Study On Preparation Of Magnetic Fe₃O₄/CPAM Composite Flocculant And Flocculation For High Algae With Low Turbidity Water

Algae are ubiquitous in rivers,lakes and reservoirs of drinking water treatment projects.The problem of eutrophication caused by seasonal algae overgrowth has a serious impact on drinking water treatment,such as producing disinfection by-products with chlorine and blocking filter.In addition,the extracellular organic matter?EOM?produced by algae can also aggravate eutrophication and affect water treatment process.Flocculation is an indispensable process in conventional water treatment,and its core is flocculant.High algae water generally has the characteristics of high algae and low turbidity,while low turbidity water can reduce flocculation efficiency.Traditional inorganic and organic flocculants also have poor removal efficiency for algae and EOM.Therefore,it is particularly important to develop a flocculant with low dosage and high efficiency.In this study,cationic polyacrylamide?CPAM?was synthesized by low-pressure ultraviolet light-induced polymerization,and then combined with nanoFe₃O₄ to form composite flocculant Fe₃O₄/CPAM.The synthesis method initiated by low-voltage ultraviolet light has the advantages of simple operation,short synthesis time and low energy consumption.Fe₃O₄nanoparticles can improve the flocculation efficiency and recycle under the external magnetic field.In this paper,the structure and morphology of the composite flocculant Fe₃O₄/CPAM were analyzed.And it was applied to the removal of high algae and low turbidity water and EOM.The main contents of this paper are as follows:?1?Preparation,structure and morphology analysis of flocculant Fe₃O₄/CPAM.CPAM was synthesized by copolymerization of methacryloxyethyl trimethyl ammonium chloride?DMC?and acrylamide?AM?by low-pressure ultraviolet light.Fe₃O₄ and ammonium persulfate?NH₄?₂S₂O₈ were added then and the composite flocculant Fe₃O₄/CPAM was formed by severe stirring.The structure,thermal stability,magnetic properties,surface morphology and surface potential of composite flocculant Fe₃O₄/CPAM were analyzed by FTIR,XRD,TGA,VSM,SEM and Zeta potentiometer,and the possible mechanism of polymerization was explored.?2?Study on the removal performance and mechanism of high algae and low turbidity water by flocculant Fe₃O₄/CPAM and recovery of magnetic materials.The effects of flocculant dosage,flocculation stirring time,stirring rate,settling rate and pH on algae and turbidity removal were investigated.The effects of dosage,pH,stirring time and stirring speed on algae and turbidity removal were investigated by orthogonal experiments,and the optimized flocculation conditions were obtained.In addition,the flocculation performance of self-made flocculant Fe₃O₄/CPAM and CPAM was compared.Comparison of flocculation effect of high algae and low turbidity water under adding magnetic field and no magnetic field with the same conditions was examined.The recycled magnet was reused and the flocculation effect before and after the reuse was compared.The flocculation mechanism of flocculant Fe₃O₄/CPAM in removing high algae and low turbidity water was studied by flocculation kinetics,optical microscopy,particle size analysis,scanning electron microscopy and energy spectrum analysis.?3?Study on the removal of EOM by flocculant Fe₃O₄/CPAM.The effect of the dosage of flocculant Fe₃O₄/CPAM on the removal efficiency of DEOM and BEOM was investigated.The composition,structure and content of DEOM and BEOM before and after flocculation were analyzed by ultraviolet spectrum,three-dimensional fluorescence spectrum?3-EEM?,X-ray photoelectron spectroscopy?XPS?,molecular weight?GPC?and infrared spectroscopy.