Adsorption removal of Pb(II) from aqueous solution by fulvic acid-coated ferrihydrite

Fulvic acid (FA) coated ferrihydrite (FA-ferrihydrite) were prepared by a coprecipitation procedure for the removal of toxic Pb(II) from water. TOC and XRD analysis showed FA-ferrihydrite contained about 14.7% (w/w) of FA which coated a part of the ferrihydrite surfaces. Compared to ferrihydrite, the total pore volume, BET surface area and surface fractal dimension of FA-ferrihydrite increased. As for ferrihydrite and FAferrihydrite, the pH of the point of zero charge (pHpzc) was 7.8 and 5.4, and the surface charge at pH 6.0 was 0.41 and -0.43 mmol/g, respectively. The maximum adsorption capacity (q max ) for Pb(II) by FA-ferrihydrite (19.26 mg/g) was significantly higher than that by ferrihydrite (11.84 mg/g). The correlation coefficients (R 2 ) of fitting Langmuir and Freundlich models 21, 22 to the adsorption data for Pb(II) by ferrihydrite were 0.993 and 0.953, and by FA-ferrihydrite were 0.981 and 0.987, respectively. This indicates that FA-ferrihydrite is a relatively high efficient adsorbent for Pb(II), and the adsorption behavior can be well described by Freundlich model 22