• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.3
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• pp.173-183
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• 2000

This study measured the zeta potential of both latex colloidal particles with carboxylate surface groups and glass beads (collectors) with silanol surface group employing various solution with different chemical characteristics. The results have been compared with the surface chemistry theory. The zeta potential of the particle and collector increased with increasing pH up to 5.0 regardless of the solution chemistry. For a monovalent electrolyte solution(sodium chloride solution) the zeta potential steadily increased until the pH reached 9.5. In contrast, little change in zeta potential was made between 5.0 and 9.5 for a divalent electrolyte solution (sodium chloride solution) the zeta potential steadily increased until the pH reached 9.5. In contrast, little change in zeta potential was made between 5.0 and 9.5 for a divalent electrolyte solution (calcium chloride solution). In other words, the more the pH decreases, the larger the effect of neutral salts, such as NaCl and CaCl$_2$, have on the ζ-potential values. In this study, the PZPC(point of zero proton condition) of the particle and collector occurred below a pH of 3.1, H(sup)+ and OH(sup)- acted as a PDI (potential determining ion), and Na(sup)+ acted as an IDI(indifferent ion). The magnitude of the negative ζ-potential values of the particle and collector monotonically increased as the concentrations of Na(sup)+ or Ca(sup)2+([Na(sup)+] or [Ca(sup)2+]) decreased (the values of pNa or pCa increased). In the case of latex particles, the ζ-potential should aproach zero (isoelectric point; IEP) asymptotically as the pNa approaches zero, while in the case of calcium chloride electrolyte, ζ-potential reversal may be expected to occur around 3.16$\times$10(sup)-2MCaCl$_2$(pCa=1.5). pH, valance and ionic strength can be used in various ways to improve the water treatment efficiency by modifying the charge characteristics of the particle and collector. Predictive capability is far less certain when EDL(electrical double layer) repulsive forces exist between the particle and collector.

• KSBB Journal
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• v.7 no.2
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• pp.118-125
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• 1992

Most of cosmetics are emulsion-type products which contain the sources of nutrition, i.e., vegetable oil, mineral oil and carbohyrate etc.. These additives are usually very susceptible to the contamination by microorganisms. The purpose of this study is to obtain the data necessary not only to prevent dermalopathia occurred by microbials but also to maintain the quality. In this experiment we observed the growth of P.aeruginosa in the cosmetics with or without antiseptics so as to prevent contamination. During the contamination period, the phase became unstable and creaming phenomina was happened together with some discoloration and bad smell. The pH of cosmetic was decreased from 7.6 to 6.0 and the concentration was increased from 1.443 to 1.453 in terms of refractive index during 40 days incubation. By adding antiseptics to the cosmetics, the number of P. aeruginosa from the challenge test method were decreased from $10^8$ cell/ml to $5{\times}10^3$ cell/ml. For the antibacterial effect against P. aeruginosa, p-hydroxy benzoic acid propyl ester in phosphoric acid buffer solution showed the best result.

• Journal of Biosystems Engineering
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• v.22 no.4
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• pp.469-478
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• 1997

This study was conducted to develop an automatic nutrient-solution mixing system for small-scale sewers. The nutrient-solution mixing system consisted of a low-cost and precise metering device and data acquisition ＆ control system with a personal computer. and, the metering device was composed of three parts those were supply pumps, metering cylinders and venturi tube. The system controlled electric conductivity(EC) and pH of nutrient-solution based on the time-based feedback control method with the information about temperature, EC, and pH of the nutrient-solution. The performance of the nutrient-solution mixing system was evaluated through the control of EC and pH while compared with those of commercial system. Also an experimental cultivation of tomato was conducted to verify and to improve the developed system. Results of this study were as follows. 1. The correlation coefficient of meteing device between the flow rate and operating time was 0.9999, and the linear reuession equation computed was y=21.759x, where y is the discharge($g$) and x is the operating time(s). 2. Calculated errors for the developed metering device and two commercial pump were $\pm$0.3% $\pm$2.45% and $\pm$1.38 % FS error respectively. 3. An automatic nutrient-solution mixing system based on a low-cost and precise metering device was developed. 4. The full scale errors of the developed system in controlling EC and pH at 23$\pm$1$^{\circ}C$ were $\pm$0.05mS/cm and $\pm$0.2, respectively 5. When using the commercial system, the controlled values of EC and pH of the 500 $\ell$ of water were 1.29 mS/cm and 6.1 pH for the setting points of 1.4 mS/cm and 6.0 pH respectively at 23$pm1^{\circ}C$. 6. The developed nutrient-solution control system showed $\pm$0.05 ms/cm of deviation from the setting EC value over the experimental cultivation period. 7. The deviation from the average values of Ca and Mg mass content in the several nutrient-solution were 0.5% and 1.8% respectively.

