The Properties Of Composite Flocculants Prepared From Polyferric Chloride And Polydimethyldiallylammonium Chloride

Coagulation/flocculation is a widely used process for particle removal in water and wastewater treatment. And the removal of colloids and dissolved organic matter by coagulation and flocculation is a widely employed treatment process. Fe(III) flocculants is principal inorganic flocculants used in wastewater treatment. And current research focuses on the development of composite high molecule coagulants, which combine superior efficiency and lower operational cost as compared with the convential ones.Synthetizing references, the a composite flocculant of polyferric chloride (PFC) and polydimethyldiallylammonium chloride (PDMDAAC), or PFC-PDMDAAC, was prepared. The chemical species distribution of ferric, zeta potential, hydrolysate properties and coagulation performance of PFC-PDMDAAC were investigated by varies physical chemistry methods. And the correlation between inorganic polymer and organic polymer in PFC-PDMDAAC and coagulation mechanism were explained.The main contents and results are following:1. The hydrolyze-polymerize process of PFC-PDMDAAC were studied by tittle alkali method, and the impact of PDMDAAC fraction weight of the composite (Wp), basicity (B) of PFC, which is [OH^-]/[Fe], and molecular weight (η) of PDMDAAC, on the hydrolyze-polymerize process of PFC-PDMDAAC were examined. The results show that the pH buffer in hydrolyze-polymerize process of PFC-PDMDAAC turn short, and the pH rapid rise region of PFC-PDMDAAC appears earlier with increasing Wp,ηand B, which denotes the content of Fe(III) monomer decreases.2. Fe-Ferron method was used to examine Fe(III) speciation of PFC-PDMDAAC, and the impact of Wp, B of PFC, andηof PDMDAAC, on the Fe(III) speciation of PFC-PDMDAAC were examined. The results show that compared with PFC, the contents of Fe(III) speciation in PFC-PDMDAAC change. When Wp = 7.0%,η= 1.02dL g^-1 and B = 0.5, the content of Fe_b is the highest and the content of Fe_c is the lowest. The contents of Fe(III) speciation of PFC-PDMDAAC change more gently than that of PFC when coagulants are added to water. This will be in favor of actual coagulation.3. Zeta potential of PFC-PDMDAAC was investigated by Zatesizer3000Hsa, and the impact of Wp, B andηon the zeta potential of PFC-PDMDAAC were examined. The results show that the positive zeta potential of PFC-PDMDAAC is higher than that of PFC. When pH is lower, the zeta potential of PFC-PDMDAAC (Wp=14.0%,B=1.5,η= 1.21dL g^-1) is the highest. When pH is higher, the zeta potential of PFC-PDMDAAC (Wp=7.0%,B=1.0,η= 0.72 dL g^-1) is the highest. Inorganic salts decrease the zeta potential of PFC-PDMDAAC. However, the effect of inorganic salts on the zeta potential of PFC-PDMDAAC is lower than that of PFC. Therefore, according to charge neutralization, the coagulation efficiency of PFC-PDMDAAC is higher than that of PFC and appliance scope of PFC-PDMDAAC is wider than that of PFC.4. TEM was used to investigate the structure and appearance of PFC-PDMDAAC, and the impact of Wp, B of PFC, andηof PDMDAAC, on the structure and appearance of PFC-PDMDAAC were examined. The results show that there are some interaction between PFC and PDMDAAC, and Wp,B can influence the structure and appearance of PFC-PDMDAAC, whileηbarely affects the structure and appearance of PFC-PDMDAAC. With Wp increasing, the grain struture increases, and branch shape matter is more distinct, and cloud shape matter decreases. With B increasing, branch shape matter is more distinct and cloud shape matter dies out.5. Laser scatter technique was used to study the size of PFC-PDMDAAC, and the impact of Wp, B of PFC, andηof PDMDAAC, on the size of PFC-PDMDAAC were examined. The results show that the size distribution of PFC-PDMDAAC is different with that of PFC, and Wp,B andηcan influence the size distribution of PFC-PDMDAAC. When Wp = 14.0%,η= 1.02dL g^-1 and B = 1.0, the effect of pH on the size of PFC-PDMDAAC is lowest. The average size of PFC-PDMDAAC is higher than that of PFC at same pH. The effect of pH on average size of PFC-PDMDAAC decreases with increasing Wp. The specific surface area of PFC-PDMDAAC is higher than that of PFC, and the specific surface area of PFC-PDMDAAC (Wp = 14.0%, B = 1.0) is the highest. 6. PDA2000 was used to determine the floc aggregation of PFC-PDMDAAC, and the impact of dosage, pH and ionic strength on the floc aggregation of PFC-PDMDAAC were examined. The results show that the average floc size and floc growth velocity of PFC-PDMDAAC are much larger than those of PFC, and the flocs variance of PFC-PDMDAAC is smaller than that of PFC Compared with PFC, PFC-PDMDAAC gives better coagulation performance in wider range of pH and ionic strength.7. PFC-PDMDAAC was used to treat synthesize kaoline and reactive blue wastewater, and the impact of Wp, B of PFC, andηof PDMDAAC, on the coagulation efficiency of PFC-PDMDAAC were examined. JS94H zeta potential analysis instrument was used to determine the zeta potential of wastewater. The coagulation mechanism of PFC-PDMDAAC for remove turbidity and color was discussed. The results of treating the synthesize kaoline wastewater show that the removal turbidity of PFC-PDMDAAC is higher than that of PFC and PDMDAAC, and the optimal dosage of PFC-PDMDAAC is lower than that of PFC and PDMDAAC. The coagulation efficiency of PFC-PDMDAAC(Wp = 7.0%, B = 1.0,η= 1.02 dg L^-1) is the highest. The coagulation mechanism of PFC,PFC-PDMDAAC and PDMDAAC for remove turbidity is different. The main coagulation mechanism of PFC is charge neutralization. The main coagulation mechanism of PFC-PDMDAAC is adsorption and bridge. The main coagulation mechanism of PDMDAAC is charge neutralization and bridge. The results of treating the synthesize reactive blue wastewater show that the color removal of PFC-PDMDAAC is higher than that of PFC and PDMDAAC, and the optimal dosage of PFC-PDMDAAC is lower than that of PFC and PDMDAAC. The color removal efficiency of PFC-PDMDAAC(Wp = 14.0%, B = 0.5,η= 0.72 dg L^-1) is the highest. The coagulation mechanism of PFC,PFC-PDMDAAC and PDMDAAC for remove turbidity is different. The main coagulation mechanism of PFC and PDMDAAC is charge neutralization. The main coagulation mechanism of PFC-PDMDAAC is adsorption and bridge.8. PFC-PDMDAAC was used to treat actual water and wastewater, optimal Wp,ηand B of PFC-PDMDAAC for different water or wastewater were examined. The results of treating the actual water prove that the coagulation efficiency of PFC-PDMDAAC is higher than that of PFC and PDMDAAC, and the optimal dosage of PFC-PDMDAAC is lower than that of PFC and PDMDAAC. Wp,B andηcan influence the coagulation efficiency of PFC-PDMDAAC, and the optimalWp,B andηis different for treating different water.The above contents are various characteristics of PFC-PDMDAAC. The primary coagulation efficiency, coagulation behavior and coagulation mechanism of PFC-PDMDAAC were confirmed. This will provide the theory for empolder and apply PFC-PDMDAAC.