Active Chlorine Concentration Research Articles

English

The LERCAFE test consists in immersing coffee seeds in an active chlorine solution, which reacts with the seeds’ endosperm, thus staining the viable parts dark green. The goal was to adapt the LERCAFE methodology to coffee seeds and assess the isoenzymatic profile of seeds subjected to the test. Two experiments were conducted, the first with adequacy of the LERCAFE test methodology, and the second experiment adequacy of the LERCAFE test methodology with the content of active chlorine quantified. A completely randomized design was used, with four replications of 50 seeds in a factorial scheme 4x4 (4 cultivars and 4 treatments of LERCAFE test). In the first experiment, it was possible to sort the cultivars into two quality levels by means of the treatments at 2.5% for 3 h, 3.5% for 2 h and 3 h. In the second experiment, it was found that the test enables determining the coffee seeds’ physiological potential by using 2 and 3% active chlorine for 5 and 3 h, respectively. The coffee seeds subjected to LERCAFE test show changes in the activity of esterase, malate dehydrogenase, superoxide dismutase, catalase and alcohol dehydrogenase enzymes, and the activation or deactivation of these enzyme systems vary with the concentration and immersion time in the solution of active chlorine. Key words: Viability, sodium hypochlorite, Coffea arabica.

Ratio of seeds and sodium hypochlorite solution on the germination process of papaya seeds

Abstract: Sarcotesta, a mucilaginous layer found in papaya seeds, negatively affects the germination of papaya seeds and its removal has been manually performed. The use of sodium hypochlorite can be an alternative to manual removal of sarcotesta in papaya seeds. The objective of this study was to evaluate the effect of different active chlorine concentrations (0, 2, 4, 6 and 8%) during 24 hours of immersion, in different proportions (10:200, 50:200, 100:200, 200:200, 300:200, 400:200, 500:200 and 600:200) of seeds number and solution volume (mL) to identify the best combination for an effective remotion of sarcotesta to improve the germination process. Germination test and first count were performed. A completely randomized design with four replications was used. Regression analysis was performed for quantitative variables with significant effect by F-test at 5% probability. Papaya seeds immersion in the ratio of 10 seeds per 200 mL of NaOCl solution (10:200, i.e. 20 mL of solution per seed), at a 2% sodium hypochlorite concentration during 24 hours of imbibition, can be used as an alternative for sarcotesta remotion for freshly harvested papaya seeds, because besides the effective remotion of sarcotesta, this technique improves the germination process.

Corrosion rate determination of austenic steels in calcium hypochlorite solutions

This paper presents the results of testing the corrosion resistance of austenitic chromium-nickel steel X6 CrNiTi 18-10 and X6 CrNiNb 18-10 in solutions of calcium hypochlorite. For the tests were used potentiodynamic measurement methods. By graphical method of linear polarization, corrosion currents and corrosion potential were obtained on the intersection of the Tafel real E = f(log i) on the basis of potentiodynamic curves for the examined steels. The comparative method to determine the corrosion current density is the polarization resistance method. Based on corrosion currents were calculated corrosion rate of tested steel. Anodic polarization curves for both austenitic steel in the investigated solutions were shot in the interval of stationary potential of up to + 2.5V, to determine the areas of activity. Test results show that with increasing of calcium hypochlorite solution concentration, increase the pH of the solution and the concentration of active chlorine which causes a reduction in the corrosion resistance of the tested steel. These steels are resistant to corrosion in a 1% solution, stable in 10% solutions, and less resistant in 50% suspensions of calcium hypochlorite.

