Production Of Sodium Hypochlorite Research Articles

Electrochemical Production of Sodium Hypochlorite from Salty Wastewater Using a Flow-by Porous Graphite Electrode

The production of sodium hypochlorite (NaOCl) from salty wastewater using an electrochemical cell has several advantages over other methods that often require hazardous chemicals and generate toxic waste, being more sustainable and environmentally friendly. However, the process of producing sodium hypochlorite using an electrochemical cell requires careful control of the operating conditions, such as the current density, flow rate, inert electrode spacing, and electrolyte concentration, to optimize the conversion efficiency and prevent electrode fouling and degradation. In this study, NaOCl was produced via a bench-scale electrochemical cell using a flowing porous graphite electrode in a continuous flow system from salty wastewater collected from the Suez Canal in Egypt. The aim of the investigation was to examine the factors that affect the concentration of NaOCl and energy consumption, such as anodic current density, salinity, inert electrode spacing, and influent feed flow rate. A lab-scale reactor with two electrodes was used to conduct the experiments. The highest NaOCl yield of 20.6% was achieved with a graphite electrode, which had high current efficiency and rigidity at a flow rate of 4.5 mL/min, a current density of 3.183 mA/cm2, an electrode space of 0.5 cm, salinity of 40,000 ppm, and a pH of 6.4. The power consumption under these conditions was 0.0137 kwh. Additionally, a statistical and least square multivariate regression technique was employed to establish a correlation for predicting the % NaOCl production. The obtained correlation had an R2 value of 98.4%. Overall, this investigation provides valuable insights into the production of NaOCl using a continuous flow system from salty wastewater, which could have potential for industrial applications in various sectors such as textiles, detergents, paper, and pulp.

A prototype for on-site generation of chlorinated disinfectant for use in rural aqueducts

Sodium hypochlorite has significant potential as a sanitation solution in hard-to-reach areas. Few studies have investigated the optimal electrolysis parameters for its production with volumes greater than 10 L. This study evaluated sodium hypochlorite production through electrolysis in a 22-L prototype and identified the optimal operating parameters. Tests were performed using graphite electrodes with areas of 68.4 cm2 at the laboratory scale and 1 865.0 cm2 at the prototype scale. A design for experiments with different operating times, chloride concentrations, and electric current intensities was developed. The optimal operating time, sodium chloride concentration, and current intensity at the laboratory scale were 120 min, 150 g of chloride per liter, and 3 A, respectively, leading to the production of 5.02 g/L of the disinfectant with an energy efficiency of 12.21 mg of Cl2 per kilojoule. At the prototype scale, the maximum sodium hypochlorite concentration of 3.99 g of chloride per liter was achieved with an operating time of 120 min, a sodium chloride concentration of 100 g of chloride per liter, and a current intensity of 70 A, reaching an energy efficiency of 42.56 mg of Cl2 per kilojoule. In addition, this study evaluated the influences of the chloride concentration, current intensity, and operating time on the production of sodium hypochlorite at the two scales, and formulated the equations showing the trends of sodium hypochlorite production and energy efficiency in the electrochemical systems. The 22-L prototype model for production of this oxidizing substance is promising for disinfection of large volumes of water in areas that are difficult to access.

Decreasing diarrhea cases through on-site sodium hypochlorite production in Madagascar

Abstract Schools from Sainte-Marie Island, off the east coast of Madagascar, participated in water, sanitation, and hygiene (WASH) programs. We report an association between the program, the sustainable access to water treatment (WT) in 20 schools, and the impact on diarrhea incidence in the region. We performed a quasi-experimental longitudinal study on the program's sustainability by accessing the continuation of point-of-use (POU) water chlorination, safe water storage (SWS), and handwashing practices on the diarrhea cases of children. Patient files from 10 health centers near the schools were consulted. Sodium hypochlorite was locally produced by the students for WT and the program's sustainability was accessed between 2016 and 2021. After the intervention, 40% of water sources were entirely replaced and 60% received improvements. A student's water club, guided by teachers, was responsible for all activities related to WT. The health centers around the schools participating in the program saw diarrhea cases drop by 58% between 2018 and 2021. There appears to be an association between a decrease in diarrhea cases and the program's implementation. The strategy used can be replicated. Nevertheless, the program's success is multifactorial, depending on community engagement, adapted technology, funding, and governmental support to ensure sustainability.

