In high-tech fields such as electronic manufacturing and semiconductor processing, etching technology is a crucial step in the production of core components like chips and circuit boards. However, the wastewater generated during the etching process contains high concentrations of heavy metals (such as copper, nickel, cadmium, etc.), acidic and alkaline substances, and trace amounts of organic matter. Direct discharge not only causes serious environmental pollution but also wastes strategic metal resources like copper and nickel. Although traditional treatment methods (such as chemical precipitation and ion exchange) can remove pollutants, they have disadvantages such as low resource recovery rate, easy to cause secondary pollution and high operating costs. Membrane chromatography technology, with its core advantages of self-separation, low energy consumption and high selectivity, is becoming the "green engine" for the resource utilization of electronic etching wastewater, converting the "pollutants" in the wastewater into high-value resources and promoting the transformation of the industry towards a circular economy model.

I. Principles of Membrane Chromatography Technology Concentration difference-driven "intelligent separation" membrane Dialysis (DD) is a membrane separation technology based on concentration difference-driven. Its core is to achieve the separation of solutes (metal ions, acid radical ions, etc.) and solvents (water) in the solution by taking advantage of the selective permeability of semi-permeable membranes (anion exchange membranes or cation exchange membranes) to ions.

• Working mechanism: High-concentration wastewater to be treated and low-concentration receiving liquid (or pure water) are respectively placed on both sides of the semi-permeable membrane. The concentration difference will drive ions in the wastewater (such as Cu²?, SO?²?) to spontaneously migrate towards the receiving liquid side, while water molecules move towards the wastewater side due to osmotic pressure. By regulating the selectivity and concentration gradient of the membrane, the target ions (heavy metals or acids) can be efficiently recovered.

• Technical advantages: Low energy consumption: No additional pressure or electric field is required. It is driven solely by the concentration difference, with energy consumption being only 1/10 of that of reverse osmosis technology. High selectivity: Specialized membrane materials such as polystyrene-based ion-exchange membranes have a high retention rate for specific ions like divalent metal ions, and the recovery purity can reach over 95%. Environmentally friendly: No chemical agents are added throughout the process, avoiding secondary pollution from the source and meeting the requirements of green manufacturing.

Ii. Heavy Metal Recovery: From "Wastewater" to "Metal Resource Pool"

The content of heavy metals such as copper and nickel in electronic etching wastewater can reach hundreds to thousands of mg/ L. Direct discharge not only pollutes the environment but also exacerbates the global shortage of metal resources. Membrane chromatography technology, through a "acid-metal" synergistic separation mechanism, achieves efficient recovery of heavy metals and recycling of acid solutions, thus becoming a key technology for developing "urban mines" in the electronics industry.

1. Acid recovery: Reduce production costs and minimize resource waste. Strong acids such as sulfuric acid and hydrochloric acid are commonly used in etching processes, and the acid concentration in wastewater can reach 1-5mol/L. Although the traditional lime neutralization method can remove acid, it will produce a large amount of sludge such as calcium sulfate, and the acid cannot be recovered. Membrane chromatography technology effectively separates acids from metal ions by selectively permeating acid radical ions such as SO?²? and Cl? through anion exchange membranes (AEM).

2. Metal ion separation: Enhance resource purity to meet high-end manufacturing demands. Electronic etching wastewater often contains various metal ions such as Cu²?, Ni²?, and Fe³?. Traditional chemical precipitation methods are difficult to precisely separate them, resulting in the purity of the recovered metals not meeting the standards. Membrane chromatography technology utilizes cation exchange membranes (CEM) to selectively retain divalent and above metal ions such as Cu²? and Ni²?, while allowing monovalent ions like Na? and K? to pass through, achieving the staged recovery of metal ions. Case: A certain circuit board factory adopted membrane chromatography technology to treat wastewater containing copper and nickel. The copper recovery rate reached 92%, the nickel recovery rate reached 88%, and the purity of the recovered metals exceeded 98%. After chemical precipitation, the concentrated liquid can be used to prepare high-value salts such as copper sulfate and nickel sulfate, which can be reused in electroplating processes, reducing the annual cost of metal salt procurement for enterprises by over 3 million yuan.

3. Acid-metal Synergistic Recovery: Building a Closed-loop resource utilization system Membrane dialysis can be coupled with electrolysis, membrane distillation and other technologies to create a "acid-metal" dual recovery closed-loop system. Process: Wastewater → Membrane evolution (acid recovery + metal concentration) → Electrolysis (preparation of high-purity metals) → membrane distillation (water recovery). Benefits: After a certain enterprise applied this system, the cost of wastewater treatment was reduced by 40%, the revenue from resource recovery covered 60% of the operating costs, and carbon emissions were reduced by 25%, making it a benchmark for the green transformation of the electronics industry.

Iii. Organic Matter Conversion: The Bridge from "Waste" to "Energy and High-Value Materials"

Although the content of organic matter (such as photoresist residue and developer additive) in electronic etching wastewater is low (usually < 500mg/L), it is highly toxic and difficult to degrade. Membrane chromatography technology can convert these organic substances into energy sources such as biogas or high-value-added products like bioplastics and carbon materials through two paths: "pre-concentration - biological conversion" or "pre-concentration - chemical conversion", achieving a closed-loop cycle of "waste - resources".

1. Pre-concentration: Enhance organic matter concentration and reduce subsequent treatment costs. Membrane chromatography can be combined with ultrafiltration (UF) and nanofiltration (NF) to first concentrate organic matter in wastewater through membrane modules, and then complete the conversion in combination with biological technologies such as anaerobic digestion or chemical technologies such as catalytic oxidation.

2. Acid-catalyzed conversion: The sulfuric acid and other acid solutions recovered by membrane precipitation from organic substances can be used as catalysts to promote the dehydration and carbonization reactions of organic substances such as developer additives, and to prepare high-value carbon materials such as carbon nanotubes and activated carbon.

Iv. Innovative Applications of Membrane Analysis Technology: Breakthroughs from Laboratory to Industrialization

Membrane material innovation: Enhancing separation efficiency and anti-pollution performance. Traditional polystyrene ion-exchange membranes have shortcomings such as being prone to contamination and having a short service life. New membrane materials (such as graphene-modified membranes and amphoteric ionic membranes) have significantly enhanced the anti-pollution ability and separation efficiency of membranes by introducing hydrophilic groups or constructing nanostructures.

2. Intelligent control system: Optimize operating parameters and reduce manual intervention. By integrating Internet of Things (IoT) and artificial intelligence (AI) technologies, it can monitor key parameters such as wastewater concentration, flow rate, and membrane pressure difference in real time, and automatically adjust system operating conditions such as the flow rate and temperature of the receiving liquid to maximize resource recovery efficiency. Membrane analysis - the "Green Symphony" of Resource Recovery Against the backdrop of the rapid development of the electronics industry, the resource utilization of etching wastewater is not only a hard requirement for environmental governance but also a strategic choice for the sustainable development of the industry. Membrane chromatography technology, with its core advantages of low energy consumption, high selectivity and environmental friendliness, converts heavy metals and organic matter in wastewater into high-value resources, promoting the electronics industry to leap from a "linear economy" to a "circular economy".

In the future, with the deep integration of membrane material innovation and intelligent control technology, membrane analysis technology will further break through the bottlenecks of efficiency and cost, providing a "Chinese solution" for the global resource crisis and environmental pollution problems, and writing a green legend of "turning waste into treasure".