• Membrane and Water Treatment
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• v.14 no.2
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• pp.55-63
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• 2023

In this study, the influence of different IEMs (ion exchange membranes) to performance of the hypochlorite electrolysis unit with Cl₂ recovery stream was investigated. More specifically, Nafion 117-a representative cation exchange membrane (CEM)-and aminated polypheylene oxide (APPO)-an anion exchange membrane (AEM)-were installed in the hypochlorite electrolysis unit, and the performance and the energy efficiency of the units were evaluated and compared. Regardless of whether CEM (Nafion 117) or AEM (APPO) was installed, the rate of hypochlorite generation was increased (by up to 24.3% and 22.2% for Nafion 117 and APPO, respectively) compared with the unit without an IEM. On the other hand, the power efficiency and the optimum operation condition of hypochlorite production units seem to depend on the conductivity and stability of the installed IEM. As the result, between Nafion 117 and APPO, higher performance and efficiency were achieved with Nafion 117, due to excellent conductivity and stability of the membrane.

• ALGAE
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• v.29 no.4
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• pp.311-319
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• 2014

The biocide sodium hypochlorite (NaOCl) is widely used for controlling algal growth, and this application can be extended to marine environments as well. This study evaluates the biocidal efficiency and cellular toxicity of NaOCl on the harmful dinoflagellate Cochlodinium polykrikoides, with emphasis on pigment production and antioxidant enzyme activity. The test organism showed dose-dependent decrease in growth rate on exposure to NaOCl, and the 72 h $EC_{50}$ was measured to be $0.584mg\;L^{-1}$. NaOCl significantly decreased pigment levels and chlorophyll autofluorescence intensity, indicating possible detrimental effects on the photosystem of C. polykrikoides. Moreover, it significantly increased the activities of antioxidant enzymes, suggesting the production of reactive oxygen species in the cells. These data indicate that NaOCl exerted deleterious effects on the photosynthetic machinery and induced oxidative damage in the dinoflagellate and this biocide could be effectively used for the control of algal blooms.

• Mycobiology
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• v.28 no.3
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• pp.123-126
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• 2000

Sodium hypochlorite alkaline was tested against Pseudomonas tolaasii causing bacterial blotch on cultivated oyster mushroom (Pleurotus ostreatus). The minimum inhibitory concentration of sodium hypochlorite against P. tolaasii contained active chlorine (AC) at 1.4 mg/l on plate assay. The highest cultivation yield was obtained from the treatment of AC 5.7 mg/l. Treatment of sodium hypochlorite at the rate of higher than AC 11.4 mg/l resulted in reduced yields at the harvest. However, the population of total bacteria on the bed surface treated with AC 5.7 mg/l of sodium hypochlorite was maintained to some extent. Inhibitory concentration against total bacteria on the bed surface was over AC 22.8 mg/l. Mushroom mycelium was damaged and its growth strongly inhibited at the concentration of AC 200 mg/l. Mushroom caps showed yellowish symptom by chemical injury by treatments of AC 74.1 mg/l or higher. Sporocarps infected by P. tolaasii were irrevocable at any concentration of sodium hypochlorite. Routine watering with AC 5.7 mg/l from mushroom initiation to the end of picking resulted in reduced bacterial blotch incidence of 40% and 86% at two mushroom farms. The treatment resulted in higher quality mushroom production compared to that conventionally watered with tap water alone.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.3
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• pp.183-189
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• 2017

Sodium hypochlorite used in water disinfection processes is generally in the production of chlorine to 0.8％. As the dose of chlorine increases, disinfection by-products (Chlorate) also increase simultaneously and exceed water quality standards. In this study, the electrolytic cell of a sodium hypochlorite generator (12％ chlorine) was adjusted to control the production of the disinfection by-products. As a result, it was possible to reduce Chlorate concentrations by more than 95％ by adjusting the pH of the electrolytic cell from 1.53 to 4.2 (normal pH of the electrolytic cell). As a low current is required to obtain these results, a 15％ improvement in the efficiency of the positive electrode is also observed. For the development of High Sodium Hypochlorite Generation can be used in a safe sodium hypochlorite solution, which is expected to contribute to improvement in the safety of the disinfection process.