Automatic devices for electrochemical water treatment with cooling of electrolyte

The most common disinfectants for water treatment are based on chlorine and its compounds. Practically, water treatments with chlorine compounds have no alternative, since they provide, in comparison to other effective processes such as ozonization or ultraviolet irradiation, high residual disinfection capacity. Unfortunately, all of chlorine-based compounds for disinfection tend to degrade during storage, thus reducing the concentration of active chlorine. Apart from degradation, additional problems are transportation, storage and handling of such hazardous compounds. Nowadays, a lot of attention is paid to the development of electrochemical devices for in situ production of chlorine dioxide or sodium hypochlorite as efficient disinfectants for water treatment. The most important part of such a device is the electrochemical reactor. Electrochemical reactor uses external source of direct current in order to produce disinfectants in electrochemical reactions occurring at the electrodes. Construction of an electrochemical device for water treatment is based on evaluation of optimal conditions for electrochemical reactions during continues production of disinfectants. The aim of this study was to develop a low-cost electrochemical device for the production of disinfectant, active chlorine, at the place of its usage, based on newly developed technical solutions and newest commercial components. The projected electrochemical device was constructed and mounted, and its operation was investigated. Investigations involved both functionality of individual components and device in general. The major goal of these investigations was to achieve maximal efficiency in extreme condition of elevated room temperature and humidity with a novel device construction involving coaxial heat exchanger at the solution inlet. Room operation of the proposed device was investigated when relative humidity was set to 90% and the ambient temperature of 38?C. The obtained results in such extreme operation conditions reveled that it was possible to obtain required concentration of 0.85% of active chlorine with maximal temperature of outlet electrolyte of 35.3?C, which is within the limits of optimal temperatures.

Desinfestação e estabelecimento in vitro de explantes de bananeira ‘Thap maeo’ (sub grupo AAB) submetidos a concentrações de cloro ativo

Most of banana plantations are still carried out using traditional seedlings types, named in Brazil as ‘chifrinho’, ‘chifre’, ‘chifrão’ (with a literal translation of little horn, horn and big horn, respectivelly) and also using rizoma pieces. Other propagation methods, such as micropropagation, have been developed and improved in order to increase the multiplication rate in a short period of time and improve the seedlings phytossanitary canditions. The aim of this study was to evaluate the ‘in vitro’ disinfection using active chlorine concentrations in explants of ‘Thap maeo’ bananas , which is a viriety resistant to black and yellow Sigatokas, as well as Panama disease. The treatments were: T1 – control without active chlorine , T2 - 0.5% of active chlorine, T3 - 1.0% of active chlorine, T4 - 1.5% of active chlorine and T5 - 2% of active chlorine. The percentage of contamination by bacteria and fungi as well as the percentage of oxidation of the explants were evaluated. It was concluded that the highest efficiency among treatments was the T5 – immersion of the explants in 2% of active chlorine, whichresullted in 82% and 88% of reduction, respectively, for bacteria and fungi.

Potato starch oxidation induced by sodium hypochlorite and its effect on functional properties and digestibility

The effects of different concentrations of sodium hypochlorite (active chlorine content at 0.1, 0.2, 1.0, 2.0, 3.0, and 4.0g/100g) on the properties of potato starch (PS) were investigated by determining the morphological, physicochemical, crystallinity, pasting, gel texture and digestive properties. The starch granules of PS oxidized with high oxidant concentrations caused cracks and pores, and oxidation mainly acts on the amorphous regions of the starch granules. As the sodium hypochlorite concentration increases, the carbonyl content, carboxyl content, solubility, and pasting temperature of PS increased, as measured using a Rapid Visco Analyser (RVA). The swelling power, breakdown, setback, and peak and final viscosities decreased according to the RVA (P<0.05). The gel strength increased under low-intensity oxidative treatments and decreased under high-intensity oxidative treatments. Oxidative treatment decreased the digestibility of gelatinized potato starch. The slowly digestible starch and resistant starch contents increased significantly, while the rapidly digestible starch content decreased after the oxidation modification (P<0.05). Overall, PS oxidation with sodium hypochlorite improved the functional characteristics of starch and decreased starch digestibility.

