Speed of Sound DVS: Moisture, Organic Vapor, and Co-Adsorption in Material Processing and Separation Science

Surface Measurement Systems’ new Dynamic Vapor Sorption (DVS) instruments utilize the patent-pending Speed-of-Sound sensor. Measuring moisture, organic vapor, and co-adsorption isotherms, this unique DVS technology opens new areas of sorption characterization for material processing and separation science. Representative sorption kinetic data and isotherms are shown below.

Material Processing: Acetone Sorption Isotherms with Background Humidity

Spray Dried Polymer Co-Adsorption Isotherms

Figure 1

Figure 1 shows Acetone sorption isotherms measured with three different background humidity conditions. The red sorption isotherm was performed from 0 to 50% P/Po of Acetone with a 10% RH background. The blue and green isotherms were measured in 20% RH and 30%RH backgrounds respectively. During the 30% RH background humidity method the sample picked up less mass than during the 20% RH background method. Mass uptake was greater during the 20% and 30% RH than in the 10% RH method suggesting Acetone and water not only compete for the same sorption sites on the sample’s surface but also water out-competes Acetone at increased concentrations. When water begins to sorb to the surface more readily than Acetone we would expect the mass uptake to drop because of water’s lower molecular weight, and the data show this.

 

Separation Material: Isomer Kinetics and Co-Adsorption

Ortho and Para-Xylene Co-Adsorption

Figure 1: Sorption kinetics of Ortho-Xylene controlled in closed-loop by the patent pending SOS sensor from Surface Measurement Systems. Percent change in mass is recorded in red and target partial pressure is in blue.

Figure 2: Sorption kinetics of Para-Xylene controlled in closed-loop by the patent pending SOS sensor from Surface Measurement Systems. Percent change in mass is recorded in red and target partial pressure is in blue.

Figure 3: Co-adsorption kinetics of Para- and Ortho-Xylene controlled independently in closed-loop by the patent pending SOS sensor from Surface Measurement Systems. Percent change in mass is recorded in red and target partial pressure is in blue.

In this co-adsorption experiment Para- and Ortho-Xylene were controlled independently using dual speed-of-sound sensors, which controlled and delivered each at equal partial pressures. The shape of the kinetics data is similar to that of the Ortho-Xylene alone, but mass uptake was limited to the maximum uptake of the Para-Xylene in Figure 2 at around 18%.

 

 

DVS Resolution