Research On The Preparation And Properties Of Polysilicate Ferric (PSF)

In this paper,a kind of ferric inorganic polymer,polysilicate ferric（PSF）coagulant was prepared by co-polymerization.The mechanism of Fe-Si reaction,hydrolysis law and coagulation performance were inspected by UV/Vis absorption scanning,X-ray diffraction,infrared spectrum and so on.The polymerization mechanism and its application were explored.The main research work was in the following areas:First of all,the preparation method of polysilicate iron was optimized.The Fe/Si molar ratio,acidifier and polymerization temperature were chosen as the main factors to investigate the effect on the coagulant morphology and coagulation performance.The results showed that the ferrosilicon bonding modes were different with the various molar ratios of Fe/Si.With sulfuric acid as an acidifier,the reaction could reach the equilibrium state quickly,and the oxidation,complexation and hydrolysis could be completed in a short time.The optimal polymerization temperature was 50℃,the activity of the electron and proton in the silicic acid molecule was increased,and the collision probability with the neighboring molecules was increased,which made the polymerization reaction of ferrosilicon reach the optimal state.Combined with the SEM technique,the PSF shape with Fe/Si molar ratio of 1.5 could be observed,the direction was obvious,the voids were scattered and the three-dimensional space was spectacular.Infrared spectra demonstrated that iron ions and polysilicic acid were complexed by some chemical bonds,instead of a simple mixture of raw materials.By monitoring the change of pH during the hydrolysis of PSF,and combining with the theoretical calculation,the distribution of PSF hydrolysis was studied.The investigations showed that the increase of Fe/Si ratio was beneficial to the complexation of Fe³⁺and OH^-to form Fe（OH）₂⁺.And with the increase of pH value of the solution system,the products of cationic hydrolysis decreased gradually.The greater the charge ratio,the faster the rate of descent.The flocculation index（FI）of PSF was detected by real-time pulsating monitor.It was found that the floc growth was divided into three stages:lag,rapid growth and steady growth.When Fe/Si=2 and the dosage was 1 mmol/L,the floc size was the largest and the structure was stable with the increase the stirring time.This paper investigated the coagulation efficiency of PSF in treating acrylic fiber wastewater,in comparison with that of polyferric sulfate（PFS）,potassium ferrate（K₂FeO₄）and polyaluminum chloride（PAC）.The results revealed that PSF had superior coagulant efficiency and the removal rates of COD and TOC were 35%and 30%,respectively.PSF also had a significant effect on the treatment of latex wastewater.The removal efficiency of COD was the best when the dosage was 10 mmol/L,which was about 73%and the turbidity removal rate was above 80%.