Scaling is a headache for both the water treatment and detergency industries. In the first case, because the formation of deposits reduces the performance of the system by increasing energy consumption and/or maintenance costs and, in the second case, because specific treatments are required to remove all the dirt properly. It is for this reason that dispersing and anti-scaling agents are used in both industries.
Anti-scaling agents act by preventing the formation of the calcium carbonate precipitate (mainly), while dispersing agents intervene once the precipitate has formed by preventing the formation of particle nuclei that end up becoming scale.
Among these anti-scaling agents, phosphonates are the most important.
The problem of phosphonates
The use of phosphorus-derived products such as phosphonates generates an environmental impact that cannot be ignored. Excess nutrients such as nitrogen and phosphorus in the waters of lakes, ponds, rivers, reservoirs, etc. … cause eutrophication of the water.
Excess nutrients cause plants and others to grow in abundance, consuming much of the dissolved oxygen during their growth and putrefaction. In addition, they bring in an abundance of organic matter (sludge).
Eutrophication affects water quality. The increase in putrefying organic matter, together with the reduction of dissolved oxygen, causes a strong odour in the water. This loss of water quality can cause many problems for both the economy of the area and the health of the people living there. It is for this reason that more and more countries are restricting phosphorus release limits.
In addition, the manufacture of phosphorus and its derivatives involves a high energy demand and a high emission of gases, which also has a negative impact on our planet.
Lack of phosphonates
The manufacture of phosphonates competes with many other industrial processes for its raw material, the phosphorus. As a result, there are large fluctuations in the price of these products. This has worsened with the arrival of Covid.
The post-pandemic situation we are experiencing has put the marketing of many products, phosphonates among them, in check. The lack of availability of both product and transport, together with the environmental impact mentioned above, have pushed many companies to redesign their formulations using an alternative to phosphonates.
An alternative to phosphonates
There are a number of dispersing and anti-scaling polymers designed to replace phosphonates in detergent formulations and for water treatment. Polymers with strong dispersing properties offering excellent control of particles fouling, suitable for moderate to severe water hardness conditions.
Higher dispersing power than phosphonates
Dispersing and anti-scaling polymers equal the ability of phosphonates to prevent precipitate formation, but greatly improve the ability to disperse them.
The following table compares the performance of dispersing and anti-scaling polymers with that of the main phosphonates: PBTC (2-Phosphonobutane-1,2,4, -tricarboxylic acid), ATMP (Amino Trimethylene Phosphonic Acid) and HEDP (Hydroxy Ethylidene Diphosphonic Acid).
The following graphs show the percentage of inhibition of calcium sulfate, kaolin clay and hydrated iron oxide for these phosphonates and for the dispersing and anti-scaling polymers. In all cases, the alternative to phosphonates performs better.
Dispersing and anti-scaling polymers: two in one
Phosphonates are powerful anti-scaling agents, but do not offer good dispersing properties. This is why they are usually accompanied in formulations by a dispersing polymer (e.g. polyacrylic acid or sodium polyacrylate). Dispersing and anti-scaling polymers, on the other hand, combine both properties at the same time, thus providing an alternative to phosphonates that does not require the addition of other polymers.
As can be seen in graph X, the properties of the inhibition of calcium carbonate of the dispersing and anti-scaling polymers are very similar to those of the combinations of PBTC phosphonate with polyacrylic acid (PAA) and with another copolymer.
An alternative to phosphonates with less environmental impact
In addition to all the arguments already made in terms of efficiency and performance, dispersing and anti-scaling polymers have a lower environmental impact than phosphonates. For example, they have been shown to release 10.8 times less phosphorus than PBTC.