Study On Preparation And Application Of Composite Flocculant Poly Aluminum-titanium-zinc Silicate In Water Treatment

In the water treatment process,flocculant,as the core element of the coagulation stage,has been concerned by relevant scholars.Polysilicate flocculant is a new type of composite inorganic polymer flocculant,which has good adsorption bridging and electrical neutralization ability,and has good effect on the removal of turbidity,organic matter and other pollutants,and is a research hotspot in recent years.In this paper,polysilicate acid,aluminum sulfate,titanium sulfate and zinc sulfate were prepared by copolymerization method.With phosphorus and turbidity as the target pollutants,the optimal preparation conditions of two kinds of PATZS were gradually determined through single factor,orthogonal and response surface tests.The morphology and structure of prepared PATZS were characterized and analyzed by scanning electron microscopy,EDS spectrum and infrared spectrum.The prepared PATZS were used to treat phosphorus,turbidity and humic acid to simulate water samples,and the influences of PATZS dosage,p H of water sample,fast stirring time and fast stirring speed,slow stirring time and slow stirring speed,standing time and other factors on pollutant removal effect were explored.To explore the effects of common co-existing substances in water on the removal of phosphorus,turbidity and humic acid by PATZS,the main research conclusions are as follows:（1）The optimum preparation conditions of PATZS dephosphorization flocculant were:n（Al）:n（Si）1.68,n（Ti）:n（Si）0.5,n（Zn）:n（Si）1.25,polymerization p H 3.67,polymerization time 1.5h.The optimum preparation conditions of PATZS turbidity removal flocculant were as follows:n（Al）:n（Si）2.17,n（Ti）:n（Si）0.2,n（Zn）:n（Si）1.14,polymerization p H 3.77,polymerization time 1.5h.With the introduction of Al,Ti and Zn,the surface morphology of flocculants changed obviously,and pore structure appeared,and the surface area of PATZS was larger.The formation of Al-O-Si,Ti-O-Si and Zn-O-Si bonds indicates that Si,Al,Ti and Zn are polymerized by chemical bonds.（2）The optimal flocculation conditions of PATZS phosphorus removal are:The flocculant dosage was 1.0 mmol/L,the p H was 9.53,the fast stirring time was 5 min,the fast stirring speed was 240 r/min,the slow stirring time was 20 min,the slow stirring speed was50 r/min,and the standing time was 92.35 min.Under these conditions,the phosphorus removal rate was 99.20%.The residual phosphorus concentration was 0.1 mg/L.（3）The optimal flocculation conditions for turbidity removal of PATZS are:When the flocculant dosage was 0.6 mmol/L,the p H was 8.20,the fast stirring time was 120 s,the fast stirring speed was 160 r/min,the slow stirring time was 33.29 min,the slow stirring speed was 62.63 r/min,and the standing time was 30 min,the turbidity removal rate was up to100%.（4）The optimal flocculation conditions for removing humic acid from PATZS are:The flocculant dosage was 1.34mmol/L,the p H was 7,the fast stirring time was 5.91 min,the fast stirring speed was 220 r/min,the slow stirring time was 15 min,the slow stirring speed was49.20 r/min,and the standing time was 60 min.Under these conditions,the humic acid removal rate was 98.20%.The residual humic acid concentration was 0.23 mg/L.（5）Ca²⁺has great influence on phosphorus removal,turbidity and humic acid of PATZS.Among common co-existing anions,Cl^-,F^-and SO₄^2-have great influence on phosphorus removal of PATZS,while F^-and CO₃^2-have great influence on turbidity removal and humic acid removal.When the initial turbidity is greater than 40 NTU,the initial turbidity has a great influence on the phosphorus removal of PATZS.With the increase of initial turbidity,the removal rate of PATZS increased gradually.Initial turbidity has little effect on removing humic acid from PATZS.（6）Through SEM analysis of the floc,it was found that the surface structure of the floc was dense and rough,forming an irregular massive structure,which was conducive to solid-liquid separation.（7）The higher the removal rate of phosphorus,turbidity and humic acid,the closer the absolute value of Zeta potential is to 0,indicating that electrical neutralization plays a dominant role in the flocculation process.