Plant Construction & Process Technology

New Challenges in Chemical Purification

Ion Exchange Resins Lead the Way to Comply with High EU Standards

07.05.2015 -

Purification of chemical compounds has become a vital part of most industrial processes. Germany, with some of the tightest chemical sector regulations in Europe, has seen ion exchange (IX) resins become the leading methodology to remove trace contaminants because of how the resins selectively, efficiently and flexibly conduct their mission. Dow Water & Process Solutions has developed a special portfolio of ion exchange resin products that purify compounds in a broad range of industrial applications including the production of biodiesel, caustic soda or lactose.

Since ancient times, people have purified chemical compounds to improve quality of life. The first attempts to filter water as a means to purify it were made by Hippocrates to treat his patients in the fourth century B.C. During the industrial revolution, purification started assuming a major role and, as a result, over the years, related regulation has intensified.

In this sense, in Germany, wastewater is treated following the highest EU purification standards. In 2006, the Registration, Evaluation and Authorization of Chemicals (REACh) regulation established a database in which any company manufacturing, marketing, importing or using chemical substances must be registered. Also in the international sphere, companies producing organic chemicals must provide a complete accounting of their production activities as a result of the Chemical Weapons Convention Treaty signed in 1993. In addition, Germany approved its own Law of Chemicals in 1980, which obligates companies to register their chemical compounds in a database that explains the substances and their properties.

It is clear, therefore, that tailored solutions are needed to adapt to a complex regulatory environment. Dow Water & Process Solutions, a leading filtration, purification and separation technology supplier, understands the challenge of achieving the appropriate chemical purity for each application and offers a wide range of advanced resin solutions to businesses, consumers, industries and municipalities around the world.

Ion Exchange Resins

Ion exchange resins are particularly well-suited to purification requirements. They act as "chemical sponges," removing more than 99% of trace contaminants with an ultratight hold. They also have a very high exchange capacity, which allows them to treat effectively many thousands of volumes of water before they need to be replaced. An exceptional selectivity for trace contaminants makes ion exchange the most cost-effective technology to eliminate these naturally occurring and synthetic pollutants.

On the one hand, IX resins are able to remove trace contaminants selectively by matching contaminant with resin for a lock-and-key fit. On the other, they are incorporated in modular tanks, enabling an installation to be easily expanded. In this sense, Dow Water & Process Solutions works side by side with companies to design the purification system that best meets their specific needs.

As a result, ion exchange resins are widely spread in the basic chemicals and petrochemicals industries as an economic and effective method to separate and purify a large number of different compounds or process streams. Moreover, in some cases, IX is the only technology available that can produce the desired levels of purity.

Products for Which Purification is Vital

Purification treatment based on ion exchange resins is essential to obtain some of the basic products needed both in industrial applications and everyday life. Biodiesel, for instance, is well-known for being used in most injection pump diesel engines but also, depending on the source of the fatty acids, to significantly dissolve crude oil in industrial processes.

Base catalyzed trans-esterification is the preferred method to produce the crude biodiesel needed for the manufacture of biodiesel fuels. However, crude biodiesel must be purified to remove the salts, soaps and residual glycerol. Amberlite BD10Dry is the easiest and most cost-effective product for a successful solution.

However, it is important to note that this technology is designed to be used in a water-free process and that the polymer beads will swell to up to three times their original volume as they absorb water. It is strongly recommended, therefore, to leave sufficient void space in the columns.

Another substance that has to pass a purification process is sodium hydroxide, also known as caustic soda. Although it is widely used in many industries - more than half of all global production has an industrial use - it is common to find chloride contaminating sodium hydroxide when low-chloride caustic soda is required. To solve this problem, the Dowex Retardion 11A8 has been developed as a unique amphoteric ion exchange resin. It features cation and anion exchange moieties in the same bead, being capable of reducing the chloride content of concentrated caustic soda. After the process, regeneration is achieved by applying only hot and deionized water.

Lactose, one of the best-known products for its use in the food and beverage and pharmaceutical industries, is treated through a combination of methods. First, lactose can be isolated from whey proteins using ultrafiltration. Then it can be purified through combinations of nanofiltration, ion exchange and chromatographic enrichment.

Some of the most successful products for lactose demineralization are the resins Amberlite FPC16 Na and Amberlite FPA42 Cl. While the latter is a strong base anion resin offering a high yield solution, the former is a gel cation resin with high osmotic stability. Completing the pair is Amberlite FPA55, an acrylic weak base anion resin with an excellent physical stability. Finally, Dowex Monosphere 99K/310 is a chromatographic separation resin designed especially for sweetener applications and purification of polyols in food and beverage applications.

One of the big advantages that the aforementioned products offer is their efficiency. IX processes often concentrate the contaminant so effectively that the loaded resin represents the smallest possible volume of waste, which means that, in some applications, they can be regenerated and used for years.

At the same time, to achieve the highest possible performance, Dowex ion exchange resins - backed by more than 60 years of IX manufacturing expertise - have been engineered to be the toughest beads on the market.

All these developments have a meeting point in Germany, where Dow Water & Process Solutions has several of its facilities. The biggest plant is in Stade, Lower Saxony, at the Elbe River between Hamburg and the North Sea. In recent years it has become renowned for developing the best wastewater solutions for industrial and residential purposes, among other application areas.