Preparation And Application Of The Eco-friendly Polysilicate-Metal-Polysaccharide Composite Flocculants

Using Na₂SiO₃·9H₂O,Al₂?SO₄?₃·18H₂O,ZnSO₄·7H₂O,MgSO₄·7H₂O,chitosan?CTS?,edible starch?St?and sodium carboxymethylcellulose?CMC?as the raw materials,five kinds of organic-inorganic composite flocculant were prepared.They are polysilicate aluminum magnesium CMC?PSiAM-CMC?,polysilicate aluminum zinc starch?PSiAZ-St?,polysilicate aluminum CMC?PSiAl-CMC?,polysilicate aluminum starch?PSi Al-St?and polysilicate aluminum chitosan?PSiAl-CTS?,respectively.The optimum preparation conditions of n[Al+?Zn or Mg?]/n?Si?,n?Al?/?Zn or Mg?,m?St or CMC?/m?Si?,reaction temperature,reaction pH were determined by means of single factor.Scanning electronic microscope?SEM?,fourier transform infrared spectrum?FTIR?and X-ray diffraction?XRD?were used to characterize the prepared flocculant.Finally differences of PSiAl-CMC flocculant,PSiAl-St flocculant and PSiAl-CTS flocculant in performance and economic benefit were discussed.The results show that the flocculant exhibited the highest coagulation efficiency when the metal/silicon molar ratio,the Al/Zn?Mg?molar ratio,the polysaccharide/Si mass ratio,reaction temperature,reaction pH had a certain influence on the performance of the flocculants.The optimal synthesis conditions of PSiAM-CMC were that n?Al+Mg?/n?Si?=0.6,n?Mg?/n?Al?=1:4,m?CMC?/m?Si?was 0.3,gelatinization temperature of CMC=60? and pH=2.The removal rates of chroma and turbidity could achieve 99% about dealing with Songhua River samples with PSiAM-CMC flocculant.The optimal synthesis conditions of PSiAZ-St were that n?Al+Zn?/n?Si?=0.6,n?Al?/n?Zn?=1:9,m?St?/m?Si?was 1 and preparation pH=1.5.The removal rates of chroma and turbidity could achieve 98% about dealing with Songhua River samples with PSiAZ-St flocculant.Several factors effect of flocculation performance include water temperature,water pH,sedimentation time and dosage were investigated in the process of coagulation.Finally differences of three types composite flocculant in performance and economic benefit were discussed.The result shows that PSiAl-CMC has the best flocculation propertiy and economic benefit of production cost.