• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.67-73
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• 2019

We carried out basic research to evaluate covering material for improving and managing contaminated benthic environments in coastal areas. Changes in nutrient concentration such as phosphate, hydrogen sulfide of contaminated sediment, and pH, Oxidation Reduction Potential (ORP) were investigated through mesocosm experiments for 6 months by covering contaminated sediment with granulated coal ash. Calcium oxide eluted from the granulated coal ash was confirmed to neutralize acidified sediment by increasing pH through hydrolysis. Also, calcium oxide and silica eluted from the granulated coal ash adsorbed and precipitated with phosphate in the sediment. The concentration of phosphate in the sediment investigated decreased by ca. 84.31 %. Similarly, the concentration of hydrogen sulfide decreased by 133.5 mg/L in one month. The hydrogen sulfide is considered to have reacted with substances such as manganese oxide which were eluted from the granulated coal ash and precipitated. Also, it was concluded that the hydrogen sulfide was reduced since anaerobic conditions in the sediment weakened. According to the results of these mesocosm experiments, granulated coal ash was found to be effective to remediate and manage benthic environments by covering the surface layer of sediment.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.4
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• pp.206-212
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• 1999

In order to evaluate the applicability of steel mill slag as a AMD (Acid Mine Drainage) neutralizer and to compare capacity of slag with that of limestone lab scale experiments were conducted. The fixed treatment experiments of AMD with slag and limestone separately for 24 hours under the stagnant condition showed that slag has higher capacity of pH increase and removal of Fe. Al and other trace elements. During the 10 days continuous step experiment the pH has been maintained and any decrease in the removal capacity of Fe and Al has not bun observed. In the trace element removal experiment slag showed higher capacity for removal of Ni, Co. Cu and Zn than limestone. The removal of trace element was more effective in AMD than in distilled water that the pH was adjusted to the same level of AMD (synthetic acid solution). It means that Fe and Al in AMD adsorbed trace elements during or after precipitation as oxide forms. In the size effect experiment, the slag of the smaller size with larger specific surface area exhibited higher capacity of pH increase and removal efficiencies of Fe. Al and other trace elements.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.3
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• pp.219-226
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• 2012

The International Maritime Organization (IMO) adopted the International Convention for the Control and Management of Ships' Ballast Water and Sediments in 2004 to prevent the transfer of aquatic organisms via ballast water. Thirty-four ballast water treatment systems were granted IMO active substance basic approval, among which twenty systems were granted final approval. This paper is an in-depth consideration of the mechanism principles of the treatment systems that received active substance basic or final approval from IMO, and on the concentration of Total Residual Oxidant (TRO). The TRO maximum allowable discharge concentration was reduced by neutralization equipment, resulting with a concentration lower than 0.2 ppm. However, between various treatment systems TRO maximum allowable dosage showed large differences, ranging from 1 to 15 ppm. The discrepancies of treatment allowable dosage concentration between different treatment systems are largely due to the properties of species and water conditions such as the temperature and turbidity, rather than the characteristics of treatment systems and the type or presence of filters etc.

• Resources Recycling
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• v.6 no.3
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• pp.28-35
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• 1997

Adsorption properities of hcavy metals (Cd, Cu, Fe, Mn, Pb, Zn) and organic compounds (Trichloroethylene and T Tetrachroethy len려 on sh$\xi$1I( oyster and ark shell) were investigated using wat$\xi$r treatment matenals, The shell powder (m띠or C crystal structurc is calcium hydroxide) showed the preference adsorption for heavy metals in order of Mn > Zn > Fe > Cd > eu > P Pb. The high removal capacities of heavy metals arc helicved to be largely due to precipitation by foonation of metal c carhonat,잃 and hydroxides at high pH caused by the $Ca(OH)_2$ component of sl1ell, immobilizatIon of heavy metals in a solid I matrix by calcium‘ and fixation by insoluble organic materials in the oystcr and ark shell. The use of sh려I in water treatment h has the potential to bc benefIcial as a source of inexpensive matcrials‘ moreover, not only treatment of waste but also e environmcntal business including environmental-purification ceramics could be better off by utili낌ng high-valued waste and d developed puri'fication ceramics and media.

