Amphoteric Polymeric Flocculants PDMDAAC-FA Synthesis, Characterization And Application

Flocculants play an important part in flocculation process of water-treatment technology. The amphoteric polymeric flocculants was highly emphasized by researchers with excellent flocculating property. The pAM and its modified products have been the most widely used in wastewater treatment. However, acrylamide monomers are harm with three serious effect (cancer-causing, deformity, mutation) causing and Neurotoxicity. So it has gained great attention in exploring non-toxic polymeric flocculants and no pollution polymerization technique. The unique cationic quaternary ammonium polyelectrolyte monomers DMDAAC have been authorized by united states public health service which could be used in the purification the drinking water. So DMDAAC as cationic and FA as anion comonomers.The pDMDAAC-FA copolymer have been obtained with water-solution copolymerization which is an environmentally friendly technology.This paper has worked with the following respects:1. DMDAAC and FA as comonomer, the pDMDAAC-FA is synthesized by aqueous solution polymerization. Using the uniform design method, the data have been multiple stepwise regression analysis by means of SAS software. The effect of monomers(X₁),initiators and auxiliary agents on copolymerization have been studied.On the regression equation of effect factors of copolymerization transformation rate as following: y = -244.4+9.2843X₁-0.06745X₁²+38.010X₃; DMDAAC monomer concentration is the most important factor, and next is the initiator. It has been proved that the transformation rate monotone increasing function of both concentration.On the regression equation of effect factors of copolymer intrinsic viscosity transformation rate as following: y = -0.1270+0.00438X₁+0.00454 X₁ X₃+0.06745X₂²;DMDAAC monomer concentration is the most important factor, and next are the initiator and FA concentration, there have interactive influence between DMDAAC and FA. The equation demonstrated that the intrinsic viscosity was a simple monotonic increasing of DMDAAC and FA concentration in the range of research2. This paper has determined solution properties by means of titration method. It was confirmed that the copolymer was amphoteric polymer. The structure of pDMDAAC-FA was confirmed by IR and 1HNMR. The weight-average molecular weight is 5.7×10⁴,which determined by GPC.3. The estimation of thermodynamics according consecration methods indicate that DMDAAC/FA could copolymerize when the reaction temperature lower than 788K(515℃),â–³G la < 0. The kinetic equation of the DMDAAC/FA copolymerization in aqueous solution are obtained by dilatometer method as follows: Rp∝[DMDAAC-IA]^3.93[K₂S₂O₈]^1.01 and the apparent activation energy is 24.99 kJ/mol , which displays that the chain termination reaction is according to the modes of mono-and bi-molecule termination.4. Using pDMDAAC-FA in the flocculation processes of dying wastewater when 80mg/L, COD_Cr ,colority removal ratios are 65.06%,93.90%, respectively. Investigating the effect of molecular and pH on flocculation efficiency in the dying wastewater treatment, Wastewater was not able to flocculated until pDMDAAC-FA average molecular weight was reaches a certain value and the pDMDAAC-FA has the relatively wide pH scope. The COD_Cr removal ratios increase using the complex of pDMDAAC-FA with PFS and the COD_Cr removal ratios was 77.8% when pDMDAAC-FA(60 mg/L)+ PFS(400 mg/L), Using the technology of the flocs retrieval utilization and saving the dosage of flocculants when using pDMDAAC-FA(50mg/L)+ PFS(300 mg/L)+ floc(100% ), COD_Cr and colority removal ratio are 75.2%,96.3% respectively and the value(BOD5/ COD_Cr = 0.35) increases and the biodegradability was improved obviously. The sequential treatment favorable conditions are created and the amount of flocculants was reduced.5. Using the Non-linear fractional theory, floc structure have been analyzed by means of image analysis software. The floc structure of pDMDAAC-FA is denser and solider than that of PFS. The floc structure of pDMDAAC-FA with comparatively big size and the narrow size distribution. It was obtained that the fractal dimension D² of the flocs were 1.7017 of pDMDAAC-FA and 1.6928 of PFS,respectively. The results show that floc structures were generated by the amphoteric polymeric flocculants with high degree of compactness and small porosity, which based on bridging flocculation mechanism.