Synthesis And Flocculation Performance Of Terpolymer P(AM-DMDAAC-BA)

It is well known that the use of flocculants can improve the efficiency of solid/liquid separation unit operations in a wide range of industrial applications. Water-soluble polymers can be used as efficient flocculants for many disperse systems such as in water treatment, paper-making, mineral processing and other fields. As the development of industrial and the people living level, the discharged wastewater has more complex than ever. Many commercial flocculants are not fit in the treatment. It is desirable to synthesis the hydrophobic polymeric flocculant with cationic charges to improve the flocculation performance of these flocculants.This paper first reviews the development and the existing problems of polymeric flocculant. On this basis, we take into account to use PAM as the molecular backbone, introducing DMDAAC as cation group, BA as the hydrophobic group to synthesis hydrophobic modified cationic polyacrymide with good flocculation performance flocculant. Terpolymers of P(AM-DMDAAC-BA) were synthesized by free radical micelle copolymerization in an aqueous solution. Composition and structure of the terpolymers were characterized by infrared spectroscopy, 'H-NMR, elemental analysis and TG. The cationic hexadecyltrimethyl ammonium bromide (CTAB) was used as the surfactant to ensure the solubilization of the hydrophobic monomer (BA) within the micelles. The redox system (potassium persulfate-natrium sulfurosum) was used as a water-soluble initiator. The effects of initiator concentration, initiator ratio, surfactant concentration, monomer concentration, reaction temperature and reaction time on the reaction conversion and intrinsic viscosity of polymers were studied. Then the effects of cation and hydrophobic group content, flocculant concentration, characteristic viscosity, pH, NaCl concentration on flocculation performance (Transmittance ,sediment volume and settling rate ) of 3 wt% celite suspensions were studied.The optimum synthesis technology of the polymers is 20wt% monomer concentration, 0.03mol% concentration of initiator, 1:2 ratio of initiators(natrium sulfurosum : potassium persulfate) and 3wt% content of surface active agent. In the condition of 10-15mol% content of cation monomer and 3mol% content of hydrophobic monomer, the good flocculant performance of the polymers are available. The intrinsic viscosity of P(AM-DMDAAC-BA) and flocculant concentration have optimum values at which the flocculation performance are the best. pH value or NaCl not only affects the conformation of hydrophobic associationcation polymer flocculant, but also affects the properties of suspension systems. In the condition of containing acid or NaCl, the flocculant performance can be improved. The effects of multivalent metal ion are more complex. The effect of Ca2+ is similar to Na+. when the dosage of A13+ exceed 0.05mol/l, the good performance also can be get.On the basis of analysis of flocculant kinetics, through measuring the floe particle diameter, the unique mechanism of flocculation can be proposed: after the neutralization and particle bridging, the floe can be associated by hydrophobic association to form bigger floe, then settle down more quickly.