H-acid (1-amino-8-naphthol-3,6-disulfonic acid) is a key intermediate in the production of acid dyes, direct dyes, and reactive dyes for wool and cotton textile dyeing. However, the wastewater generated during the crystallization mother liquor production stage has long been a critical challenge restricting the development of the dye intermediates industry.

This type of wastewater exhibits the typical characteristics:
1.High Concentration – COD levels usually reach 20–50 g/L, with extremely high color intensity.
2.High Acidity – pH value is typically around 2.
3.High Salinity – containing large amounts of inorganic salts such as sodium sulfate and ammonium sulfate.
4.High Biological Toxicity – carrying large quantities of structurally stable naphthalene-based organic compounds that are highly resistant to natural degradation.

Traditional treatment processes have proven inadequate:
The adsorption efficiency of macroporous resins is limited; chemical oxidation methods are costly and often result in secondary pollution residues; catalytic wet oxidation requires enormous energy consumption; and the high-salinity environment directly inhibits the biochemical activity of activated sludge, significantly reducing treatment efficiency.

Technological Breakthrough: The “Two Extraction, One Stripping” Process with Centrifugal Extractors

Backed by years of technical expertise, Zhengzhou Tiei Extraction has developed an integrated “Two Extraction, One Stripping” process centered on the CWL-M Series Centrifugal Extractor. Based on the principle of complexation extraction, this process fully leverages the centrifugal extractor’s core advantages of high-speed mixing and rapid phase separation, transforming H-acid wastewater from a high-cost burden into a resource recovery platform capable of generating economic value.

1.pH Adjustment and Extractant Preparation
The H-acid wastewater is first precisely adjusted to the optimal pH range to maximize extraction efficiency. At the same time, a high-performance extractant specifically designed for H-acid mother liquor is prepared, typically formulated with an optimized ratio of tertiary amine solvents, diluents, and co-solvents.

2.Two-Stage Cross-Current Extraction (“Two Extraction”)
The conditioned wastewater and extractant are fed into the CWL-M Series Centrifugal Extractor at an optimized ratio.
Inside the unit, the high-speed rotating drum generates strong centrifugal force, enabling rapid mixing and highly efficient mass transfer between the wastewater and extractant. During this process, naphthalene sulfonic organic compounds are transferred from the aqueous phase into the organic extractant phase. After the first extraction stage, the wastewater enters a second cross-current extraction stage to further improve organic removal efficiency.
Experimental data indicate that, following two-stage cross-current extraction, the COD value of the wastewater can be reduced from tens of thousands of mg/L to below 1,000 mg/L; the H-acid content drops to less than 0.1%, and the wastewater becomes nearly colorless.

3.One-Stage Stripping (“One Stripping”)
The organic phase loaded with extracted compounds then enters the stripping stage, where it comes into full contact with an alkaline solution (such as 10% NaOH solution) inside the centrifugal extractor. The organic compounds are transferred from the extractant phase into the stripping solution. The resulting high-concentration stripping liquor can then be evaporated and concentrated in subsequent processing steps to produce naphthalene-based water-reducing agents, which are widely used as concrete admixtures, achieving true waste-to-value conversion. Meanwhile, the extractant is regenerated and recycled back into the extraction stage, with a recycling efficiency exceeding 99%.

Through this process, high-value organic compounds in H-acid wastewater are efficiently recovered. The treated raffinate (aqueous phase) contains only trace levels of organics and can be smoothly transferred to the biological treatment stage for further processing.

Equipment Advantages: The CWL-M Series Centrifugal Extractor Tailored for the Industry

The outstanding performance of the CWL-M Series Centrifugal Extractor in H-acid wastewater treatment stems from a technical architecture that differs fundamentally from traditional extraction equipment, as well as the results of continuous engineering optimization. As a leading manufacturer of centrifugal extraction equipment, Zhengzhou Tiei Extraction has developed comprehensive technical customization specifically for the extreme operating conditions of dye intermediate wastewater treatment.

1.Corrosion-Resistant Design for Harsh Acidic and High-Salinity Conditions
H-acid wastewater typically has a pH as low as 0.5 and a salt concentration of up to 14%, placing extremely stringent demands on equipment corrosion resistance.
The critical components of the CWL-M Series Centrifugal Extractor are manufactured from special alloys or high-performance composite materials, enabling long-term operation under severe acidic and high-salinity chemical corrosion. This significantly extends service life while reducing replacement and maintenance costs.

2.High-Efficiency Mass Transfer and Rapid Phase Separation, Significantly Reduced Processing Time
Compared with traditional mixer settlers that require residence times of tens of minutes, the CWL-M centrifugal extractor utilizes a high-speed centrifugal force field to achieve complete mixing and phase separation within just a few seconds.Under the same processing capacity, the equipment features an extremely short residence time and processing efficiency far exceeding that of traditional equipment, while also significantly reducing the required footprint.

3.Ultra-Low Power Consumption for Reduced Operating Costs
Energy consumption is a major cost challenge in industrial wastewater treatment. The CWL-M centrifugal extractor has been systematically optimized for low power operation. For example, the CWL650-M centrifugal extractor consumes only 4 kW during actual operation. Compared with traditional annular centrifugal extractors, the CWL-M centrifugal extractor requires only 10%–30% of the power consumption. In industrial applications treating hundreds of thousands of tons of wastewater annually, this translates into substantial electricity cost savings.

4.Fully Enclosed Continuous Operation for Safety and Environmental Compliance
The complete system supports fully enclosed continuous operation, minimizing extractant volatilization and virtually eliminating solvent emissions and odor issues on-site. At the same time, the equipment supports precise automated control, reducing dependence on manual supervision and minimizing human operational errors, while ensuring the stable and reliable quality of the treated effluent.

5.Minimal Extractant Loss for a Low-Cost Recycling System
Thanks to its superior separation performance, the centrifugal extractor effectively minimizes extractant entrainment losses during phase separation. When integrated with an efficient solvent recovery system, the extractant can be recycled for long-term reuse, dramatically reducing reagent consumption per ton of treated wastewater. This establishes a truly controllable and economically sustainable low-cost wastewater treatment model.

Solvent extraction technology with the CWL centrifugal extractor at its core, relying on its five major advantages of high efficiency, low energy consumption, space saving, environmental protection, and recyclability, is becoming the preferred choice for H-acid wastewater pretreatment. Combined with subsequent processes such as MVR mechanical vapor recompression evaporation and advanced biological treatment, centrifugal extraction pretreatment provides a solid technical foundation for the full-process closed-loop resource recovery treatment of H-acid wastewater.

Zhengzhou Tiei Extraction Technology Co., Ltd., an advanced manufacturer of centrifugal extraction equipment, can provide full-process solutions ranging from process verification, laboratory-scale testing, pilot-scale validation, complete industrial equipment supply, to long-term operation and maintenance technical support, helping H-acid production-related enterprises achieve both environmental compliance and economic benefits at the lowest overall cost. Welcome contact us and inject new technological power into your H-acid wastewater treatment!
Email: sales@tieiextraction.com
Whatsapp: +86 19069612820