**2. Electrodialysis bipolar membrane: principles and definitions**

Industrial wastewater differs in industrial pollutant components depending on the types of industries in which they are formed. This difference plays a major role in the selection of wastewater treatment technologies.

Treatment technologies applied for wastewater recycling; Secondary Treatment (IA), Nutrient Removal, Filtration, Surface Filtration, Microfiltration (MF), Ultrafiltration (UF), Flotation, Nanofiltration (NF), Reverse Osmosis (TO), Electrodialysis (ED), Carbon Adsorption, Ion Exchange, Advanced Oxidation and Disinfection [1]. **Figure 1** shows the corresponding pore sizes of the pressureoperated membranes and their ability to hold specific wastewater components.

Membrane Processes (mainly reverse osmosis (RO) systems) and desalination plants are increasing day by day. In last two decades, over 10.000 membrane treatment plants have been established in most countries [3]. Daily treatment capacity of these plants may access 100 million m3/day in 2020.

With the introduction of low cost membrane modules in the 1960s and 1970s, membranes were widely used in industrial areas [4]. RO process (pore diameter < 0.0001 μm) can remove dissolved solids, bacteria, viruses and other microorganisms present in water [5]. By operating RO systems, which is one of the wastewater recycling processes, both high quality process water (filtrate flow) production is provided, and concentrate flow with high pollution load but low flow (silk) is formed. In RO systems with flow and concentrate modifications, approximately almost 90% filtrate and 10% concentrate can be formed from the inlet flow at high pressure [3].

The disposal of the concentrate from Membrane systems is still the main focus of most scientific research. This is an important issue for most country for the protection of water bodies and soil. As well known, discharged wastewater streams are still being used for irrigation. High salt content in concentrate streams means desertification of most valuable agricultural areas. The concentrate originating from membrane processes should be disposed or treated with feasible system.

Bipolar membranes are a type of ion-selective membranes first introduced in the 1950s (**Figure 2**). Bipolar membranes are composite membranes consisting of a Cation exchange membrane and an Anion exchange membrane [7]. Cation exchange membrane and anion exchange membranes, which are among ion exchange membranes, are heterogeneous, while bipolar membranes are homogeneous. Homogeneous bipolar membranes can be prepared from many different

**119**

lyte solution.

processes [7].

the functional groups or chemicals [7]:

*A New Approach for Membrane Process Concentrate Management: Electrodialysis Bipolar…*

materials. The properties of bipolar membranes formed from different materials are

Earlier studies on electrodialysis began before the World War II in Germany. Industrial and pilot scale applications have been developed since 1950. The first applications were about obtaining drinking water from sea water. Later, in applications in the food industry, it was tried to produce demineralized sugarcane sugar. If we consider the electrodialysis system as a black box, as a result of natural brine feeding, acid and base are formed at the output of the system, this picture is shown

Electrodialysis processes is one of the membrane process that the driving force is an electrical field. EDBM system consist of anionic, cationic and bipolar membranes [9]. EDBM systems are widely used in chemical industry, in food industry,

Using bipolar membranes together with ion exchange membranes in electrodialysis processes, high quality process water production can be possible and EDBM may become a more viable method for industrial wastewater treatment applications [10]. In the EDBM process, direct current (DC) is supplied to the electrodes to electrolyse the water molecules. Electrical potential between anode and cathode works as a driving force for the movement of electrons in electrolyte solution [8]. In EDBM process, bipolar membranes realizes the acid and base production in electro-

Organic acids such as lactic acid, ascorbic acid, salicylic acid, amino acid and inorganic acids such as hydrofluoric (HF) acid, sulfuric acid (H2SO4), hydrochloric acid (HCl) can be produced using EDBM systems. Alkali bases potassium hydroxide (KOH), Sodium Methoxide (CH3NaO) can also be produced in this systems [11].