Sodium hypochlorite for sarcotesta remotion from papaya seeds: anatomical studies

Although papaya world production is high, the integument of papaya seeds, called sarcotesta, is an obstacle in the seedling production process. The aim of this work was to develop techniques to facilitate the removal of papaya seed sarcotesta for seedlings production. For that, two assays were developed. For the first one, the seeds were immersed in different concentrations of active chlorine (0, 2, 4, 6 and 8%) at ratio 600:200 seeds/mL of solution, respectively, besides the study of intact seeds and seeds subjected to the sieve method + stagnant water. For the second one, the seeds were immersed in active chlorine 2% in different ratios (10: 200; 200: 200; 400: 200 and 600: 200), and the concentration of 0% at ratio 10:200 and the sieve method + stagnant water. The effect of the treatments was evaluated by germination test and scanning electron microscopy. Sodium hypochlorite did not remove completely sarcotesta, but damaged it. In ratio 10:200 in a concentration of 2% of active chlorine for 24 hours, the embryo and the endosperm were not affected, resulting in 80% of germination, which can be an alternative to sarcotesta manual removal.

DESINFESTAÇÃO IN VITRO DA BANANEIRA 'FARTA VELHACO (SUB GRUPO AAB)' EM DIFERENTES CONCENTRAÇÕES DE CLORO ATIVO

RESUMO: A maioria dos plantios de bananeira são realizados utilizando mudas tradicionais do tipo chifre e rizomas. Outros métodos de propagação, como a micropropagação, vêm sendo desenvolvidos e aperfeiçoados com fim a elevar a taxa de multiplicação em curto espaço de tempo e melhorar a qualidade fitossanitária das mudas. Contudo, a contaminação por bactérias e fungos é um dos maiores problemas dessa técnica. O objetivo do presente trabalho foi avaliar a desinfestação in vitro utilizando concentrações de cloro ativo em explantes de bananeira 'Farta Velhaco'. O delineamento experimental utilizado foi inteiramente casualizado constituído de cinco tratamentos e cinco repetições, sendo cada uma destas representada por cinco explantes em diferentes concentrações de cloro ativo durante vinte minutos, quais sejam: T1 - testemunha sem cloro ativo; T2 - 0,5% de cloro ativo; T3 - 1,0% de cloro ativo; T4 - 1,5% de cloro ativo; e T5 - 2% de cloro ativo. Foram avaliadas as porcentagens de contaminação por bactérias e fungos, como também a porcentagem de oxidação dos explantes. Os dados foram submetidos às análises de variância e de regressão. Os resultados permitiram concluir que a maior eficiência dentre os tratamentos testados foi o de imersão dos explantes em 1% de cloro ativo, o qual proporcionou redução em 95% e 90%, respectivamente, para bactérias e fungos e 60% dos explantes oxidados. Concluiu-se que essa concentração pode ser utilizada para o controle de contaminações para micropropagação de bananeira ´Farta Velhaco'.

Study on disinfection by-products formation according to kind of salt in on-site production

Although disinfection in drinking water treatment plants provides a safer water supply by inactivating pathogenic microorganisms, harmful disinfection by-products may be formed. In this study, the disinfectant, chlorine, was produced on-site from the electrolysis of salt (NaCl), and the by-products of the disinfection process, bromate and chlorate, were analyzed. The provisional guideline levels for bromate and chlorate in drinking water are and , in Korea, respectively. Bromide salt was detected at concentrations ranging from 6.0 ~ 622 mg/kg. Bromate and chlorate were detected at concentrations ranging from non-detect (ND) ~ 45.3mg/L and 40.5 ~ 1,202 mg/L, respectively. When comparing the bromide concentration in the salt to the bromate concentration in the chlorine produced by salt electrolysis, the correlation of bromide to bromate concentration was 0.870 (active chlorine concentration from on-site production: 0.6-0.8%, n=40). The correlation of bromate concentration in the chlorine produced to that in the treated water was 0.866.

