• Environmental Engineering Research
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• v.16 no.3
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• pp.149-157
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• 2011

Nanofiltration (NF) experiments were conducted to investigate fouling of Al-hydroxide precipitate and the influence of organic compound, inorganic compound, and their combination, i.e., multiple foulants. $CaCl_2$ and $MgSO_4$ were employed as surrogates of inorganic compounds while humic acid was used as surrogate of organic compound. The flux attained from NF experiments was fitted with the mathematical fouling model to evaluate the potential fouling mechanisms. Al-hydroxide fouling with a cake formation mechanism had little effect on the NF membrane fouling regardless of the Al concentration. The NF fouling by Al-hydroxide precipitate was deteriorated in presence of inorganic matter. The effect of Mg was more critical in increasing the fouling than Ca. This is because the Mg ions enhanced the resistances of the cake layer accumulated by the Al-hydroxide precipitate on the membrane surfaces. However, the fouling with Mg was dramatically mitigated by adding humic acid. It is interesting to observe that the removal of the conductivity was enhanced to 61.2% in presence of Mg and humic acid from 30.9% with Al-hydroxide alone. The influence of dissolved matter (i.e., colloids) was more negative than particulate matter on the NF fouling for Al-hydroxide precipitate in presence of inorganic and organic matter.

• Korean Journal of Materials Research
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• v.8 no.2
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• pp.126-130
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• 1998

Aluminum sulfate, $AI_{2}(SO_4)_3\cdot18H_2O$ was prepared by adding of kaolin-dissolved sulphuric acid into ethanol and its thermal decomposition behavior was discussed. As-synthesized high purity precipitate particles were platelike shapes of $2\mu\textrm{m}$ size. With increasing drop rate of leach liquor into ethanol, the crystallite sizes of the precipitate decreased. The apparent activation energies for dehydration and sulfate decomposition of the precipitate were $11.9Kcal mol^{-1}$ and $48.2kcal mol^{-1}$ respectively.

• Journal of the Korea Organic Resources Recycling Association
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• v.14 no.4
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• pp.151-160
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• 2006

Anaerobic treatment of landfill leachate was studied to investigate the behaviors of pollutant and the characteristics of microorganism for 10 months. The upflow anaerobic sludge blanket (UASB) reactor achieved about 90% chemical oxygen demand (COD) removal at organic loading rates(OLR) up to $20kgCOD/m^3.d$. At higher OLR ($8-20kgCOD/m^3.d$), the propionate concentration increased, indicating that converting propionate to acetate was the rate-limiting step. Nevertheless, increase in the precipitate inside and on the surface of granules as well as on the wall of the reactor resulted in operational problems. The main inorganic precipitate in the granule was calcium compound. Although specific methanogenic activity (SMA) was not affected seriously in this study, metals had to be removed prior to anaerobic treatment so as to be free from the excessive inorganic accumulation that resulted in operational problems.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.11
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• pp.55-61
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• 1990

Thermal stability of $TiSi_{2}$ with C54 structure and morphology degradation of poly silicon layer resulted from the formation of TiAs precipitate through the reaction between $TiSi_{2}$ and arsenic ion implanted in poly silicon have been studied.

• Journal of the Korean Ceramic Society
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• v.35 no.4
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• pp.325-332
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• 1998

Crystalline TiO2 ultrafine powders were prepared simply by heating and stirring aqueous TiOCl2 solution with {{{{ {Ti }^{4+ } }} concentration of 0.5 M from room temperature to 10$0^{\circ}C$ under 1 atmoshpere. The crystallinity and the particle shape of TiO2 ultrafine powders obtained by simple precipitation method were analyzed us-ing XRD(X-ray diffractometer). SEM(scanning electron microscopy) and TEM(transmission electron mi-croscopy) TiO2 crystalline precipitate with rutile phases is fully formed at the temperatures of up to $65^{\circ}C$ and then TiO2 crystalline precipitate with anatase phase starts to be formed above temperatures $65^{\circ}C$ showing its full formation at 10$0^{\circ}C$ These behaviors of TiO2 crystalline precipitate directly from an aqueous TiOCl2 solution would be caused due to the existence of {{{{ OMICRON ^2+ }} ions from distilled water which oxydize TiOCl2 to TiO2 not hydrolyzing it to Ti(OH)4 Here thermodynamically stable TiO2 rutile phase generally formed at higher temperature is practically precipitated at lower temperatures in this study This may be due to the precipitation by very slow reaction enough to make TiO2 particles allocated into stable rutile structure.

