Abstract
The radiation‐induced polymerization of acrylamide was studied to prepare a high molecular weight and highly effective polyacrylamide flocculant. Among various solvents, mixtures of water–tert‐butyl alcohol and water–acetone were found to be suitable for the synthesis of the high molecular weight polyacrylamide. For polymerization in acetone–water mixtures, the molecular weight of polymer increases with monomer concentration; but at the high concentration, intermolecular imidation of amide groups tends to take place during the polymerization to from crosslinked and water‐insoluble polymer. The water‐soluble polymer with the largest molecular weight of 6.7 × 10^6^ is produced in the polymerization with monomer concentration of 2.91 moles/1. at 0°C at a dose rate of 6.2 × 10^2^ rad/hr in acetone–water mixture containing 60 vol‐% water. The crosslinking of polymer of the formation of water‐insoluble polymer could be avoided by the addition of K~2~CO~3~ or NaOH to raise the pH of the reaction mixture above 6.5. The flocculation effects were evaluated from sedimentation speed of kaolin suspension and transparency of the separated water. The sedimentation speed is proportional to the intrissic viscosity of the polymer in the range of 4 to 23 dl/g. The polymers prepared in this study show much higher sedimentation speed than commercial polyacrylamide flocculants. The transparency of the separated water is higher than 93%, similar to the results with commercial flocculants.