Decolorization of Coloring Wastewater by Magnetic Separation
1. Formation of Magnetic Flocks of Dispersed Dyes by Magnetic Particles
Decolorization of a dye solution is carried out by forming magnetic flocks of dye aggregates. Photograph 1 shows that after the magnetic feeding of dispersed dye assisted by magnetic particles and coagulant, the suspension is isolated by a magnet.
Photograph 1. Magnetic Separation of Dispersed Dyes, (a): suspension of dispersed dyes, (b): magnetic separation after the magnetic feeding by a magnet.
Similarly, it is also possible to remove the color of acidic dyes by the magnetic separation procedure using cationic coagulants. Photograph 2 shows that a mixture of phthalocyanine dye and paper fiber is magnetically separated .
Photograph 2. Magnetic Feeding and Magnetic Separation for a Mixture of Phthalocyanine Dye and Paper.
2. Adsorption of Water-Soluble Dyes by Magnetic Activated Carbons (MACs)
MACs have high specific surface areas due to their microporous structure and a high adsorption ability for a variety of water-soluble substances. MACs modified with the dispersion of the magnetic particles can be easily pulled up by a magnet. It is effective to use MACs to remove the contaminants in solution by the magnetic force. Photograph 3 shows that MACs can easily adsorb the ionic dyes (Methylene Blue and Orange II) and can be collected by a magnet.
Photograph 3. Adsorption of Dyes (MB and Orange II) on MAC and Magnetic Separation.
Fig.1. Flow Chart for the Wastewater Treatment by MAC.
The system for wastewater treatment is constructed according to the flow chart as shown in Fig. 1. The colored wastewater from a dyeing factory are treated in an adsorption tank by MAC and followed by the magnetic separation. Contaminated MAC is refined in a recovering tank by an oxidizing agent such as hydrogen peroxide. Water from a magnetic separation tank is reused as recicling water.
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