In electrodialysis systems that separate water with bipolar membranes, an acid - base is formed from a very efficient energy-related salt concentration due to the accumulation of hundreds of cell units between 2 electrodes, such as conventional electrodialysis

Some catalytic reactions take place in electrodialysis systems using bipolar membranes. Reactions between water molecules and functional chemical groups occur as Eq. (1), (2), (3), (4) [12]. The catalytic mechanism is underlined by chemical reaction model of water dissociation, that is, the water splitting could be considered as some type of proton-transfer reaction between water molecules and

biochemistry industry and environmental protection technologies [9].

*DOI: http://dx.doi.org/10.5772/intechopen.93985*

given in the table below (**Table 1**).

*Water splitting function of a bipolar membrane [6].*

**Figure 2.**

in the picture below [8] (**Figure 3**).

#### **Figure 1.**

*Pressure operated membrane technology [2].*

*A New Approach for Membrane Process Concentrate Management: Electrodialysis Bipolar… DOI: http://dx.doi.org/10.5772/intechopen.93985*

#### **Figure 2.**

*Electrodialysis*

**2. Electrodialysis bipolar membrane: principles and definitions**

(IA), Nutrient Removal, Filtration, Surface Filtration, Microfiltration (MF), Ultrafiltration (UF), Flotation, Nanofiltration (NF), Reverse Osmosis (TO), Electrodialysis (ED), Carbon Adsorption, Ion Exchange, Advanced Oxidation and Disinfection [1]. **Figure 1** shows the corresponding pore sizes of the pressureoperated membranes and their ability to hold specific wastewater components. Membrane Processes (mainly reverse osmosis (RO) systems) and desalination plants are increasing day by day. In last two decades, over 10.000 membrane treatment plants have been established in most countries [3]. Daily treatment capacity of

With the introduction of low cost membrane modules in the 1960s and 1970s,

membranes were widely used in industrial areas [4]. RO process (pore diameter < 0.0001 μm) can remove dissolved solids, bacteria, viruses and other microorganisms present in water [5]. By operating RO systems, which is one of the wastewater recycling processes, both high quality process water (filtrate flow) production is provided, and concentrate flow with high pollution load but low flow (silk) is formed. In RO systems with flow and concentrate modifications, approximately almost 90% filtrate and 10% concentrate can be formed from the inlet flow at high pressure [3]. The disposal of the concentrate from Membrane systems is still the main focus of most scientific research. This is an important issue for most country for the protection of water bodies and soil. As well known, discharged wastewater streams are still being used for irrigation. High salt content in concentrate streams means desertification of most valuable agricultural areas. The concentrate originating from membrane processes should be disposed or treated with feasible system. Bipolar membranes are a type of ion-selective membranes first introduced in the 1950s (**Figure 2**). Bipolar membranes are composite membranes consisting of a Cation exchange membrane and an Anion exchange membrane [7]. Cation exchange membrane and anion exchange membranes, which are among ion exchange membranes, are heterogeneous, while bipolar membranes are homogeneous. Homogeneous bipolar membranes can be prepared from many different

in the selection of wastewater treatment technologies.

these plants may access 100 million m3/day in 2020.

Industrial wastewater differs in industrial pollutant components depending on the types of industries in which they are formed. This difference plays a major role

Treatment technologies applied for wastewater recycling; Secondary Treatment

**118**

**Figure 1.**

*Pressure operated membrane technology [2].*

*Water splitting function of a bipolar membrane [6].*

materials. The properties of bipolar membranes formed from different materials are given in the table below (**Table 1**).

Earlier studies on electrodialysis began before the World War II in Germany. Industrial and pilot scale applications have been developed since 1950. The first applications were about obtaining drinking water from sea water. Later, in applications in the food industry, it was tried to produce demineralized sugarcane sugar. If we consider the electrodialysis system as a black box, as a result of natural brine feeding, acid and base are formed at the output of the system, this picture is shown in the picture below [8] (**Figure 3**).

Electrodialysis processes is one of the membrane process that the driving force is an electrical field. EDBM system consist of anionic, cationic and bipolar membranes [9]. EDBM systems are widely used in chemical industry, in food industry, biochemistry industry and environmental protection technologies [9].

