Preparation Of Inorganic Polymer Composite Flocculant PAFS

In this research, The Poly Aluminum Ferric Sulfate （PAFS） flocculants wasproduced by industrial by-products FeSO₄·7H₂O and aluminum sulfate for industrial use,concentrated nitric acid as strong oxidant. Polymeric ferric sulfate aluminum （PAFS）composite coagulant was prepared by direct oxidation method. the structure of thePAFS was characterized by FTIR （fourier transform infrared spectrometer）, XRD （x-raydiffraction） and SEM （scanning electron microscope）. It applied to domestic wastewater.Based on the single-factor test designed, experimental conditions optimization,degradation effect and degradation mechanisms were studied. At the same time it wasapplied to treat dyeing wastewater and sewage in order to provide certain data and thebasis for the development of a new efficient multifunctional coagulant.The main contents of the thesis is as follows:（1） The Poly Aluminum Ferric Sulfate （PAFS） flocculants was produced byindustrial by-products FeSO₄·7H₂O and industrial-grade aluminium sulphate,concentrated nitric acid as strong oxidant, phosphoric acid for the stabilizer and basicityadjusted by sodium hydroxide. The effect of Al/Fe,SO₄^2-/Fe,NO₃^-/Fe,Al/Fe molar ratioand basicity （OH/Fe） was studied to prepared Poly Aluminum Ferric Sulfate （PAFS）.Through single factor test, The effect of reaction temperature, reaction time,Al/Fe,SO₄^2-/Fe,NO₃^-/Fe,Al/Fe molar ratio and basicity （OH/Fe） on the coagulationeffect were used to determine the optimum preparation conditions. PAFS wasdeveloped to apply to sewage removal and turbidity removal and it was efficient andcost-effective.The results showed that optimum condition: reaction temperature,reaction time, Al/Fe,SO₄^2-/Fe,NO₃^-/Fe,Al/Fe molar ratio and basicity （OH/Fe） were,80.0℃,60.0min,0.38,0.45,0.11,0.10, respectively. When PAFS was used on sewagein this prepared conditions, the removal rate of TP, COD, the turbidity were98.6%,79.1%,98.1%, respectively.（2） FTIR anAlysis shows that PAFS contain polymer Fe-O-Fe and Al-O-Al. XRDanAlysis shows that when Fe/Al molar ratio is0.11, the product of PAFS appearedsome new strong diffraction peak intensity compared with PAFC. Because newproducts were joined the Aluminium and other ions on the basis of PFS,PAFS hasformed a lot of new phase, which indirectly showed PAFS was Aluminum and ironhydroxyl polymer and Aluminum and iron cross copolymer. Through SEM, PAFS framework is based on the structure of PFS and combined with a large number ofAluminum ferric polymers branched chain on the surface of PFS. PAFS has a fluffy andpresent class fold petals shaped surface structure is because of the addition of Al3+, itpresents the strong condensed matter consistented with the appearance of the actualdisplay viscosity. This kind of structure shape has a large specific surface area andstrong adsorption bridging ability, which will colloid and suspended particles volumesweep down and forming floc in the treatment of the pollutants through the trap and theadsorption of small particles.（3） Using PAFS in the treatment of urban domestic wastewater and it was foundthat the removal rate of TP、COD and turbidity were optimized when the rapid stirringspeed of350rpm, fast mixing time of60s, the slow stirring speed of40rpm, slowstirring time15min, the dosage of PAFS is25.0mg/L and the pH value of8.5. And onthis basis, rapid stirring speed, fast mixing time and dosage were selected for responsesurface analysis. Through Box-Behnken experiment design and response surfaceanalysis, optimization grouping of these3main influence factors was realized; aquadratic response surface model and optimum level values were obtained. It was foundthat the optimization grouping of the main influence factors for the removal of CODwere as following: rapid stirring speed being358rpm, fast mixing time being0.90min,the dosage of PAFS being21.8mg/L. And under the optimum conditions, the removalrate of COD was60.6%. A regression analysis was utilized to evaluate the fitness of themodel.（4） The treatment efficiency were evaluated by investigated sludge volume,thereduction of removal rate of COD and turbidity of printing and dyeing wastewater andPAFS with common flocculant （PFS, PAC and CPAM） comparative study by usingsingle factor. The removal rate of COD is achieved80.0%, the removal rate ofturbidity is achieved92.0%and the sludge volume is52.8mL when rapid stirring speed200rpm, fast mixing time of120s, the slow stirring speed of60rpm, slow stirring time8min,the coagulant dosage was0.30g/L and pH is8.5. Meanwhile, compared with thecommon coagulant （PFS, PAC and CPAM） in application of Printing and dyeingwastewater treatment, Self-make PAFS is higher than PFS, PAC and CPAM on theremoval of COD and turbidity.