The objectives of this work were to quantify the effects of pH and competing ions in the
presence and absence of other competing ions on arsenic removal during coagulation with ferric
chloride. An additional objective was to compare in-situ formed ferric hydroxides vs. granular ferric
oxide media as arsenic adsorbents on the basis of µg As sorbed/g Fe(III). Finally, attempts were
made to use the MINEQL+ chemical equilibrium modeling program to predict arsenic adsorption as
a function of pH and competing ions. The removal of As(V) was highly pH dependent while As(III)
was largely independent of pH in the NSFI-53 challenge water. The adsorption of As(V) which is
charged in the pH range of 6.5-8.5 was significantly higher than uncharged As(III). The in-situ
formed hydroxides had significantly higher adsorption capacities compared to the granular media
due to high effective surface area of FeOOH coagulant. All three competing ions--silicate,
phosphate, and vanadate--interfered with arsenic adsorption, and the level of interference depended
on the competing ion concentration and the presence or absence of other competing ions. The
unmodified Mineql+ chemical equilibrium modeling program could not simulate As(III) or As(V)
adsorption onto Fe(OH)<sub>3</sub> during FeCl<sub>3</sub> coagulation. Includes figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 340 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 9 |
| Published : | 06/01/2006 |
