Flocculation of clayed waste water

摘要

Anionic A 120, nonionic N 100, cationic C 460 and C 581 flocculants, as well as Al_2(SO_4)_3 coagulant, were used in purifying clayed waste water. The pH dispersion was 7.8, with 25.93 kg/m~3 of solids (clays and quartz). 54percent of solid particles had less than 10 #mu#m in diameter. The settling rate without any flocculant was 0.4 m/hr. Effectiveness of the used flocculants was: A 120 N 100 C460. In the presence of 100 g/t A 120, the settling rate was about 25 m/hr, the supernatant was colourless and had transmission of 98percent. The best flocculation result can be explained by the adsorption of anionic flocculant A 120 on AlOH~+_2 or SiOH~+_2 surface sites and by the electrostatic interaction on Al-O~(partial deriv-) -H~(partial deriv+) or Si -O~(partial deriv-) -H~(partial deriv+) centres, bridging two or more dispergated particles. A combination of flocculants, C 581 (40g/t) and A 120 (100 g/t), gave a similar settling rate, but shorter time of sedimentation (3 minutes). C 581 cations are adsorbed on negative particle surface sites (AlO~- or SiO~-), giving more positive surface centres for adsorption of anionic A 120 flocculant.