• 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.

• Archives of Pharmacal Research
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• v.13 no.1
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• pp.28-32
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• 1990

Precipitation and purification of amylase secreted by Streptomyces aureofaciens 77 in liquid inorganic salts-starch medium under the optimum conditions were carried out. Ammonium sulphate fractionation was used to precipitate amylase in cell free culture filtrate. (NH/sub 4/)/sub 2/ SO/sub 4/ at a concentration of 50-70% saturation gave the highest enzyme yield. The obtained precipitates were redissolved in phosphate buffer (pH 7.0) and subjected to dialysis. The dialyzed enzyme preparation was applied to DEAE-cellulose column chromatography which resulted in an increase of purification up to 59.48 fold. A further step of purification was done by applying the obtained purified sample to Sephadex-G200 column chromatography which resulted in ann increase of purification up to 73. 92 fold. The results clearly indicated that the isolated amylase from S. aureofaciens 77 was only on type.

• Journal of the Korean Chemical Society
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• v.40 no.8
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• pp.535-541
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• 1996

In preparation of fine alumina powders with use of vesicle, the effect of variation of pH in extravesicular dispersion system to mechanism of precipitation and shape and size distribution of precipitate was investigated. The results of observation by TEM and turbidimeter were obtained as follows. Reaction between aluminum ion and hydroxyl ion to produce precipitate within vesicle was initiated at pH 11.4 and spherical fine precipitates, about 50 nm size, were formed at pH 12.0. About pH 12.3, size of precipitates in vesicle grew twice as great as those formed below pH 12.0 because of the agglomeration and coalescence of vesicleswith time.

• Journal of Environmental Science International
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• v.8 no.6
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• pp.711-716
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• 1999

This research explored the feasibility of preparing and utilizing a prefonned polymeric solution of Al(III) for coagulation in water treatment. Slow base(NaOH) injection into supersaturated aluminum chloride and aluminum sulfate solutions did produce high yields of Al polymers useful to water treatment applications. The method of characterization analysis was based on timed spectrophotometer with ferron as a color developing reagent. The hydrolytic Al species were divided into $monomeric(Al_a),\;polymeric(Al_b),\;and\;precipitate(Al_c)$ from the difference in reaction kinetics. The analysis of PACl's characteristics showed that the quantity of polymeric Al produced at value of$ r(OH_{added}/AI)=2.2$ was $83\%$ of the total aluminum in solution, as showing maximum contents and precipitated Al was dramatically increased when r was increased above 2.35. In addition, the characteristics of polyaluminum sulfate (PAS) showed that polymeric Al contained at r = 0.75 was $18\%$ of the total aluminum in solution. The synthesized PACI and PAS were stable during storing period, as indicating negligible aging effect. The effect of sulfate ion on PACI was dependent on the concentration of sulfate ion. That is, polymeric species decrease and precipitate species increase as sulfate ion concentration increased. It can be concluded that the sulfate cause the formation of $Al(OH)_{3(S)}$ at low pH. However, The effect of calcium ion was negligible for distribution of Al species.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.55-59
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• 1999

The Rapid Expansion of Supercritical fluid Solutions (RESS) process was applied to particles coating. Microcapsules prepared by spray drying were used as the core particles, and two kinds of paraffin were used as the coating materials. Supercritical $CO_{2}$ solutions of paraffin were expanded through the short nozzle into the bed that was fluidized by air. Extraction temperature and pressure were varied at $50~120^{\circ}C$, $150~200\;kg/\textrm{cm}^2$, respectively. The thickness of theoritical coating layer ws measured, and precipitate coating layer on surface was analyzed by using SEM, FT-IR. The release behaviors of $Mg^{2+}$ ions were inspected by atomic absorbance spectrophtometer.