High aluminum and iron fly ash can be used to make flocculants
In this work, aluminum and iron existing in coal fly ash were extracted by the
method of hydrochloric acid leaching. Effects of solid-liquid ratio, reaction
temperature, reaction time, acid concentration, and raw ash mesh on recovery
efficiencies of Al2O3 and Fe2O3 were
investigated. X-ray diffraction analysis indicated that anhydrite, hematite,
mullite and quartz were the dominant minerals in the raw fly ash sample.
X-ray fluorescence technique was applied to determine the mass fractions of
chemical components in the raw ash and leached residues, while the
concentrations of Al2O3 and Fe2O3 in
leaching solutions were measured by titration method. The optimal recovery
efficiencies of Al2O3 and Fe2O3,
obtained under the reaction condition of 95°C, 5 h, acid concentration of
20 wt.%, a solid-liquid ratio of 1:3.5 and raw ash mesh of 400, were 42.75% and
35.10%, respectively.
After removing the leached residues, the leaching solutions were employed to
manufacture flocculants of polymeric aluminum ferric chloride for treating the
oil recovery wastewater from polymer flooding, which possessed high contents of
suspended solids (SS) and oils.
Microfiltration membrane and ultraviolet spectrophotometer were utilized to
determine the contents of SS and oils in water samples. Through adjusting Al/Fe
molar ratio to 20:1 and basicity to 70%, the maximum removing efficiencies of SS
and oils can be achieved, respectively 96.1% and 91.5%. Moreover, increasing the
iron content and basicity of flocculants within certain ranges contributed to
improving the settling characteristic of flocs.