• Journal of the Korean Ceramic Society
• /
• v.34 no.10
• /
• pp.1009-1014
• /
• 1997

Ammonia gas was blown into the solution of zirconium ion to induce precipitation of supersaturated zirconium ion at gas-liquid interface with increase in pH. The influence of pH on the phase and particle size of precipitate and calcined powders has been investigated. At pH 4.5 of zirconium solution, maximum yield of 98.7% was obtained. Above pH 4.5, there was no more increase of yield. Above pH 5.5, large aggregates consisting of primary particles were observed in precipitate and calcined powders. At pH 4.5, almost aggregate-free fine spherical zirconia powders were obtained.

• Korean Journal of Metals and Materials
• /
• v.49 no.2
• /
• pp.137-144
• /
• 2011

Strengthening mechanisms in an ordered intermetallic compound containing coherent precipitates of lower antiphase boundary energy than the matrix were investigated on the basis of the interaction between the deformation induced dislocations and the disordered precipitates in an $Ll_2$ ordered $Ni_3Al$-based alloy. Extra work was needed to pull out the dislocations from the precipitate, which was dependent on the difference in the antiphase boundary energy between the matrix and the precipitate, as well as the size and volume fraction of the precipitate. The strength of the $Ll_2$ ordered ${\gamma}^{\prime}$ phase containing fine precipitates of the disordered ${\gamma}$ phase was examined using the proposed model. The model can explain almost quantitatively the age hardening behavior of the $Ll_2$ ordered ${\gamma}^{\prime}$ phase.

• Applied Chemistry for Engineering
• /
• v.10 no.1
• /
• pp.41-45
• /
• 1999

Simulated liquid waste containing 50 ppm cobalt ion was treated by precipitate flotation using the surfactant of sodium lauryl sulfate. The effects of initial cobalt ion concentration, pH, surfactant concentration, removal time, gas flow rate and foreign ions were estimated on removal efficiency. 35% $H_2O_2$ was added for pre-treatment stage before precipitate flotation. As the result of pre-treatment, optimum removal pH and the pH of treated water being discharged were lowed and optimum removal pH range was broadened. For the result of this experiment, 99.8% removal efficiency was obtained at the condition of 50ppm of initial cobalt ion concentration, pH 9.5, 70 mL/min of gas flow rate, and 30 min of removal time. Attraction between precipitate and surfactant was supposed to be influenced by solubility and chemical affinity among species in sloution as well as zeta potential. The influence of foreign ions such as, $NO_3{^-}$, ${SO_4}^{-2}$, $Na^+$, $Ca^{+2}$ on the removal efficiency was also observed. Removal efficiency by precipitate flotation containing 0.1 M of ${SO_4}^{-2}$ ion decreased to 90% due to the decrease of zeta potential and interruption of precipitation.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.56 no.2
• /
• pp.204-211
• /
• 2023

This study investigated the physicochemical properties and palatability-enhancing effects of the alcohol precipitate, in the enzymatic extracts of Sargassum confusum C. Agardh (SC), obsained using the crude enzyme of Shewanella oneidensis PKA 1008. We analyzed the oligosaccharides recovered from the alcohol precipitate using a thin-layer chromatography for SC-degrading extracts, pH, color, reducing sugar, and viscosity. Thin-layer chromatography showed that after treating with the crude enzyme for 60 h, the polysaccharides were degraded into tetramers, dimers, and trimers and pH increased in the alcohol precipitate (EtOH Sedi). In terms of color, the redness and yellowness of alcohol precipitate/supernatant (EtOH Sedi+Super) and the brightness of EtOH Sedi were the highest among enzyme treated for 0 h and 60 h, EtOH Sedi, and EtOH Sedi+Super. In the reducing sugar analysis, EtOH Sedi showed the lowest value of 13.63 ㎍/mL, and the lowest viscosity of 1.13. In terms of the sensory evaluation, EtOH Sedi+Super showed the highest value with respect to the overall preference. These results suggest that the crude enzyme of S. oneidensis PKA 1008 is effective at degrading polysaccharides, and its recovery increases the palatability of the alcohol precipitate.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.28A no.5
• /
• pp.375-379
• /
• 1991

Formation of TiAs precipitate through the reaction between TiSi2 with C54 structure and heavily doped arsenic ion in poly-silicon, and influence of TiSAs and silicon distribution resulted from the reaction TiSi2+As ->2Si on the morphology degradation have been studied.

• Journal of Korean Society of Water and Wastewater
• /
• v.26 no.2
• /
• pp.229-236
• /
• 2012

The analysis of Al (III) hydrolysis species with PACls prepared by different basicity showed that mononmeric Al species were reduced while precipitate Al species were increased with an increase in basicity for PACls. In the case of the PACl with 13.6% basicity, monomeric Al species were 81%, polymeric Al (III) species 19%, precipitate Al (III) species was 0%, as showing the dominant monomeric Al species. The PACl with 13.6% basicity showed above 80% of turbidity removal efficiency without any restabilization. In addition, the PACl with 13.6% basicity showed higher organic removal expressed by $UV_{254}$ which was caused by lower coagulation pH. The PACl containing the higher amount of monomeric Al species was the most beneficial for T-P and $PO_{4}-P$ removal.

