The Study of Processes of Iron Hydroxide Coagulation and Sedimentation

摘要

Migration behavior of radionuclides forming pseudoradiocolloids with iron hydroxide depends on physicochemical behavior of iron hydroxide. It was determined that pH of the solution and iron concentration are the main parameters affecting processes coagulation and sedimentation of iron hydroxide. Time dependences of iron hydroxide coagulation and sedimentation being obtained using ultrafiltration and turbidimetry methods were analyzed. Integral and differential curves of size distribution of iron hydroxide particles were obtained using the method of laser diffraction. At the whole pH range studied, monomodal size distribution was observed in the solution containing 25 mg L~(-1) of iron; whereas in the solution containing 100 mg L~(-1) of iron bimodal size distribution was observed. This difference indicates different mechanisms of coagulation that was additionally confirmed by analysis of kinetic curves. It was found that the best conditions for formation and further sedimentation of iron hydroxide were pH 6-8 and iron concentration of at least 50 mg L~(-1). At these conditions, the time of half-precipitation of the iron hydroxide precipitate did not exceed five minutes.