgenstern, 1976;Pham and Fredlund, 2011;Choudhry et al, 2014;Bea et al, 2011). Hence, SWCC plays a central role in understanding the behaviour of an unsaturated soil.…”