ARCHIVED REPORTS XR0012553 - Laserfiche WebLink

Home Browse Search

announce hey findings of 1lhe rt•scarch vraopment of total surface area towels- turbulent drlfusion and spray an, project that is luny documented in a lions for organic solutes. bubble transfer through water bodre- sepankte reperr of the same title(see Solid and liquid vape, pressures are and interfacial regions to the atmo- PrajretReport orderinginlormarion at discussed and a correl.;:mn is suggested sphere. It is shown that the Whitman bae1F/ for estimating vapor pressures of Two resistance model is a specific case organic,solutes from the melting and of a multiple resistance model in which Introduction boiling point. the resistances are expressed as a The volatilization of organic sub- Henry's law constant is obviously function of a diffusive quantity(either a stances from water bodies to the relevant to valalrlization calculations, difrusivity and diffusion path length or atmosphere can be a very significant and,being the ratio of vapor pressure to their combination in the lorm of a mass environmental pathway, especially for solubility, can be correlated and pre- liar+sfcr coe!:icienq arv! the prevailing those substartce3 which have high dicied approximately from the individual phase fugacity capacity.An example is vapor pressures and relatively low correlations and predictions for vapor given of such a multiple resistance water solubilities, i.e.. they exhibit a pressure and solubility,The relationship caicu:ation.Mechanismsof mass Trans- preferential partitioning into the atmo- between Henry's law constant and ter and correlations are discussed sphere. The rate of this process may solute-water relative volatilityisexplored including a brief review of the effect of control ambient aqueous concenualions with a view to developing a method by surface films. and atmospheric concentrations.Vola- which a simple distillation procedure Experimental Volatilization , tilizarion may significantly influence the can be used to estimate the Henry's law P substance's environmental persistence constant for sparingly soluble organic Systems or half-life. - • solutes o:solutes of a low Henry's law There has been some confusion in the Prediction of volatilization rates constant. literature about the relationships be requires the combination of thermody- The thermodynamic analysis shows !ween laboratory volatilization systems namic (i.e-, equilibrium) information that the directly ind readily experi- with different air-water contacting about the solute'and kinetic or mass mentally accessible properties ofmolec- geometries. Such systems include transfer information, the general sup- ular structure. solid and liquid vapor beakers (which may be stirred or position being that the rate of transfer is pressure, melting point and boiling exposed to air currents),wind lunnels proportional to the departure of the point,aqueous solubility.octanol-water and sparged vessels in which•a bubble system from equilibrium:with a propor- partition coefficient arid Henry's law swarm is directed through a pool of tionality constant applying in the form of constant are closely related and prove to water.A general mass transfer mathe- E diffusivities or mass transfer coefficients.. be functions '61 certain fundamental manta: model is assembled which is properties, namely activity coefficients applicable to most of these systems-It is - Physical Chemistry in water and octanol phases and solute shown that depending on the values at The report first reviews the equilibrium fugacity, which are not directly acces- • the prevailing mass transfer coefficients physical chemistry of hydrophobic sibfe experimentally. The relationships the interfacial surface area.and the gas organic l chemistry water,including between the experimentally accessible rate,the general equation reduces to a disc!+scan s aqueous wl water. incty,vapor quantities"enable some to be predicted number of particular solutions.Measure- pressure-sorption, us soluthil ter vapor ti- from others,and if data are available for ment of a transfer rate at a condition tion coefficient and air -er partition a11,consistencychecks can be made.An close to equilibrium is suitable for coefficient or Henry's law constant. illustrative example is given for naphtha- obtaining Henrys law cors:ants.since lene in which the available experi- the amount transferred is limitedbythat In relating equilibrium concentrations s, it is c mental data are critically reviewed with constant- Conditions may also exist in in environmental phase Wiens to use the concept a fugacity Bather a view to establishing the most probable which the amount transferred is con- actual values. The approach may be trolled by kinetic processes it either the than chemical potential,and a detailed useful in predicting property'data for liquid phase or the gas phase or both. ac.-aunt is presented of methods by. substances for which no experimental under which regimes mass transfer co- which this approwh may be used to data are available and for checking the efficierts may be obtained. In extreme calculate the environmental partitioning consistency of reported experimental conditions where H is very small,them characteristics of organic solutes-This data obtained for environmenta I assess- is a negligible solute volatility regime- approach may have broader applicability mens purposes to environmental modelling of toxic The relationshipbetween the octano]- Bench Scale Volatilization. substances. The approach is to relate water partition coefficient and aqueous Apparatus fugacity to concentration using a solubility is explored using the fugacity As part of the experimental work, a fugacity capacity as the proportionality approach, and a,new correlation is small scale volatilization apparatus was constant- developed between these two pfnptrties developed consisting of a 30-cm- The fundamental determinants of using the fugacity ratio,(i.e..the ratio of diamete,- by 30-cm-deep glass tank. aqueous solubility of sparingly soluble solid and subcooled liquid vapor Pres- containing 6liters ofwater.Windwaves solid and liquid organic compounds are sures)as a function of entropy of fusion were generated at the air-water interface discussed, and methods of correlating for substances below their melting by blowing air from abloom.:: tangentially solubility in the form of aqueous phase points. into the tank a,a kno,-,n flow rate.The. activity coefficient against molecular Ao swirling motion of tt a air generated a - properties fuch as total surface area, carbon number or molar volume are mass Translzr corresponding swirs.ng motion in the reviewed.It is su9gested that a fruitful A review is presented of the meth- water. The volatilization rates of Yn "`" aria for the research is the further de- anisms of mass transfer bymolecular and organic compounds were studied in this