Preparation of a coated Ti anode for producing acidic electrolyzed oxidizing water

Coated Ti anodes have been prepared for producing acidic electrolyzed oxidizing water (AEOW). To improve the performance of anodes, the influence factors (sintering temperature, heat treatment time and dip-coating times) were systematically explored. The results show that the optimum sterilizing effect of AEOW is obtained in the case of sintering at 450 °C for 1 h with as many dip-coatings as possible. The sintering temperature is a critical factor. A lower temperature leads to better reaction selectivity, whereas a higher temperature results in a longer lifetime. A short heat treatment time leads to inadequate coating oxidation, a long heat treatment time prolongs the lifetime but results in high SEC. Increasing the number of dip-coatings could enhance the coating-substrate adhesion, thus extending the anode lifetime. The electrode prepared by optimization could replace the platinized Ti anode to produce AEOW. AEOW could be used as an effective disinfectant for eliminating Escherichia coli and Staphylococcus aureus. The sterilization ability is based on the combined effect of active chlorine concentration (ACC), low pH and high oxidation–reduction potential (ORP).

Analysis of active chlorine releasing and pH of sodium hypochlorite solutions used in Endodontics

The use of a suitable irrigation solution and a correct root system shape effectively contributes to the success of endodontic treatment. Among the irrigating solutions used in Endodontics, sodium hypochlorite has been the most used because of many qualities. However, this substance must have chemical stability of its properties, by maintaining the potential of hydrogen (pH) and chlorine concentrations appropriately. Objective: The aim of this study was to evaluate active chlorine releasing and pH of some sodium hypochlorite solutions used in endodontic clinical practice. Material and methods: The solutions tested in this study were 0.5% Dakin, 1% Milton, 2% Chlorinated Soda, and household bleaches (Brilux®and Qboa®), which were opened at the same period and first used, with the same storage modus but with different manufacturing dates. The pH was measured with a digital device, and the active chlorine content was obtained through iodometric titration. Results:All solutions presented chlorine content not smaller than that informed in the flasks, ranging from 1% to 2.4%; pH was higher in all solutions, between 9 and 13. Conclusion: Based on the method applied and the results obtained, it was possible to conclude that sodium hypochlorite solutions used specifically in Dentistry (Dakin and Milton solutions and Chlorinated Soda), showed on the labels the hypochlorite content. On the other hand, household bleaches (Brilux® and Qboa®) showed the chlorine content. It was not possible to compare pH authenticity, due to lack of description on the label.

Preparation and characterization of a positively charged nanofiltration membrane based on poly(arylene ether sulfone) with tertiary amine groups

A type of poly(arylene ether sulfone) with pendant tertiary amine groups (PSDA) was synthesized via nucleophilic substitution polymerization of 3,3′-dimethylaminemethylene-4,4′-oxybisphenol (DABP) and 4,4′-bisfluorodiphenyl sulfone(BFDPS). The resulting polymer was used to prepare a nanofiltration membrane via a convenient one-step phase inversion process. The preparation conditions were investigated; the optimum parameters were 30 wt% PSDA, 30 wt% THF, 40 wt% DMF casting solution, and 10 s evaporation time. The zeta potential test indicated that the PSDA membranes were positively charged below pH 11.0. The results of the membrane performance testing showed that the trend for rejection was RFeCl3 > RMgCl2 ≈ RCaCl2 > RNaCl > RNa2SO4 (R=rejection), which was a typical positively charged nanofiltration membrane performance. The PSDA membrane also showed excellent chlorine tolerance; no obvious performance change was observed after exposure to an aqueous NaOCl solution (active chlorine concentration no less than 1000 ppm) for 15 days.

