Effects of calcium oxide on the surface properties of industrial sludge by analyzing rheological and electrical properties

Rheological properties in the dynamic regime and complex conductivity measurements were performed on the wastewater sample containing different calcium oxide content. The complex viscosity (η*), the elastic (G’) and loss moduli (G’’) exhibited a linear behavior as a function of angular frequency. These rheological properties were well described by a power-law. Therefore; The values of G’0, G’’0 and η0 corresponding to angular frequency (ω = 1 rad/s) were extracted. Their evolution as a function of calcium oxide content showed that there is a critical amount of calcium oxide content (3 %), from which these parameters showed a net transition indicating the existence of two regions. Similar behavior has been observed from the analysis of the complex conductivity. The hopping conductivity, the ionic strength and the associated relaxation time showed also a net transition at (3 %). A conductivity relaxation behavior was observed in the high frequency and a more detailed analysis of such behavior is reported. This behavior was attributed to the localized relaxation process due to the short-range hopping motion of ions trapped inside the aggregations. The evolutions of the rheological and the electrical properties were analyzed by an equation including two power laws. This equation was able to fit very well their evolution as well to predict the optimal amount of calcium oxide (3 %) needed to achieve the coagulation process.