As a key intermediate for a wide range of acid, direct, and reactive dyes used in wool and cotton textile dyeing, H-acid generates wastewater during the production of its crystallization mother liquor that is characterized by high color, strong acidity, high COD concentrations (up to 20–50 g/L), and significant biological toxicity. Due to the presence of large amounts of structurally stable naphthalene-based organic compounds and supersaturated sodium sulfate, conventional oxidation and biological treatment processes are unable to achieve effective treatment or resource recovery. As global production capacity continues to shift toward China, the development of efficient, cost-effective, and environmentally friendly treatment technologies has become an urgent industry demand.

Among the various treatment routes for H-acid extraction equipment and processes, solvent extraction stands out due to its simple operation, controllable costs, and strong potential for resource recovery. In response to the specific characteristics of this wastewater, Zhengzhou Tiei Extraction Technology Co., Ltd. has developed an integrated “two-stage extraction, one-stage stripping” process centered on the CWL-M series centrifugal extractors.
In this process, two-stage cross-current extraction is first applied to efficiently transfer H-acid and other organic compounds from the wastewater into the extractant phase. This is followed by a single-stage stripping step to obtain a high-concentration organic solution for subsequent production of naphthalene-based superplasticizers, while simultaneously enabling recycling of the extractant. Finally, the raffinate aqueous phase is sent to downstream biological treatment, where it can stably meet discharge standards.

Compared with the limited adsorption efficiency of macroporous resins, the high costs of chemical oxidation, the substantial energy consumption of catalytic wet air oxidation, and the inhibitory effects of high-salinity conditions on activated sludge, the CWL-M centrifugal extractor—benefiting from its high mass-transfer efficiency and rapid phase separation capability—can stably perform mixing, separation, and stripping operations under continuous operation. This enables a significant reduction in operating costs while markedly improving organic compound recovery rates and overall system energy efficiency.

This process has been successfully implemented at multiple manufacturing enterprises, achieving not only compliant wastewater discharge but also generating substantial economic benefits through resource recovery. Zhengzhou Tiei Extraction Technology Co., Ltd. offers a complete solution—from process validation to turnkey equipment supply—helping enterprises achieve environmental compliance and their long-term sustainability objectives.
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