pH值对工程废浆稳定、絮凝及固结特性的影响

在影响药剂真空预压法处理工程废弃泥浆效果的诸多因素中，pH值是其中最重要的因素之一。文中关于pH值对工程废弃泥浆稳定、絮凝和固结特性的影响进行了研究。首先探讨不同pH值时废浆中土颗粒Zeta电位的变化规律；然后研究泥浆不同pH时絮凝剂APAM的最佳添加量和不同pH值调节方式时废浆的絮凝效果；最后通过固结试验分析了在絮凝剂APAM添加量相同情况下不同pH值导致废浆的不同固结特性。研究结果表明：①土颗粒表面Zeta电位的绝对值随废浆pH值的增大而减小，颗粒粒径随pH值的减小呈增大趋势，特别是在酸性条件下，废浆中土颗粒更容易发生聚沉，小于0.01mm的土颗粒多变为0.01~0.02mm的土颗粒；②不同pH值的废浆在达到最佳絮凝状态时各条颗分曲线相差不大，但是APAM的最优添加量随着废浆的pH值变化而变化；③pH值的不同调节方式对废浆的絮凝效果有较大影响，相同pH值时，采用CaO调节方式得到的废浆絮体粒径要比采用NaOH调节方式得到的废浆絮体粒径要大；④固结试验表证明pH值接近中性泥浆絮体的固结系数最大，建议在药剂真空预压处理工程废弃泥浆时将pH值调节至中性。研究成果对药剂真空预压乃至压滤、离心法处理工程废弃泥浆实践均具有一定的实际指导意义。

Effects of pH value on stability,flocculation and consolidation characteristics of waste slurry

 pH value is one of the most important factors affecting the treatment effect  of the additive agent combined vacuum preloading method on the construction waste slurry. Hence, the effects of pH on stability, flocculation and consolidation characteristics of construction waste slurry were studied. First of all, the changing law of the Zeta electric potential of soil particles in the waste slurry for different pH values was studied; then, the optimal amount of the flocculation agent of APAM added into the slurry with different pH values and the flocculation effects of the waste slurry prepared by different methods of adjusting pH values were studied; finally, the consolidation characteristics of the waste slurry with different pH values were analyzed based on the consolidation tests. The results show that: (1) the absolute value of Zeta electric potential on the surface of soil particles increases as the pH value of waste slurry decreases, and the particle size increases with the decrease of the pH value. Especially when the pH value is less than 7, the soil particles are easy to be aggregated and soil particles whose particle sizes are less than 0.01mm may turn to soil particles whose particle sizes are between 0.01mm and 0.02mm; (2) the particle size distribution curves are almost the same when the waste slurry reaches the best flocculation state, although the pH value of slurry is different. The optimal additive amount of APAM varies with the pH values; (3) the method of preparing the slurry with a certain pH value has a great influence on the flocculation effect on the waste slurry. The flocs of waste slurry prepared using CaO are larger in particle size compared to those prepared using NaOH; (4) the consolidation test results show that the consolidation coefficient of slurry reaches the peak value when pH value is close to be neutral. It is suggested that the pH value be adjusted to be neutral before the waste slurry is treated by the additive agent combined vacuum preloading method. The research results have practical significance for the treatment methods such as the additive agent combined vacuum preloading method, the filter pressing technique and the centrifugal method.