Kyunghoi Kim

Combined adsorption and oxidation mechanisms of hydrogen sulfide on granulated coal ash

Hydrogen sulfide is highly toxic to benthic organisms and may cause blue tide with depletion of dissolved oxygen in water column due to its oxidation. The purpose of this study is to reveal the combined adsorption and oxidation mechanisms of hydrogen sulfide on granulated coal ash that is a byproduct from coal electric power stations to apply the material as an adsorbent for hydrogen sulfide in natural fields. Sulfur species were identified in both liquid and solid phases to discuss removal mechanisms of the hydrogen sulfide with the granulated coal ash. Batch experiments revealed that hydrogen sulfide decreased significantly by addition of the granulated coal ash and simultaneously the sulfate ion concentration increased. X-ray absorption fine structure analyses showed hydrogen sulfide was adsorbed onto the granulated coal ash and successively oxidized by manganese oxide (III) contained in the material. The oxidation reaction of hydrogen sulfide was coupling with reduction of manganese oxide. On the other hand, iron containing in the granulated coal ash was not involved in hydrogen sulfide oxidation, because the major species of iron in the granulated coal ash was ferrous iron that is not easily reduced by hydrogen sulfide.

Mechanisms of hydrogen sulfide removal with steel making slag.

In the present study, we experimentally investigated the removal of hydrogen sulfide using steel-making slag (SMS) and clarified the mechanism of hydrogen sulfide removal with the SMS. The results proved that SMS is able to remove hydrogen sulfide dissolved in water, and the maximum removal amount of hydrogen sulfide per unit weight of the SMS for 8 days was estimated to be 37.5 mg S/g. The removal processes of hydrogen sulfide were not only adsorption onto the SMS, but oxidation and precipitation as sulfur. The chemical forms of sulfide adsorbed onto the SMS were estimated to be sulfur and manganese sulfide in the ratio of 81% and 19%, respectively. It is demonstrated here that the SMS is a promising material to remediate organically enriched coastal sediments in terms of removal of hydrogen sulfide. Furthermore, using SMS is expected to contribute to development of a recycling-oriented society.

Field experiments on remediation of coastal sediments using granulated coal ash.

Field experiments were carried out to evaluate the effect of Granulated Coal Ash (GCA) on remediation of coastal sediments in terms of removing phosphates and hydrogen sulfide. Phosphate concentrations in the sediment were kept below 0.2 mg/l after the application of GCA, whereas those in the control sites increased up to 1.0 mg/l. The concentration of hydrogen sulfide in the sediment was maintained at almost zero in the experimental sites (GCA application sites) for over one year, whereas it ranged 0.1-2.4 mg S L(-1) in control sites. Meanwhile, individual number of benthos increased in the experimental sites by several orders of magnitude compared to the control sites. The major process involved in hydrogen sulfide removal by GCA was thought to be the increase in pH, which suppresses hydrogen sulfide formation. From our findings, we concluded that GCA is an effective material for remediating organically enriched coastal sediment.

Involvement of Nrf2-mediated heme oxygenase-1 expression in anti-inflammatory action of chitosan oligosaccharides through MAPK activation in murine macrophages

Chitosan and its derivatives have been reported to have anti-inflammatory effects in vitro and in vivo. It is also suggested that chitosan and its derivatives could be up-regulating heme oxygenase-1 (HO-1) in different models. However, the up-regulation of HO-1 by chitosan oligosaccharides (COS) remains unexplored in regard to anti-inflammatory action in lipopolysaccharide (LPS)-stimulated murine macrophages (RAW264.7 cells). Treatment with COS induced HO-1 expression in LPS-stimulated RAW264.7 cells, whereas the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) was decreased. Pretreatment with ZnPP, a HO-1 inhibitor, reduced the COS-mediated anti-inflammatory action. HO-1 induction is mediated by activating the nuclear translocation of NF-E2-related factor 2 (Nrf2) using COS. Moreover, COS increased the phosphorylation of extracellular signal regulated kinase (ERK1/2), c-Jun N-terminal kinase/stress-activated protein kinase (JNK), and p38 MAPK. However, specific inhibitors of ERK, JNK, and p38 reduced COS-mediated nuclear translocation of Nrf2. Therefore, HO-1 induction also decreased in RAW264.7 cells. Collectively, COS exert an anti-inflammatory effect through Nrf2/MAPK-mediated HO-1 induction.

A pilot study on remediation of sediments enriched by oyster farming wastes using granulated coal ash

In order to evaluate the ability of granulated coal ash (GCA), a byproduct of coal thermal electric power stations, to remove hydrogen sulfide from organically enriched sediments, a pilot study was carried out at oyster farming sites, where sediments were enriched with oyster feces and dead oysters. Concentration of hydrogen sulfide in the interstitial water of the sediment decreased to nearly zero in both experimental sites, whereas it remained over 0.2mg/l in the control site. Concentration of acid volatile sulfide (AVS) in the sediment also decreased significantly in both experimental sites, while remained over 0.4 mg/g in the control site. Increases were observed in both the number of benthic microalgae species and the individual number of benthic animals in the surface sediments. This may have been due to the decrease in hydrogen sulfide.

Remediation of muddy tidal flat sediments using hot air-dried crushed oyster shells

In order to prove that hot air-dried crushed oyster shells (HACOS) are effective in reducing hydrogen sulfide in muddy tidal flat sediments and increasing the biomass, field experiments were carried out. The concentration of hydrogen sulfide in the interstitial water, which was 16 mg SL(-1) before the application of HACOS, decreased sharply and maintained almost zero in the experimental sites (HACOS application sites) for one year, whereas it was remained at ca. 5 mg SL(-1) in the control sites. The number of macrobenthos individuals increased to 2-4.5 times higher than that in the control site. Using a simple numerical model, the effective periods for suppression of hydrogen sulfide were estimated to be 3.2-7.6 and 6.4-15.2 years for the experimental sites with 4 and 8 tons per 10 × 10 × 0.2m area, respectively. From these results, it is concluded that HACOS is an effective material to remediate muddy tidal flats.

