Adsorption of Gas-Phase Cyclohexanone on Atmospheric Water Films

The fate of atmospheric volatile organic compounds (VOCs) strongly depends on the partitioning processes on the surface of aerosols, which are coated with a thin water film. However, the behavior of VOCs in the aqueous film of aerosols is difficult to measure. In this work, the interfacial partition constant of cyclohexanone was determined using a novel flow-tube reactor. A thin, aqueous film placed in the reactor was exposed to cyclohexanone gas. The subsequent partitioning was measured using chromatography techniques. The quality control tests were first conducted to ensure the accuracy of the adsorption experiments. The cyclohexanone concentration was then plotted as a function of film thickness to obtain the partitioning constants. As the thickness of the water film decreased, the aqueous concentration of cyclohexanone increased, indicating that surface adsorption played a dominant role in the uptake of cyclohexanone. According to the temperature dependence of the interfacial partition constant, the solvation enthalpy and entropy of cyclohexanone were obtained. The results of this study would help to elucidate the effect of atmospheric water film on the gas–aerosol partitioning of VOCs, and thus can help to better understand the fate of VOCs in the atmosphere.

Effect of Circulation Flowrate on the Performance of a Spiral Finned Freeze Concentrator

Progressive freeze concentration (PFC) has emerged as a viable technology for concentration of liquid solution. In this study, a newly designed spiral finned crystallizer to improve productivity of PFC process was proposed. The spiral fin is presented based on the advantage of additional surface area to the spiral finned crystallizer. The performance of spiral finned crystallizer was analysed by the system efficiency and the effect of circulation flowrate. It was found that the efficiency of the system has significantly improved in terms of a lower effective partition constant and a higher recovered solute. An effective partition constant of 0.35 and a recovered solute of approximately 0.96 g of glucose per 1 g of initial glucose were obtained. Thus, spiral finned crystallizer for PFC system is evidently an effective system to concentrate solution and to produce pure ice crystal.

Progressive Freeze Concentration of Coconut Water: Effect of Circulation Flowrate and Circulation Time

Progressive freeze concentration integrated with a coil crystallizer was applied to concentrate coconut water in order to increase its sugar content. In progressive freeze concentration system, only a single ice is formed as a layer on cooled surface. It is introduced as an alternative in compensating the disadvantages of conventional method of freeze concentration, called suspension freeze concentration. In this research, the efficiency of the progressive freeze concentration system was determined through effective partition constant (K) value and percent increment of sugar content. Hence, the effect of circulation flowrate ranging from 2000 to 2800 ml/min and circulation time from 10 to 18 minutes on those two variables was then investigated through experiments designated using one factor at a time. From the experimental work, it was found that higher efficiency results at higher circulation flowrate of 2800 ml/min based on lower K and high percentage of sugar increment achieved. It was also found that the percentage of the sugar increment is high when the period given for circulating the solution is increased and the most suitable circulation time is 14 minutes.