• Membrane Journal
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• v.25 no.5
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• pp.447-455
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• 2015

In this study, Polysulfone (PSf) and polyetherimide (PEI) as the anion exchange polymers were aminated in the different ratio whereas the polyether ether ketone (PEEK) as the cation exchange polymer was sulfonated. The bipolar membranes of SPEEK (sulfonated PEEK)/APSf (aminated PSf) and SPEEK/APEI (aminated PEI) were prepared by the double-casting method. The surfaces of bipolar membranes were fluorinated in accordance with the amination ratio and applied to produce the hypochlorite. As the amination increased, the hypochlorite concentration is also increased. Typically, for SPEEK/APSf 3 : 1 membrane, the produced hypochlorite concentration was 61.0 ppm and its durability was 220 min for the non-fluorinated membrane while for the fluorinated membrane, the concentration of 58.6 ppm and its durability lasted 570 min. Also for SPEEK/APEI 3 : 1 membrane, the hypochlorite concentrations of 60.1 ppm and 58.3 ppm for before- and after-fluorination, respectively were observed whereas the durability was remarkably developed from 150 min to 440 min. Therefore, the surface fluorination takes an important role for the development of the membrane durability.

• Journal of Electrochemical Science and Technology
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• v.15 no.2
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• pp.268-275
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• 2024

The study examined the electrogeneration of hypochlorite ions (ClO^-) via electrolysis of aqueous NaCl solutions using a dimensionally stable anode-type (DSA-type) electrode based on platinum and palladium oxides supported on titanium mesh (Ti/PtPd(10%)O_x). The electrogenerated ClO^- was quantified on the basis of the absorption band at 292 nm (A_λ = 292) of the UV-Vis spectrum. The effect of initial pH, concentration of NaCl, cell potential difference and electrolysis time were investigated in this study. The results showed that the electrolysis of aqueous NaCl solutions increases the solution pH up to high values (≥ 8.0) that favor the formation of ClO^- over chlorine or hypochlorous acid. The hypochlorite concentration increases significantly at pH values > 7.0 and shows a linear trend with increasing NaCl concentration and with increasing cell potential difference. When the cell potential and NaCl concentration are held constant, the maximum hypochlorite value during electrolysis depends on both the cell potential and NaCl concentration. The Ti/PtPd(10%)O_x anode favors the production of hypochlorite ions, making this anode a promising material for use in electrochemical oxidation of wastewater via an indirect mechanism.

• Journal of Microbiology and Biotechnology
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• v.17 no.3
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• pp.445-453
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• 2007

The effect of an electrochemically generated oxidation-reduction potential and electric pulse on ethanol production and growth of Saccharomyces cerevisiae ATCC 26603 was experimented and compared with effects of electron mediators (neutral red, benzyl viologen, and thionine), chemical oxidants (hydrogen peroxide and hypochlorite), chemical reductants (sulfite and nitrite), oxygen, and hydrogen. The oxidation (anodic) and reduction (cathodic) potential and electric pulse activated ethanol production and growth, and changed the total soluble protein pattern of the test strain. Neutral red electrochemically reduced activated ethanol production and growth of the test strain, but benzyl viologen and thionine did not. Nitrite inhibited ethanol production but did not influence growth of the test strain. Hydrogen peroxide, hypochlorite, and sulfite did not influence ethanol production and growth of the test strain. Hydrogen and oxygen also did not influence the growth and ethanol production. It shows that the test strain may perceive electrochemically generated oxidation-reduction potential and electric pulse as an environmental factor.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.1
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• pp.122-127
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• 2013