• Resources Recycling
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• v.28 no.5
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• pp.68-73
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• 2019

Ilmenite is one of the principal ores for the production of titanium dioxide. To produce titanium dioxide with purity higher than 99.9% from ilmenite, Ti(IV) should be separated from the dissolved impurities such as Fe(III), Si(IV), and Mn(II) present in ilmenite. In this work, a hydrometallurgical process was investigated to recover pure titanium dioxide from ilmenite by HCl leaching followed by separation and hydrolysis of Ti(IV). An optimum leaching condition was obtained by investigating the effect of HCl concentration, pulp density, and leaching time on the leaching percentage of Ti(IV), Fe(III), Si(IV), and Mn(II). Ammonium hydroxide and sodium hydroxide solutions were employed as neutralizing agents to hydrolyze Ti(IV) from the stripping solution of Ti(IV). Titanium dioxide of the anatase phase was obtained by calcination of the hydrolyzed precipitates with $NH_4OH$ solution. A hydrometallurgical process can be developed to produce pure $TiO_2$ powders from ilmenite.

• Korean Journal of Environmental Agriculture
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• v.20 no.1
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• pp.20-27
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• 2001

Stream water chemistry in the abandoned Boeun Jeil coal mine area was studied for a period of 3 months, including rainy and dry season. The stream waters were a nearly neutral and slightly alkali condition, and $Mg-SO_4$ type with Mg>Ca>Na>K and $SO_4>HCO_3>Cl>NO_3$. Chemical composition of the stream water was quite irregular during the experimental period. Concentrations of Na, K, $HCO_3$, U, Sr, and Cr decreased by $10{\sim}30%$ during rainy season, caused by dilution effects with rain. The concentration of Ca, Mg, $NO_3$, Cd, and Co increased during the rainy season, caused by more easily dissolved from bedrocks or mine drainage with slightly acidic condition than dry season. The stream water was enriched in Mg, Ca, $HCO_3$, $SO_4$, Al, Fe, Zn, Ni, Co, Cr, Cd, Sr and U. Concentrations of Na, Mg, Ca, $SO_4$, $HCO_3$, Fe, Zn, Ni, Sr, and U decreased linearly with distance from the mine adit. These elements were strongly controlled by dilution of unpolluted water influx and/or adsorption on the clay minerals and iron oxyhydroxide precipitates. This mine area exhibited two main weathering processes ; 1) oxidation with acidification derived from Fe sulphides, and 2) pH buffering due to Ca and Mg carbonate dissolution. This weathering processes were followed by adsorption of metals on iron oxyhydroxides and precipitation.

• Korean Journal of Materials Research
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• v.4 no.8
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• pp.934-944
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• 1994

Effects of residual chloride on thermal decomposition behaviour of a-stannic acid and physical properties of $SnO_{2}$ powder were observed. The powder was fabricated by hydroxide method; $\alpha$-stannic acid was precipitated by mixing acqueous solutions of $SnCl_{4}$ and $NH_{4}$OH . The precipitate was washed with $NH_{4}NO_{3}$ solution while washing was controlled to be of three grades to modify its residual chloride content. The precipitate was dried at $1100^{\circ}C$ ~ 24h and calcined in air at $500^{\circ}C$ ~ $1100^{\circ}C$ for one hour. Thermal decomposition behaviour of $\alpha$-stannic acid was examined by a DT-TGA and a FTIR. Chemical composition and physical properties of $SnO_{2}$ powder were observed by an AES, a BET and a TEM, respectively. With a reduction in chloride content, the relative crystallite size of $SnO_{2}$ powder slightly increased by a low-temperature-calcining. However, at a high calcining temperature(T), the reverse relation occured. It was suggested that chloride ion replaces part of lattice oxygen site of a-stannic acid. Also, chloride ion on the site was suggested to retard de-hydration as well as crystalization at a low T while to promote crystal growth of $SnO_{2}$ by forming oxygen vacancy at a high T.

• KSBB Journal
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• v.21 no.3
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• pp.181-187
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• 2006

In this study, problems related with pH control in electrokinetic(EK) bioremediation of phenanthrene contaminated soil were observed, and the effects of pH control methods on the removal efficiency were investigated to search a further application strategy. In a preliminary experiment, it was found out by flask cultivation that a certain sulfate concentration was needed to degrade phenanthrene well using Sphingomonas sp. 3Y. However, when $MgSO_4$ was used as sulfate source in EK bioremediation, the bacterial activity reduced seriously due to the abrupt decrease of pHs in soil and bioreactor by the combination of magnesium and hydroxyl ions. When another strong buffering compound was used to control the pH problem, the good maintenance of the bacterial activity and pHs could be observed, but the removal efficiency decreased largely. When a low concentration of $MgSO_4$ was added, the removal efficiency decreased somewhat in spite of the good maintenance of neutral pHs. With the addition of NaOH as a neutralizing agent, the removal efficiency also decreased because of the increase of soil pH. Consequently the selection of electrolyte composition was a very important factor in EK bioremediation and some sulfate sources suitable for both bacterial activity and contaminant degradation should be investigated.

