Study On Synthesis And Flocculating Performance Of Cationic Polyacrylamide Flocculant In Treatment Of Wastewater

Three different kinds of cationic polyacrylamide flocculants were synthesized by aqueous solution polymerization using acrylamide(AM), methacryloyloxyethyltrimethyl ammonium chloride(DMC) and acryloyloxyethyltrimethyl ammonium chloride(DAC) as monomers. The structure of obtained products were characterized by FT-IR, theirs capability of flocculating performances were investigated in wastewater.The influences of factors, such as initiator system, oxidant-reductant concentration, the mass ratio of oxidizer to reductant, azo-compound types and concentration, reaction temperature, pH value, monomer concentration, cationic degree, drying time and temperature, types and concentration of chelator, chain-increase agent, solubilizing agent and surfactant on the intrinsic viscosity of product were studied. The results showed that the effects of increase-chain agent and chelator concentrations on the improving of intrinsic viscosity of product were inapparent, that with the increasing of urea concentration, the intrinsic viscosity of product increased at first and then decreased, but there was no obvious improvement on the solubility of product and that with the increasing of surfactant concentration, both the intrinsic viscosity and the solubility of product decreased. In flocculanting experiment, the effects of intrinsic viscosity, cationic degree and dosage of cationic flocculant on its flocculating performances were investigated.The obtained optimum reaction conditions for synthesis of P(DMC-AM) were (NH₄)₂S₂O₈ and CH₃NaO₃S·2H₂O concentration 0.0150%, the mass ratio of (NH₄)₂S₂O₈ to CH₃NaO₃S·2H₂O 0.7:1.0, azo-initiator concentration 0.0125%, reaction temperature 25℃, pH value 6.0, monomer concentration 40%, cationic degree 40%, reaction time 2.5h, drying temperature 60℃, drying time 16.0h, EDTA·2Na concentration 0.0002%, urea concentration 0.005%, surfactant concentration 7.5%. The obtained optimum flocculating conditions were pH value of wastewater 6.0, the intrinsic viscosity of cationic polyacrylamide 11.9234dL·g^-1, cationic degree 40%, the dosage 0.027%, velocity of centrifuge 1500 rpm, time of centrifuge 30min. Under above conditions, the transmittance of treated wastewater was 98.0%, the flocculating rate was 66.0%, dewatering rate was 70.0%.The obtained optimum reaction conditions for synthesis of P(DAC-AM) were pH value 6.0, (NH₄)₂S₂O₈ and CH₃NaO₃S·2H₂O concentration 0.0125%, the mass ratio of (NH₄)₂S₂O₈ to CH₃NaO₃S·2H₂O 1.0:1.0, azo-initiator concentration 0.0125%, monomer concentration 35%, cationic degree 30%, reaction temperature 25℃. Under above conditions, the intrinsic viscosity of product was 13.8535dL·g^-1. The obtained optimum flocculating conditions were the intrinsic viscosity of P(DAC-AM) 13.8535dL·g^-1, cationic degree 30%, the dosage 0.027%. Under above conditions, the transmittance of treated wastewater was 99.6%, dewatering rate was up to 90.0%.The obtained optimum reaction conditions for synthesis of P(DAC-DMC-AM) were pH value 6.0, (NH₄)₂S₂O₈ and CH₃NaO₃S·2H₂O concentration 0.0150%, the mass ratio of (NH₄)₂S₂O₈ to CH₃NaO₃S·2H₂O 0.7:1.0, azo-initiator concentration 0.0125%, monomer concentration 40%, cationic degree 35%(the mass ratio of DAC to DMC 1.0:1.0), reaction temperature 25℃. Under above conditions, the intrinsic viscosity of product was 11.9035dL·g^-1. The obtained optimum flocculating conditions were cationic degree of P(DAC-DMC-AM) 35%, the intrinsic viscosity 11.9035dL·g^-1, the dosage 0.027%. Under above conditions, the transmittance of treated wastewater was 98.9%, the flocculating rate was 66.2%, dewatering rate was 81.0%. To our knowledge, there is no literature report about the studies on P(DAC-DMC-AM) flocculant.