搅拌条件对氢氧化镁混凝性能及絮体特性的影响

通过氯化镁在碱性条件下经搅拌生成氢氧化镁处理活性橙染料模拟配水，研究了搅拌条件对氢氧化镁混凝性能和絮体特性的影响。以絮凝指数FI与zeta电位为考察指标，对絮体形成机理进行了探讨，并对絮体形貌进行观察，旨在揭示絮体形成过程与絮凝效果的关系。结果表明，延长快速搅拌时间有利于絮体形成，以搅拌45s为最佳，再延长则会导致絮体被打碎，脱色处理效果变差；慢速搅拌时间以3min为最佳，过长也会导致絮体破碎。在最佳搅拌时间基础上发现搅拌速度也是影响混凝性能和絮体特性的主要因素。快搅或慢搅搅速过低，则不利于形成絮体或絮体增长；若搅速过高，形成的絮体会被打碎，这些都使得脱色处理效果变差。实验条件下，在Mg²⁺计投加量为150mg/L时，以转速250r/min或速度梯度G值126.3，快速搅拌45s，之后转速60r/min或G值18.5，慢速搅拌3min，氢氧化镁混凝性能最佳，可充分发挥其吸附、电性中和、卷扫与网捕作用，对活性橙染料配水的色度去除率达到95%以上。

Effects of mixing on magnesium hydroxide coagulation performance and floc properties

The effect of mixing conditions on the coagulation performance and floc properties of magnesium hydroxide was studied by the reaction of magnesium chloride in an alkaline condition and treatment of simulated reactive orange dyes wastewater. Based on the flocculation index(FI) and the zeta potential, the mechanism of floc formation was discussed, and the floc morphology was observed to reveal the relationship between floc formation process and coagulation performance. The results showed that the rapid mixing time is favorable for floc formation, and the optimum time is 45s. While longer rapid mixing time will result in floc broken and poor treatment effect. Similarly, the best slow mixing time is 3min. Prolong mixing time will lead to floc broken. Using the optimum mixing time, it was found that the mixing speed was also the main factor affecting the coagulation performance and floc properties. Lowering rapid and slow mixing speeds are not conducive to the formation and growth, respectively. However, higher mixing speed will make the floc broken and consequently reduce the treatment efficiency. When dosage of Mg²⁺ is 150mg/L under laboratory conditions, the optimum conditions for the coagulation performance of magnesium hydroxide were as follows:rapid mixing for 45s at 250r/min or G value of 126.3, followed by slow mixing for 3min at 60r/min or G value of 18.5. Coagulation mechanisms of adsorption, charge neutralization and precipitate enmeshment should be suitable for this process. The removal efficiency of reactive orange dye water is more than 95%.