Turning Waste Salt into Industrial Raw Material

Driven by the dual pressures of the "dual carbon" goals and strict environmental policies, "zero discharge" of industrial wastewater and the harmless, resource-oriented disposal of waste salt have become key bottlenecks constraining the green transformation of conventional industries. Based on industry pain points, and relying on deep membrane technology accumulation and rich engineering practice experience, Jiuwu Hi-Tech has built an efficient, stable and economically significant comprehensive solution for waste salt disposal and utilization. This solution breaks the limitations of conventional end-of-pipe treatment, and through a full-process closed-loop design combining multiple technologies, converts industrial waste salt into high value-added industrial raw materials, successfully solving the challenge of industrial waste salt disposal and helping enterprises fully move toward a new stage of green, circular and low-carbon development.

PART 01 Core Technical Architecture: Three Key Modules Build an Efficient Disposal System

Jiuwu Hi-Tech's waste salt disposal and utilization technology takes "source reduction, process purification, terminal resource utilization" as its core concept, deeply integrating advanced technical means such as physical, chemical and membrane separation, and forming three interconnected technical modules: "organic matter reduction", "salt purification and concentration" and "resource utilization".

Organic matter reduction: deep pre-treatment and purification

Organic matter in waste salt and high-salinity wastewater is the primary obstacle to its resource utilization. If organic matter is not effectively removed, it not only leads to poor crystal appearance and reduced purity of the subsequently crystallized salt, but also causes severe fouling of membrane modules. Jiuwu Hi-Tech flexibly combines three reduction technologies according to the organic characteristics of different waste salts:

Incineration technology: Suitable for thorough destruction of organic matter in waste salt with high concentration, poor biodegradability and relatively high calorific value; high-temperature incineration oxidizes and decomposes organic matter, achieving harmlessness.

Advanced oxidation processes (AOPs): Using strongly oxidizing free radicals, it efficiently breaks the chemical bonds of macromolecular organic matter, degrading it into small molecules or directly mineralizing it into water and carbon dioxide, significantly reducing COD.

Membrane purification technology: Special organic membranes and/or ceramic membranes clarify and purify the waste salt solution, precisely intercepting macromolecular organic matter and suspended solids, ensuring brine clarity and stable operation of subsequent processes.

Salt purification and concentration: precise salt separation and efficient reduction

Different salts differ greatly in crystallization characteristics and economic value; how to efficiently separate and concentrate mixed salts is the core of resource utilization.

High-concentration brine nanofiltration salt separation technology: Relying on the selective rejection differences of special nanofiltration membranes for monovalent salts (such as sodium chloride) and divalent salts (such as sodium sulfate), it achieves efficient separation of monovalent and divalent salts, greatly improving the purity of subsequent single-salt crystallization.

MVR / freeze crystallization technology: Combining mechanical vapor recompression (MVR) evaporation technology with freeze crystallization technology, it precisely controls crystallization conditions according to the solubility characteristics of different salts with temperature, precipitating salts with low energy consumption.

Electrodialysis membrane concentration technology: Using electrodialysis to deeply concentrate dilute brine under an electric field, further increasing brine concentration and reducing the energy consumption and equipment investment of the evaporation system.

Resource utilization: turning waste into treasure and circular regeneration

The purified brine and solid salt are no longer a heavy environmental burden, but valuable resources that can re-enter the industrial production cycle.

Industrial alkali feedstock application technology: The refined high-purity sodium chloride or sodium sulfate brine can directly meet the feed standards of the industrial alkali industry (chlor-alkali industry and soda ash industry), replacing natural raw salt for electrolytic alkali production or salt dissolving production.

Bipolar membrane acid-base preparation technology: Using bipolar membrane electrodialysis technology, salts (such as NaCl, Na₂SO₄) are directly dissociated and converted into high value-added acids (hydrochloric acid, sulfuric acid) and alkalis (sodium hydroxide) under an electric field, achieving in-situ conversion of "salt to acid/alkali".

Direct industrial-grade reuse: The crystallized solid salt can reach industrial-grade standards (such as industrial-grade anhydrous sodium sulfate) and be sold directly as commercial salt, or reused in upstream printing and dyeing, papermaking and other production stages.