The hypochlorite ion ($OCl^-$) is a widely used disinfecting agent in pig rearing in Korea, but its residual effect on $CH_4$ production from pig slurry is unclear. The objective of this study was to investigate the inhibition effects of residual $OCl^-$ on $CH_4$ production during the initial anaerobic digestion stage of pig slurry. Three organic concentrations (9.9, 26.2 and 43.7 g/L) of volatile solids (VS) were tested with the addition of 52.3 mg/L $OCl^-$, ten times of the typical concentration used in Korea, or without $OCl^-$ (Control) in anaerobic batch culture. The culture was run under mesophilic ($38^{\circ}C$) conditions for 20 d. At the lowest organic concentration with $OCl^-$, the VS degradation was 10.3% lower (p<0.05) than Control, while at the higher organic concentration with $OCl^-$, it did not differ from Control. $CH_4$ yields were higher in the control treatments than their $OCl^-$ counterpart cultures, and $CH_4$ yields of Control and $OCl^-$ treatments at the organic concentrations of 9.9, 26.2 and 43.7 g/L differed in the probability level (p) of 0.31, 0.04, and 0.06, respectively. Additionally, $CH_4$ concentration increased steeply and reached 70.0% within 4 d in the absence $OCl^-$, but a gradual increase up to 60.0% was observed in 6 d in the $OCl^-$ treated cultures. The $R_m$ (the maximum specific $CH_4$ production rate) and ${\lambda}$ (lag phase time) of 9.9 g/L with $OCl^-$ were 8.1 ml/d and 25.6 d, while the $R_m$ was increased to 15.1 ml/d, and ${\lambda}$ was reduced to 11.4 d in PS-III (higher organic concentration) with $OCl^-$. The results suggest that a prolonged fermentation time was necessary for the methanogens to overcome the initial $OCl^-$ inhibitory effect, and an anaerobic reactor operated with high organic loadings was more advantageous to mitigate the inhibitory effect of residual hypochlorite ion.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.124.2-124.2
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• 2010

Generally, a coolant of the nuclear power plant is manufactured by electrolyzing the sea water near the plant for making the sodium hypochlorite(NaOCl), which is used for sterilizing the bacteria and the shellfishes sticking to the drains or the pumps at the outlet of the cooling system due to $8-10^{\circ}C$ warmer temperature than the inlet sea water. During manufacturing the sodium hypochlorite, the hydrogen with the high purity is also produced at the anode side of the electrolyzer. This paper describes a novel power plant system combined with the polymer electrolyte membrane(PEM) fuel cell, the wasted hydrogen from the sea water electrolyzer and the wasted heat of the nuclear power plant. The present status over the exhausted hydrogen at twenty nuclear power plants in Korea was investigated in this study, from which an available power generation is estimated. Furthermore, the economic feasibility of the PEM fuel cell power plant is also evaluated by a current regulations over the power production and exchange using a renewable energy shown in Korea Power Exchange(KRX).

• Membrane and Water Treatment
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• v.6 no.1
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• pp.27-42
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• 2015

In this study, poly (phenylene oxide) (PPO) and poysulfone (PSf) were sulfonated and aminated respectively. Both sulfonated poly (phenylene oxide) (SPPO) and aminated polysulfone (APSf) were characterized via the measurement of FT-IR, swelling degree, ion exchange capacity (IEC), and ion conductivity. Then the surfaces of these membranes were modified by surface fluorination using 2000 ppm $F_2$ gas against $N_2$ gas for 1 h at room temperature. The surface fluorinated SPPO and APSf membranes were characterized again to determine any differences between the pristine and fluorinated membranes. In total, 3 types of bi-polar membranes were prepared by varying the IEC of the APSf and having a fixed value for the IEC of the SPPO. The hypochlorite concentration generated by using the surface fluorinated membranes was dependent on the IEC of the APSf and ranged from 683 to 826 ppm, while there was a considerable improvement in the durability of the surface fluorinated membranes as they remained intact even after operating for 4 h.