Hypochlorous Acid Preparation With Pretreated Cation Exchange
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Solution Overview
Problem
Weakly acidic cation exchange resins initially produce hypochlorous acid solutions with pH below 3, leading to chlorine gas generation, which is dangerous and ineffective for sterilization, despite their theoretical capacity to maintain pH above 3.5.
Innovation Solution
Pre-treat weakly acidic cation exchangers with a neutral salt solution of a strong acid and strong base before contacting hypochlorite solution, adjusting the pH to 3.5 or higher to prevent chlorine gas generation and ensure effective sterilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If weakly acidic cation exchanger is used to lower pH of sodium hypochlorite solution, then sterilization effectiveness is improved, but chlorine gas is generated at initial stage
Solution Approach 1:
The patent applies preliminary action by pre-treating the weakly acidic cation exchanger with a neutral salt solution before contacting it with the hypochlorite solution. This preliminary treatment adjusts the initial pH drop that would otherwise occur, preventing chlorine gas generation while maintaining the sterilization effectiveness of the hypochlorous acid solution.
Solution Approach 2:
The patent uses a neutral salt solution as an intermediary substance to mediate between the cation exchanger and the hypochlorite solution. The neutral salt solution temporarily occupies the exchange sites on the cation exchanger, preventing direct contact between the hypochlorite and the exchanger that would cause excessive pH drop and chlorine gas formation.
2Quantity of substance
If acid solution is mixed with sodium hypochlorite to lower pH, then hypochlorous acid concentration is increased, but chlorine gas is generated creating safety hazards
Solution Approach 1:
The patent replaces dangerous acid solutions with a neutral salt solution that can be easily prepared and disposed of. The neutral salt solution serves as a temporary, safe alternative that achieves the same pH adjustment goal without generating harmful chlorine gas, making the process safer and simpler.
Solution Approach 2:
The patent changes the parameter being used for pH adjustment from acidic substances to neutral salt solutions. By changing the chemical nature of the pH-adjusting agent from acid to neutral salt, the process achieves the desired hypochlorous acid concentration without the harmful side effect of chlorine gas generation.
3Quantity of substance
If electrolysis method is used to produce hypochlorous acid, then pH is lowered, but device complexity and maintenance cost increase
Solution Approach 1:
The patent replaces the mechanical/electrical electrolysis system with a simple chemical ion exchange system. Instead of using an electrolyzer with electrodes and electrical power, the invention uses a weakly acidic cation exchanger with neutral salt solution, eliminating complex equipment while achieving the same goal of producing hypochlorous acid solution.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method produces hypochlorous acid solutions with pH 3.5 to 7, effectively preventing chlorine gas formation and maintaining high sterilization efficacy without the risks associated with acid mixing.
Implementation Method 1
an aqueous solution of hypochlorite is brought into contact with a weakly acidic cation exchanger to exchange a cation constituting the hypochlorite with hydrogen ions
Implementation Method 2
a weakly acidic ion exchanger that has a buffering effect above the pH at which chlorine gas is generated
Data Source
AI summary
Provided is a method for preparing a hypochlorous acid aqueous solution by which a weakly acidic hypochlorous acid aqueous solution having a pH of about 3.5-7 can be obtained without substantially generating chlorine gas even immediately after regeneration or even with a new weakly acidic cation exchange resin. In a method for preparing a hypochlorous acid aqueous solution wherein an aqueous solution of hypochlorite is brought into contact with a weakly acidic cation exchanger to exchange a cation constituting the hypochlorite with hydrogen ions to increase the concentration of hypochlorous acid in the aqueous solution, a neutral salt solution of a strong acid and a strong base in an amount that may obtain the hypochlorous acid aqueous solution having a pH of at least 3.5 when the hypochlorite aqueous solution is brought into contact with the weakly acidic cation exchanger is brought into contact, prior to the contact between the hypochlorite aqueous solution and the weakly acidic cation exchanger, with a weakly acidic cation exchanger that has been regenerated or has not been substantially subjected to cation exchange.