PART 02 Complete Process Route: From Mixed Salt to High-Value Products

Jiuwu Hi-Tech's waste salt disposal and utilization system has formed a standardized process evolution path, ensuring that industrial waste salt achieves maximum value enhancement at every stage.

Main process chain

Mixed salt (solid mixed salt / high-salinity concentrate)

→ Salt dissolving (prepared into a uniform solution)

→ Refining pre-treatment (impurity removal, decolorization, organic matter reduction)

→ Nanofiltration salt separation (NaCl / Na₂SO₄ separation)

→ Diversified resource utilization (crystallization, decomposition, reuse)

The collected industrial solid mixed salt or high-salinity concentrate first enters the salt dissolving system to be prepared into a uniform solution; after impurity removal, decolorization and organic matter reduction, it enters the nanofiltration salt separation system to achieve efficient separation of different salt components such as sodium sulfate and sodium chloride; it is then diverted to three downstream deep-processing routes according to the target product.

Route 1: Crystallization route

The separated sodium sulfate-enriched liquid enters the evaporation / freeze crystallization system and is purified into high-purity anhydrous sodium sulfate, meeting industrial-grade standards for the chemical, detergent and other industries.

Route 2: Decomposition route

The purified high-purity brine enters the bipolar membrane decomposition system and is split under an electric field into high-purity acid products (such as hydrochloric acid and sulfuric acid) and alkali products (such as sodium hydroxide), which can be directly reused in the factory's own production stages or neutralization system, greatly reducing the enterprise's acid and alkali procurement costs.

Route 3: Refining and reuse route

The deeply refined brine does not need crystallization and can be delivered directly to downstream production lines as feed liquid for direct recycling, eliminating crystallization energy consumption with excellent economics.

PART 03 Industry Applications and Demonstration Cases

Jiuwu Hi-Tech's waste salt disposal and utilization technology has been successfully applied in printing and dyeing, mine water, chemicals, papermaking, industrial salt purification and other key fields.

Demonstration case

High-salinity wastewater and waste salt resource recovery zero-discharge project at a large chemical industrial park

Project background

The chemical industrial park hosts numerous enterprises, and the industrial wastewater generated has extremely complex composition, with not only very high salinity (mainly sodium chloride and sodium sulfate) but also high organic concentration and high toxicity. The park's original wastewater treatment system could not effectively handle the crystallized mixed salt, resulting in tens of thousands of tons of industrial waste mixed salt per year, classified as hazardous waste, severely constraining the park's sustainable development and expansion plans.

Solution

Jiuwu Hi-Tech customized a comprehensive disposal solution of "pre-treatment organic matter reduction + nanofiltration salt separation + MVR + bipolar membrane acid-base production" for the park:

Deep organic pre-treatment: A combined process of "advanced oxidation + ceramic membrane" deeply degrades and filters organic matter in the waste salt solution, providing high-quality feed water for the subsequent membrane and crystallization systems.

Efficient salt separation and crystallization: A highly selective nanofiltration membrane system precisely separates sodium sulfate from sodium chloride. The sodium sulfate-enriched liquid enters the MVR / freeze crystallization system to produce high-quality anhydrous sodium sulfate; the sodium chloride-enriched liquid is further concentrated.

Bipolar membrane resource conversion to acid and alkali: The concentrated high-purity sodium chloride solution is fed into a bipolar membrane electrodialysis unit and directly converted into hydrochloric acid and sodium hydroxide solutions meeting industrial reuse standards, all returned to production lines of chemical enterprises in the park.

Jiuwu Hi-Tech's waste salt disposal and utilization technology is not only an environmental treatment solution, but also an efficient resource recycling system. By deeply integrating the three core technologies of organic matter reduction, salt purification and concentration, and resource utilization, Jiuwu Hi-Tech successfully helps industrial enterprises convert the heavy burden of waste salt into a value-rich "second resource". In the future, the company will continue to rely on strong R&D innovation capabilities and rich engineering implementation experience, continuously promoting the application expansion of membrane technology in the industrial environmental protection field, and injecting inexhaustible momentum into the green transformation and high-quality circular development of China's industry.