Diffusion Coefficient Of Phenol Research Articles

Sampling of Phenol in Water by Diffusive Gradients Using Thin Film Technique

Abstract For the first time, new diffusive gradients in thin film (DGT) device using molecularly imprinted polymers as the binding agents and the nylon membrane as the diffusive layer have been developed for the sampling of phenol in water. The diffusion coefficient of phenol through the nylon membrane was 0.79 × 10−6 cm2 s−1, which was measured by the diffusion cell method. The binding agent of the DGT device was prepared by precipitation polymerization by molecularly imprinted technique using methacrylic acid as the functional monomer and ethyleneglycodimethacrylate as the crosslinker. The accumulated mass of phenol by the DGT device increased linearly with time (R2 = 0.9940). The ratio of the concentrations sampled by the DGT device to the concentration of the bulk solution was 0.97 ± 0.06. The results confirmed that the developed DGT device was suitable for the quantitative sampling of phenol in aqueous solution. The performance of the DGT device was independent of pH in the range 3–7 and ionic strength 0.0001–0.1 mol L−1. As a conclusion, the DGT device can be used for accurately sampling phenol in water.

Sensitivity Analysis of Phenol Degradation with Sulfate Reduction Under Anaerobic Conditions

This study derives a mathematical description of the kinetics of phenol degradation with sulfate reduction by an anaerobic mixed-culture biofilm on an inert medium. The model incorporates the mechanisms of diffusive mass transport and Monod kinetics. It is solved using both the orthogonal collocation method and Gear’s method. Sensitivity studies were performed to investigate the dependence of process dynamics on the model parameters pertaining to biokinetic parameters, liquid film mass transport, and the biofilm and reactor operational parameters. Sensitivity analysis quantifies the magnitude of the effect of each variable on the simulated results using the least-square method. The transient-state process dynamics are sensitive to the biokinetic parameters including yield coefficient of phenol-utilizing bacteria, Monod maximum specific utilization rate of phenol, and the decay coefficient of phenol-utilizing bacteria. The process efficiency is also sensitive to biofilm parameters such as biofilm density of phenol-utilizing bacteria and initial biofilm thickness , and to such operational parameters as the influent phenol concentration and the hydraulic retention time of the system. The process dynamics are relatively insensitive to mass transport parameters, including the film transfer coefficient of phenol and the diffusion coefficient of phenol. Sensitivity analysis of the process dynamics to model parameters helps determine how to alter process conditions to enhance removal efficiency.

Computer simulation of the structure and dynamics of phenol in sodium montmorillonite hydrates

SummaryMonte Carlo and molecular dynamics computer simulations have been used to study the structure and dynamics of phenol‐water solutions in the bulk and confined within the interlayer pores of sodium montmorillonite clays, as a function of pressure and temperature. Conditions have been chosen to mimic those encountered at burial depths of up to 6 km, thereby enabling us to shed light on subsurface processes including groundwater contamination and oil and gas migration. The structural data show that the phenol molecules are able to form a donor hydrogen bond to the clay surface. In addition, the phenolic –OH group is solvated by approximately three water molecules, and is also able to coordinate directly to an interlayer sodium cation. The phenolic aromatic ring is surrounded by approximately 25 water molecules in the bulk, compared to 18 in the compacted clay. Interlayer diffusion increases by an order of magnitude as temperature is increased from 275 K to 460 K. However, diffusion decreases by a factor of 2–4 as we move from the bulk into a clay hydrate of layer spacing ∼17 Å. For example, at 275 K the diffusion coefficient of phenol is 8.3 × 10−10 m2 s−1 in bulk solution, compared to 2.5 × 10−10 m2 s−1 in the clay.

Effect of ultrasound on desorption kinetics of phenol from polymeric resin

This work mainly involves the study of desorption kinetics of phenol from polymeric resins under the influence of an ultrasound field. A new phase equilibrium-kinetics model (PEKM), for estimation of diffusion coefficient was proposed, kinetic experiments of phenol desorption on NKA-II resin in the presence and the absence of ultrasound were separately conducted, and diffusion coefficients of phenol within an adsorbent particle were estimated by means of proposed PEKM. Results showed that the use of ultrasound could enhance the diffusion of phenol within the resin. The diffusion coefficient of phenol in the resin in an ultrasonic field increased by an order of magnitude in comparison with the diffusion coefficient in the absence of ultrasound. The more intense the ultrasonic field the larger was the diffusion coefficient.

Phenol Adsorption in Immobilized Activated Carbon with Alginate Gels

Calcium alginate-activated carbon composites were used for phenol adsorption from aqueous solutions. These composites were prepared by mixing different amounts of powdered activated carbon with a 3% (w/v) sodium alginate solution, and then dripping the mix into a calcium solution. Spherical beads were obtained with different amounts of powder-activated carbon immobilized inside the calcium alginate matrix. The adsorption on immobilized adsorbents modified the distribution equilibrium. A modified Langmuir equation was considered for analyzing adsorption isotherms and solid phase interactions. The kinetic of phenol adsorption on mixed gels is controlled by the diffusion of phenol in the particle over the gel phase, so the process can be described by one diffusional parameter: the effective diffusion coefficient of phenol in the gel phase.