• Journal of the Korean Applied Science and Technology
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• v.36 no.1
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• pp.355-361
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• 2019

The red pigment extracted from Serratia marcescens 2354 (ATCC 25419) was prodigiosin (PG), which was dissolved in methanol and measured for ultraviolet and visible light absorption spectra. It was the typical absorption spectrum of PG in an acid solution with ${\lambda}_{max}=537nm$. When the concentration of PG was increased from $1.0{\times}10-5M$ to $9.0{\times}10-5M$ in the methanol solution, the absorption intensity at 537 nm was increased, the absorption intensity at 467 nm was decreased, and the isosbestic point at 500 nm was observed. This phenomenon can be regarded as a result of reversible acid-base equilibrium reaction considering 537 nm and 467 nm of PG absorption band in acid and base solution respectively and isosbestic point of 500 nm. On the other hand, when the concentration of PG was reduced from $6.0{\times}10-4$ to $1.0{\times}10-4M$ in acetic acid buffer solution at pH 4.75, a new absorption band with ${\lambda}$ max at 500 nm appeared. This absorption band appears only in the aqueous solution of pH 4.75 and does not appear in the pure methanol solution of the same pH. This is due to the conversion of the PG molecule from the ${\alpha}$-isomer to the ${\beta}$-isomer by $H_2O$. In other words, it was confirmed that the color change of the PG can be caused by the concentration of the solution and the characteristics of the solvent.

• Analytical Science and Technology
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• v.8 no.3
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• pp.293-298
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• 1995

The stability of brass coated on steel cords with pH and applied constant potential changes in aqueous solution has been investigated by AC impedance measurements. In solutions of the constant pH, as a applied constant potential is shifted to positive potential, the coating pore resistance is reduced. The fact indicates that as a applied constant potential is shifted to positive potential, the brass coated is dissolved more in solution. The stability of brass coated on steel cords decrease in the order pH=7.1 > pH=4.0 > pH=10.0. The above results are demonstrated by the data of scanning of electronic microscopy(SEM)/energy dispersive spectrometer(EDS).

• Journal of the Korean Ceramic Society
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• v.26 no.2
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• pp.157-166
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• 1989

The effect of pH variation in starting solution on the characteristics of hydroxyapatite precipitates and powder prepared by the wet method was investigated. Hydroxyapatite precipitates was agglomerated, the average agglomerated particle size was decreased in the range from 2 to 6${\mu}{\textrm}{m}$ with increasing pH values in starting solution. The aspect ratio of rod-shaped hydroxyapatite particle was rapidly increased at pH 11 and 11.5. The maximum specific surface area, 91.1$m^2$/g, was at pH 10.5. Dried powder prepared at high pH values contained more minutes CO2 than that prepared at low pH values. The poor crystallinity was maintained up to $600^{\circ}C$ regardless of the pH values in starting solutions. However, the second phase or high crsytalline hydroxypatite phase appeared above 80$0^{\circ}C$. In pH 9.5 and pH 10, $\beta$-whitlockite transformed to $\alpha$-whitlockite at 120$0^{\circ}C$, while in pH 10.5-11.5, hydroxyapatite phase was maintained up to 120$0^{\circ}C$.

