Flocculants are polymers that promote flocculation by formation of links between themselves and thus enable suspended particles to aggregate. When the suspended particles are flocculated into larger ones, they are settled in devices like thickeners and clarifiers and removed with the underflow. The flocculants accelerate the settling process, which leads to the potential use of smaller thickeners. Flocculants can also be used to aid filtration.
Flocculation is employed for a variety of applications from mineral processing to purification of drinking water.
• Concentrate and Tailings thickeners in the mining industry
• Water treatment plants
• Filtration aid
• Sewage applications
• Treatment of industrial waste water streams
• Clarification processes
Requirements of flocculant polymers are that they be strongly adsorbed onto the particles and that they are capable of spanning the gap between the particles. Synthetic polymers of high molecular weight are long enough for one end of a single molecule to adsorb onto one particle and the other end onto a second particle. Higher molecular weight polymers can adsorb on several particles at once, forming a three-dimensional matrix.
In general, the higher the molecular weight the better the flocculation and the faster the sedimentation rate. In the case of filtration, however, the lower molecular weight products can be more effective. This is because the flocs formed with high molecular weight products are relatively large, trapping water within the structure and increasing the final moisture content of the filter cake.
Most synthetic flocculants are based on polyacrylamide and its derivatives. Flocculants generally carry either a positive (cationic) or a negative (anionic) charge. Polyacrylamide itself essentially is nonionic and the desired ionic character is produced by copolymerisation with other monomers. Anionic polyacrylamides are produced by copolymerisation with acrylic acid, while for cationic polymers one of […]