• Clean Technology
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• v.12 no.2
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• pp.101-106
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• 2006

HT-$LiCoO_2$ powders were synthesized from hydroxide precursors in this study. The cobalt hydroxide compounds with hydrotalcite-like(${\alpha}$-phase) and/or brucite-like(${\beta}$-phase) structures as a component of the precursor were prepared in various PH conditions using precipitation method. It was found that various phase and compositions of cobalt hydroxides could be tailor-prepared via a careful control of preparation parameters such as the concentration ratio of $[OH^-]/[CO^{2+}]$ and aging time. The hydroxides $Co(OH)_2$ and LiOH were mixed with aqueous methyl-alcohol. The precursor of a HT-$LiCoO_2$ was synthesized via subsequent processes including evaporation, drying and aging. The transformation of tailor-made ${\beta}$-phase $Co(OH)_2$ to CoOOH and formation of solid solution in the precursor were achieved during aging. These results cause HT-$LiCoO_2$ to be synthesized at low temperature($600^{\circ}C$ ) for a short time(10min).

• Polymer(Korea)
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• v.31 no.1
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• pp.53-57
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• 2007

In this study, the flame retardancy and tensile properties of epoxy acrylate resin containing flame retardants based on phosphorous, bromine or metal hydroxide are investigated. It was found that the enhancement in flame retardancy of epoxy acrylate with decabromodiphenyl oxide (DECA) addition was better than the addition of 2,2,2-trichloroethyl dichlorophosphate (TCEDP). It seems that the high loading of TCEDP may delay the formation of crosslinking network and consequently decreases the conversion of epoxy acrylate. It was found that magnesium hydroxide ($Mg(OH)_2$) does not improve the flame retardancy of epoxy acrylate after added up to 40 wt%. The synergic effects were clearly observed for epoxy acrylate containing DECA/TCEDP combined flame retardants.

• Clean Technology
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• v.20 no.1
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• pp.51-56
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• 2014

In this study, PSf-$Al(OH)_3$ beads were prepared by immobilizating aluminum hydroxide $Al(OH)_3$ with polysulfone (PSf). The removal experiments of the fluoride ions by PSf-$Al(OH)_3$ beads were conducted batchwise and the parameters such as pH, initial fluoride concentration, and coexisting ions were investigated. The maximum removal capacity obtained from Langmuir isotherm was 52.4 mg/g and the optimum pH region of fluoride ions was in the range of 4 to 10. The removal process of fluoride ions by PSf-$Al(OH)_3$ beads was found to be controlled by both external mass transfer at the earlier stage followed by internal diffusion at the later stage. The presence of coexisting anions such as $HCO_3{^-}$, $SO{_4}^{2-}$, $NO_3{^-}$, and $Cl^-$ had a negative effect on removal of fluoride ions by PSf-$Al(OH)_3$ beads.

• Resources Recycling
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• v.18 no.6
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• pp.38-45
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• 2009

Dissolution characteristics of magnesite ore in hydrochloric acid solution and removal of impurity were investigated. The dissolution yield increased with increasing temperature and with decreasing particle size. The optimum conditions for dissolution were found to be reaction period of 120 min, reaction temperature of $80^{\circ}C$ and mean particle size of 100. Under optimal dissolution condition the extraction of Mg was 98%. It was found that most of Si and Al exist in the residue, and they can be removed by filtering. Dissolved impurity ions were precipitated as metal hydroxides by pH adjustment. Polymers were used as coagulants for metal hydroxides and the suitable coagulant dosage was 1mg/100ml of non-ionic polymer.

• Resources Recycling
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• v.22 no.6
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• pp.48-54
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• 2013

The methods to separate and remove copper in the mixed solution ((399 ppm Cu, 208 ppm Fe, 15.3 g/L Ni, 2.1 g/L Co) with nickel, cobalt and iron were investigated. With hydroxide precipitation method, copper and iron ions were completely precipitated and removed from the solution at pH 7 while some nickel and cobalt also were precipitated. 99.75% copper could be precipitated and removed as copper sulfide from the solution with adding $Na_2S$ (1.25 w/v concentration) of 2 times equivalent of Cu at pH 1. Copper was selectively absorbed on TP 207 ion exchange resin at equilibrium pH 2.0 and could be eluted from copper-loaded resin using 5% $H_2SO_4$.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1B
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• pp.91-96
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• 2009

Layered double hydroxide is synthesized and used in the arsenate adsorption experiments. The shapes of two materials analyzed by TEM showed that unheated material is amorphous in shape, micro-sized while heat treated material showed more crystallized in shape and nano-sized. X-ray diffraction showed this result more obvious. $N_2$ adsorption-desorption results showed that the materials are mesoporous and the specific surface area of the heated material is more than two times larger than the unheated material. Adsorption of As(V) is expected to be more in the heated material than the unheated material. Kinetic test of arsenate adsorption showed very fast reaction. The reactivity of Fe with As(V) might be the main factor for this result. The reaction kinetic of the heated and the unheated materials were similar and even the adsorption isotherms showed similar results for both materials. Both materials are found to be useful in remediation of soil and groundwater polluted by waste mine tailings consist of high concentration of As(V).

• Resources Recycling
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• v.2 no.2
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• pp.16-21
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• 1993

This study was carried out to investigate the settling characteristics of Fe(II) and Fe(III) hydroxide precipitates formed by pH adjustment of aqueous solution to remove ferrous and ferric ion in waste water. The results obstained in this study are as fellows : The settling rate was effectively increased with increasing the pH values of aqueous solution regulated by CaO and with increasing the amount of flocculant, on the other hand, application of excess flocculants decreased the settling rate. It is desirable that the concentration of iron ion is kept under $10^{-2}$ mol/ㅣ because the settling rate was decreased with increasing the concentration of iron hydroxide precipitates.

• Proceedings of the Materials Research Society of Korea Conference
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• 2004.05a
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• pp.41-41
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• 2004

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2016.05a
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• pp.333-334
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• 2016

• Korean Journal of Soil Science and Fertilizer
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• v.27 no.3
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• pp.168-178
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• 1994

Acid sulfate soils occur extensively in Gimhae area where they have been formed from the brackish alluvial sediments along the sea coast and river estuary. The strong acid environment enhances silicate weathering and thus affects the soil clay minerals. The minerals were identified through chemical, X-ray diffraction and thermal methods. The ratio of $SiO_2$ and $Al_2O_3$ in the clay fractions ranged from 3.14 to 3.77, indicating that the distribution of the clay minerals were 1 : 1 and 2 : 1 minerals. Cation exchange capacity in the clay fractions was low due to high contents of 1 : 1 minerals and hydroxy interlayered vermiculite(HIV). The B and C horizon rich in jarosite have large amounts of yellow streaks which reflect high content of $Fe_2O_3$ and $K_2O$. Vermiculite and illite were quantified from thermogravimetry(TG), kaolin minerals from both TG and differential thermal analysis(DTA), and HIV from X-ray diffraction analysis. The dominant clay minerals were kaolin minerals, vermiculite, illite and HIV. HIV considered to be formed, especially, in acid soil environments. The minor minerals were quarts, feldspar, jarosite, pyrite, hematite and goethite. Kaolin minerals were the most abundant clay minerals throughout the acid sulfate soil. Kaolin minerals, however, increased towards the top of horizons throughout the soils and HIV decreased towards the top of horizons in the soil of Gimhae series and Haecheog series. Alteration of HIV to kaolin minerals during weathering of low pH condition in deep soil horizons may explain the high quantities of kaolin minerals and the relatively low quantities of HIV in the soil at top horizons.