Effect of kaolin on floc properties for reactive orange removal in continuous coagulation process

Magnesium hydroxide was used as a coagulant for treating reactive orange wastewater in a real continuous process. Effects of kaolin on coagulation performance and floc properties were investigated with controlled experiments through floc size distribution, zeta potential, scanning electron microscopy and Fourier transform infrared spectroscopy. Kaolin had significant influence on magnesium hydroxide-reactive orange floc formation and growth. The results showed that average floc size reached 16.31, 12.88 and 20.50 μm, respectively, in the rapid mixer, flocculation basin and sedimentation tank when kaolin concentration was 10 mg/L and reactive orange initial concentration was 0.25 g/L. The floc size tended to increase with the increase of kaolin suspension to 10 mg/L. All of the flocs under investigation showed that floc breakage led to decreased average floc size and remained stable in the flocculation basin. Reactive orange and kaolin could be removed effectively in the continuous coagulation process. Reactive orange was adsorbed in the surface of magnesium hydroxide through charge neutralization and adsorption.

Formation, breakage and re-formation of flocs formed by cationic starch

The efficiency of flocculation can be significantly improved through floc breakage and re-formation under appropriate conditions. To obtain a better understanding of the mechanisms involved and to relate floc properties to separation efficiency, the effects of mixing conditions on the formation, breakage and re-formation of flocs formed by kaolin and cationic starch were investigated through conventional jar test procedure and continuous optical monitoring. It has been found that the breakage of flocs was fully reversible and the polymer flocculant could resist strong shear; even having been sheared for four times, the flocculation index (FI) value would be higher than that of the original flocs. The results indicated flocs formed at neutral and alkaline conditions had better shear resistance than those at acidification conditions, and the mode of floc rupture was large-scale fragmentation.

A Research on the Morphology and Composition of Flocs (Part 1: Floc Breaage Disregarded)

The characteristics of flocs aggregated in flocculation have been paid more and more attention for a long time. In this paper, a new classification and analyses method dealing with the flocs is developed. The flocs formed after flocculation is divided into four kinds, including the left primary particles, linear flocs with all component particles in a line, planar flocs with all component particles on a plane and volumetric flocs with all component particles in a three-dimensional space. By analyzing the formation approaches of different kind of flocs regardless of the floc breakage, the number of every kind of floc is analyzed to be related with the suspension concentration mathematically. After comparing the different items in the models describing the relationship of floc number and concentration, a series of simplified expressions are presented. Lastly, a mathematical equation relating the measurable suspension viscosity with the numbers of different flocs is obtained.