Preparation Of Modified Starch-Polysilic Acid Composite Flocculant And Study On Its Flocculation Performance

In recent years,there is a sharp shortage of fresh water resources available to human beings,and the situation of water pollution is becoming more and more serious.Human production,life and even life safety have been directly affected.Therefore,it is urgent to develop new environmental and efficient water treatment technologies and new products to solve the problem of water pollution.Flocculants are widely used in water treatment because of their high efficiency,simple operation and low cost,accounting for 3/4 of water treatment agents.Therefore,it is very important to develop flocculants that keep pace with the times to control water pollution.Up to now,there are more than 300 kinds of flocculants,but the performance of different flocculants is uneven: among them,the traditional inorganic flocculants are the most mature ones,but they have large dosage,large sludge yield,and easy to residual metal ions,resulting in secondary pollution of water environment;the synthetic organic macromolecule flocculant PAM used in the market has high flocculation efficiency and wide application range,but its monomer is toxic and non-biodegradable.Natural macromolecule flocculants have a wide range of sources and can be biodegraded,but their molecular chains are short,their solubility is low,and they are usually not charged,so their treatment effect is limited.Therefore,in the face of complex water quality and changeable water treatment process,the development of new flocculant products is an important way to solve water environmental pollution with high efficiency and costeffectiveness,and the major challenges it faces.In this paper,a new modified starch-based flocculant was prepared from natural corn starch by a series of modification methods,such as activation,etherification and copolymerization.The main contents are as follows: The effects of starch to sodium silicate mass ratio,starch to etherifying agent mass ratio,reaction time and UV intensity on the preparation of CS-PSi composite flocculant were studied by single factor control variable method,using cationic substitution degree and simulated kaolin flocculation turbidity removal rate as evaluation indexes,and the preparation conditions of CS-PSi composite flocculant were optimized by Fourier transform infrared spectroscopy(FT).IR,1HNMR,TG-DSC and FESEM were used to characterize the structure and morphology of CS-PSi.Finally,the flocculation performance of CS-PSi was systematically investigated by simulating kaolin water samples and activated sludge.The results show that:1)The optimum conditions for the preparation of CS-PSi are: the mass ratio of starch to sodium silicate is 4:2,the mass ratio of starch to etherifying agent is 4:4.5,the ultraviolet light intensity is 30.7mW/cm2,the etherification reaction is 3h,and the polymerization reaction is 2h.2)Fourier transform infrared spectroscopy(FTIR)and nuclear magnetic resonance(NMR)analysis showed that new Si-C,Si-O and C-N bond absorption characteristic peaks and quaternary ammonium cationic hydrogen groups appeared on CS-PSi,which confirmed the successful combination of polysilicic acid and cationic starch and resulted in new products.Scanning electron microscopy analysis showed that CS-PSi had welldeveloped surface pore,obvious stratification,stereoscopic flocculation and significant flocculation advantages.The results showed that the product had good thermal stability and was not easy to decompose.3)CS-PSi has a good flocculating effect on simulated kaolin suspension with a wide range of pH.The optimum dosage of CS-PSi is 10 mg/L and the turbidity removal rate is 97%.The optimum dosage of CS-PSi for activated sludge conditioning is 40 mg/L,and the solid content of dewatering filter cake is 18.21%.Under the same conditions,the solid content of sludge is only 4.52% after PAM conditioning,and the effect of CS-PSi conditioning and dewatering is good.Water is a necessary substance for human survival,and water pollution will directly affect human health and life safety.In the face of the current severe water pollution situation,the available freshwater resources are increasingly scarce,so it is imperative to develop new environmental and efficient water treatment technologies and new products.