科研之友
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摘要
Effects of floc aging and pH adjustment on the particle composition and coagulation of the reflux water were investigated using laser particle size analyzer, and the mechanisms of aging and pH adjustment on floc properties were explored by the aging experiments of Al(OH)3 gel (Al-gel). The results showed that the particle size of raw water displayed a unimodal distribution, and the particle size of the influent flocs presented a bimodal distribution. Meanwhile, there was a decrease of the particle d50 of reflux water with the increase of aging time. The growth rate of the flocs increased as the reflux flocs that were subjected to reflux coagulation after being aged at pH=5 for 12h had the highest floc d50 growth rate (1.16μm/s) and produced the flocs with a higher fractal dimension (2.35). The results of Al-gel aging experiment demonstrated that hydroxyl-bridging and crystallization reactions occurred during aging, leading to a reduction in the number of reactive groups on the floc surfaces, which was not conducive to the interaction with raw water particles. The pH adjustment had different effects on the flocs. For example, the aging at pH=5accelerated the hydroxyl-bridging and crystallization reactions, while the aging at pH=9 may involve dissolution-precipitation-crystallization interactions.
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