engleski

The effect of 818A and 827N flocculant on the seawater magnesia process

Possibilities of application of the anionic 818A flocculant (polyacrilamide) by the Dutch firm Hercules were studied in order to increase the settling rate of magnesium hydroxide from seawater and to define the optimum conditions during the precipitation process. The efficiency of the 818A flocculant has been compared to the nonionic 827N flocculant. Examinations were carried out with different degrees of completeness of precipitation and with different quantities of the 818A flocculant. The dependence obtained were described by appropriate analytical expression. The study had shoved that the settling rate is higher at nonstechiometric precipitation, i.e. precipitation when quantity added is lower than the stoichiometrically required quantity of the precipitation agent. This has been explained by the Mg(OH)_2 particle model. In order to interpret the experimental data obtained by batch-settling tests a calculation of a continuous thickener was made applying the Kynch theory. It was observed that at 100 percentage precipitation the quantity of the precipitate obtained was 23.05 kgh^-^1, while that obtained at 80 percentage precipitatiuon was 52.69 kgh^-^1, which indicates a considerable increas in the thickener productive capacity. Thus, it could be seen that the settling rate of magnesium hydroxide slurry was very important in computing the thickening area required.

magnesium hydroxide from seawater; settling rate; nonstoichiometric precipitation; effect of flocculant

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