Risk analysis of the sodium hypochlorite production process: Focus on the chlorine line

Mainly in the first part of COVID-19 pandemics, sodium hypochlorite was used as disinfectant, surprisingly also to spray over people. Several hazards may be associated to the production of this compound, such as chlorine gas toxicity and explosive hazards, due to the presence of hydrogen and chlorine, and corrosive hazards. Thus, loss prevention strategies must be ad-hoc developed to mitigate the risks. In the present work, the risk assessment of the first block of the process was performed, focusing the attention on chlorine risks. To this end, HAZOP analysis was first performed to identify the most critical top event, noticing the major issues in the quality of the final product and in the release of chlorine from pipes. Then, the fault tree analysis was built to calculate its failure rate. CFD simulations were used instead of empirical model to assess with a rigorous approach the chlorine dispersion, taking into account all the boundary conditions. In particular, by setting a hazardous chlorine concentration of 180 ppm corresponding to 50% fatalities for chlorine exposition for an exposure of 60 min, results without aspiration demonstrate the possibility for the cloud to impact workers at ground level also very far from the source point, while the chlorine cloud is moved upwards with a maximum length of 6.5 m when an aspiration is used, although the air ventilation speed is kept low.

SUBSTANTIATION OF TECHNOLOGICAL INDICATORS OF APPLICATION OF A GAS-DIFFUSION CATHODE IN ELECTROCHEMICAL SYNTHESIS OF HYPOCHLORITE SOLUTIONS

A gas diffusion electrode was used to implement depolarization of the cathodic process with atmospheric oxygen to improve the production of sodium hypochlorite by electrolysis of an aqueous solution of sodium chloride. As materials for the implementation of depolarization of the cathode process on a porous cathode from the grid, we selected: manganese oxides, cobalt oxides, ruthenium oxides. These oxides are characterized by low overvoltage of the oxygen reaction. Oxides of selected metals were applied to a mesh current lead by thermal decomposition of coating solutionsю. The gas diffusion electrode consisted of a lined titanium current lead, a dispersant of gas made of porous graphite, and an external mesh working element, on which cathodic reactions occurred. The preparation of a catalytically active layer of oxide-metal coatings was carried out by thermal decomposition of coating solutions. This method fully complies with the requirements for oxide-metal electrodes for the electrolysis of aqueous solutions of sodium chloride: the ability to control the composition of the composite coating in a wide range of component concentrations. On the current-voltage cyclic dependences of the cathodic process, for all the materials studied, certain areas of oxygen reduction and combined oxygen reduction and hydrogen evolution are observed. The first section of oxygen reduction is observed to the equilibrium potentials of the hydrogen reaction (approximately –0.42 V). The oxygen reduction rate is small and amounts to 3...5 mA/cm2. There is no difference in the current-voltage dependence due to the high potential sweep speed, which does not lead to oxygen depletion in the case of cathode operation without air supply. In the second section (at potentials, more negative equilibrium potentials of the hydrogen reaction), a significant increase in the rate of the cathodic reaction due to hydrogen evolution is observed. Oxygen, in this case, is reduced at the limiting current density. In the third section (more than –1.5 V), the speed of the cathodic process is almost completely determined by the rate of hydrogen evolution. The effect of air supply to the gas diffusion cathode is observed when comparing the reverse stroke of cyclic current–voltage dependences. On the surface of the steel mesh, an increase in the reverse current is observed in the potential range –1.0 to 0 V. Which indicates an increase in adsorbed particles involved in the cathodic process. As shown earlier, this range of potentials corresponds to the 1st and 2nd sections of the obtained dependences in which the predominant oxygen reduction occurs. Therefore, an increase in the reverse current, with potentials more positive than 1.0 V, can be explained by the effect of oxygen adsorption on the surface of gas-permeable mesh steel cathodes when air is supplied. The addition of hypochlorite ion has practically no effect on the current density in the first and second sections of the current – voltage dependences. A decrease in the cathodic current density is observed at potentials more negative from the equilibrium potential of the hydrogen reaction. This indicates a certain inhibition of the process of hydrogen evolution. In the third section, the current density also decreases. This indicates that 0.08 mol∙dm3 hypochlorite ions do not participate in cathodic reduction. Recommended current density for the studied design of the gas diffusion cathode is 15 mA/cm2 at a temperature of 291...293 K. The cathodic recovery of hypochlorite ions, under these conditions, is reduced by 55...60 %.