Using bipolar membranes together with ion exchange membranes in electrodialysis processes, high quality process water production can be possible and EDBM may become a more viable method for industrial wastewater treatment applications [10].

In the EDBM process, direct current (DC) is supplied to the electrodes to electrolyse the water molecules. Electrical potential between anode and cathode works as a driving force for the movement of electrons in electrolyte solution [8]. In EDBM process, bipolar membranes realizes the acid and base production in electrolyte solution.

Organic acids such as lactic acid, ascorbic acid, salicylic acid, amino acid and inorganic acids such as hydrofluoric (HF) acid, sulfuric acid (H2SO4), hydrochloric acid (HCl) can be produced using EDBM systems. Alkali bases potassium hydroxide (KOH), Sodium Methoxide (CH3NaO) can also be produced in this systems [11].

In electrodialysis systems that separate water with bipolar membranes, an acid - base is formed from a very efficient energy-related salt concentration due to the accumulation of hundreds of cell units between 2 electrodes, such as conventional electrodialysis processes [7].

Some catalytic reactions take place in electrodialysis systems using bipolar membranes. Reactions between water molecules and functional chemical groups occur as Eq. (1), (2), (3), (4) [12]. The catalytic mechanism is underlined by chemical reaction model of water dissociation, that is, the water splitting could be considered as some type of proton-transfer reaction between water molecules and the functional groups or chemicals [7]:


#### **Table 1.**

*Ion exchange polymers of bipolar membrane layers [8].*

$$\text{B} + \text{H}\_2\text{O} \leftrightarrow \text{BH}^\* \dots \text{OH}^- \leftrightarrow \text{BH}^\* + \text{OH}^- \tag{1}$$

$$\text{B} \text{H}^\* + \text{H}\_2\text{O} \leftrightarrow \text{B} \dots \text{H}\_3\text{O} \leftrightarrow \text{B} + \text{H}\_3\text{O} \tag{2}$$

$$\text{A}^- + \text{H}\_2\text{O} \leftrightarrow \text{AH} \dots \text{OH}^- \leftrightarrow \text{AH} + \text{OH}^- \tag{3}$$

$$\text{AH} + \text{H}\_2\text{O} \leftrightarrow \text{A}^- \dots \text{H}\_3\text{O}^\* \leftrightarrow \text{A}^- + \text{H}\_3\text{O} \tag{4}$$

**121**

**Figure 4.**

**Figure 3.**

**3. Usage areas of EDBM process**

*membrane; M +, cation; X- anion; H +, hydrogen ion; R, OH−*

The bipolar membrane electrodialysis process is used in the latest technological way as an integrated process for the supply of potable water and industrial salt water and recovery of industrial effluent. On the other hand, both in chemical processes and environmental protection processes, they have been successfully applying in recent years. Another field of use of bipolar membrane is the chemical industry, where new products such as H2SO4 and NaOH are produced from a salt such as Na2SO4. Indeed, this method has become widespread recently and is used successfully. Especially, the production of acid and base without producing

*Bipolar membrane and EDBM: BP, bipolar membrane; A, anion selective membrane; C, cation selective* 

*functions; (b) acid and base production; (c) acid production; (d) base production [12].*

 *or CH3O. (a) Bipolar membrane and its* 

*A New Approach for Membrane Process Concentrate Management: Electrodialysis Bipolar…*

*DOI: http://dx.doi.org/10.5772/intechopen.93985*

*Schematic illustration of EDBM process as a black-box [8].*

where BH<sup>+</sup> and A− refer to the catalytic centers. The catalytic sites provide an alternative path with low effective activation energy for water splitting into hydrogen and hydroxyl ions [7]. EDBM configurations including acid base production schematic diagrams are given in **Figure 4** [12].

