As a vital pillar of the global economy, the textile industry is expanding at a rapid pace. Chemical fibers, as the core raw material of this industry, have already accounted for more than 70% of the world's total fiber output. However, behind the glamorous industrial scale, the industrial wastewater generated in the chemical fiber production process has become an "ecological bottleneck" restricting the sustainable development of the industry - this type of wastewater is complex in composition, has a high content of toxic and harmful substances, and is extremely difficult to biodegrade. It has long been a "tough nut to crack" in the field of industrial wastewater treatment. Traditional treatment approaches, whether it is the "simple interception" of physical adsorption, the "neutralization with chemicals" of chemical precipitation, or the "microbial decomposition" of biological degradation, although they can reduce the concentration of pollutants to a certain extent, generally have prominent problems such as high energy consumption, high risk of secondary pollution, and low resource recovery and utilization rate. Against this backdrop, bipolar membrane electrodialysis technology, with its three core characteristics of "clean separation, resource recycling, and efficient conversion", offers a disruptive solution for the treatment of chemical fiber wastewater, ranging from "end-of-pipe treatment" to "source control". This article will deeply interpret the breakthrough significance of bipolar membrane technology in the clean treatment of chemical fiber wastewater from three major sections: the logic of technological innovation, core application value, and future development trends.
I. Technological Innovation: "Precise Ion Separation + In-situ Acid-Base Regeneration Driven by Electric Field
Bipolar Membrane (BPM), as an innovative special ion-exchange membrane, is composed of three layers: the cation exchange layer (CEL), the anion exchange layer (AEL), and the intermediate catalytic layer (CL). The core innovation lies in the fact that "water dissociation and ion directional migration can be achieved without external reagents." Under the action of a direct current electric field, the intermediate catalytic layer will catalyze the dissociation reaction of water molecules, generating hydrogen ions (H?) and hydroxide ions (OH?). Driven by the electric field force, these two ions migrate directionally towards the cathode and anode respectively - this process not only achieves the precise separation of cations and anions in the chemical fiber wastewater, but also can simultaneously "in-situ regenerate" acids and bases Lay the foundation for subsequent resource recycling and advanced processing.

Taking the wastewater from polyester (PET) production, which has the largest output in the chemical fiber industry, as an example, its main pollutants include terephthalic acid (TPA), ethylene glycol (EG), and sodium sulfate (Na?SO?), etc. The bipolar membrane electrodialysis system achieves clean treatment through a "three-step method"
Water dissociation initiation: The electric field triggers the dissociation of water molecules in the intermediate catalytic layer of the bipolar membrane, generating H? and OH?. The reaction formula is: H?O\(\xrightarrow{electric field}\)H?+OH?;
Ion directional migration: H? penetrates the cation exchange layer and moves towards the cathode, combining with anions such as SO?²? and TPA? in the wastewater. OH? moves towards the anode through the anion exchange layer and reacts with cations such as Na? in the wastewater.
Acid-base regeneration + resource separation: High-purity sulfuric acid (H?SO?) and terephthalic acid (TPA) are generated on the cathode side, with reaction formulas of 2H?+SO?²?→H?SO? and H?+TPA?→TPA, respectively. Sodium hydroxide (NaOH) is generated on the anode side, with the reaction formula being OH?+Na?→NaOH. Meanwhile, the neutral organic compound ethylene glycol (EG) is retained in a dedicated compartment, achieving efficient separation from acids and bases.
Through the design of multi-compartment membrane stacks, this system can effectively prevent side reactions from occurring, and the regenerated acids and bases can be directly reused in the production of chemical fibers (for example, TPA is reused in the polyester polymerization reaction, and NaOH is used in the fiber alkali washing process), thus establishing a closed-loop system of "wastewater treatment - resource regeneration - production reuse".
Ii. Core Values: Three Breakthroughs to Break the Traditional Governance Deadlock
1. No chemical additives: Cut off the secondary pollution chain from the source
The traditional treatment of chemical fiber wastewater requires a large amount of chemical reagents such as acids, alkalis and flocculants, which not only increases the cost of raw material procurement and transportation, but also generates sludge and waste residue containing heavy metals and refractory organic matter, forming a vicious cycle of "treating pollution but creating new pollution". Bipolar membrane technology completely breaks this predicament: it only relies on electrical energy to drive the dissociation of water molecules, without the need to add any chemical reagents throughout the process, eliminating the risk of secondary pollution from the root. Take the treatment of polyester wastewater as an example. The traditional process requires purchasing concentrated sulfuric acid from outside to adjust the pH value, which not only poses transportation safety risks but also generates a large amount of waste acid and waste liquid. Bipolar membrane technology can generate sulfuric acid in situ, which not only saves the cost of purchasing and storing chemical reagents but also avoids the environmental pressure caused by the discharge of waste acid.
2. High-value resource utilization: Transforming "Wastewater" into "raw material warehouse"
The substances such as terephthalic acid (TPA), ethylene glycol (EG), and sodium sulfate (Na?SO?) contained in the chemical fiber wastewater are not "pollutants" that cannot be utilized, but rather "potential raw materials" with high recycling value. Due to insufficient separation accuracy, traditional treatment methods often directly discharge it or incinerate it at low value, resulting in serious waste of resources. Bipolar membrane technology achieves high-value resource recovery through precise ion separation and purification.