• Economic and Environmental Geology
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• v.43 no.2
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• pp.137-148
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• 2010

The Myoungbong mine located in Boseong-gun, Jellanamdo consists of Au-Ag bearing quartz veins which filled the fissures of Bulguksa granitic rocks of Cretaceous. The tailings obtained from the Myungbong mine were used to investigate the effects of various processes, such as oxidation of primary sulfides and formation(alteration) of secondary and/or tertiary minerals, on arsenic immobilization in tailings. This study was conducted via both mineralogical and chemical methods. Mineralogical methods used included gravity and magnetic separation, ultrasonic cleaning, and instrumental analyses(X-ray diffractometry, energy-dispersive spectroscopy, and electron probe microanalyzer) and aqua regia extraction technique for soils was applied to determine the elemental concentrations in the tailings. Iron (oxy)hydroxides formed as a result of oxidation of tailings were identified as three specific forms. The first form filled in rims and fissures of primary pyrites. The second one precipitated and coated the surfaces of gangue minerals and the final form was altered into yukonites. Initially, large amounts of acid-generating minerals, such as pyrite and arsenopyrite, might make the rapid progress of oxidation reactions, and lots of secondary minerals including iron (oxy)hydroxides and scorodite were formed. The rate of pH decrease in tailings diminished, in addition, as the exposure time of tailings to oxidation environments was prolonged and the acid-generating minerals were depleted. Rather, it is speculated that the pH of tailings increased, as the contribution of pH neutralization reactions by calcite contained in surrounding parental rocks became larger. The stability of secondary minerals, such as scorodite, were deteriorated due to the increase in pH, and finally arsenic might be leached out. Subsequently, calcimn and arsenic ions dissociated from calcites and scorodites were locally concentrated, and yukonite could be grown tertiarily. It is confirmed that this tertiary yukonite which is one of arsenate minerals and contains arsenic in high level plays a crucial role in immobilizing arsenic in tailings. In addition to immobilization of arsenic in yukonites, the results indicate that a huge amount of iron (oxy)hydroxides formed by weathering of pyrite which is one of typical primary minerals in tailings can strongly control arsenic behavior as well. Consequently, this study elucidates that through a sequence of various processes, arsenic which was leached out as a result of weathering of primary minerals, such as arsenopyrite, and/or redissolved from secondary minerals, such as scorodite, might be immobilized by various sorption reactions including adsorption, coprecipiation, and absorption.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.5
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• pp.448-454
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• 2000

This study was to examine the physicochemical characteristics of coagulation reaction between ignited oyster shell powder (IOSP) and red tide organisms (RTO), and its feasibility, in developing a technology for the removal of RTO bloom in coastal sea,IOSP was made from oyster shell and its physicochemical characteristics were examined for particle size distribution, surface characteristic by scanning electron microscope, zeta potential, and alkalinity and pH variations in sea water. Two kinds of RTO that were used in this study, Cylindrotheca closterium and Skeletonema costatum, were sampled in Masan bay and were cultured in laboratory. Coagulation experiments were conducted using various c(Incentrations of IOSP, RTO, and a jar tester. The supernatant and RTO culture solution were analyzed for pH, alkalinity, RTO cell number, IOSP showed positive zeta potentials of $11.1{\~}50.1\;mV\;at\;pH\;6.2{\~}12.7$, A positive zeta potential of IOSP slowly decreased with decreasing pNa 4,0 to 2,0. When pNa reached zero, the zeta potential approached zero, When a pMg value was decreased, the positive zeta potential of IOSP increased until pMg 3.0 and decreased below pMg 3.0. IOSP showed 4.8 mV of positive zeta potential while RTO showed -9.2 mV of negative zeta potential in sea water. A positive-negative EDL (electrical double-layer) interaction occurred between $Mg(OH)_2$ adsorption layer of IOSP and RTO in sea water so that EDL attractive force always worked between them. Hence, their coagulation reaction occurred at primary minimum on which an extreme attractive force acted because of charge neutralization by $Mg(OH)_2$ adsorption layer of IOSP. As a result, the coagulation reaction was rapidly processed and was irreversible according to DLVO (Deriaguin-Landau-Verwey-Overbeek) theory. Removal rates of RTO were exponentially increased with increasing both IOSP concentration and G-value. The removal rates were steeply increased until 50 mg/l of IOSP and reached $100{\%}\;at\;400\;mg/l$ of IOSP. Removal rates of RTO were $70.5,\;70.5,\;81.7,\;85.3{\%}$ for G-values of $1,\;6,\;29,\;139\;sec^(-1)$at IOSP 100 mg/l, respectively. This indicated that mixing (i.e., collision among particles) was very important for a coagulation reaction.