*A New Approach for Membrane Process Concentrate Management: Electrodialysis Bipolar… DOI: http://dx.doi.org/10.5772/intechopen.93985*

#### **Figure 3.**

*Electrodialysis*

*Anion exchange layer*

Poly-vinylidene fluoride blend with poly-vinyl benzyl chloride

Poly-divinylbenzene-codimethylamino

Poly-methyl methacylate-coglycidyl

Grafted perfluorinated polymer

Poly-butadiene-co-styrene Sulfonic acid

Poly-sulfone Aminated

*Ion exchange polymers of bipolar membrane layers [8].*

propyl methacrylamide

*Cation exchange layer*

methacrylate

membranes

*Separate contact layer* Poly-vinyl amine

**Table 1.**

Poly-viylbenzylchrloride-codivinylbenzene resin

**Polymer(s)** İ**on exchange** 

Poly-styrene-co- divinylbenzene Tertiary and

**group**

Poly-sulfone Di-amines Crosslinked homogeneous

Poly-sulfone Quaternary amines Homogeneous

Anion exchange resin Not specified PVC binder Poly-ether sulfone Quaternary amines Homogeneous

quaternary amines

Quaternary amines

Poly-styrene-co- divinylbenzene Sulfonic acid Heterogeneous (polyvinylchloride

Sulfonic acid

Poly-styrene-co- divinylbenzene Phosphoric acid Poly-ethylene binder Nafion Sulfonic acid Homogeneous

Poly-phenylene oxide or poly-styrene Sulfonic acid Homogeneous Poly-ether sulfone Sulfonic acid Homogeneous Poly-sulfone Sulfonic acid Homogeneous Poly-ether ether ketone Sulfonic acid Homogeneous

Different diamines Crosslinked

**Remarks**

binder)

Sulfonic acid Heterogeneous (polyvinyl benzyl

chlorideco-styrene binder)

Crosslinked resin, heterogeneous

**120**

where BH<sup>+</sup>

and A−

schematic diagrams are given in **Figure 4** [12].

B H O BH OH BH OH <sup>2</sup>

BH H O B H O B H O 2 33

A H O AH OH AH OH <sup>2</sup>

AH H O A H O A H O 23 3

alternative path with low effective activation energy for water splitting into hydrogen and hydroxyl ions [7]. EDBM configurations including acid base production

+ − +− +↔…↔ + (1)

− −− + ↔… ↔ + (3)

− +− + ↔… ↔ + (4)

refer to the catalytic centers. The catalytic sites provide an

<sup>+</sup> + ↔… ↔ + (2)

*Schematic illustration of EDBM process as a black-box [8].*

#### **Figure 4.**

*Bipolar membrane and EDBM: BP, bipolar membrane; A, anion selective membrane; C, cation selective membrane; M +, cation; X- anion; H +, hydrogen ion; R, OH− or CH3O. (a) Bipolar membrane and its functions; (b) acid and base production; (c) acid production; (d) base production [12].*

#### **3. Usage areas of EDBM process**

The bipolar membrane electrodialysis process is used in the latest technological way as an integrated process for the supply of potable water and industrial salt water and recovery of industrial effluent. On the other hand, both in chemical processes and environmental protection processes, they have been successfully applying in recent years. Another field of use of bipolar membrane is the chemical industry, where new products such as H2SO4 and NaOH are produced from a salt such as Na2SO4. Indeed, this method has become widespread recently and is used successfully. Especially, the production of acid and base without producing

waste and the production of organic - inorganic acids increased the interest in this method. Many researchers have worked on this subject. It is possible to find many studies especially on acetic acid, propionic acid, gluconic acid, citric acid and lactic acid. In fact, some model studies have started to be carried out recently. Biotechnological research is ongoing to reduce costs in the electrodialysis process in order to reduce the cost in order to ensure acid recovery.

When ED and EDBM processes are compared with other treatment methods, it is an important advantage that it provides recovery from pollutants in wastewater and salt water. Studies show that it is possible to recover pollutants from solutions with one or more contaminants. In addition to this, the process of making acid and base production possible with EDBM process takes another step forward [13].
