To fix and neutralize: how we tamed silver. A word about bactericides for water
- Silver is useful! Here is my favorite spoon! And holy water, which is stored year!
“Come on, silver is a heavy metal.” How about a favorite lead spoon?
Two conflicting beliefs are simultaneously true. We understand how to live with this not only for a long time, but also qualitatively.
Silver, like gold, has been used as a bactericide since ancient times. But not because it works great, but because there were simply no other options until the opening of Fleming penicillin. To throw a silver spoon into a glass in the hope of neutralizing the bacteria is effectively about the same as knocking on them with a hammer.
Silver is indeed a harmful metal. Until recently, its maximum permissible concentration (MPC) in water was the same as that of lead, namely, 0.05 mg / l. Recall speech about millionths of a gram. The taste and color can not be determined. SanPin’s lead requirements are now tougher and the limits of what is permitted stop at 0.03 mg / l.
Silver and gold in ionic , rather than metallic form (!), Are xenobiotics, that is, poisons for living cells.
Poisons are the same as lead, mercury or arsenic. With constant use, even in concentrations below the MPC, heavy metals accumulate in the body and include a countdown to chronic poisoning. But doesn’t this property help us protect ourselves from dangerous diseases?
After all, poison is a bactericide, and bactericide is good. So is YES or NO?
The main problem of most bactericides, which makes sense to use for water purification, is that they are not competent in the question “Who are we attacking?”. They don't care: that Koch's wand, that healthy cell of your liver.
Helping, do no harm
It is necessary to separate the concepts of bactericidal and bacteriostatic for filters. The filter, which is bactericidal, is able to destroy all life that enters it, regardless of concentration. There are practically no such household filters. As a rule, these are special products for use in harsh conditions when it comes to survival.
Bacteriostaticity - the ability to prevent the proliferation of bacteria inside the filter, because it should not be a favorable environment for the reproduction of microorganisms, and the "output" of bacteria should not be more than the "input". To ensure this task, a “socially acceptable” bactericide must still be present in the filter.
Choose from two evils
The latest generations of bactericides are able to act selectively and neutralize specific strains. However, a narrow spectrum for our purposes is not enough, the composition of the water in a single tap is unknown to us. It's like being on industrial tuna fishing with pike equipment.
From the point of view of medicine, silver in the ionic form is not the most effective bactericide, but with a broad spectrum of action and does not cause acute poisoning in humans. Silver is incorporated into the cell's enzyme molecule, replacing ions of other metals (for example, cobalt). The enzyme stops working, and the bacterium or human cell (which is the same thing for silver) loses the ability to multiply and feed, dying from hunger or loneliness.
So silver is dangerous, useless or useful?
The main way to ensure the bacteriostaticity of the filter throughout the world is silvering activated carbon. A small amount of coal impregnated with a silver salt concentrate is mixed with ordinary activated carbon. Silver is recovered from salt and "stuck" in the form of the smallest metal crystals in coal pores. However, metallic silver is ineffective and to achieve the desired effect, you have to use it more.
In a number of European countries, including Germany, the use of silver in stationary filters is prohibited. Under the pressure of the water supply network, flushing can occur spontaneously, with the risk of exceeding the MAC. For pitcher water purifiers, silver is acceptable if the content to 0.05 mg per liter of purified water is not exceeded.
Unlike metallic silver, ions of this metal are much more effective as a bactericide. But it is much more difficult to keep silver in the filter in this form. It either interacts with coal, turning into metal, or strives to slip into a glass. And this is a threat to health.
To solve the problem of transforming the activity of silver into a blessing, that is, into an active and safe form, we need a new introductory one.
Less is more
Interesting horizons to solve the voiced problem open up when the ionic form of the metal is forcibly "planted" on the ion exchanger. In our case, this is Aqualen-2 , a chelated ion exchange fiber that selectively binds heavy metals, including silver. So, on the one hand, they remain in the active ionic form, and on the other, they are not washed from the fiber into the water.
It would be more correct to say: we are not “silver” coal, we are “silver” Aqualen-2.
Why is it safe?
- The concentration of silver inside the filter requires a low;
- When the active substance, in our case, the silver ions are not in solution, but are bound on the surface of the ion exchanger, then the antibacterial activity is manifested locally. The filter is protected from flowering, while water treated with bound silver, does not have a bactericidal effect, and therefore is safe for the body.
Why is it effective?
- Active silver interacts with the environment from the surface on which it is fixed. The larger the surface, the larger the process. One of the features of the fiber is a huge interaction area. In more detail about what role Aqualen plays in the traditional mixture of activated carbon and ion exchange resin, we describe in this video:
So feel free to stir the tea with a silver spoon. The biggest trouble that lurks in this action - the danger of burns, because silver, among other things, has unsurpassed thermal conductivity. But to drink "silver water" or to keep a silver coin in a carafe with water is not worth it: the first is harmful, and the second is meaningless.