Study On The Development And Mechanism Of Modified Starch Composite Flocculant

During the process of wastewater treatment, the flocculation is one of very common and economical techniques. The flocculant is the key of this technique. and its properties influence directly flocculation efficiency. The development of new and highly effective flocculant is the core of the technology that optimizes flocculation process, and is also a project on which researchers in environmental science concentrate.In this paper, solid waste(FeSO4) from industry and starch were modified by cation reaction ,grafting reaction and composite reaction to prepare a starch modified inorganic-organic composite flocculant(PFCNS). The optimal procedure was determined by orthogonal experiments. The reaction conditions were as following: the polyferric sulfate(PFS) was prepared with n(FeS04)/n(H2SO4) molar ratio 1:0.4 and n(FeSO4)/n(H2O2) molar ratio 1:0.6; the cation flocculant(M) was prepared with n(organic amine)/n(halogen alkyl) molar ratio 1:1 at 45℃ for lh;starch was preliminary gelled with 10% starch and 5% NaOH at 65℃-75℃ for 2h; grafting was carried at 50℃-60℃ for 2h after the solution with M /(starch) weight ratio 1.5:1 was activated for 30s ; PFS and M reacted with their weight ratio 3:1 at 60 - for 3h.The jar test showed that there was a widely pH range for the flocculant (PFCNS) that was prepared by optimal parameters, and PFCNS was hardly affected by temperature and aid flocculant .In the course of beer wastewater treatment, consumption of PFCNS was low and turbidity removal efficiency was high ; subsiding was rapid and the CODcr removal ratio was high .Its flocculation performance was superior to that of PFS and PAC.The flocculation mechanism experiments showed that PFCNS had more positive charges than PFS and characterized typical agglomeration and absorption-bridging. The best pH range was 6 - 8.5. The best flocculation species was the iron hydrolysis polymer after forming Fe(OFT)4~. Comprehensive analysis showed its outstanding flocculation performance depended on its special molecule structure, and was the result that electricity counteract was in cooperation with agglomeration and absorption-bridging.