Comparison of the performance of chitosan and a cationic polyacrylamide asflocculants of emulsion systems

Food industries contribute significantly to the pollution of water streams. Oil in wastewaters must be removed to prevent fouling of process equipment , to reduce interference with subsequent water-treatment units, and to comp ly with water-discharge requirements. Polyelectrolytes are frequently used to coagulate and flocculate colloidal systems. A model system of a sunflowe r oil/water emulsion was used to analyze the effect of: (i) emulsion drople t sizes, (ii) surfactant chain length (sodium dodecyl sulfate and sodium te tradecyl sulfate), (iii) ionic strength, and (iv) pH, on the doses of chito san (natural cationic polyelectrolyte) and a cationic polyacrylamide, neces sary to neutralize electrical charge and to get flocculation. Methods used were: turbidimetry, jar test, colloidal titration, and light microscopy obs ervation. Results showed that the increase of NaCl concentration reduces th e doses of chitosan and polyacrylamide to reach zero colloidal charge; thes e doses increase with the surfactant chain length. pH variation did not sho w any influence on the chitosan dose necessary to flocculate the system. Re dispersion of the emulsion was observed in chitosan and polyacrylamide trea tments.