the usual remedial practice for cell removal in open water is to spread clay on the
surface of seawater through the flocculation of alga and mineral particles. However, this study was made to synthesis
a novel natural cationic polymeric flocculant grafted by quarternary ammonium monomer N-(3-chloro-2-
hydroxypropyl) trimethyl ammonium chloride (CHPTAC) onto the backbone of corncob powder. The graft process
was characterized by elemental analysis, Fourier-transform infrared spectrometer and scanning electron microscope
techniques. A set of experiments were carried out to assess the feasibility of the flocculant to remove the
dinoflagellate, Alexandrium tamarense. Results showed that after adding an aqueous slurry of 0.15 gl
-1
, the seawater
culture containing Alexandrium tamarens 104
cells ml-1
was removed by 70% within 6 h. After an exposure period of
12 h, it was removed by 90%. Selection of monomer concentration in synthesis process, flocculant slurry aging time
and the particle size of the flocculant were found to be important parameters affecting removal efficiency. These
studies showed the cationic modified flocculant can be utilized as a promising substance for reducing adverse effects
from harmful algal blooms in seawater, although considerable work remains before this approach can be used on
natural open waters.