| Coagulation was widely used in industrial wastewater pretreatment.Coagulation performance directly affected the efficiency of subsequent biological treatment or advanced oxidation treatment.The increase of removal rate of refractory organics by coagulation could reduce the organic load of subsequent treatment processes and improve water treatment efficiency.In the study,microbial flocculant(MBF)possessing rich anionic groups was modified by cationic monomer,and amphoteric microbial flocculant(MBF-g-P(AM-DAC))was synthesized.MBF-g-P(AM-DAC)had good decolorization performance.The optimal synthesis conditions and synthesis mechanism of MBF-g-P(AM-DAC)were studied.MBF-g-P(AM-DAC)and polyaluminum silicate(PSA)were combined to treat Congo red(CR)dye wastewater.The effects of factors on CR removal rate were investigated.The coagulation mechanisms were further analyzed.In addition,a hydrophobically modified polymer flocculant(P(AM-HFBMA))with rich fluorocarbon groups was synthesized via micellar polymerization of hexafluorobutyl methacrylate(HFBMA)and acrylamide(AM).It had a good removal efficiency of four soluble dyes in simulated wastewater.It was emphasized to analyze the synthesis mechanism of P(AM-HFBMA)and the different roles of P(AM-HFBMA)and polyferric aluminum chloride(PAFC)in the simulated wastewater treatment.The main contents of the research are as follows:(1)Under thermal initiation conditions,the graft copolymerization of MBF and AM and Acrylatoethyl Trimethyl Ammonium Chloride(DAC)took place,and we obtained the amphoteric macromolecular microbial flocculant MBF-g-P(AM-DAC).Through Fourier transform infrared spectroscopy(FTIR),thermogravimetric-differential thermal analysis(TG/DSC),X-ray photoelectron spectroscopy(XPS)and X-ray diffraction analysis(XRD),we studied the composition,structure and characteristics of MBF-g-P(AM-DAC),and found that MBF-g-P(AM-DAC)owned abundant active groups such as amino,hydroxyl,carboxyl,ammonium and acyloxy groups.In the study of the synthesis mechanism of MBF-g-P(AM-DAC),it was found that the graft copolymerization occurred on the amino group of MBF.AM as a highly active monomer promoted the graft copolymerization of cationic monomer DAC and MBF.We analyzed the specific surface area of the flocs produced by MBF-g-P(AM-DAC)in pure water,and found that its floc had a large specific surface area and a large number of porous structures,which was beneficial to enhancing its adsorption and net catching and sweeping of coagulation performance.(2)The self-made MBF-g-P(AM-DAC)and polyaluminum silicate(PSA)were used in the treatment of simulated Congo red(CR)dye wastewater.The removal rate of CR was high;the flocs formed after coagulation were large and dense;the settling rate was fast,and the settling time was short.When used PSA alone to treat CR,the flocs were small and loose;the settling rate was slow,and CR removal rate was low.PSA and MBF-g-P(AM-DAC)played different roles in CR wastewater treatment.PSA helped neutralize the charge,but the flocs were small;Although the charge neutralization effect of MBF-g-P(AM-DAC)was weak,MBF-g-P(AM-DAC)could greatly help increase the particle size of flocs.The unsaturated active sites on MBF-g-P(AM-DAC)and flocs,and the higher specific surface area contributed to the adsorption of CR,and there were physical adsorption and chemical adsorption.(3)Under UV-initiated conditions,HFBMA and AM underwent graft copolymerization to obtain fluorocarbon hydrophobically modified polymer flocculant P(AM-HFBMA).Through characterization and analysis,it was found that P(AM-HFBMA)has abundant active groups such as fluorine groups,amide groups,and ester groups.Micellar polymerization was helpful to synthesize high molecular polymer(P(AM-HFBMA))with microblock structure.A small amount of SDS adhered to the surface of P(AM-HFBMA)improved the hydrophilicity of P(AM-HFBMA).P(AM-HFBMA)had many active sites,which could enhance the interaction with SDS and dyes.(4)The fluorocarbon-containing hydrophobically modified polymer flocculant P(AM-HFBMA)was applied to the treatment of a variety of simulated dye wastewater.For the simulated wastewater with a concentration of 250 mg/L,the best removal rate of P(AM-HFBMA)could reach 90%.The coagulation performance of P(AM-HFBMA)was better than three commercially available PAMs.When PAFC was used in combination with P(AM-HFBMA),PAFC was mainly used for neutralization,and P(AM-HFBMA)was mainly used for bridging and helped to produce flocs;A small amount of SDS attached to the surface of P(AM-HFBMA)could enhance the interaction of P(AM-HFBMA)with dyes through charge attraction and hydrophobic association.The abundant fluorine groups on P(AM-HFBMA)formed hydrogen bonds with dyes and SDS,which also enhanced their interaction,and the hydrophobic association maked the flocs easy to separate from water.Adsorption existed with this coagulation process. |
