• Proceedings of the Korean Environmental Sciences Society Conference
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• 2006.05a
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• pp.365-369
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• 2006

[ $O_3$ ]/catalyst를 이용한 고급산화공정에서 pH변화에 따른 1,4-dioxane의 화학적 분해 특성을 알아보기 위해 이 실험을 수행하였다. 초기 pH를 6, 8, 10으로 조절하여 변화를 보면 오존의 pH 완충효과에 의해 시간이 지남에 따라 알칼리와 산의 경우 중성 쪽으로 중화되는 것을 확인하였다. 그리고 시간에 따른 1,4-dioxane의 제거율은 pH 10 > pH 8 > pH 6 의 순서로 나타는 것을 보였다. 이는 오존이 산성에서는 안정하지만 알칼리성에서는 불안정함으로 인해 자기분해를 일으켜 OH라디칼의 생성을 촉진시켜 제거율이 높게 나타났다. 초기 pH를 조절한 실험, 초기 pH를 일정하게 유지한 실험에서의 50분 후의 최종 제거율은 비슷하였지만, 초기 pH를 일정하게 유지한 실험에서 제거율이 꾸준히 감소하는 것을 알 수 있었다.

• Korean Journal of Food Science and Technology
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• v.24 no.3
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• pp.232-235
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• 1992

Effect of temperature and initial pH were studied on the pH change of MSG solution during heating. The heating temperature and initial pH of 2% MSG solution were in the range of $100{\sim}120^{\circ}C$ and $pH\;2{\sim}9$, respectively. The results showed that the pH of MSG solution was more rapidly decreased as the temperature increased and the initial pH decreased due to pyroglutamic acid formation from MSG thermal degradation. A linear relationship was obtained between pH decreased and logarithmic value of heating time and the decreasing rate constant of pH were calculated from the slope. The pH decreased$({\Delta}pH)$ after 3 hrs of heating was 1.2 at the initial pH 4 and $120^{\circ}C$ and 0.33 at pH 5 and $120^{\circ}C$ while little pH change measured at the range of $pH\;6{\sim}9$. Activation energy calculated for pH decrease during heating was 11.77 and 22.26 kcal/mole at pH 4 and pH 5, respectively.

• Journal of the Korean GEO-environmental Society
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• v.11 no.1
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• pp.19-26
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• 2010

The batch experiments and response surface methodology (RSM) have been applied to the investigation of the cadmium (Cd) adsorption by coal fly ash (CFA). CFA having maximum Cd removal mass of 8.51 mg/g were calculated from Langmuir model. Cd removal reaction with different initial pH ranged from 4 to 9. When the initial pH was higher, Cd was removed more by adsorption and precipitation. These results suggest that the lower pH cause an increase of $H^+$ ion concentration which competed with Cd ions for exchange sites in CFA. Also, The Cd adsorption was mathematically described as a function of parameters initial Cd concentration ($X_1$), initial pH ($X_2$), and initial CFA mass ($X_3$) being modeled by use of the Box-Behnken methods. Empirical models were developed to describe relationship between the experimental variables and response. Statistical analysis indicates that tree factors ($X_1$, $X_2$, and $X_3$) on the linear term (main effects), and tree factors ($X_1X_2$, $X_1X_3$, and $X_2X_3$) on the non-linear term (Interaction effect; cross-product) had significant effects, respectively. In this case, the value of the adjusted determination coefficient (adjusted $R^2=0.9280$) was closed to 1, showing a high significance of the model. Statistical results showed the order of Cd removal at experimental factors to be initial initial pH > initial Cd concentration > initial CFA mass.

• Journal of Animal Science and Technology
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• v.47 no.4
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• pp.615-624
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• 2005

The cPCR technique was used to monitor rumen fermentation and attachment of Fibrobacter succinogenes to cellulose at different pH in the in vitro culture medium. The target fragments of 16S rDNA(445 bp) were amplified from genomic DNA of F. succinogenes with specific primers and internal controls(205 bp) were constructed. Cell counts were estimated from the amounts of genomic DNA, which was calculated from cPCR results. F. succinogenes in pH 6.8 and 6.2 showed apparently higher attachment than in pH 5.8 during all incubation time. There were some difference between pH 6.8 and 6.2 in the degree of attachment, but the different was not significant (P>0.05). Cellulose degradation increased in process of incubation time and the increasing rate was higher when initial pH was higher. The pH in culture medium decreased regardless of initial pH in course of incubation time. After 24 h of incubation, medium pH was dropped by 0.24, 0.58 and 0.16 units from original medium pH 6.8, 6.2 and 5.8, respectively. More gas was produced at higher initial pH in the same manner as in cellulose degradation. In summery, Initial pH of rumen culture in vitro significantly influenced cellulose digestion, gas production, pH change and bacterial attachment. Especially, low pH(5.8) resulted in much lower bacterial attachment and fiber digestion compared to higher medium pH.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2004.11a
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• pp.67-70
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• 2004

역세척 후 응집제를 여과사에 주입한 수 여과를 실시한 결과 초기에 높게 나타났던 탁도의 거의 제거되는 것을 알 수 있었으며 pH의 변화에 따른 초기의 탁도 변화는 pH5와 pH7에서 보다 낮은 탁도의 수질을 얻을 수 있었다. pH5부근에서 알루미늄의 존재형태가 $Al(OH)^{2+},\;Al(OH)_2^+$로 많이 존재하며, pH7에서는 $Al(OH)_3$으로 존재하여 모래 표현의 (-) 전하를 감소시킬 수 있는 결과로 판단되었다.