Feasibility of Producing Sodium Hypochlorite for Disinfection Purposes using Desalination Brine

On the Fernando de Noronha archipelago of northeast Brazil, the water supply comes from the desalination of seawater. The main environmental problem related to desalination is the brine resulting from the process, comprised of highly concentrated salts. The present study aimed to produce oxidant solutions from brine for disinfection purposes. The experiment was carried out on a laboratory scale. The brine had a chloride concentration of 40000 mg/L. The electrolysis process lasted twenty-four hours, monitoring pH, electrical conductivity, temperature, and chlorine. The sodium hypochlorite production was 2.27% and 3.61% m/m. The oxidant solutions were tested on domestic effluents and achieved a 99.99% removal rate of thermotolerant coliforms while maintaining the concentration of organochlorines below the upper limit established by legislation for the disposal of effluents. Therefore, the use and more proper brine disposal are sustainable alternatives, enabling the on-site production of sodium hypochlorite on the archipelago in a safe, effective, reliable way and comparable to other oxidants.

Risk Analysis of the Sodium Hypochlorite Production Process: Focus on the Chlorine Line

Risk Analysis of the Sodium Hypochlorite Production Process: Focus on the Chlorine Line

Thermo-economic analysis of chlor-alkali electrolysis for hydrogen production in the electrochlorination plant: Real case

This study deals with the implementations of electrochemical technology for the on-site production of sodium hypochlorite (NaOCl) and hydrogen from seawater for utilization in the steam power plant. The effects of electrical current and seawater temperature on the performance of electrochlorination system are investigated. The obtained results show that current efficiency increases with increasing electrical current. The current efficiency of the system is calculated as 94% at a maximum electric current with a value of 4000 A and maximum temperature with a value of 30 °C. Electricity consumption increases for the unit generation of available chlorine in the case of both enhancements of electrical current and seawater. Hydrogen generation is directly proportional to the variation of the electrical current. Also, improvement in seawater temperature provides more efficient hydrogen generation. Moreover, energy and exergy efficiencies of the whole system are positively affected by an increase of current. However, energy and exergy efficiencies are determined to be 50.4% and 3.04%, respectively, under the best operational conditions. Besides, the cheapest product cost of the hydrogen gas is calculated as $4.04/kg under the greatest electrical current and seawater temperatures.

SUBSTANTIATION OF TECHNOLOGICAL INDICATORS OF APPLICATION OF A GAS-DIFFUSION CATHODE IN ELECTROCHEMICAL SYNTHESIS OF HYPOCHLORITE SOLUTIONS

