水体中Cr(Ⅵ)对不同混凝剂混凝过程的影响

Effect of Cr(Ⅵ) on Coagulation Process of Different Coagulants

研究了工业废水中Cr(Ⅵ)在不同颗粒物浓度影响下对不同铝形态混凝剂的影响过程,通过考察浊度去除率以及出水余铝、余铬浓度甄别了混凝效率,并利用混凝过程中剩余p H值、Zeta电位以及絮体性质揭示水中Cr(Ⅵ)在不同浊度下的混凝机制.结果表明,在低浊度条件下,Cr(Ⅵ)对高聚合态Alb的混凝过程具有较大影响,而对低聚合态Ala无明显影响;在高浊度条件下,水中浊度较高时颗粒物会吸附部分Cr(Ⅵ)从而降低其与Alb之间的作用.Alb在混凝中主要发挥电中和作用,其对颗粒的脱稳和絮体的再生具有重要的作用,Ala水解形成的部分Alc在混凝中主要发挥架桥网捕作用,其对絮体的生产和强度因子具有重要作用.同时Cr(Ⅵ)的存在会增强Al13絮体的强度因子,但其消耗了部分正电荷会导致絮体恢复因子降低.

In this study, the effect of Cr（Ⅵ） in industrial wastewater on the coagulation of different aluminum forms under the influence of different particle concentrations was investigated. The coagulation efficiency was determined by examining the removal rate of turbidity, residual aluminum, and residual chromium and by using the residual pH value, zeta potential, and floc properties of the coagulation to reveal the coagulation mechanism of Cr（ Ⅵ ） in water under different turbidities. The experimental resuhs show that under low turbidity conditions, Cr（ Ⅵ ） greatly influences the coagulation process of highly polymerized A1b , yet has no obvious effect on oligomeric A1a. Under high turbidity conditions, particulate matter will adsorb part of the Cr（VI） in high turbidity water, thus reducing its interaction with A1b. The main role A1b plays in coagulation is charge neutralization. It plays the same role in the stability of the particles and floc regeneration. The main role of A1c formed by hydrolysis of A1 is bridging effects and sweep flocculation, which plays an important role in floc production and strength factor. At the same time, the existence of Cr（VI） enhances the strength factor of Al13 flocs, but the consumption of some of the positive charge will lead to a reduction in the floc recovery factor.