Partial Characterization of Tamarind (Tamarindus indica L.) Kernel Starch Oxidized at Different Levels of Sodium Hypochlorite

The effects of different levels of sodium hypochlorite (1–4 g/100 g dry solids active chlorine) on the physicochemical, pasting, and structural properties of tamarind kernel starches were investigated. The isolated starch had low traces of non-starch components, such as protein, fat, and ash, indicating its purity. Both the carboxyl and carbonyl contents in the oxidized starches increased significantly with the increase in chlorine concentration. The introduction of carboxyl and carbonyl groups resulted in significantly lower amylose content. The swelling power of oxidized starches was significantly lower than native starch and the solubility values increased when the chlorine concentration increased at all the measured temperatures. The percentage of light transmittance increased progressively after oxidation. Pasting properties showed that in treatments at high active chlorine concentrations, the peak viscosity decreased more drastically than in treatments at low chlorine concentration, indicating a greater degradation of starch. The morphology of the starches was not altered after oxidation. After oxidative treatment no change in the X-ray diffraction pattern was observed but intensity of the peaks increased. Therefore, tamarind kernel being underutilized raw material, has a great potential as a non-conventional source of starch and desirable properties of this starch can be enhanced by oxidation for applications in food industry.

Energy-saving removal of methyl orange in high salinity wastewater by electrochemical oxidation via a novel Ti/SnO2-Sb anode—Air diffusion cathode system

Electrochemical oxidation is an effective method in removal of organic pollutant from high salinity wastewater (NaCl), by producing active chlorine at anode or hydrogen peroxide at cathode. To solve the existing problems including low efficiency, high cost and energy consumption, a Ti/SnO2-Sb anode (TSSA)-air diffusion cathode (TSSA-ADC) system was investigated for methyl orange (MO) removal from NaCl solution, using single TSSA system as control. The phase composition of TSSA was examined by X-ray diffraction. Accumulated concentrations of active chlorine, hydrogen peroxide, MO removal rate, TOC, pH value were recorded at different current densities. The results indicated that Sb-doped rutile SnO2 was formed on the TSSA. The TSSA and the ADC exhibited good catalysis to chlorine evolution and oxygen reduction, respectively. Although MO were almost completely removed in both systems, higher TOC removal, shorter running time and lower energy consumption were attained in the TSSA-ADC system. pH value was more stable (6.0–6.4) in the TSSA-ADC system than that in the TSSA system (6.0–9.4), predicting its stronger capacity in anti-scaling when treating high salinity wastewater with hard ions like Ca2+ and Mg2+.

Development of a certified reference material for the mass concentration of active chlorine in water and its application for an interlaboratory comparison

The article discusses the development of a certified reference material (CRM) of mass concentration of active chlorine in water, GSO 10138-2012, which was performed in the Ural Scientific Research Institute for Metrology (UNIIM), Russia. For this purpose, N-chlorobenzenesulfonamide sodium salt trihydrate (chloramine B) was selected. Identification and purity assessment of the chloramine B reagent were conducted by applying gas chromatography with mass spectrometric detection. The CRM’s certified value was determined by oxidation–reduction titration. Its uncertainty was estimated by combining the contributions from characterization, inhomogeneity and instability. The article also presents the results of an interlaboratory comparison in which 42 Russian laboratories participated.

Thermal degradation behavior of hypochlorite-oxidized starch nanocrystals under different oxidized levels

The thermal degradation behavior of hypochlorite-oxidized starch nanocrystals (OSNCs) was evaluated in this study. Carbonyl and carboxyl groups in OSNCs increased from 0.006 and 0.091mmol/g to 0.033 and 0.129mmol/g, respectively, as the active chlorine concentration increased from 1% to 4% (w/w). Compared with starch nanocrystals (SNCs), the initial degradation temperature of OSNCs with 4% oxidization decreased from 273°C to 253°C. Two degradation processes were detected using differential thermal analysis. The activation energy of the low-temperature process increased with increasing oxidization level because of removal of sulfate esters and reduction of the decomposition products of H2O during oxidation. With increasing temperature, the H2O generating from decarboxylation and decomposition of the carboxyl groups may catalyze SNCs depolymerization, leading to decrease in the activation energy of the high-temperature process. OSNCs (4% oxidized level) can be used in dry process below 253°C to avoid degradation.