• Applied Chemistry for Engineering
• /
• v.9 no.2
• /
• pp.243-248
• /
• 1998

This study investigated the separation and the property of palladium precipitate formed by ascorbic acid in a simulated radioactive liquid waste, which was composed of 10 elements((Pd, Ru, Rh, Nd, Cs, Sr, Fe, Ni, Zr, Mo). Pd was separated selectively by using reduction characteristics of metal ions contained in the simulated waste with ascorbic acid. When the nitric acid concentration was 0.5 M, the Pd over 99.5% was precipitated by adding 0.04 M ascorbic acid. Nitric acid concentration is important at the reduction reaction of Pd ion. The precipitation yield of Pd was decreased as the concentration of nitric acid was increased. The Pd precipitate was re-dissolved in reaching at an equilibrium when the concentration of nitric acid was high and ascorbic acid was added with a small amount. The Pd precipitate formed by ascorbic acid was Pd metal and was aggregated by particles less than $1.0{\mu}m$.

• Korean Journal of Materials Research
• /
• v.10 no.6
• /
• pp.445-449
• /
• 2000

Nickel ferrite $(Ni_{0.75}Fe_{2.25}O_4$ was synthesized by co-precipitation method in order to investigate its behavior under conditions of the reactor coolant system in pressurized light water nuclear power plants. Ammonia or potassium carbonate was used as a solution pH control agent, and aqueous ammonia or potassium carbonate solution or secondary distilled water was used as a co-precipitate washing agent. The effects of the pH control agent and the co-precipitate washing agent on the production yield on the basis of the Ni/Fe molar ratio and the particle characteristics of final products were investigated by XRD, SEM, EDX and XPS. The production yield was almost congruent with that of the initial aqueous mixture in case of using potassium carbonate as a pH control agent, while in case of using ammonia, it was quite changed. The difference seemed to be due to the effects of $Ni^{2+}{\leftarrow}NH_3$complexation in the aqueous solution and of the pH of co-precipitate washing agent.

• Korean Journal of Food Science and Technology
• /
• v.7 no.4
• /
• pp.250-253
• /
• 1975

The acid milk containing grape juice was prepared from natural grape juice, acid milk and sugar as raw materials, and the stability of the drink was studied. The following results were obtained. 1. The milk mixed with natural grape juice formed coagulated precipitate by coupling of the colloidal materials in the juice with the milk protein and the formation of precipitate was accelerated by pasteurization. 2. The pectin in natural grape juice was affected on the stability of the product, and the stability increased with decrease in the content of pectin. When the content of pectin in natural grape juice was lower than 2.5mg%, the precipitate was not formed in the drink containing 10 to 20% of the juice. 3. The acid milk drink containing the natural grape juice treated with pectinase, not formed precipitate by pasteurization at $85^{\circ}C$, for 20 minutes and can be preserved for long term.

• Journal of the Mineralogical Society of Korea
• /
• v.22 no.2
• /
• pp.139-151
• /
• 2009

Mineralogical characteristics of secondary precipitate formed at some mineral water springs in Gyeongbuk Province, Korea were studied in relation to water chemistry. The chemical water types of mineral water springs are mostly classified as $Ca-HCO_3$ type, but $Na(Ca)-HCO_3$ and $Ca-SO_4$ types are also recognized. Ca, Fe, and $HCO_3\;^-$ are the most abundant components in the water. The pH values of most springs lie in 5.76${\sim}$6.81, except Hwangsu spring having pH 2.8. Saturation indices show that all springs are supersaturated with respect to iron minerals and oxyhydroxides such as hematite and goethite. The result of particle size analysis shows that the precipitate is composed of the composite with various sizes, indicating the presence of iron minerals susceptible to a phase transition at varying water chemistry or the mixtures consisting of various mineral species. The particle size of the reddish precipitate is larger than that of the yellow brown precipitate. Based on XRD and SEM analyses, the precipitate is mostly composed of ferrihydrite (two-line type), goethite, schwertmannite, and calcite, with lesser silicates and manganese minerals. The most abundant mineral fanned at springs is ferrihydrite whose crystals are $0.1{\sim}2\;{\mu}m$ with an average of $0.5\;{\mu}m$ in size, characterized by a spherical form. It should be interestingly noted that schwertmannite forms at Hwangsu spring whose pH is very low. At Shinchon spring, Gallionella ferruginea, one of the iron bacteria, is commonly found as an indicator of the important microbial activity ascribed to the formation of iron minerals because very fine iron oxides with a spherical form are closely distributed on surfaces of the bacteria. A genetic relationship between the water chemistry and the formation of the secondary precipitate from mineral water springs was discussed.