Studies on Fluoride Removal from Wastewater by Polysilicate Aluminum Iron Sulfate Coagulant

摘要

The fluoride removal efficiency from wastewater by using a new type polymeric coagulant polysilicate aluminum iron sulfate (PSFAS) was studied by using the jar test method. The effect of pH value, molar ratio of (Al3+ + Fe3+) to SiO2, and dosage of the coagulant on the fluoride removal efficiency was also investigated. The species of Al( ) and Fe( )in PSFAS were determined by the Ferron timed complex colorimetric method. The values of Alb in PSFAS are not a significant difference for the different molar ratios of (Fe+Al)/SiO2. But the values of Feb in PSFAS decrease with increases (Fe+Al)/SiO2 molar ratios. It was also found that the stability of PSFAS decreased with the increase of molar ratio. The PSFAS was characterized by the infrared spectrometer (IR) and transparent electron microscopy (TEM). After coagulation, the new peak of 708.81 cm-1 appeared. TEM showed that PSFAS has pores with a larger specific surface area. The fluoride removal mechanisms of PSFAS were also discussed. Experimental results showed that PSFAS had more than 95% fluoride removal efficiency with a wider range of pH from 4.0 to 9.0.