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Because of the higher arsenic capacity of in situ-formedhydroxides and the growing popularity of zirconiumand titanium oxyhydroxide media for arsenic removal,a comparative study of iron versus titanium and zirconiumcoagulants was conducted. Arsenite [As(III)] andarsenate [As(V)] removal using zirconium and titaniumcoagulants was compared with removal using ferricchloride (FeCl;sub;3;/sub;) and alum in a standard challengewater. As(III) adsorption was significantly lower thanAs(V) adsorption at all pH levels with all coagulants.The highest As(V) loadings both on mass and molarbases were observed with FeCl;sub;3;/sub;. As(V) removalincreased with decreasing pH with all coagulants. Thesmall amount of As(III) removal observed was generallyindependent 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) byperoxide resulting from titanium(III) hydrolysis. Thetypes of sludge produced by all coagulants passed thetoxicity characteristic leaching procedure and the wasteextraction 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) chemicalcoagulation costs were five to 20 times higher thanthose for As(V). Alum was four to eight times the costof FeCl;sub;3;/sub; for As(V) removal. Includes 49 references, tables, figures.

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Edition: Vol. 100 - No. 2 Published: 02/01/2008 Number of Pages: 13 File Size: 1 file , 620 KB