Print Email Facebook Twitter Flocculation of clay suspensions by anionic and cationic polyelectrolytes Title Flocculation of clay suspensions by anionic and cationic polyelectrolytes: A systematic analysis Author Shakeel, A. (TU Delft Rivers, Ports, Waterways and Dredging Engineering; University of Engineering & Technology Lahore) Safar, Z. (TU Delft Environmental Fluid Mechanics) Ibanez Sanz, M.E. (TU Delft Environmental Fluid Mechanics) van Paassen, L.A. (Arizona State University) Chassagne, C. (TU Delft Environmental Fluid Mechanics) Date 2020 Abstract The characteristics of clayey suspensions, majorly composed of quartz microparticles, in the presence of anionic and cationic polyelectrolytes were investigated using different techniques. A wide range of clay concentrations was used, i.e., from 0.07 to 1000 g/L for different experimental techniques, based on the fact that the clay concentration possible to analyze with selected experimental methods was significantly different. The optimum flocculant to clay ratio was defined as the ratio that gives the fastest initial floc growth by static light scattering or fastest initial settling velocity by settling column experiments. In case of anionic polyelectrolyte, it was observed that the optimum flocculant dose depends on the amount of cations present in the system. For suspensions made with demi-water, a lower optimum flocculant dose (<1 mg/g) than for suspensions prepared in tap water (2.28 mg/g) was observed. At these lower salinities, the supernatant remained turbid in all the experiments and was, therefore, not a good measure for optimal anionic based flocculation. The equilibrium floc size at a given shear rate was found to be independent on the shear history of the floc and only dependent on the current applied shear. This was confirmed by both light scattering and rheological analysis. In case of cationic polyelectrolyte, the optimum flocculant ratio (5–6 mg/g) corresponded to the ratio that gives the lowest electrophoretic mobility for each clay concentration and to the ratio that gives the fastest settling velocity for the highest clay concentrations (12–15 g/L), where static light scattering measurements were not possible. All investigation techniques, therefore, proved to be good indicators for predicting the optimum flocculant to clay ratio. For the lowest concentrations (1.75–8.7 g/L) studied by settling column measurements, the optimum flocculant ratio was observed to increase with decreasing clay concentration, for fixed mixing conditions. The optimum flocculant to clay ratio was not always corresponding to the clearest supernatant and the size of flocs at optimum dosage was dependent on the mixing efficiency. The equilibrium floc size at a given shear rate was found to be dependent on the shear history of the floc and the current applied shear. This was confirmed by both light scattering and rheological analysis. Subject Anionic and cationic polyelectrolytesClayElectrophoresisParticle size distributionRheologySettling rate To reference this document use: http://resolver.tudelft.nl/uuid:2361c207-c197-4ec8-8aa1-923dbe46a7f8 DOI https://doi.org/10.3390/min10110999 ISSN 2075-163X Source Minerals - Open Access Mining & Mineral Processing Journal, 10 (11), 1-24 Part of collection Institutional Repository Document type journal article Rights © 2020 A. Shakeel, Z. Safar, M.E. Ibanez Sanz, L.A. van Paassen, C. Chassagne Files PDF minerals_10_00999_v2.pdf 6.08 MB Close viewer /islandora/object/uuid:2361c207-c197-4ec8-8aa1-923dbe46a7f8/datastream/OBJ/view