Preparation And Properties Of Anionic Polymer Emulsion Flocculant

In the alumina industry, in order to obtain the raw material sodium aluminate solution in line with production requirements, it is of vital importance to use a suitable kind of flocculant to separate the red mud from the slurry mix. Generally speaking, the red mud mixture contains Fe3+, Ca2+ and other metal ions. Anionic polymeric flocculant can connect together the particles to form large floc by charge neutralization, bridging adsorption, and other effects, prompting the solid-liquid separation, thus speeding up the red mud settling. High polymerization rate and high molecular weight can be achieved via inverse emulsion polymerization at the same time. Emulsion flocculant has the advantages of fast dissolution rate and low use cost, in addition, all aspects of performance are superior to traditional aqueous solution polymerization product, therefore the development of the anionic flocculant with high solid conten, high molecular weight and high settlement performance is the goal of red mud settling flocculant.Three types of anionic polymer flocculant were prepared via inverse emulsion polymerization. Copolymerization of acrylamide and sodium acrylate were synthesized in the method of inverse emulsion, and the optimum process condition were obtained as follows: Isoparaffin was used as the continuous phase, the mass ratio of oil phase to water phase was 1:1, n(AANa):n(AM)=1:3, the monomer concentration was 50 wt%, the emulsifier(Span60/OP-10) was 10%, the concentration of initiator(potassium persulfate) was 0.3 wt%(based on monomer mass). As a result, the molecular weight of copolymer product is 1.92*106. In consideration of the toxicity of polyacrylamide and the purity requirement of sodium acrylate, ammonium polyacrylate was prepared by inverse emulsion polymerization, a kind of environmental friendly emulsion flocculant. Many factors that affect product performance were discussed and the preferred preparation conditions were identified:the concentration of monomer was 55 wt%, the mass ratio of oil phase to water phase was 0.6:1, emulsifiers were 8%, HLB was about 7, ammonium persulfate was used as initiator in an amount of 0.3 wt%. On the basis of the previous two chapters, we found that red mud sedimentation rate was faster when the flocculant contains anionic groups, and higher supernatant clarity was obtained while containing a variety of functional groups. Consequently, the inverse emulsion copolymerization of acryamide and ammonium acrylate was studied in details. Some conditions such as the mass ratio of oil phase to water phase, monomer concentration, initiator concentration were optimized. The results were showed as follows:n(AANH4):n(AM)=3:1, the mass ratio of oil phase to waterphase was 1:1, monomer concentration was 50 wt%, compound emulsifier was 8%, initiator(ammonium persulfate) concentration was 0.3 wt%. The product has highest molecular weight, up to 2.46*106. The obtained emulsion flocculants can increase the settling rate and significantly improve supernatant turbidity.