NIRE Annual Report		1998

Objectives

The magnetic solid flocculants (MSF) are produced in order to separate fine particles in suspension without changing liquid property. The MSF is made up by fine magnetite particles covered with cation or anion polyelectrolyte, and has high zeta potential (+ or -) in wide pH range. Fine particles in suspension are flocculated by the zeta potential of the MSF and the flocks are recovered by magnetic force (show in Fig.1). The cationic MSF is produced and the surface charge property of the MSF is investigated.

Results

1) Durability of zeta potential.

Fig.2 shows the zeta potential durability of the MSF by using 4 kinds of polyelectrolytes with different molecular weight (shown in Table 1). A, B and C of polyelectrolytes which are higher molecular weight keep high zeta potentials after several water washings. This result means that these MSF can be used repeatedly.

2) Applicable pH range.

Fig.3 shows the zeta potential of the MSF made by polyelectrolyte C. The pH range of the MSF indicating over 10mV is expanded to pH9.4. This MSF is useful as a cationic flocculants in the wide pH range from 2 to 9.4 without adding surfactants and pH regulators. In the flocculation tests of quartz suspension, quartz particles of -10m are flocculated and recovered quickly. Then, the pH of the suspension changes to 2.5, and only the MSF can be recovered from the flocks easily.

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