Why are phosphorus-containing printing and dyeing auxiliaries restricted?

An Egyptian fresco from about 2000 BC graphically depicts a group of men doing laundry.

At that time, washing clothes was completely done by traditional physical methods - using external force to hit the clothes, and then relying on the flow of river water to wash away the dirt on the clothes.

This method is time-consuming and labor-intensive, the results are not satisfactory, and the clothes are often broken.

But because there is no better way, it has been around for at least 3,000 years.

Later, people stumbled upon the fact that the dirty-looking grass ash actually has the effect of cleaning clothes.

Plant ash is the ashes after burning plants and contains the mineral elements contained in plants. Its main component is potassium carbonate, which is alkaline when dissolved in water.

Under alkaline conditions, oils and fats are hydrolyzed into higher fatty acid salts and glycerol, two water-soluble substances.

Therefore, the effect of removing oil stains from clothes is achieved.

Until modern times, some remote villages in China still have the ancient method of using plant ash to wash clothes.

As early as 600 BC, the wise Phoenicians* made soap by mixing goat fat and herb ash.

It is said that the soap formula was originally derived by a strange coincidence.

At one feast, a cook accidentally spilled lard into the herbal ash water used to wash hands, and the two mixed into a gooey mass.

After the banquet, the chef smeared the things on his hands and washed them. Although he was not used to the hand feeling, he was surprised to find that the cleaning effect was much better than that of grass and wood ash.

Since then, people have also tried to use other animal oils, vegetable oils, alkali salts and plant ash to make washing products.

It wasn't until the 19th century that chemists understood how soap really works as a stain remover.

Soap's powerful detergency is due to its main ingredient, sodium stearate, and its unique molecular structure.

Sodium stearate is a surfactant whose molecular structure resembles a matchstick, with a hydrophilic group* at one end and a lipophilic group at the other.

When the clothes are coated with soap and mechanically rubbed in water, the "small matches" infiltrate into the gaps of the clothes with a water-in-oil structure with lipophilic groups on the outer layer and hydrophilic groups on the inner layer, occupying every corner.

After that, the lipophilic group finds the target of oil stain particles and binds them firmly.

The hydrophilic group firmly grasps the surrounding water molecules, helping the partner to pull the enemy from the clothes into the water.

When the enemy is captured, the battle is not over yet.

At this time, the "match" turns the direction to form an oil-in-water structure with the hydrophilic group on the periphery and the lipophilic group on the inner layer, so that the dirt is dispersed in the water and cannot be returned to the clothes.

A final rinse removes the heroic "Match Warrior" and its captives, and the clothes are clean.

However, the soap with strong fighting ability is not perfect.

During the First World War, several main battlefields on the front line fought vigorously, and the aid supplies in the rear were also consumed.

The manufacture of soap required a large amount of animal or vegetable oil, which was in short supply at that time due to the tight supply of animal and vegetable oils.

At this time, the washing powder developed and synthesized by the German Henkel company in 1907 also emerged at the right time, replacing the C position of soap in detergents and successfully debuted.

The biggest difference between washing powder and soap is the source of raw materials.

Washing powder is a synthetic detergent, the main component is a surfactant based on sodium alkyl benzene sulfonate, and some auxiliaries are mixed.

The principle is similar to soap, and it also has a group of heroic "match warriors" fighting against dirt.

However, its raw materials are cheaper and easier to obtain due to artificial synthesis, and the addition of additives also makes the efficacy and intended purpose of the washing powder gradually perfect.

Therefore, both the cost and the use effect of washing powder are superior to soap.

However, due to the sodium stearate in the soap and the sodium alkylbenzene sulfonate in the washing powder, a synergistic detergency effect can be produced.

And the soap can inhibit the foaming ability of the washing powder, so that the clothes can be easily rinsed clean.

Therefore, commercial washing powder generally contains 3% to 5% of soap ingredients, which makes the washing effect of washing powder better.

In addition to the difference in form, the detergent products such as laundry detergent, laundry beads, and anhydrous laundry essence developed after washing powder are mainly the competition and optimization of auxiliary ingredients.

Most of the tap water we use to wash clothes in our lives is hard water with high concentrations of mineral ions. (Of course, except for local tyrants who have the conditions to use water purification equipment to convert hard water into soft water)

When washing clothes with hard water, calcium and magnesium ions will react with anions such as silicic acid and carbonic acid in detergents or dirt to form insoluble precipitates.

Precipitation can build up limescale on clothes or washing utensils, reducing the cleaning efficiency of the detergent. The performance is that there is no foam when washing clothes, which wastes the decontamination effect of the "little matches" who work hard.

The pioneers of detergents - Germany not only pioneered the "powder" era of detergents, but also found a way to eliminate redeposition of dirt at the end of World War II.

The use of polyphosphates is an important step in the development of the synthetic detergent industry.

In traditional washing powder, sodium tripolyphosphate (STPP) is mainly used as a washing aid.

It can complex with metal ions in water to form soluble complexes, thereby eliminating precipitation.

At the same time, STPP can keep the aqueous solution in a weak alkaline state, which has a significant synergistic effect with the most commonly used surfactants.

Therefore, it also effectively enhances the washing performance of the washing powder, and STPP has been widely used for a long time.

The principle is actually not complicated, but the process of discovery spanned two world wars.

However, just as people praise and enjoy the convenience brought by phosphorus-containing washing powder to life, it brings unexpected blows to human beings from another aspect.

Many seaside countries around the world began to suffer from red tides frequently.

That is, marine algae and other plankton proliferate in large numbers, occupying the living space of fish organisms, and at the same time, red tide organisms gather in fish gills to suffocate them due to lack of oxygen, resulting in large-scale death of aquatic animals.

The decomposition of their corpses quickly consumes oxygen in the water, secretes harmful substances, and pollutes the water environment.

As the top of the food chain, humans are very likely to ingest fish, shrimp and shellfish containing red tide toxins secreted by red tide organisms, causing human poisoning.

There were 4,448 red tides in the Seto Inland Sea in Japan between 1976 and 1991, and the direct economic losses reached hundreds of billions of yen.

Since the late 1980s, severe red tide disasters have occurred many times in my country.

In 1998, a red tide with the largest area, the most serious losses and the longest duration occurred in the Bohai Bay.

At that time, the direct economic loss of the coastal aquaculture industry exceeded 500 million yuan.

After investigation and analysis, the phosphorus element in the detergent silently carried the pot.

Phosphorus is an important source for the growth of algae and other aquatic plants in water, and orthophosphate dissolved in water happens to be the first to be utilized by algae.

"Eutrophication" refers to the fact that the phosphorus source of algae is too abundant, so that they grow and reproduce rapidly.

Although it cannot be entirely blamed on the once popular hero of STPP, it is indeed the culprit of the disaster.

According to statistics, in the past few years when my country's crazy use of phosphorus-containing washing powder, about 450,000 tons of phosphorus were discharged into ground water through washing wastewater every year.

Although the water itself has the ability to degrade nitrogen and phosphorus to a certain extent, it is indeed too large for such a large dose.

After finding the "murderer", many countries have taken measures to ban phosphorus in detergents to remedy it.

Perhaps the lesson learned is too profound, and the island country Japan has become one of the countries with the highest degree of phosphate-free in the washing industry.

As early as 1988, the production of phosphorus-free washing powder in Japan accounted for 97% of the total amount of washing powder, and now all of them have achieved no phosphate.

Most European countries have almost completely realized the phosphate-free production of detergents.

In my country, the use of phosphorus in detergents has also been gradually restricted from local governments.