EDTA2Na and EDTA4Na, their core skill is "chelation". In human terms, it can firmly clamp metal ions such as calcium, magnesium, iron, and aluminum in water like crab claws, removing them from the membrane surface and turning them into something soluble in water to wash away. This thing is not cheap, so it is generally not used as a staple food, but as a "tonic", used on hard bones that cannot be washed by conventional washing methods, especially those iron deposits and compound deposits.
Let's talk about acid washing first.
What does acid washing mainly deal with? It's inorganic salt scaling, such as calcium carbonate, calcium sulfate, and metal oxides (the most typical being rust). There are two commonly used acids:
1. Citric acid: This is the most commonly used, mild, safe, and membrane friendly. It also has some chelating ability on its own, but not as strong as EDTA. The usual concentration used is 1-3% (by weight), for example, adding 10 to 30 kilograms of citric acid to one ton of cleaning tank water. The pH should be adjusted to 3-4, either with ammonia water or NaOH. Do not adjust with hydrochloric acid, as it will produce sodium citrate precipitate, which is blind. two Hydrochloric acid (HCl): This guy is powerful, cheap, and has a fast dissolution rate for calcium carbonate deposits. But it is highly corrosive, dangerous to operate, and has a slightly stronger attack on the membrane, so it is used less now. The concentration is generally controlled at 0.5-1% (weight ratio), and 5 to 10 liters of 36% concentrated hydrochloric acid are added to one ton of water (acid must be added to the water during operation, and protective gear must be worn!). The pH is also controlled at 3-4.
When will EDTA2Na be added? How to add? The evaluation of the title of Senior Engineer in Advertising 2025 has begun! Under the age of 55, those who meet two conditions can be evaluated for positive technology education. When you suspect or determine that there is a large amount of calcium sulfate or iron scale in the scale, using acid alone is not effective. Calcium sulfate has low solubility in acid, and iron scale will re precipitate if not washed in time after being dissolved by acid. At this moment, EDTA2Na came on stage.
Proportion: Add an additional 0.5% -1.5% EDTA2Na (5 to 15 kilograms per ton of water) to your pickling solution (whether it is citric acid or hydrochloric acid). Principle: The acid first loosens and dissolves the large scale, and then EDTA2Na goes up to "clamp" the calcium and iron ions inside, forming a stable soluble substance to prevent it from re depositing onto the membrane, which is equivalent to achieving "ultimate dissolution". This way, the cleaning efficiency is much higher.
Let's talk about alkaline washing.
What does alkaline washing mainly deal with? It's organic pollution, oil pollution, and most importantly, biofouling. Microbial corpses and their secreted mucus stick to the membrane like glue, which is particularly annoying.
The commonly used alkali is one type: sodium hydroxide (NaOH): whether it is liquid alkali (about 30% liquid) or flake alkali (solid, higher purity, easy storage), they are all the same thing, and they are all prepared into NaOH solution in the end. It is the absolute mainstay of alkaline washing, with a concentration generally ranging from 0.1% to 0.5% (by weight, calculated as 100% NaOH), and the pH needs to be adjusted to 11-12. Add approximately 3 to 10 kilograms of liquid alkali (calculated at a concentration of 30%) to one ton of water. During alkaline washing, a surfactant (such as sodium dodecylbenzenesulfonate) with a concentration of 0.025% -0.05% will definitely be compounded. Its function is to penetrate, emulsify, and peel off oil stains and biofilms from the surface.
When will EDTA4Na be added? Biological clay is not purely organic, it contains a large amount of metal ions, especially iron ions, which act as a "steel skeleton" for the clay, making it particularly strong. It is difficult to thoroughly wash it with alkali and surfactants alone.
Proportion: Add an additional 0.5% -1.5% EDTA4Na (5 to 15 kilograms per ton of water) to your alkaline washing solution (NaOH+surfactant). Principle: NaOH and surfactants are responsible for destroying the organic matter, while EDTA4Na is specifically responsible for dismantling its "metal skeleton" and chelating the iron and calcium ions inside. Once the skeleton disperses, the entire mud structure collapses, and the cleaning effect is much more thorough. EDTA4Na is alkaline and perfectly suited for alkaline washing environments.
A few practical instructions:
1. Dissolution sequence: When preparing the medicine, first pour the EDTA (2Na or 4Na) dry powder into the cleaning box, add water and stir to dissolve thoroughly, and then add acid (or alkali) to adjust the pH. Do not do the opposite. 2. Temperature: Heating the cleaning solution to 30-40 degrees Celsius (do not exceed 40 degrees!) will greatly improve the effect. 3. Circulation and soaking: Cycle for 30-60 minutes first, then close the inlet and outlet, soak for 1-2 hours to allow the medicine to fully react, and then recycle. This process can be repeated. 4. Rinsing: Rinsing after washing is crucial. It is necessary to thoroughly rinse the membrane shell and waste liquid inside the membrane with produced water until the conductivity of the incoming and outgoing water is close, to prevent secondary pollution.
By doing this, basically even the most difficult dirt to clean can be removed by 80-90%. Remember, cleaning is a craft and experience is important. After each wash, summarize the results.
