Synthesis And Application Of Rice Starch Grafted Acrylamide In Settling Of Red Mud

Red mud settling separation in alumina production is an important process, affects the alumina production productivity and product quality, our country bauxite mainly is diasporic bauxite, digesting the red mud add domestic flocculant sedimentation performance is poor, add import flocculent sedimentation performance is good but the price is high, so it is necessary to develop efficient flocculant suitable for our country red mud settlement separation. Starch grafted acrylamide polymer has starch and polyacrylamide dual characteristics, and as starch and acrylamide graft copolymerization mainly in starch surface, particle size of rice starch is smaller, has larger specific surface area, therefore the rice starch and acrylamide polymerization and flocculation effect is more excellent.Use the oxidation and reduction initiator system, aqueous solution polymerization to synthesize rice starch graft acrylamide polymer. Through orthogonal test and single factor experiment, inspected reaction temperature, initiator concentration, EDTA-2Na concentration, urea concentration, acrylamide monomer and rice starch mass ratio and reaction time on the polymerization reaction product chain relative molecular mass, the monomer conversion rate and the grafting efficiency, determine the optimum process conditions:reaction temperature40℃, initiator concentration2.22×10-3mol/L, EDTA-2Na concentration2.68×10-4mol/L, urea concentration0.133mol/L, acrylamide monomer and rice starch mass ratio2:1, reaction time4h. In this condition, obtain the product of the branched chain relative molecular mass7.82×106, the monomer conversion rate98.6%, the grafting ratio67.3%, the grafting efficiency87.2%, and the product has good dissolve performance.Put grafted copolymer modified to anionic by after hydrolysis method, inspected hydrolysis temperature, hydrolysis time and theory hydrolysis degree on the hydrolysis product of the relative molecular mass and actual hydrolysis degree, determine the optimum hydrolysis conditions:hydrolysis temperature80℃, hydrolysis time3h, theory hydrolysis degree20%. In this condition, obtain pure graft copolymer hydrolysis product (HSP) with branch chain relative molecular mass 7.97×106, the actual hydrolysis degree13.2%, mixture hydrolysis product of graft copolymer and polyacrylamide (HSPM) with relative molecular mass8.29×106, the actual hydrolysis degree13%.Use the hydrolysis products and the major domestic and foreign commercial flocculant product in the Bayer process red mud settlement separation, investigated the effect of the flocculant type and additives on the red mud settling velocity, the supernatant turbidity and low-flow liquid to solid ratio, the results show that:the homemade flocculant HSP and HSPM add amount of each0.1g (1kg dry red mud), red mud settling velocity reaches its maximum, each is3.08mm/s and2.83mm/s, the supernatant turbidity reaches its minimum, each is253NTU and232NTU, and low-flow liquid to solid ratio is2.87and3.02, the overall performance is superior to domestic products, almost equal to imported products.