• Microbiology and Biotechnology Letters
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• v.20 no.4
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• pp.371-376
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• 1992

The growth and cultural characteristics of Bacillus sp. SH-8 and SH-8M were investigated at various pH conditions. Bacillus sp. SH-8 showed normal growth pattern above pH 9.0. However, with the pH adjusted below 7.7, 0.$D_{550}$ decreased rapidly with concomitant reduction in viable cell numbers. In contrast, Bacillus sp. SH-8M demonstrated growth capability at pH 7.7, but with slightly reduced growth rate at pH 6.9. Similar results were obtained when those two strains were cultivated on the solid medium. Both of them showed short rod shapes at pH 10.2. However, at pH 7.7 only Bacillus sp. SH-8 was observed to have elongated rod shape. Extracellular pH of both the strains, when cultured at initial pH of 10.2, reached to 9.0 after the incubation of 28 hours. At the initial pH of 9.0 and 9.6, the extracellular pH was reduced at the beginning of cultivation, but elevated after 12 hours. When cultured at initial pH of 6.9 and 7.7, extracelluar pH of Bacillus sp. SH-8M increased to 8.0 and 8.7, respectively, while that of Bacillus sp. SH8 remained constant pH 7.0. The highest sporulation rate of Bacillus sp. SH-8 and SH-8M was obtained at the initial pH of 10.2 and after the incubation of 3 days with the sporulation rate of 95% and 85%, respectively.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.874-878
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• 2012

In the submerged fermentation of fungi, it was known pH had significant effect on the citric acid production. Various growth conditions were applied with different buffer on citric acid production by Aspergillus niger NRRL 567 grown on peat moss to find the optimum pH and most effective buffer solution. The initial pHs of different buffer solutions significantly influenced on the citric acid production and A. niger NRRL 567 produced citric acid more efficiently at high pHs. A phosphate buffer and a carbonate buffer with pH 8.6 and pH 10.0 were identified as suitable buffer solutions for citric acid production. The maximal citric acid production of 564.3 g/kg solid substrate was achieved employing carbonate buffer at pH 10.0.

• Journal of the Korea Organic Resources Recycling Association
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• v.24 no.4
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• pp.5-9
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• 2016

In the modern industrial society, huge amount of organic wastes have exceeded the society's self-cleaning capability, caused pollution of the whole environment, including water quality, soil, and the air, and become a big burden of waste treatment. Moreover, the emission of green house gases brought by the continual combustion of fossil fuels has facilitated the global warming. The simultaneous effect of initial and operational pH on $H_2$ yield was expressed using mathematical equation and optimized. The optimal initial and cultivation pH was 7.50 and 6.01, respectively. Addition of livestock wastewater to food waste substantially decreased the amount of alkali requirement and also improved the $H_2$ fermentation performance.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2002.05b
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• pp.163-167
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• 2002

$TiO_2$ 고정화 지지체를 이용한 유기인계농약의 광분해에 대한 연구 결과 다음과 같은 결론을 얻을 수 있었다. Chlorpyrifos의 광분해 제거효율을 초기 pH 9에서는 반응시간 200분만에 완전 분해되었으며, 초기 pH 7, 5에서는 각각 반응시간 240분, 260분만에 완전히 분해되었다. 또한 Diazinon인 경우 초기 pH 9에서는 반응시간 200분만에 완전 분해되었으며, 초기 pH 7, 5에서는 각각 반응시간 220분, 240분만에 완전히 분해되었다. Chlorphyrifos와 Diazinon은 pH가 증가할수록 즉 산성에서 염기성쪽로 갈수록 반응속도가 증가하는 것을 볼 수 있었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.179-186
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• 1998

We have been investigated the effects of the initial pH of the aquous solution, reaction temperature and time for the flaking of the soda-lime glass container. Flaking of glass occuurred in the cases of the $121^{\circ}C$, above pH 11 of solution with no $Mg^{2+}$ ions in solution. The pH of the solution approached to pH 10 under the conditions of below pH 9 of start solution. The flaking mechanism of the glass seem to be composed of formation of leached layer of $Ca^{2+}$ and $Na^{2+}$ ion and separation of these layers during the cooling by the difference of thermal expansion between leached layer and glass surface. The leaching of alkali ions in glass depends on the pH condition of the start solution and the temperature. In the case of $Mg^{2+}$ ions are added, $Mg^{2+}$ ions accelerate the flaking of the sodalime glasses and forms the magnesium silicate compound which result in the decrease of the pH of the solution.