A gas diffusion electrode was used to implement depolarization of the cathodic process with atmospheric oxygen to improve the production of sodium hypochlorite by electrolysis of an aqueous solution of sodium chloride. As materials for the implementation of depolarization of the cathode process on a porous cathode from the grid, we selected: manganese oxides, cobalt oxides, ruthenium oxides. These oxides are characterized by low overvoltage of the oxygen reaction. Oxides of selected metals were applied to a mesh current lead by thermal decomposition of coating solutionsю. The gas diffusion electrode consisted of a lined titanium current lead, a dispersant of gas made of porous graphite, and an external mesh working element, on which cathodic reactions occurred. The preparation of a catalytically active layer of oxide-metal coatings was carried out by thermal decomposition of coating solutions. This method fully complies with the requirements for oxide-metal electrodes for the electrolysis of aqueous solutions of sodium chloride: the ability to control the composition of the composite coating in a wide range of component concentrations. On the current-voltage cyclic dependences of the cathodic process, for all the materials studied, certain areas of oxygen reduction and combined oxygen reduction and hydrogen evolution are observed. The first section of oxygen reduction is observed to the equilibrium potentials of the hydrogen reaction (approximately –0.42 V). The oxygen reduction rate is small and amounts to 3...5 mA/cm2. There is no difference in the current-voltage dependence due to the high potential sweep speed, which does not lead to oxygen depletion in the case of cathode operation without air supply. In the second section (at potentials, more negative equilibrium potentials of the hydrogen reaction), a significant increase in the rate of the cathodic reaction due to hydrogen evolution is observed. Oxygen, in this case, is reduced at the limiting current density. In the third section (more than –1.5 V), the speed of the cathodic process is almost completely determined by the rate of hydrogen evolution. The effect of air supply to the gas diffusion cathode is observed when comparing the reverse stroke of cyclic current–voltage dependences. On the surface of the steel mesh, an increase in the reverse current is observed in the potential range –1.0 to 0 V. Which indicates an increase in adsorbed particles involved in the cathodic process. As shown earlier, this range of potentials corresponds to the 1st and 2nd sections of the obtained dependences in which the predominant oxygen reduction occurs. Therefore, an increase in the reverse current, with potentials more positive than 1.0 V, can be explained by the effect of oxygen adsorption on the surface of gas-permeable mesh steel cathodes when air is supplied. The addition of hypochlorite ion has practically no effect on the current density in the first and second sections of the current – voltage dependences. A decrease in the cathodic current density is observed at potentials more negative from the equilibrium potential of the hydrogen reaction. This indicates a certain inhibition of the process of hydrogen evolution. In the third section, the current density also decreases. This indicates that 0.08 mol∙dm3 hypochlorite ions do not participate in cathodic reduction. Recommended current density for the studied design of the gas diffusion cathode is 15 mA/cm2 at a temperature of 291...293 K. The cathodic recovery of hypochlorite ions, under these conditions, is reduced by 55...60 %.

Ecodesign of technology for electrolytic sodium hypochlorite production for drinking water disinfection

the paper deals with the variant of partial diversification of water supply facilities where the surplus of electrolytically generated hydrogen produced by electrolysis of sodium hypochlorite - water disinfectant -can be used for heating of production facilities and nearby consumers, production of conditioned water for technological needs from atmospheric precipitations, which confirms the possibility of economically expedient participation of the water supply enterprise in forming the regional market.

Environment-friendly solutions for the disposal of waste generated during drinking water disinfection with electrolytic sodium hypochlorite

The present article is concerned with the problems of recycling and reuse of waste generated in the electrolytic production of sodium hypochlorite at water treatment plants. New engineering solutions aimed at ensuring environmental safety and lack of waste during large-scale production of sodium hypochlorite from aqueous solutions of common table salt are recommended herein.

