Membrane evolution technology: Green Innovation and Practical Breakthrough in Copper Smelting Processes

In the copper smelting industry, the disposal of electrolytic lean liquid and resource recycling are the core bottlenecks for sustainable development. The traditional lime neutralization method not only leads to the waste of acid and copper resources but also causes environmental pollution. However, the membrane analysis technology based on concentration gradient has become the key to solving this problem and promoting the industry to steadily move towards "zero emissions".

I. Technical Principle: Molecular-level separation innovation dominated by concentration Difference

Membrane chromatography technology utilizes the selective permeability of ion-exchange membranes to achieve the directional migration of solutes. The core logic is as follows: 1. Membrane material properties: The anion membrane is positively charged, allowing anions such as SO₄²⁻ and Cl⁻ to pass through. Channels with a valence of 0.1-0.5nm can block metal ions with a valence of more than two, such as Fe²⁺ and Cu²⁺. The cation membrane is negatively charged, allowing only cations such as H⁺ and Na⁺ to pass through while retaining anions and organic substances. 2. Concentration difference driving force: The raw liquid chamber containing waste acid and the recovery chamber filled with pure water are separated by a membrane. Under the effect of a concentration difference of 5% to 25%, SO₄²⁻ and Cl⁻ diffuse to the lower concentration side, while OH⁻ in the recovery chamber migrates in the opposite direction to the raw liquid chamber to combine with H⁺ to form water, achieving efficient separation of acid and metal ions. 3. Multi-level series design: For the system where sulfuric acid and hydrochloric acid coexist in the waste liquid, a three-stage series membrane stack of "anion membrane + cation membrane + anion membrane" is adopted to successively complete the recovery of sulfuric acid, hydrochloric acid and copper ion interception. The recovery rate of sulfuric acid reaches 85%, the recovery rate of hydrochloric acid is 80%, and the interception rate of copper ions is no less than 95%.

Ii. Core Application Scenarios: Resource utilization treatment of copper smelting waste liquid

1. Copper removal and acid recovery from electrolytic lean solution: The electrolytic lean solution contains 45g/L copper ions, 20% sulfuric acid, and various impurity ions. Membrane chromatography technology achieves precise separation through anion membranes: - Acid recovery: SO₄²⁻ passes through the anion membrane into the recovery chamber driven by the concentration difference, and H⁺ migrate synchronously. The final recovered acid concentration reaches 16.5%, with a recovery rate of 82%. - Copper retention: Due to the large hydration radius of 0.74nm, copper ions are intercepted by the anion membrane, reducing the copper ion concentration in the residual liquid to 4g/L, with a retention rate of 91%.

2. Leachate acidity control and impurity removal: During the copper leaching process, leachates with a pH value less than 1 can cause flocculation of the extractant, affecting the copper recovery efficiency. Membrane chromatography technology separates sulfuric acid from impurities through anion membranes: - Acid recovery and utilization: The recovered dilute acid (containing 1g/L of copper and 130g/L of sulfuric acid) can be directly reused as a stripping agent after being replenished with 40g/L of acid, avoiding abnormal reduction in the pH of the leachate. - Iron impurity removal: The concentration of sulfuric acid in the residual liquid is reduced to 40g/ L. Iron ions are precipitated through hydrolysis and discharged with the slag, with a retention rate of 90%.

3. Resource utilization of waste acid from flue gas treatment: The waste liquid from the washing of smelting flue gas contains 15%-20% sulfuric acid, 2%-3% copper ions, and impurities such as zinc and arsenic. The membrane analysis technology combined with the chemical precipitation method is used for synergistic treatment: - Acid recovery: Through the series connection of five-stage membrane stacks, the sulfuric acid recovery rate is 80%, and the purity of the recovered acid is no less than 80%. - Heavy metal retention: The copper ion retention rate is ≥95%, and the copper ion concentration in the residual liquid is reduced to below 5mg/L, meeting the discharge standards. - Cost reduction and pollution control: After the residual liquid from dialysis enters the neutralization system, the alkali consumption is reduced by 50% and the sludge production is decreased by 60%.

Iii. Direction of Technological Breakthroughs and Process Optimization

1. Membrane material innovation and upgrading - Lead-resistant membrane research and development: In response to lead impurities in waste liquid, modified anion membranes are developed to address the issue of reduced membrane flux caused by lead ion deposition, extending the membrane's lifespan to 3-5 years. - High-throughput membrane design: Polyphenylene ether-based anion membranes are adopted, and through the benzene ring bromination and amination cross-linking process, the membrane selectivity is increased to 99.5%, the anti-pollution performance is enhanced by 30%, and the annual depreciation cost is reduced to 50,000 yuan per set.

2. Iterative optimization of the process mode

Modular system development: We have launched small mobile membrane analysis systems with a processing capacity of 10-20m³/d and large fixed membrane analysis systems with a processing capacity of 100-500m³/d. The cost per ton of water treatment has been reduced to 6-8 yuan, which is much lower than the 12-15 yuan of traditional methods. - Integrated process construction: By integrating membrane chromatography with electrodeposition and crystallization technologies, a complete chain of "recycling - purification - reuse" is formed. Some enterprises have increased the concentration of recovered acid to over 40% and controlled the lead impurity content below 0.1g/L through this process.

3. Intelligent control empowerment

Integrating the Internet of Things and AI algorithms, it can monitor key parameters such as the voltage, flow rate and temperature of the membrane stack in real time and automatically adjust the operating conditions. By predicting the trend of membrane fouling through machine learning models and initiating the backwashing program in advance, the system downtime was reduced by 50% and the operational stability was improved to 95%.

Iv. Strategic Value and Industry Impact

The application of membrane analysis technology in the treatment of copper smelting waste liquid not only helps enterprises meet environmental protection compliance requirements but also creates significant economic value through resource utilization: - Cost savings: For every ton of waste acid treated, 0.8 tons of sulfuric acid and 0.05 tons of copper can be recovered, saving the enterprise over 7 million yuan in costs annually. - Carbon reduction achievements: Compared with traditional evaporation methods, the carbon emissions per ton of water treatment are reduced by 65%, providing strong support for enterprises to achieve their carbon neutrality goals. - Industrial upgrading drive: Promote the transformation of the copper smelting industry from "end-of-pipe treatment" to "resource recycling", and enhance global market competitiveness. Membrane chromatography technology, with its microscopic advantage of "concentration differentiation-driven", is reshaping the industry landscape of copper smelting waste liquid treatment. From the separation of polyacid systems to the deep interception of metal ions, from process optimization to digital empowerment, this green technology has become the core driving force for the high-quality development of China's copper smelting industry. In the future, with the deep integration of materials science, digital technology and process integration, membrane evolution technology will be promoted and applied in more fields, providing a Chinese solution for the green development of the copper smelting industry.