Experimental Study of Groundwater Contamination By Phenol From Water/Heavy Oil Emulsion

Abstract A leaching experiment was conducted at 4 ° C to study the transport of phenol and chloride from a quiescent, viscous Cold Lake W/O emulsion into flowing fresh water. Test results indicated that phenol and chloride were transferred through different mechanisms. The rate-determining step for phenol transport was the slow molecular diffusion of phenol in emulsion. This was successfully modelled by a de-coupled second order diffusion equation from which the diffusion coefficient of phenol in emulsion was determined to be 2.2 x?10−8 cm2/s. Chloride was transported through direct contact of the emulsified water droplets with the leaching water in an 82 µm thick coalescence layer. The transport was essentially complete in less than two days and no further leaching was observed for the rest of the experiment. The bulk emulsified water was stable with no coalescing or segregation with time. The phenol/chloride transport model can be readily scaled to predict the mass transfer of these two chemicals from a contaminated zone into a flowing aquifer as shown in a subsequent paper. No appreciable air oxidation or biological degradation of phenol was detected within the experiment time frame of 61 days. Introduction Similar to coal gasification, the Cold Lake steam stimulation process also generates highly toxic by-products in the formation. These by-products, including various types of phenols, carboxylic acids and other high molecular weight acidic compounds generically classified as humic acids(1), are weak acids. Being soluble both in bitumen and especially in the high pH steam condensate, these compounds are brought to the surface by the produced water and bitumen. Cold Lake bitumen tends to form a stable, highly viscous water in oil emulsion with the produced water under minimal stress. The water content in the emulsion(2) can be as high as 40%. After separation, part of the produced water is softened and re-cycled for steam generation and the excess produced water, together with other harmful waste streams, are injected through a disposal well into an isolated zone to avoid aquifer contamination. In 1988, a leaky seal in the abandoned well C7-13 at Cold Lake caused an accidental spill of bitumen in the form of a water-in-oil emulsion and produced water into a near-surface aquifer zone where the bitumen and the produced water were in a danger of being contacted by the flowing aquifer(3). Although the W/O emulsion was practically immobile at the formation temperature of 4 ° C due to its high viscosity, the toxic phenolic compounds could still be expected to leach slowly into the flowing stream, posing a threat of potential groundwater contamination. To assess the environmental impact of phenol contamination on groundwater, water was produced from a newly drilled well and continuously monitored for chloride and phenol levels. In the meantime, experiments were designed and conducted in the lab to study the rate and mechanism of the release of phenol into fresh water. Experiments were also carried out to quantify the extent of natural degradation of phenol via air oxidation and biological pathways.

Diffusion of phenol through a biofilm grown on activated carbon particles in a draft‐tube three‐phase fluidized‐bed bioreactor

Diffusion of phenol through a biofilm attached to activated carbon particles was investigated. The biofilm was grown on activated carbon particles in a draft-tube three-phase fluidized-bed bioreactor operating in a fed-batch mode. It was found that phenol did not adsorb on the biofilm and that the diffusion coefficient of phenol within the biofilm varied from 13 to 39% of its corresponding value in water. The diffusion coefficient of phenol within the biofilm was reduced by increasing the biofilm density. An extensive literature review of diffusion of substrates through biofilms indicated that this conclusion could be extended to biofilms grown on flat surfaces, rotating cylinders, and even bioflocs.

DIFFUSION OF PHENOL IN STRETCHED POLYESTER FILMS

The effect of stretching of polyester films on the diffusibity of phenol has been studied. The films were prepared by the uniaxial stretching under a constant width or simultaneously biaxial stretching in several magnifications. The diffusion coefficient was determined from the permeability measured using an apparatus described in the previous paper as a function of phenol concentration. Then, the following results were obtained; (1) The diffusion coefficient of phenol in the amorphous region of polyester film was markedly dependent on the concentration of phenol. (2) The diffusion coefficient of phenol at a constant concentration and temperature, increased at the initial stage of stretching, then decreased with increasing the stretching ratio.(3) The apparent activation energy, calculated from the temperature dependence of diffusion coefficient, decreased with increasing the concentration of phenol.From these results, the internal fine structure of stretched polyester films were discussed relating to the change of the configurational entropy depending on the sorbed phenol. It was suggested that the amorphous polymer chains were ordered more tightly as increasing the stretching ratio, and this structural change leveled off at a certain magnification; about 3.5 times for uniaxial stretching and about 2.5 times for simultaneously biaxial stretching.

DIFFUSION OF PHENOL IN POLYESTER FILMS

The diffusion coefficient of phenol in polyester films was estimated at various concentrations and temperatures in order to elucidate a role of carriers in dyeing process of polymer. The diffusion coefficient of phenol in the amorphous region of polymer increased with increasing both concentration and temperature. This suggests that the sorbed phenol accelerates the segmental motion of the polymer chain.At the same time, dynamic moduli of two kinds of films were measured in phenol solutions at various temperatures and the dynamic moduli in the amorphous region EA' was calculated assuming the phenol was sorbed only in the amorphous region of polymer. Linear relationship was generally obtained between the EA' and the diffusion coefficients in amorphous region DA(c)in high concentration region of phenol. However, EA' deviated slightly from linear relation in low concentration region, which was attributed to the internal fine structure of each sample.

DIFFUSION OF PHENOL IN POLYESTER FILMS CRYSTALLIZED BY HEAT TREATMENT

The permeability of phenol in the amorphous region of polyester films which were crystallized by heat treatment at various temperatures, was measured as a function of phenol concentration and permeation temperature. The results are as follows.The diffusion coefficient of phenol in the amorphous region is strongly dependent upon the concentration of phenol, and the dependency varies with the temperature at the heat treatment. Since every activation energy for the diffusion obtained here is almost equal to each other, it is proposed that the mechanism of the diffusion may not change with the heat treatment. The change of entropy for the sorption of phenol decreases with increase in the treatment temperature to 180°C, while it increases above 180°C.From these results and the relation between the diffusion coefficient and the dynamic modulus for the same film measured in the phenol solution, it is suggested that the strain in some polymer chain of which both ends are fixed by crystallites increases with increase in the treatment temperature or crystallinity of the film, and that the other polymer chains having one free end remain without additional strain so that the diffusion becomes mainly to be controlled by the latter polymer chain.