1222. Are Reduced Concentrations of Chlorine-Based Disinfectants Effective Against Candida auris?

BackgroundCurrently, sporicidal disinfectants such as bleach are recommended for daily and terminal disinfection of the rooms of patients with Candida auris colonization and/or infection. However, bleach and other chlorine-based disinfectants can have adverse effects on surfaces and personnel. Disinfectant solutions with reduced chlorine concentrations are commonly used for other pathogens, but it is not known if diluted or alternative products maintain efficacy against C. auris both in vitro and in vivo.MethodsWe tested the efficacy of different concentrations of a sodium dichloroisocyanurate (NaDCC) product and sodium hypochlorite using the method recommended by the Environmental Protection Agency (EPA) for evaluation of the efficacy of liquid disinfectants against C. auris (EPA MLB SOP MB-35-00) and in a simulated patient room. Carriers were exposed to each disinfectant for 1 and 2 minutes. Log reductions were calculated by subtracting viable organisms recovered after disinfectant exposure vs. deionized water controls.ResultsAs shown in the figure, the NaDCC product at 4306 ppm tested with a 2 minute contact time reduced C. auris by ≥5 log10 colony-forming units (CFU) but had reduced efficacy with shorter exposure time or lower concentrations. Sodium hypochlorite was effective with 1 or 2 minute exposure times at a concentration of 6,500 ppm, and was effective at 4,000 ppm with an exposure time of 2 minutes. In the simulated patient room, NaDCC reduced C. auris contamination by ≥6 log10 CFUs on all surfaces.ConclusionA chlorine-based NaDCC product was effective at reducing C. auris. Both NaDCC and sodium hypochlorite products exhibited reduced efficacy at lower concentrations, particularly at concentrations below 4000 ppm. The NaDCC products were also effective in reducing contamination in the simulated patient room. UV-C treatment was an effective adjunct to manual cleaning. Disclosures All authors: No reported disclosures.

Technical and economical design of PV system and hydrogen storage including a sodium hypochlorite plant in a small community: Case of study of Paraguay

The increasing use of renewable power sources for distributed generation (DG) has made the application of storage systems a necessity to ensure the continuous supply. This paper analyzes technically and economically an autonomous sodium hypochlorite plant using a renewable energy source and a hydrogen storage system in the Western Region of Paraguay. In this region, there is abundant underground brackish water to produce industrial and energetic hydrogen. In addition, an isolated photovoltaic (PV) system feeds with electricity an electrolyzer, used for sodium hypochlorite production, and the brackish water and freshwater pumping systems. The hydrogen and fuel cell are used as backup system in the operation of the electrolyzer. Preliminary results show that hydrogen stored during the day can increase hypochlorite production by up to 31%. The PV solar system surplus can supply the demand of an off-grid community near the plant. The results show that the plant's return on investment (ROI) is 7 years.

Disposal of waste generated during drinking water disinfection with electrolytic sodium hypochlorite

The present article is concerned with the problems of recycling and reuse of waste generated in the electrolytic production of sodium hypochlorite at water treatment plants. New engineering solutions aimed at ensuring environmental safety and lack of waste during large-scale production of sodium hypochlorite from aqueous solutions of common table salt are recommended herein.

A comparative performance analysis of stand-alone, off-grid solar-powered sodium hypochlorite generators.

Sodium hypochlorite (NaClO) is a chemical commodity widely employed as a disinfection agent in water treatment applications. Its production commonly follows electrochemical routes in an undivided reactor. Powering the process with photovoltaic (PV) electricity holds the potential to install stand-alone, independent generators and reduce the NaClO production cost. This study reports the comparative assessment of autonomous, solar-powered sodium hypochlorite generators employing different photovoltaic (PV) technologies: silicon hetero-junction (SHJ) and multi-junction (MJ) solar cells. For Si hetero-junctions, the series connection of either four or five SHJ (4SHJ and 5SHJ, respectively) cells was implemented to obtain the reaction potential required. MJ cells were illuminated by a novel planar solar concentrator that guarantees solar tracking with minimal linear displacements. The three solar-hypochlorite generators were tested under real atmospheric conditions, demonstrating solar-to-chemical conversion efficiencies (SCE) of 9.8% for 4SHJ, 14.2% for 5SHJ and 25.1% for MJ solar cells, respectively. Simulations based on weather databases allowed us to assess efficiencies throughout the entire model year and resulted in specific sodium hypochlorite yearly production rates between 7.2–28 gNaClO cm−2 (referred to the PV surface), depending on the considered PV technology, location, and deployment of electronics converters. The economic viability and competitiveness of solar hypochlorite generators have been investigated and compared with an analog disinfection system deploying ultraviolet lamps. Our study demonstrates the feasibility of off-grid, solar-hypochlorite generators, and points towards the implementation of SHJ solar cells as a reliable technology for stand-alone solar-chemical devices.

