Preparation Of Inorganic Flocculant Composite Of Fe(Ⅲ)-Al(Ⅲ)-Si(Ⅲ) For Pretreatment Of Landfill Leachate

An inorganic flocculant composite of Fe(III)-Al(III)-Si(IV) (PFASiC) were optimally prepared and used to pretreat landfill leachate in this paper. With the addition of an alkali silicate, the flocculant was made using iron chloride and aluminium chloride as main raw materials. Under high shear mixing, through polymeric and aging reactions, the flocculant, a reddish brown solution, with different basicities and pH values, was finally made. Optimum reaction conditions were selected.The experimental results showed that removal rate of COD_Cr of landfill leachate was the highest when the ratio of Fe(III):Al(III):Si(IV) was 10:1:0.786. Moreover, basicity, addition of flocculant composite and pH values of landfill leachate would influence the flocculation effect. The results also demonstrated that, under the conditions of the basicity of PFASiC at around 0.57, the addition of PFASiC at around 170mL flocculant per liter leachate (Fe(III) 2.97g/L, Al(III) 0.14g/L, Si(IV) 0.12g/L), pH 5-7, the best flocculating effect could be achieved, and COD_Cr removal rate could reach to 55%.Microscopic crystal structure of PFASiC had been observed using a microscope; it could be found that the flocculants (PFASiC) had different microscopic crystal structures at different basicities. In addition, the prepared composite PFASiC was analyzed using Fourier transform infrared spectroscopy, and the flocculant was found to be a kind of inorganic composite with strong -OH bonding. The Ferron method was used in measuring the species distribution and transformation of PFASiC aggregate.