Method to determine molecular diffusivities of phenol in bitumen

Abstract

Phenols, carboxylic acids and other water‐soluble compounds in bitumen constitute a potential source of groundwater pollution. To assess the extent of damages that could result from a spill, a water extraction method was used to determine the molecular diffusion of phenol in bitumen. This method involves the diffusion of phenol through bitumen into the flowing water in a well‐stirred cell. From the phenol concentration in water, the phenol flux and hence the phenol diffusion coefficient in bitumen can be deduced. An approximate dimensionless solution was obtained by de‐coupling the diffusional flux from the concentration buildup in water. The phenol diffusion coefficient was determined to be 4.0 ± 0.3 × 10−8 m2/s at 22°C. The derivation and the properties of the dimensionless solution were also discussed in the paper.

Critical review of mutual diffusion coefficient measurements for liquid solvent + bitumen/heavy oil mixtures

“…where C s,n is the concentration of the volatile solvent in nitrogen gas, Q is the volumetric flow rate of nitrogen gas at [1] Modified transpiration [3,4] Taylor dispersion [5] Nuclear magnetic resonance [6][7][8][9][10] …”

Propagation of Phenol in Aquifer With Reversible Adsorption

“…The reduced velocity v/(1+b) can be regarded as the effective phenol propagation rate. The boundary condition, which defines the flux into the water phase at the bitumen-aquifer interface, becomes: Comparing Equations (14), (15) with Equations (1), (2), it is evident that the solution to Equations (14) and (15) can be obtained simply by replacing the phenol concentration C(x,y,t), velocity v, dispersion coefficients D w,x and D w,y in Equation (4) with the corresponding reduced entities, i.e., the entities divided by the factor of (1+b).…”

“…Based on the "decouple" assumption, the phenol convective-dispersive equation in water phase can be set up 4 (Equation 1) with a flux boundary condition (Equation 2): (2) where A = transfer area = Ldz, <L 2 >, J = phenol flux into the water phase, J (mg/s), C o = effective phenol concentration in water/bitumen emulsion, gm of phenol/cc of emulsion, v = interstitial velocity in porous medium cm/s. It has been known that Green's function does satisfy the convective-dispersive equation 8 , therefore it is a general solution to Equation (1).…”

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Previous study [1][2][3] indicated that phenol transport from spilled bitumen into flowing aquifer was controlled by slow molecular diffusion of phenol in bitumen as the ratedetermining step. This simplified de-coupled transfer mechanism has led to a 2 dimensional planar flow analytical solution, which described the time-dependent phenol concentration in a flowing stream 4 .

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Modeling of Pollutant Transport from a Stationary Phase into a Flowing Stream with Reversible Adsorption

“…These compounds, which are soluble both in oil and water, can leach slowly into the subsurface aquifer, posing a threat of groundwater contamination to the environment. Previous studies (Tang, 1999;Tang and Zhang, 2000) revealed that molecular diffusion of phenol in bitumen was the rate-determining step and the transfer mechanism could be adequately described by a de-coupled second-order convective-dispersive equation from which the diffusion coefficients of phenol were determined to be 2:2 10 8 cm 2 /s at 4 ı C in water-bitumen emulsion and 4:0˙0:3 10 8 cm 2 /s at 22 ı C in bitumen.…”