Abstract
"Magnetic solid flocculant" (MSF) is a new type flocculant with high magnetic intensity and high positive charge which is useful for the flocculation of fine particles in suspension. The MSF prepared by adsorbing cationic polyelectrolytes to the surface of magnetite particles have abilities to capture fine particles by electrostatic force in a wide pH range and to recover the flocs quickly by magnetic force without changing liquid property. In this study, four kinds of cationic polyelectrolytes are used in preparing MSF and the optimum condition of MSF production is investigated. For all cases, higher pH (especially above pH 7) during polyelectrolytes adsorption gives MSF higher surface potential, and higher polyelectrolyte concentration gives better MSF dispersion. It is observed that three kinds of polyelectrolytes above 300,000 of molecular weight do not detach from a magnetite surface even after several washings. This result indicates that the MSF keeps stable high surface potential and, therefore, can be used repeatedly. Among the four kinds polyelectrolytes used in this study, polyethyleneimine type (molecular weight: 300,000) is the best for MSF production. The optimum condition is as follows; polyelectrolytes concentration: 1,000 ppm, adsorption pH: pH 8, washing after adsorption: 3 times. The MSF produced under optimum condition has large positive potential of around 40 mV in 10-3mol/l NaCl solution in a wide pH range.
