Feed Phenol Concentration Research Articles

Novel membrane bioreactor with gas/liquid two-phase flow for high-performance degradation of phenol.

The use of a membrane bioreactor with cell retention to achieve high biomass concentrations has been examined for phenol degradation by the bacteria Alcaligenes eutrophus. This process is particularly interesting for toxic substrates as the hydraulic dilution rate and the growth rate are independently controlled. In the case of a transitory excess of phenol, this potentially toxic situation can be overcome by modifying the substrate concentration or the dilution rate without any loss of cells. The injection of a gas phase at the filter inlet increased both the permeate flow rate (by a factor of 1. 75) and the oxygen transfer capacity (by a factor of 1.5). This has enabled the cell concentration to reach a maximal value of 60 g L-1 with a hydraulic dilution rate of 0.5 h-1 and a phenol feed concentration of 8 g L-1. The volumetric productivity of this process corresponds to a phenol degradation rate approaching 100 kg m-3 day-1. The on-line measurement of the characteristic yellow color of 2-hydroxymuconate semialdehyde, a metabolic intermediate of the phenol degradation pathway, in the permeate provides an interesting basis for process control of phenol supply into the reactor since the color intensity correlates directly to the specific rate of phenol degradation.

Separation of aqueous phenol through polyurethane membranes by pervaporation

The separation of a phenol-water mixture using a polyurethane membrane by a pervaporation method was investigated. Polyurethane was selected as a membrane material because its affinity for phenol was considered to be high. Polyurethane was prepared by the polyaddition of 1,6-diisocyanatohexane and polytetramethyleneglycol. The polyurethane layer was sandwiched with a porous polypropylene membrane (Celgard® 2500). Pervaporation measurement was carried out under vacuum on the permeate side, and the permeate vapor was collected with a liquid nitrogen trap. The phenol concentration in the permeate solution increased from 0 to 65 wt % with increasing feed concentration of phenol from 0 to 7 wt %. The total flux also increased up to 930 g m-2 h-1 with increasing phenol partial flux. In the sorption measurement at 60°C, the concentration of phenol in the membrane was 68 wt %, which was higher than that of the permeate solution. Therefore, it was considered that the phenol selectivity was based on high solubility in the polyurethane membranes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:469–479, 1997

Separation of aqueous phenol through polyurethane membranes by pervaporation

The separation of a phenol-water mixture using a polyurethane membrane by a pervaporation method was investigated. Polyurethane was selected as a membrane material because its affinity for phenol was considered to be high. Polyurethane was prepared by the polyaddition of 1,6-diisocyanatohexane and polytetramethyleneglycol. The polyurethane layer was sandwiched with a porous polypropylene membrane (Celgard® 2500). Pervaporation measurement was carried out under vacuum on the permeate side, and the permeate vapor was collected with a liquid nitrogen trap. The phenol concentration in the permeate solution increased from 0 to 65 wt % with increasing feed concentration of phenol from 0 to 7 wt %. The total flux also increased up to 930 g m-2 h-1 with increasing phenol partial flux. In the sorption measurement at 60°C, the concentration of phenol in the membrane was 68 wt %, which was higher than that of the permeate solution. Therefore, it was considered that the phenol selectivity was based on high solubility in the polyurethane membranes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:469–479, 1997

On the kinetics of phenol oxidation in supercritical water

AbstractPhenol oxidation in supercritical water was carried out in a tubular laboratory‐scale reactor operated at a temperature range of 380°C to 450°C and pressures between 230 and 265 bar. The phenol feed concentrations were between 500 and 1,000 mg/L, while oxygen was fed into the reactor at 50 to 1,000% of the stoichiometric amount needed to oxidize phenol completely to carbon dioxide. Phenol conversions from 16 to 96% were attained as the reactor residence times varied from 15 to 203 s. The oxidation obeys a parallel‐consecutive reaction scheme that involves multiring, intermediate products such as phenoxy‐phenol, biphenol, dibenzo‐dioxin, maleic acid, and succinic acid. Experimental results showed that the phenol disappearance rate is represented well by a power‐law kinetic model in which the rate is proportional to the 0.4 power of the oxygen mole fraction and roughly linearly proportional to the phenol mole fraction. The pressure effect on the disappearance rate was appropriately accounted for by introducing the molar volume of the reaction mixture, which was readily calculated by an equation of state. Total organic carbon reduction can be estimated by a lumped kinetic equation. In the P‐T region the activation energy of the phenol disappearance was 124.7 kJ/mol.

