Jong M. Park

Removal of cationic heavy metal from aqueous solution by activated carbon impregnated with anionic surfactants

To increase their capacity to adsorb heavy metals, activated carbons were impregnated with the anionic surfactants sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), or dioctyl sulfosuccinate sodium (DSS). Surfactant-impregnated activated carbons removed Cd(II) at up to 0.198 mmol g(-1), which was more than an order of magnitude better than the Cd(II) removal performance of activated carbon without surfactant (i.e., 0.016 mmol g(-1)) even at optimal pH (i.e., pH 6). The capacity of the activated carbon to adsorb Cd(II) increased in proportion to the quantity of surfactant with which they were impregnated. The kinetics of the adsorption of Cd(II) onto the surfactant-impregnated activated carbon was best described by a pseudo-second-order model, and was described better by the Freundlich adsorption isotherm than by the Langmuir isotherm. The surface charge of activated carbon was negative in all pH ranges tested (2-6). These results indicate that surface modification with anionic surfactant could be used to significantly enhance the capacity of activated carbon to adsorb cations.

Evaluation of the interaction between biodegradation and sorption of phenanthrene in soil-slurry systems

This work develops and utilizes a non-steady-state model for evaluating the interactions between sorption and biodegradation of hydrophobic organic compounds in soil-slurry systems. The model includes sorption/desorption of a target compound, its utilization by microorganisms as a primary substrate existing in the dissolved phase, and/or the sorbed phase in biomass and soil, oxygen transfer, and oxygen utilization as an electron acceptor. Biodegradation tests with phenanthrene were conducted in liquid and soil-slurry systems. The soil-slurry tests were performed with very different mass transfer rates: fast mass transfer in a flask test at 150 rpm, and slow mass transfer in a roller-bottle test at 2 rpm. The results of liquid tests indicate that biodegradation of the soil-soluble organic fraction did not significantly enhance the biodegradation rate. In the slurry tests, phenanthrene was degraded more rapidly than in liquid tests, but at a similar rate in both slurry systems. Modeling analyses with several hypotheses indicate that a model without biodegradation of compound sorbed to the soil was not able to account for the rapid degradation of phenanthrene, particularly in the roller-bottle slurry test. The model with sorbed-phase biodegradation and the same biokinetic parameters, but unique mass transfer coefficients, simulated the experimental data in both slurry tests most successfully. Reduced mass transfer resistance to bacteria attached to the soil is the most likely phenomenon accounting for rapid sorbed-phase biodegradation.

Thiocyanate degradation by Acremonium strictum and inhibition by secondary toxicants

Acremonium strictum, capable of degrading 7.4 g thiocyanate l−1, was isolated from wastewater condensate from coke-oven gas. Ammonia and sulfate were the final products from thiocyanate degradation with a stoichiometric ratio of near 1:1. The highest degradation activity was at pH 6. Although the degradation rate started to be inhibited above 4 g thiocyanate l−1, thiocyanate was completely degraded up to 7.4 g l−1 within 85 h in shake-flask cultures. The degradation of thiocyanate was inhibited by phenol above 625 mg l−1, by cyanide above 16 mg l−1, and by nitrite above 100 mg l−1. However, ammonia and nitrate had negligible inhibition on thiocyanate degradation up to 3 g l−1 and 1.5 g l−1, respectively.

Mathematical evaluation of activated carbon adsorption for surfactant recovery in a soil washing process.

The performances of various soil washing processes, including surfactant recovery by selective adsorption, were evaluated using a mathematical model for partitioning a target compound and surfactant in water/sorbent system. Phenanthrene was selected as a representative hazardous organic compound and Triton X-100 as a surfactant. Two activated carbons that differed in size (Darco 20-40 mesh and >100 mesh sizes) were used in adsorption experiments. The adsorption isotherms of the chemicals were used in model simulations for various washing scenarios. The optimal process conditions were suggested to minimize the dosage of activated carbon and surfactant and the number of washings. We estimated that the requirement of surfactant could be reduced to 33% of surfactant requirements (from 265 to 86.6g) with a reuse step using 9.1g activated carbon (>100 mesh) to achieve 90% removal of phenanthrene (initially 100mg kg-soil(-1)) with a water/soil ratio of 10.

Multiple shoot culture of Dianthus caryophyllus using mist culture system

A mist bioreactor system for the plant tissue cultures was developed. Using this system, the growth of Dianthus caryophyllus multiple shoots was directly measured. Tissue growth in mist bioreactor system was far better than that on agar medium and almost comparable to that in liquid medium. The mass increase (final dry weight/initial dry weight) in the mist culture was 2.85 while 3.28 in the liquid flask culture. Shoots were seriously vitrified in flask culture but these vitrifications could be considerably cured by using the mist culture system.

Estimation of oxygen transfer in soil slurry bioreactor

The apparent volumetric O transfer coefficient in a soil slurry bioreactor was significantly affected by the particle size of the soil and its clay content but less affected by the concentration of organic matter. The k L a values in the slurry of 40% (w/v) soil content ranged from 60% to 80% of that in water. O requirement was estimated for a bio-remediation: O was limiting in heavily contaminated soil and in soil with high clay content.

Variations of photosynthetic activity and growth of freshwater algae according to ozone contact time in ozone treatment

The activity of freshwater algae in drinking water supply at various ozone contact times was investigated to evaluate ozonation processes used for sterilization of algae. O production rates of algae just after ozonation were severely retarded even by short ozone contact. The algal growth rate was also declined with increase of ozone contact time and completely inhibited by ozonation for 60 min. These results implied that the usual treatment time applied in conventional ozonation processes is not sufficient but at least 60 min of ozonation is required for a complete sterilization of freshwater algae in drinking water source.