Study On Preparation And Properties Of Polysilicate Inorganic Polymer Flocculant

Coagulation was an important technology used generally in water treatment. The cost of coagulants approximately account for 50 percent of the total cost of the water treatment. Therefore, the researches of high efficient and cheap coagulants have been concerned.Polysilicate-ferric-zinc (PSZF) was a new type of inorganic complex polymer flocculants. It's made up by adding ferricion and zincion into polysilicate-sulfate, and it had not only the property of electricity neutralization of ferric and zinc, but also the property of adsorption and framing of polysilicate-sulfate. The flocculation performance of PSZF was better than that of traditional flocculants. The preparation conditions, flocculation performance, practice effect and flocculation mechanism were fully investigated in this paper.1. The optimum preparation conditions of polymerized silicic acid were as follows: experiment action temperature 20-25℃, activation pH 2.0-5.0, concentration of sodium silicate 0.3-0.5 mol/L. Adding metal salts could restrain the polymerization of silicic acid. Different metal salts made different performance of restraining. The performance of restraining of Al₂(SO₄)3 and Fe₂(SO₄)₃ were better than that of ZnSO₄ and CuSO₄.2. PSZF was prepared under the optimum technical conditions of concentration of sodium silicate 0.4 mol/L, activation pH 1.7, activation time 30 min , mol ratio of Zn and Fe to SiO₂ 1.0 and mol ratio of Zn to Fe 2.0. Also the mode of adding chemical had been considered.3. Kinetics conditions could make remarkable effect on the flocculation performance of PSZF. The optimum kinetics conditions of PSZF which accorded with the value G and GT of coacervation-flocculation were got by experiment as following: rapid stirring rate 250 r/min, rapid stirring time 2 min, slow stirring rate 80 r/min, slow stirring time 5 min. With this condition, the removal of turbidity was upon 90%.4. By investigating the flocculation performance, we found that pH had no effect on the flocculation efficiency. When dosage of PSZF was 2mL/L and pH of wastewater was 8, the removal of turbidity was 95.6%. Before and after the flocculation experiment, the change of Zeta potential could redound to explain the flocculation mechanism of PSZF. The original turbidity could make some influence on the flocculation performance of PSZF. The removal of turbidity at 20-30℃of PSZF was better than that of any other temperatures. It had good stability effect. The form and flocculation efficiency of PSZF almost had no more change with the condition of handling it placed at nature. PSZF crassitude and close-grained floc was observed.5. In order to test practice effect in sewage treatment, landscape water, Huangpu River water and dyeing wastewater were to get disposal by using PSZF. The flocculation efficiency of PSZF was better than that of PS PSF and PFC. Besides the good performance of the removal of turbidity, COD removal rate of PSZF could attain 68%. When dosage of PSZF was 5mL/L and pH of dyeing wastewater was 3, the removal of colority was 86.6%. Compared to the PSF, PSZF could save nearly half dosage. According to the facts, PSZF was a new-style and high efficiency coagulation. The future of developing PSZF flocculant is promising.6. Mechanism of flocculation and structure characterizations of PSFZB were Studied. Particular analysis was carried out with IR spectrometry for the binding mechanism of the polymeric silicic acid and metal ions. The results showed that the structure of this new flocculant was polymeric with O- and OH- bridges. By TEM, different component have great effect on flocculants Structure. Fe Zn and Si had trend to form chainlike and branched structure. Structure characterizations of PSZF was different of polymeric silicic acid and common polysilicate, it had nicer flocculation efficiency and stability because of its special web-like structure. By studying flocculating mechanism it had abilities of charge neutralization, absorbing and bridging, network, so it had the best flocculation effect.