Aluminum Formate: Synthesis, Coagulation Behavior And Mechanism

Aluminum formate(AF),a degradable and non-corrosive coagulant,was synthesized from aluminum hydroxide and formic acid.Aluminum formate has been seen as a superior coagulant which could be decomposed under the UV light without corrode equipment during the water supplement.The morphological characteristic,hydrolysis mechanism,molecule structure and coagulation behavior had been studied in this research by SEM,TEM,XPS,FT-IR,mass spectrum and XRD,and the flocculation properties of the dual-coagulation system were characterized by FT-IR and SEM.(1)Results showed that aluminum formate expressed a 3D porous structure under the TEM measurement,and the aluminum complex,which could form into large amorphous polymers,detected by 1H NMR and 13C NMR proved TEM result as well.Aluminum formate(C3H3AlO6),aluminum formate hydrate(C3H3AlO6·3H2O)and aluminum hydrogen formate(C3H3AlO6·2H2O2)which detected by XRD analysis were the main component of aluminum formate coagulant.The hydrolysates of AF became small,the positive charge increased and the undetected species decreased with that HCOOH/Al ratio growing from 1.5 to 4.0.The hydrolysates of AF 1.5 was similar toPAC's.(2)AF was used in advanced treatment and the coagulation behavior showed that AF 3.0 expressed a best coagulation behavior on glucan removal process(removal efficiency more than 55%),and the main coagulation mechanism was physical absorption rather than chemical bond bridging.BSA removal efficiency decreased following the HCOOH/Al molar ratio and pH condition growth,and AF 1.5 had the best BSA removal ability(58%).Aluminum formate captured BSA molecule by chemical bond such as means of NO-Al-,Al2(SO4)3 rather than the physical absorption effect in glucan coagulation process.According to the coagulation behavior of all kinds of AF samples,the optimized HCOOH/Al was chose to 3.0.(3)Optimized AF sample(AF 3.0)was used in reactive blue wastewater treatment,andPAC was selected as a control.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 variance analysis,the between AF/PA and PAC/PA were insignificant macroscopic.The interaction between coagulants and PA was proved by SEM images,which showed that the flocs became larger when PA was added.FT-IR spectra indicated that AF captured pollutants by means of C=C=O bonds,and PAC captured pollutants by ?=CH,-C=C-and ?=CH.Overall,although the interaction between AF and PA was weaker than that of PAC/PA,AF/PA showed better coagulation efficiency than PAC/PA in dye wastewater treatment.