Application of Granulated Coal Ash for Remediation of Coastal Sediment

본 논문에서는 석탄회 조립물을 이용한 저질개선 기술의 안전성 및 저질개선기구에 대해 논하고, 일본 카이타만 석탄회 조립물 피복구간에서의 저질개선효과에 대해 검토하였다. 석탄회 조립물의 중금속 농도 및 용출량은 일본의 환경기준을 만족하는 것으로 조사되었으며, 석탄회 조립물의 저질개선기능은 다음과 같이 요약할 수 있다. (1) 인산염 및 황화수소의 제거 (2) 산성 저질의 중화 (3) 투수성의 증가 및 이로 인한 환원상태 저질의 개선 (5) 지반강도의 증가 (6) 부착성 조류의 서식 기반. 일본 카이타만에서 실시한 현장실증실험 결과로부터 연안저질의 pH중화, 인산염 및 황화수소농도 감소 등 석탄회 조립물의 저질개선효과가 검증되었으며, 이에 따른 저서생물의 증가가 확인되었다. 석탄회 조립물을 이용한 연안저질의 개선기술이 실용화 된다면 오염저질의 정화에 소요되는 비용의 절감은 물론 산업부산물인 석탄회의 재활용에 기여할 것으로 기대된다.Abstract − This paper aims to explain the safety assessment and remediation mechanism of Granulated Coal Ash(GCA) as a material for the remediation of coastal sediments and to evaluate the improvement of the sediment inKaita Bay, where GCA was applied. The concentrations of heavy metal contained in GCA and the dissolvedamounts of heavy metal from GCA satisfied the criteria for soil and water pollution in Japan. The mechanisms onthe remediation of coastal sediments using GCA is summarized as follows; (1) removal of phosphate and hydro-gen sulfide (2) neutralization of acidic sediment (3) oxidation of reductive sediment (4) increase of water perme-ability (5) increase of soil strength (6) material for a base of seagrass. From the results obtained from the fieldexperiment carried out in Kaita Bay, it was clarified that GCA is a promizing material for remediation of coastalsediment. This remediation technology can contribute to promote waste reduction in society and to decrease cost ofcoastal sediment remediation by applying GCA in other polluted coastal areas. Keywords: Granulated Coal Ash(석탄회조립물), Remediation of Coastal Sediment(연안저질개선), HydrogenSulfide(황화수소 ), Phosphate(인산염)

Quantitative Measurement on Removal Mechanisms of Phosphate by Class–F Fly Ash

ABSTRACT The role of Class-F fly ash in the removal of phosphate from aqueous solutions and the removal mechanism were quantitatively investigated. The relative contributions of precipitation and adsorption with various pH conditions showed that precipitation was predominant under alkaline conditions, whereas adsorption was effective under acidic conditions. The precipitation accounted for 79% of the total phosphate removal without adjusting the pH of the solution. This result suggests that the phosphate was predominantly removed by precipitation with fly ash, and that adsorption on hydroxylated oxides may have contributed to the removal of phosphate. The precipitate was revealed to be calcium hydrogen phosphate (CaHPO4) from X-ray absorption fine structure analysis. The adsorption process was expressed well by the Freundlich isotherm and phosphate adsorption by fly ash is favorable (n = 1.308).

MODELING THE SETTLING VELOCITY OF ORGANIC SETTLING MATTER WITH THE CONSIDERATION OF ORGANIC PROPERTIES

Estimating the settling velocity of organic settling matter (OSM) under the effects of organic properties is necessary for developing a pelagic-benthic coupled ecosystem model to evaluate the coastal environment, where OSM deposits on the sea bottom. In this study, laboratory experiments were performed with several materials, such as bentonite, OSM and suspended matter, using a particle distribution analyzer to reveal the effects of organic properties on the settling factors (e.g. effective density, fractal dimension). Prom the experimental results, it was found that the effective density of each material decreased in association with the increase in particle size from a certain size. Comparing these results to the organic properties of materials, it is evident that the organic properties, such as the absorption amount and the decomposition degree of organic matter, strongly affect the physical properties, such as the fractal dimension and the effective density. Furthermore, a model formula of the settling velocity, in which the effects of the organic properties are considered, has been suggested.

MODELING OF SETTLING AND DEPOSITION OF SUSPENDED ORGANIC MATTER CONSIDERING BIODEGRADATION

To design a model for the settling of Suspended Organic Matter (SOM), the decomposition rate of organic matter, and variations in the particle size and the density of SOM were studied in the course of decomposition. The decomposition rate of SOM is estimated using the analyzed results of SOM properties (i.e. particle density, particle size, IL, and resolvability). The Multi-G Model, which formulates the decomposition of organic matter derived from phytoplankton, was chosen to calculate the decomposition rate of SOM. The parameters of each fraction in the Multi-G Model were estimated on the basis of the correlation between the deposition age and the decomposition rate of SOM. In addition, it has become possible to determine the mean decomposition rate of organic matter using the C/N ratio. Temporal variations of the particle size and the particle density of SOM during decomposition were estimated from the C/N ratio, and approximate expressions for the variations were proposed. Based on these results, it is possible to calculate the settling velocity of SOM in considering the variation of its properties due to decomposition