• The Journal of Korean Physical Therapy
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• v.10 no.1
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• pp.1-6
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• 1998

The purpose of this study was to determine the of effective concentration of procaine iontophoresis for durarion of cutaneous local anesthesia. Forty-five healthy students with an age range of 19 to 34 years$(21\pm2.7)$, were participated in this study. The subjects were randomly assigned into 5 groups. Bach 9 subjects received iontophoresis on the flexor surface of dominant forearm with soft cotton pad $(3.5\times3.5cm)$ soaked in 2ml of $2\%$ (pH 5.28), $4\%$ (pH 5.12), $8\%$ (pH 4,98), $16\%$ (pH 4.72), $32\%$ (pH 4.52) procaine hydrochloride solution at 4mA for 10 minutes (total current 40mA min) using anodal direct current. The study was performed in a randomized, double-blind design, After procaine iontophoresis, the duration of anesthesia were evaluated at five minute intervals on five random locations in the iontophoretically area using a 21-gauge sterile hypodermic needle pressed with 1mm invagination unitl sharp pin-pricking pain sensation returned. The data were analyzed with one-way ANOVA to determine significant differences between groups. Duncan post hoc was performed at level .01. The relationship between anesthetic duration and procaine concentration was assessed with Pearson Product-Moment Correlation Coefficients. ANOVA tests showed significant differences in the anesthetic duration between the concentration of procaine solution (p<.001). Procaine iontophoresis with $4\%$ concentration produced cutaneous Socal anesthesia of significantly longer duration(15.56 min) than iontophoresis with $2\%,\;8\%,\;16\%$, and $32\%$ of procaine GCl(p<.01). Whereas the anesthetic duration had no correlation with concentration of procaine solution (r=-0.41, NS). These results support the $4\%$ procaine solution was an effective concentration of iontophoresis for induced cutaneous local anesthesia.

• Resources Recycling
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• v.12 no.1
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• pp.33-40
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• 2003

Mn was extracted by using a nitric acid from the reduced ferromanganese dust and the basic experiments were taken to refine the manganese nitrate solution by means of precipitation of Ca, Mg oxalate. The dust was generated in AOD process producing a medium-low carbon ferromanganese and collected in the bag filter. Manganese oxide content in the dust was about 90% and its phase was confirmed as $Mn_3$$O_4$. $Mn_3$$O_4$ in the dust was reduced to MnO by roasting with activated charcoal. The main impurities in the extracted solution prepared by leaching the reduced dust with nitric acid were Na, K, Fe, Si, Ca, Mg etc. Among them, Fe was removed by controlling pH of the solution more than 4 and precipitating $Fe(OH)_3$, simultaneously silicious material solved in the solution was removed by co-precipitation with the ferric hydroxide. Addition of 150 g reduced dust into 4N HNO3 solution 1$\ell$ was appropriate to control the pH of the solution to pH 4. To differ greatly the solubilities of manganese oxalate and calcium or magnesium oxalate in a solution containing a high concentration of Mn, pH of 4 or less and addition of ($NH_4$)$_2$$C_2$$O_4$ in equivalent with Ca and Mg are recommended. At this time, the higher temperature was the shorter the precipitation reaction time was needed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.47-48
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• 2015

Recycled aggregate used in a site is strong alkali due to calcium hydroxide attached on its surface. Accordingly, many environmental problems arise. Therefore, as basic research to reduce pH of recycled aggregate, this study tries to reduce the strong alkalinity of recycled aggregate by using mixture solution based on sodium phosphate and ammonium chloride. As a result, original aggregate has the strong alkalinity of pH 11.23, whereas pH of recycled aggregate immersed in mixture solution decreased as more mixture rate increased, and mostly pH 9.8 or less was found.

• Journal of Sericultural and Entomological Science
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• v.39 no.1
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• pp.67-72
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• 1997

As a condition for obtaining the silk I type crystal that has stability and high reproducibility, after dissolving silk fibroin crystalline part (Fcp), the changes of recrystallized crystal structure according to dialytic pH were examined by x-ray diffraction and differential thermal analysis. The Fcp was obtained from the aqueous solution of silk fibroin enzymatic proteolyzed by chymotrypsin. The crystal structure of Fcp showed silk II type. When the Fcp was dissolved by 10M LiBr aqueous solution, the Fcp1 showed the silk II type at pH 9. However, besides the silk II type, the silk I type structure begins to appear at pH 8 and only the silk I type structure was found below pH 6. On the other hand, the Fcp2 that calcium chloride was used in the dissolution found only the silk I type crystal structure below pH8.