Preparation And Application Of Polysilicate Metal Salt-organic Composite Flocculants

Flocculation is one of the most commonly used economic and effective pretreatment methods in the field of water treatment.With the continuous development of social modernization,environment friendly and high flocculation efficiency flocculants are gradually favored by people.In this paper,the application of polysilicate metal salts and organic composite flocculants in water treatment is mainly studied.Polysilicate aluminium magnesium-cationic polyacrylamide(PSAM-CPAM)and polysilicate aluminium calcium-sodium alginate(PSAC-SA)composite flocculants were prepared.In this paper,the evaluation indexes of PSAM-CPAM flocculant were color and turbidity removal rate.The morphology and bonding structure of flocculant and flocs were analyzed by scanning electron microscopy,energy spectrum and fourier transform infrared spectroscopy,and the flocculation mechanism was deeply explored by Zeta potential analysis.The preparation and flocculation conditions of PSAM-CPAM were optimized by single factor variable experiments.The results were as follows: the optimum preparation pH value of PSAM-CPAM was 2.0,the temperature of PSAM was 40?,the polymerization temperature of CPAM was 50?,the molar ratio of Al and Mg to Si was 1.0,the molar ratio of Al to Mg was 9:1,and the pH value of flocculated water was 7.0,the temperature of water sample was about 25?,the settling time was 25 minutes and the dosage was 1.0 mL/L(each of PSAM and CPAM is 0.5 mL).The maximum turbidity and color removal rate of Songhua River were 98.4% and 98.0% respectively by stepwise flocculation.In the process of flocculation,charge neutralization,bridging adsorption and co-precipitation played a dominant role.The PSAM-CPAM flocculant not only improves the flocculation performance significantly,but also avoids the possible second pollution by stepwise flocculation,which makes it possible for the wide application of organic flocculants.In this paper,the evaluation indexes of PSAC-SA flocculant were color and turbidity removal rate.The morphology and bonding structure of the flocculant were analyzed by scanning electron microscopy,fourier transform infrared spectroscopy and X-ray diffraction.The preparation conditions and flocculation conditions were optimized,and the flocculation mechanism was explored.The preparation and flocculation conditions of PSAC-SA were optimized by single factor variable experiments.The results were as follows: the optimum preparation pH value of PSAC-SA composite flocculant was 3.0,reaction temperature was 40?,the molar ratio of aluminium and calcium was 1.0,the molar ratio of aluminium to calcium was 8:2,the mass ratio of sodium alginate to silicon was 0.04,and the flocculating water sample pH value was 7.0,water temperature was 25?,and dosage was 1.0 mL/L.When applied to Songhua River water,the best flocculation performance can be achieved.The removal rates of turbidity and color were 98.8% and 97.6%.In the flocculation process,bridging adsorption plays a dominant role.PSAC-SA flocculant has a wide range of raw materials and can be biodegraded.Composite with polysilicate metal salts flocculant can significantly improve the flocculation performance and sustainable development of green environment.