Oxidation of potato starch with different sodium hypochlorite concentrations and its effect on biodegradable films

The objective of this study was to evaluate the effects of oxidation with sodium hypochlorite at different concentrations of active chlorine (0.5, 1.0 and 1.5 g/100 g) on the physicochemical, morphological, pasting, thermal and gel texture properties of potato starch. The native and oxidized starches were used in different concentrations (3.0, 4.0 and 5.0 g starch/100 mL) for the preparation of biodegradable films using glycerol as plasticizer. The films were evaluated for their mechanical properties, color, water solubility and permeability of water vapor. The degree of oxidation potato starches was more intense as there was an increased concentration of active chlorine in the reaction. Films made with oxidized starch with the highest level of active chlorine had lower tensile strength when compared to native starch films. Also, these films had a lower water solubility and water vapor permeability as compared to the native starch films.

Effective treatment of cadmium–cyanide complex by a reagent with combined function of oxidation and coagulation

The treatment of heavy metal–cyanide complex in industrial wastewater generally involves various processing units, such as chemical oxidation, hydrolysis precipitation and coagulation. A novel dual function reagent (PACC), which contains high content of active chlorine and Al13 polymer, shows a promising potential to shorten the process and heighten the treatment efficiency for cadmium–cyanide complex ([Cd(CN)4]2−). The results indicated that PACC is able to simultaneously achieve the complete oxidation of cyanide (CN−) by active chlorine and the subsequent coagulation of cadmium ion (Cd2+) by Al13 polymer. Two stages were carried out for complete CN− oxidation and effective Cd2+ coagulation. The first stage involves the conversion of CN− to cyanate (CNO−), and the second stage involves the conversion of CNO− to nitrogen and the coagulation of the liberated Cd2+. The optimum pH values for the first stage and the second stage are pH 11 and pH 8.5, respectively. The two stages for effective treatment of [Cd(CN)4]2− at the optimal pH condition totally need about 43 min at active chlorine dosage 130% of the theoretical requirement for CN− decomposition. Under the optimal conditions for [Cd(CN)4]2− treatment, the stoichiometric weight ratio of Cl2/Al in PACC is 2. This study presents a novel reagent and method to remove heavy metal–cyanide complexes from wastewater.

Facile preparation of surface N-halamine chitin nanofiber to endow antibacterial and antifungal activities

N-halamine chitin nanofiber (NF) film was prepared by the reaction of chitin NF film with sodium hypochlorite solution to endow the film with antibacterial and antifungal activities. The amount of active chlorine content loaded on the chitin NF film depended on the sodium hypochlorite concentration and reaction time. FT-IR, UV–vis, XRD, and TG analyses showed that the NH bond was substituted to the NCl bond and that the reaction took place at the chitin NF surface. After chlorination, the characteristic nanochitin morphology was maintained. Although the active chlorine content of the film gradually decreased by disassociation of the NCl bond, chlorine was rechargeable into chitin NF by another sodium hypochlorite solution treatment. The chlorinated chitin NF film showed strong efficacies against Gram-negative and -positive bacteria of Escherichia coli and Staphylococcus aureus, respectively. Moreover, the films showed 100% and 80% inhibition of spore germination when faced against Alternaria alternata and Penicillium digitatum fungi, respectively.

Direct chronoamperometric determination of free available chlorine in soil samples using built-in diffusion layer coated glassy carbon electrode

In this work, a glassy carbon electrode supplied with a built-in diffusion layer and a short-time chronoamperometric method were used for obtaining reliable concentration values from I–t curves recorded in tortuous media. It was proved that short-time chronoamperometric transients taken with the modified electrode in tortuous matrices can be evaluated using calibrating data recorded in simple aqueous standards. The applicability of the in situ analytical method was tested for determination of active chlorine concentration in different bleaching powder treated soil samples. Iodometric titrations were employed for comparison. The results prove that residual concentration of active chlorine can be estimated with 0.66 % relative standard deviation using the proposed in situ chronoamperometric measuring methods in humid soil slurry after bleaching powder disinfection.