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Novasep Ion Exchange Technologies

Ion Exchange Technologies

Novasep is a world leader in the food, bio and chemical industries for batch and continuous ion exchange processes.

Our ion exchange applications in the life sciences markets are constantly growing since ion exchange is a very versatile tool to solve a large number of purification problems.

Novasep actively participates in the development of new continuous ion exchange technologies, and processes combining ion exchange technology with other technologies, such as membrane filtration, in order to offer optimized answers to the market’s needs.

Basic Ion Exchange Techniques

Decalcification
Salt conversion
Decationation
Deacification
Demineralization

Selection
Decolorization
Separation
Catalysis
Enzyme mobilization

Definition of ion exchange in the glossary.

Ion Exchange Resins

Ion exchange resins consist of a polymeric matrix and a functional group with a mobile ion which can be exchanged with other ions present in the solution to be treated. The most common synthetic structures are:

Cross-linked polystyrene
Cross-linked polymethacrylate
Phenol-formaldehyde


Strong acid cationic resin polystyrenic type	Strong base anionic resin polyacrylic type

The polystyrene type is the most commonly used. The functional group determines whether the ion exchange resin is a cationic type or an anionic type. Although an infinite quantity of functional groups can be attached to the polymeric matrix, the most commonly used in the industry are:

Active group	Structure	Type of resin
Sulfonic	R-SO₃ H	Strong acid cation (SAC)
Carboxylic	R-COOH	Weak acid cation (WAC)
Ammonium	R-N (CH₃)₃ Cl - R-N (CH₃)₃ OH Cl- R-N (CH₃)₂	Strong base anion (SBA) type I Strong base anion (SBA) type II Weak base anion (WBA)
Chelating	R-SH R-CH₂ N(CH2 COOH)₂ R-CH₂ NHCH₂ CH₂ PO₃ H	Chelating resins

Ion exchange resins are most often available in a moist bead form (granular or powdered forms are sometimes used and a dry form is also available for applications in solvent media) with a particle size distribution typically ranging from 0.3 – 1.2 mm (16 – 50 mesh) with a gel or macroporous structure. Nowadays, ion exchange resins with a uniform particle size distribution are available resulting in optimum industrial operations.

Ion Exchange Reactions

Salt conversion: The most typical application is softening or decalcification.

2R-Na + Ca²⁺ -> 2R-Ca + 2 Na+

Organic acids can be also converted into their salts by passing them through a cationic resin in the appropriate form. We can also mention the Quentin process where potassium and sodium ions are exchanged against magnesium in order to minimize sugar loss in the final molasses.

Demineralization
The use of a cationic exchanger in hydrogen form followed by an anionic exchanger in hydroxyl form removes all ionic species present in a feed solution. The following figure illustrates a simple pass deashing process.

The mechanism can be illustrated as follows

Production cycle:
- On the cationic side
R-SO₃ H + NaCl -> RSO₃Na + HCl
2 R-SO₃H + CaCl2 -> (R-SO₃)₂Ca + 2 HCl
- On the anionic side
SBA type R-N(CH₃)₃OH + HCl -> R-N(CH₃)₃Cl + H2O
WBA type R-N(CH₃)₂ + HCl -> R-N+H(CH₃)₂ Cl-+H+
Regeneration cycle: The reverse reaction takes place by passing an acid (HCl or H₂SO₄ ) on the cationic resin and an alkaline solution (NaOH, NH₄OH) on the anionic resin.

Deacidification:
An acidic feed solution can be passed through a weak or strong base resin in OH- form, all or only strong acids will be removed. Fruit juices can be debitterred on a weak base resin.

Catalysis:
Ion exchange resins can be used for acid or alkaline catalysis, a sucrose solution can be hydrolized into glucose and fructose by passing them through a cationic resin in hydrogen form. Another application is the possibility to immobilize some enzymes (glucoisomerase, lipase, lactase, amylase,...) on resin matrix in order to carry out an enzymatic conversion.

Recovery and concentration:
Valuable or toxic substances can be recovered from various solutions, i.e. the nickel used for the hydrogenation of polyols can be recovered on a WAC resin. Metals from the plating or mining industries can be removed with ion exchange or chelating resins.

Example of the removal of a metal with a chelating resin

The availability of numerous types of ion exchange resins allows their combination in various designs and applications.
Novasep has developed a unique expertise in designing ion exchange systems with co- or counter-current operations, upflow process, simple or double pass, continuous operations...

Applexion® Continuous Ion Exchange Processes

A typical ion exchange resin process includes several steps such as:

production,
backwashing,
regenerant injection,
regenerant displacement,
fast rinse,
eventually sweetening off and sweetening on,
stand-by.

Each of these sequences - except production - are time consuming and affect plant productivity. Therefore the food and pharmaceutical industries have been looking for better cost performance designs.

Continuous processes have always been a request from the industry anticipating smooth operations, intermediate storage reduction and constant quality of the product and effluents.

An ion exchange resin process can be qualified as continuous when all individual steps are carried out at the same time.
In batch operations, while one column is in production the second one is in regeneration. This implies that the production time has to be equal to the time spent for all the regeneration sequences.

According to the inlet feed salinity, we can end up with several options:

when inlet salinity is on the low side, the production time is longer than the regeneration time. This results eventually in stand-by periods.
in contrast, when the inlet salinity is on the high side, the regeneration time is much longer. Therefore, in order to ensure a smooth operation, the flow is slowed down during production to equilibrate both durations.

In order to achieve a continuous production, the first attempts consisted of a large intermediate storage tank (the tank capacity representing the regeneration sequences) or in two lines operating in parallel.

Later on, a "true" continuous system was developed through an arrangement consisting of several small discrete rotating columns. Another approach consisted in moving the resin beds in a loop design divided into 4 zones (production, rinsing, regeneration, rinsing).

Most of these early systems, although providing some real advantages, did not have a great industrial success. Physically moving the resin beds resulted in attrition losses. The operation mode was quite complicated.

In order to achieve a continuous process, we can either move the columns or the resins. However both technologies present some drawbacks (either mechanical concerns or resin lifetime issues). In the Applexion® continuous IEX process, our continuous ion exchange process derived from the SMB (Simulated Moving Bed) technology, only the inlets and outlets are shifting.

Novasep Ion Exchange Systems & Products

Novasep has developed numerous ion exchange systems and products for the life science industries.

We continuously test, pilot and develop new grades of resins in order to propose state-of-the-art technologies.

We have gained an outstanding expertise in selecting the most appropriate and best performing resin types available from the market.

Discover our list of ion exchange resins, available for numerous applications and designs.

Benefits & Advantages of Applexion® Continuous Ion Exchange Technology

The main advantages of such a design are:

continuous flow (feed, water, effluents),
savings on equipment,
lower resin inventory,
savings on regenerant and water consumption,
flexibility (adding cells or on-line maintenance).

Applexion® continuous IEX process offers the industry a truly continuous ion exchange or adsorption system by using multi-cell columns equipped with multi-port valves. Depending on the process, the number of cells in each of the zones can be adapted to optimize resin utilization and minimize system size and overall capital investment and operating costs.

Discontinuous process

Continuous process diagram (cationic columns)

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