An enhanced coagulation using ferric chloride and poly-ferric chloride coagulant assisted by polyamidine:Performance and mechanisms

The deterioration of water caused by industrial production is a thorny problem.Solving the problem cogently through innovative coagulationstrategies has been recognized of important practical significance.In this work,a simple enhanced coagulation by using ferric chloride(FC)and poly-ferric chloride(PFC)coupled with polyamidine(PA)were tried to remove the toxic organics.The results shown that PA addition could obviously enhance coagulation performances of the iron-based coagulants.The synergic coagulation process and mechanism were studied and discussed in detail based on the coagulation behaviors,flocs properties,removal eficiency and zeta potentials.FC and PFC remove organics mainly through charge neutralization and adsorption-bridging,resulting in a good purification performance.While PA with a higher charge density showed better purification performance due to enhanced charge neutralization.It is worth mentioning that the addition of PA could make the coagulants adapt to a wider pH range,and remove the toxic organics more effectively.That is to say,the practical adaptability of the coagulant was enhanced.This work thus provides a simple strategy to effectively purify wastewater and further improve the water safety.

Novel cationic polyamidine:Synthesis,characterization,and sludge dewatering performance

In this study,a new and facile route was employed for synthesis of polyamidine with abundant cations and attractive five-membered ringlike structural unit.N-vinylformamide and acrylonitrile copolymerized firstly to form intermediates,and the intermediates were processed with hydrochloric acid to produce polyamidine.A series of polymerization conditions（e.g.polymerization time,temperature and dosage of initiator） were optimized through productivity,viscosity and cationic degree as evaluation.SEM analysis illustrated that the amidinization process could reduce the size of spaces between molecular and created compact structure,which would contribute to good flocculation performance and high viscosity.FT-IR,XPS and NMR spectra presented a rather clear structure of polyamidine.34.3%of sludge was sedimentated through the flocculation of polyamidine in the early stages.In contrast,only 6.8%of sludge was sedimentated by polyacrylamide.The moisture content in dehydrated floc could be reduced to 77.7%when 60 mg/L polyamidine was added.These results demonstrated that the polyamidine showed a great potential in the practical application of sludge dewatering.

Metal-free multicomponent polymerization toward cationic polyamidines

Cationic polymers,also known as polycations,are considered to be the most potential non-viral gene carriers due to their unique advantages such as the ability to bind the negative charge of nucleic acid molecules.Multicomponent polymerization(MCP)is a one-step,tandem strategy to construct complex structures based on multicomponent reactions.Herein,we developed a metal-free MCP method based on three monomers of p-dinitrovinylbenzene(p-DNVB),1,1-dimethylethyl N,N-dibromocarbamate(BocNBr_(2)),and bis-secondary-amines with a ratio of 1:2:1,to access a library of Boc-substituted polyamidines with well-defined structures and suitable molecular weights(M w ranging from 4400Da to 11,000Da)in high yields(up to 85%)under mild conditions.Upon the removal of Boc groups,a series of water-soluble polymers with cationic property were prepared and their gene binding capability was further evaluated.

Aluminum formate(AF): Synthesis, characterization and application in dye wastewater treatment

Aluminum formate（AF）, a degradable and non-corrosive coagulant, was synthesized from aluminum hydroxide and formic acid. Polyamidine（PA）, as a coagulation aid, was combined with AF for dye wastewater treatment. AF was characterized by XPS, FT-IR, viscosity, zeta potential, mass spectrum and XRD, and the flocculation properties of the dual-coagulation system were characterized by FT-IR and SEM. The results showed that COOH, Al2 O3-Al and O2-Al bonds were formed in the AF synthesis process, and AF had a higher molecular weight and higher charge neutralization ability than PAC. The hydrolysates of AF were determined to contain Al（13）Al（11） and Al2, and the components of AF were confirmed to comprise a mixture including aluminum formate（C3H3AlO6） and its hydrate. When the color removal efficiency reached 100% in jar tests, the optimized dosage of AF/PA was 18.91/0.71 mg/L,while the optimized dosage of PAC/PA was 21.19/0.91 mg/L. According to the variance analysis, the interaction between AF/PA and PAC/PA were insignificant in macroscopic view. FT-IR spectrum indicated AF captured pollutant by means of CCO bond, PAC captured pollutant by δ CH, ／CC／ and δ CH. Overall, although the coagulation mechanism of AF was different from that of PAC, AF/PA showed better coagulation efficiency than PAC/PA in dye wastewater treatment.