Kinetics of growth and catechol production byBacillus stearothermophilus BR321

A continuous bioprocess for the specialty chemical catechol has been developed usingBacillus stearothermophilus BR321. Themeta pathway for phenol degradation has been blocked at the catechol 2,3-dioxygenase enzyme using transposon mutagenesis. As a result, the organism grows on a dilute growth medium supplemented with phenol and accumulates catechol. In batch culture, catechol concentrations up to 1 mM were obtained. A kinetic model has been developed to describe batch growth for different initial phenol concentrations. In continuous culture conducted at a diluation rate of 0.12 hr−1, steady states were obtained for feed phenol concentrations up to 0.24 mM, resulting in catechol concentrations up to 0.08 mM. Above this phenol concentration, oscillatory dynamics were observed.

Contribution of adsorptive or acid–base interaction between phenol molecules and polyvinylpyridine membrane to the large permeability of phenol through the membrane

AbstractPermeability of phenol from aqueous solution to organic solvent through a microporous membrane made of cross‐linked poly (4‐vinylpyridine) (polyvinylpyridine membrane) was about 12 times larger than that through a microporous membrane made of polyethylene (polyethylene membrane) having similar thickness, porosity, and mean pore diameter with those of polyvinylpyridine membrane. Adsorptive or acid–base interaction between phenol molecules and polyvinylpyridine membrane was shown to play an important role in this unusally rapid permeation of phenol through the membrane. The amount of phenol contained in polyethylene membrane per unit volume of the pores was about six times larger than the phenol concentration in the feed aqueous solution. However, the amount of phenol contained in polyvinylpridine membrane per unit volume of the pores was 80–260 times larger than the feed phase concentration. The rapid permeation of phenol through poly‐vinylpyridine membrane was thus explained in terms of the extensive enrichment of phenol in the membrane due to the adsorptive or acid–base interaction between phenol molecules and the membrane. © 1993 John Wiley & Sons, Inc.

Dynamics of phenol degradation by Pseudomonas putida

Pure cultures of Pseudomonas putida (ATCC 17484) were grown in continuous culture on phenol at dilution rates of 0.074-0.085 h(-1) and subjected to step increases in phenol feed concentration. Three distinct patterns of dynamic response were obtained depending on the size of the step change used: low level, moderate level, or high level. During low level responses no accumulations of phenol or non-phenol, non-glucose-dissolved organic carbon, DOC(NGP), were observed. Moderate level responses were characterized by the transient accumulation of DOC(NGP) with a significant delay prior to phenol leakage. High level responses demonstrated a rapid onset of phenol leakage and no apparent accumulations of DOC(NGP). The addition of phenol to a continuous culture of the same organism on glucose did not result in transient DOC(NGP) accumulations, although transient phenol levels exceeded 90 mg l(-1). These results were consistent with intermediate metabolite production during phenol step tests coupled with substrate-inhibited phenol uptake and suggested that traditional kinetic models based on the Haldane equation may be inadequate for describing the dynamics of phenol degrading systems.

Metabolic responses of microorganisms growing on inhibitory substrates in nonsteady state culture

AbstractThe dynamics of metabolic activity of Pseudomonas putida cultured on phenol in a nonsteady state, resulting from simultaneous step increases (or decreases) in dilution rate and feed phenol concentration, were studied. Metabolic activity was determined by the uptake rate, defined as the mass of phenol degraded by a unit mass of bacteria in unit time. A minimum duration of nonsteady state was necessary to induce the metabolic pathway. The induction time for Pseudomonas putida cultured on phenol was approximately 30 min, irrespective of the type of disturbance applied.The Monod‐Haldane equation was applied to fit the experimental values of uptake rate and the best kinetic parameters were calculated by the nonlinear least squares technique. Values of the kinetic parameters differed both for each parameter and type of disturbance investigated. For simultaneous step increases in dilution rate and feed phenol concentration, the value of um in the transient state first increased monotonically approximately four times and then decreased monotonically to the new steady state value after three residence times. Values of Ks and Ki attained those at the new steady state after three residence times, the highest being approximately three times greater than those of the steady state prior to disturbance. For simultaneous step decreases in D and SO, values of um, Ks and Ki reached those at the new steady state values after four residence times.

Removal of Phenol in Wastewater by Wet Air Oxidation

Abstract The Wet Air Oxidation process was developed by F.J. Zimmermann for removing suspended solids from waste waters, notably waste water from pulp mills. The basic idea behind the process is to combine the waste stream and air under suitable conditions so that liquid water is present. In theory waste organic is oxidized to CO2 and water, and thus removed by conversion to a harmless gas. In practice there are problems with incomplete combustion and tar formation especially in the oxidation of phenol. This project was undertaken to try and resolve these problems. Furthermore, specifications in the literature are for mixed reactors, which have financial disadvantages due to mixer sealing problems. This study is part 1 of a two part study to investigate unmixed reactors for the job of Wet Air Oxidation. The study was made in an unmixed reactor at temperatures of 200 and 250°C Pressure was varied from 800 to 2200 psi, and residence times from 0.25 to 2 hours. Phenol feed concentration was either 1400 or 3000 mg/L for all runs. Conversions of over 99% were achieved for conditions at the highest pressure and either temperature.