СПОСОБ ПОВЫШЕНИЯ КПД ЭЛЕКТРОЛИЗНЫХ УСТАНОВОК В ГРУППОВОМ ВОДОПРОВОДЕ ЛИМАНСКОГО РАЙОНА ПУТЕМ ПРИМЕНЕНИЯ ВОДОРОДНЫХ ТЕХНОЛОГИЙ

One of the main units in the water supply network of MUC "Liman water pipelines" is a water purification plant. Analysis of the water purification plant operation in Olya village revealed problems of imperfect use of electrolysis and overall nonrational application of power resources and electric equipment for water purification. There have been found main areas of concern in the plant of sodium hypochlorite production. There has been proposed the method for increasing efficiency of the station and reducing energy costs, as well as for increasing service life of the equipment. This method is based on the use of hydrogen as a fuel for heating the electrolyte before it enters the galvanic bath.

Infection prevention and patient safety improvement in developing countries thanks to sodium hypochlorite production devices

The technology developed by Antenna Technologies has allowed reaching some promising results. In Guinea Conakry, The sales of Sodium Hypochlorite (SH) flasks in a limited zone (target population for 2014: 7'218’882) represent a calculated coverage ratio of 27,5% (2014: 3'390'637 flasks sold at very low price to lowest income group). In Burkina Faso, the excellent results obtained by a pilot study under the auspices of the Health Ministry suggests that a scaling-up phase with the ambition to equip 63 health districts and 9 regional hospitals should be undertaken in a close future.

A Polarity Switching Technique for the Efficient Production of Sodium Hypochlorite from Aqueous Sodium Chloride Using Platinum Electrodes

A novel, periodic polarity-switching technique is developed for the electrolytic production of sodium hypochlorite from aqueous sodium chloride. The technique employs a flow-through cell having two identical platinum electrodes. Polarities of these electrodes are periodically swapped. The main purpose of this step is to prevent the growth of platinum oxide film and thereby retain high initial activity of the electrodes throughout the operation. The performance of this mode of operation is evaluated using the cumulative productivity and current efficiency of the cell as indicators. Typical ranges of parameters used are as follows: concentration of Cl– ions, 0.1–0.5 M; switching frequency, 0.01–1 Hz; and current density, 100–700 A m–2. The productivity of the switching mode is 5–6 times higher and its current efficiency is 15%–20% higher than that of the DC mode. The switching frequency has a strong influence on both the cumulative production rate and the average current efficiency and an optimal switching ...

The Potential in Water Supply and Sanitation Services of the On Site Production of Sodium Hypochlorite (OSEC) Driven by PV Solar Source

This study aims at evaluating the impact of an On Site Electro Chlorination (OSEC) device, a system for the sodium hypochlorite production, on the improvement of health and hygienic standards in Mesoamerica focusing on Chiapas-Mexico and Costa Rica, as well as in Africa, Western Sahara (Refugees Camp) and Tanzania. The threat of infectious diseases and the importance of cleaned and treated water with the consequent high impact on the vulnerable population have been studied in each of the above countries. In this framework the production of low cost sodium hypochlorite through a stand-alone system powered by PV solar source could be a good starting point in improving sanitation conditions, assuring the disinfection of water and clothes, and improve food safety. The cost analysis shows that producing sodium hypochlorite with an OSEC solar system could lead to 10 to 15 times saving with respect to the purchasing of it at market price, above all in developing countries. Furthermore, the LCA study highlights the low environmental impact of the on-site production of sodium hypochlorite through qualitative and quantitative data that demonstrate how this system has pollutant emissions from 14 to 56 times lower than the equivalent industrial process (N factor). The paper describes as well possible practical applications of the sodium hypochlorite in the African and Latin American context. Additionally, it demonstrates the potential to create an impact on the social context and microenterprises specialised in the production of hygiene and sanitation products, managed by local people selling at affordable prices and reaching the poorest villages of developing countries.

The Potential in Water Supply and Sanitation Services of the On Site Production of Sodium Hypochlorite (OSEC) Driven by PV Solar Source

The Potential in Water Supply and Sanitation Services of the On Site Production of Sodium Hypochlorite (OSEC) Driven by PV Solar Source