Surface chemical studies on SiC suspension in the presence of chitosan

The surface chemical characteristics of SiC suspension were examined in the presence of chitosan, a cationic polymer. The adsorption density of chitosan onto SiC showed a distinct maximum around pH 7, and the isotherms exhibited Langmuirian behaviour. The isoelectric point (i.e.p.) of SiC was located at pH 3 and the presence of chitosan shifted the i.e.p. values towards the alkaline pH region in proportion with the amount of polymer added. Consequent to the addition of chitosan, the zeta potential value of SiC surface was increased to +30 mV in the pH range of 2–5, while it was >−40 mV between pH 9.5 and 11.5. The favourable pH regimes for the stability of SiC dispersions were found to be between pH 2–6 and 9–11, with the optimum concentration of chitosan. The FTIR spectral measurements provided evidence in support of hydrogen bonding forces between chitosan and SiC surface.