氯化镁用于染料废水的脱色研究

COLOR REMOVAL FROM WASTEWATER CONTAINING DYE USING MAGNESIUM CHLORIDE

研究了MgCl_2处理若干种类的活性染料及分散染料的脱色效果,比较了MgCl_2/Ca(OH)_2、Al_2(SO_4)_3.PAC、FeSO_4/Ca(OH)_2的脱色效果。探讨了MgCl_2的脱色机理。实验结果表明,MgCl_2的脱色效果与染料种类、脱色的pH条件,脱色剂的用量有关;MgCl_2的脱色率随pH值升高而增加,对于活性染料废水,当pH=12.5左右时脱色率达最佳;对于分散染料废水,pH=12.0左右时脱色率达最佳;MgCl_2/Ca(OH)_2的脱色效果优于 PAC、Al_2(SO_4)_3、FeSO_4/Ca(OH)_2的脱色效果;MgCl_2的脱色机理为:(1)Mg^(2+)能与含有—OH,—SO_3H、—COOH基因的染料化合物起反应,生成稳定的螯合物,该螯合物在碱性条件下通过混凝作用从水中分离出来;(2)MgCl_2在高pH值下依靠水解生成的Mg(OH)_2胶体沉淀物对染料分子的吸附和卷扫沉降作用达到脱色目的。

The effectiveness of color removal of MgCl_2 used to treat waste water containing dye has been studied. The effeciency of decolorization of MgCl_2/Ca(OH)_2 has been compared with that of Al_2 (SO_4)_3, PAC, and FeSO_4/Ca(OH)_2. The mechanism of decolorization of MgCl_2 has also been investigated. The experimental results show that the effeciency of decol-orization of MgCl_2 relates to the type of dye structure and depends on the pH value of wastewater and amount of decolorant used. Treatment of wastewater containing reactive dye with MgCl_2 yielded an optimum color removal ratio when pH value of solution is equal to or above 12.5. MgCl_2 produced excellent decolorization effect for dispersed dye waste in ba-sic aqueous medium(pH≥12.0). For both the reactive and dispersed dye waste,MgCl_2/Ca (OH)_2 was shown to be superior to Al_2 (SO_4)_3, PAC, and FeSO_4/Ca(OH)_2 for removing color. The mechanism of color removal of MgCl_2 is that: (1) Magnesium ion reacts with hy-droxy, Carboxy or Sulfonic acid group of dye compound to form stable chelate. complex, the chelate complex can be removed from the wastewater by flocculation in basic aqueous medi-um; (2) the dye particles would sorb onto the surface of the MgCl_2, a gelatinous precipitate,to produce good color removal result.