Henry's law constant and overall mass transfer coefficient for formaldehyde emission from small water pools under simulated indoor environmental conditions

The Henry's law constant (HLC) and the overall mass transfer coefficient are both important parameters for modeling formaldehyde emissions from aqueous solutions. In this work, the apparent HLCs for formaldehyde aqueous solutions were determined in the concentration range from 0.01% to 1% (w/w) and at different temperatures (23, 40, and 55 °C) by a static headspace extraction method. The aqueous solutions tested included formaldehyde in water, formaldehyde-water with nonionic surfactant Tergitol NP-9, and formaldehyde-water with anionic surfactant sodium dodecyl sulfate. Overall, the measured HLCs ranged from 8.33 × 10(-6) to 1.12 × 10(-4) (gas-concentration/aqueous-concentration, dimensionless). Fourteen small-chamber tests were conducted with formaldehyde solutions in small pools. By applying the measured HLCs, the formaldehyde overall liquid-phase mass transfer coefficients (KOLs) were determined to be in the range of 8.12 × 10(-5) to 2.30 × 10(-4) m/h, and the overall gas-phase mass transfer coefficients were between 2.84 and 13.4 m/h. The influences of the formaldehyde concentration, temperature, agitation rate, and surfactant on HLC and KOL were investigated. This study provides useful data to support source modeling for indoor formaldehyde originating from the use of household products that contain formaldehyde-releasing biocides.