Terephthalic acid (TPA) : The recycled purity can reach over 99%, and it can be directly used as the core raw material for polyester synthesis, reducing the raw material procurement costs for enterprises.
Ethylene glycol (EG) : After being purified by nanofiltration or distillation, it can be reused in polymerization reactions, forming a raw material cycle.
Sodium hydroxide (NaOH) : The regenerated alkali solution can be directly used in the alkali washing and degumming processes of chemical fiber production, reducing the consumption of fresh alkali solution.
Data shows that the comprehensive resource recovery rate of bipolar membrane technology exceeds 90%, significantly reducing the overall cost of wastewater treatment and achieving a win-win situation of "environmental governance" and "economic benefits".
3. Strong adaptability: "Flexible treatment solutions" for complex water quality
The composition of chemical fiber wastewater fluctuates greatly and there are many types of pollutants (coexistence of organic acids, alcohols, esters, salts, etc.). Traditional biological treatment methods are limited by the tolerance of microorganisms and are difficult to adapt to the fluctuations in water quality. Chemical treatment methods require frequent adjustments to process parameters and have poor processing flexibility. Bipolar membrane technology demonstrates extremely strong adaptability thanks to the selective permeability of the membrane and its modular design.
Outstanding resistance to shock loads: The multi-stage series membrane stack structure can be flexibly adjusted according to changes in water quality, easily coping with fluctuations in wastewater concentration.
Leading separation efficiency: The retention rates for both cations and anions exceed 99%, effectively removing conductive ions from wastewater, reducing conductivity, and ensuring that the treated wastewater meets production reuse standards.
Low operating cost: It can operate stably under normal temperature and pressure without the need for high-temperature and high-pressure equipment. Equipment maintenance is simple, and energy consumption is only 50% to 70% of that of traditional processes.
Iii. Future Trends: Mutual Empowerment through Technological Iteration and Industrial Integration
Membrane material upgrade: Breaking through the dual bottlenecks of "stability" and "cost"
The current large-scale application of bipolar membrane technology is mainly constrained by the stability of membrane materials and production costs. In the future, innovation in membrane materials will focus on three major directions:
Anti-pollution modification: Through techniques such as surface hydrophilic group grafting and anti-pollution coating coverage, the adsorption and deposition of organic substances on the membrane surface are reduced, thereby extending the membrane's service life.
Low energy consumption optimization: By using nano-catalysts to optimize the structure of the catalytic layer, the overpotential of water molecule dissociation is reduced, and the operating voltage is lowered to below 2V, achieving an energy-saving breakthrough of over 30%.
High selectivity research and development: Develop dedicated bipolar membranes for specific pollutants (such as TPA?, SO?²?) to further enhance the purity of resource recovery.
2. Process Integration: Building a "Full-process Closed-loop Governance System"
Bipolar membrane technology does not exist in isolation. In the future, it will be deeply coupled with various processing technologies to form a full-process solution
Combined with nanofiltration technology: By pre-concentrating the target pollutants in the wastewater through nanofiltration, the treatment efficiency and resource recovery rate of the bipolar membrane system can be enhanced.
Combined with electrochemical oxidation: Deeply oxidize the separated neutral organic substances (such as refractory small molecules) to achieve zero discharge of wastewater;
Coupling with crystallization process: By linking the regenerated acid solution with the crystallization unit, high-purity sodium sulfate crystals can be prepared, expanding the application scenarios of resource recovery (such as the glass and papermaking industries).
3. Policy and Market: The "Explosion of Essential Demand Market" under the Green Transformation
With the increasingly strict global environmental protection policies (such as the mandatory implementation of China's "Discharge Standard of Water Pollutants for Textile Dyeing and Finishing Industry" GB 4287-2012), chemical fiber enterprises are facing the environmental protection pressure of "production suspension upon non-compliance". Bipolar membrane technology, with its core advantages of "cleanliness, efficiency and resource utilization", has become a key choice for enterprises to meet environmental protection requirements. Meanwhile, under the impetus of the "dual carbon" goals, its low energy consumption feature can help enterprises reduce carbon emissions and enhance market competitiveness. In the future, with the continuous decline in the cost of membrane materials and the improvement of technological maturity, bipolar membrane technology will gradually replace traditional treatment processes and become the mainstream solution for treating chemical fiber wastewater, promoting the textile industry to move towards a high-quality development stage of "clean production and resource recycling".
Bipolar membrane electrodialysis technology, with "water separation" at its core, has broken the passive model of traditional wastewater treatment of "polluting first and then treating" through technological innovation, achieving a fundamental transformation from "pollutant removal" to "resource recycling". Its core characteristics of "no chemical additives, high-value recycling, and low energy consumption operation" precisely align with the global trend of industrial green transformation, providing solid technical support for the chemical fiber industry to break through environmental protection predicaments and achieve sustainable development. In the future, with the in-depth advancement of technological iteration and industrial integration, bipolar membrane technology will be expanded and applied in more industrial wastewater treatment fields, leading a green revolution related to ecological protection and industrial upgrading.