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The physical treatment methods of dye intermediates wastewater include coagulation sedimentation method, adsorption method, air flotation method, electrodialysis method, crystallization separation method, rectification method, ion exchange method, extraction method, etc. Some of the more commonly used methods are briefly described below:
The coagulation sedimentation method has developed rapidly in recent years and is one of the main methods for the purification of dye wastewater. For dye wastewater with complex composition, it is first homogenized and precipitated, and then neutralized by adding an appropriate amount of acid or alkali, and then adding a coagulant to flocculate and precipitate.
The coagulation and precipitation method of dye intermediates is mainly used for the decolorization of dye wastewater, and the treatment effect of naphthalene dyes is good, but that of anthraquinone dyes is poor. The treatment effect of coagulation and precipitation of dye intermediate wastewater depends on the selection and dosage of coagulants and coagulants, the pH value of wastewater, and the hydraulic conditions of coagulation. The removal rate of chroma by this method is about 70%~90%, and the removal rate of CODCr is about 50%~80%.
Adsorption method can remove color, odor, heavy metal ions and organic matter in water. Due to the difference in adsorption capacity of adsorbents for different types, that is, adsorbents have selectivity. Therefore, dye intermediate wastewater is treated by adsorption method, and the choice of adsorbent is a key factor affecting the treatment effect. The most commonly used adsorbent is activated carbon.
The extraction method of dye intermediate wastewater is to use the difference in the solubility of organic matter in water and organic solvent, select a suitable solvent, and mix with water, so that the organic matter is rapidly transferred from water to the solvent phase, and then the two phases are separated. The phase is processed, while the solvent phase contains the dye.
Crystallization is to control the physical conditions, so that dyes or salts are crystallized and separated from water, so as to achieve the purpose of removing pollutants in water. This method eliminates the need for additional chemicals to be added to the water. The acid waste liquid in the production process of J acid is treated by freezing separation method, and the waste liquid is frozen to -10~-20℃, so that Na2SO4 in the waste liquid is crystallized, and then filtered to remove. After the filtrate is heated and concentrated, it is returned to the original production process for use.
The air flotation method is that after the wastewater is coagulated, the pollutants in the water are floated by adding air. Depending on the nature of the wastewater, different air flotation methods are used.
Dye wastewater mainly composed of hydrophobic dyes, reduction, and ice dyeing generally adopts the pressure dissolved air flotation method; the wastewater contains hydrophilic substances, salt substances, substances to be separated in ionized form, or benzene rings. Aniline compounds with substituent groups, other air flotation water purification technologies have better effects, and these air flotation technologies include electrolytic condensation air flotation, ion air flotation, adsorption air flotation, etc.
