Because of the higher arsenic capacity of in situ-formed
hydroxides and the growing popularity of zirconium
and titanium oxyhydroxide media for arsenic removal,
a comparative study of iron versus titanium and zirconium
coagulants was conducted. Arsenite [As(III)] and
arsenate [As(V)] removal using zirconium and titanium
coagulants was compared with removal using ferric
chloride (FeCl<;sub>;3<;/sub>;) and alum in a standard challenge
water. As(III) adsorption was significantly lower than
As(V) adsorption at all pH levels with all coagulants.
The highest As(V) loadings both on mass and molar
bases were observed with FeCl<;sub>;3<;/sub>;. As(V) removal
increased with decreasing pH with all coagulants. The
small amount of As(III) removal observed was generally
independent of pH. Alum did not remove any As(III).
The highest As(III) loadings were observed with titanium(III), which appeared to be oxidized to As(V) by
peroxide resulting from titanium(III) hydrolysis. The
types of sludge produced by all coagulants passed the
toxicity characteristic leaching procedure and the waste
extraction test. When chemical costs were compared,
FeCl<;sub>;3<;/sub>; was the most cost-effective coagulant for As(III)
and As(V) at all three pH values, and As(III) chemical
coagulation costs were five to 20 times higher than
those for As(V). Alum was four to eight times the cost
of FeCl<;sub>;3<;/sub>; for As(V) removal. Includes 49 references, tables, figures.
| Edition : | Vol. 100 - No. 2 |
| File Size : | 1
file
, 620 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 13 |
| Published : | 02/01/2008 |
