INOR 202 |
| Arsenic can be removed cost-effectively from drinking water using hydrous iron oxide based adsorptive media. The uptake of arsenic on these media is strongly influenced by the silica content and pH of the water; the capacity for arsenic decreases as both pH and silica increase. These effects have been investigated on two hybrid inorganic-organic arsenic adsorbants. Static As(V) capacities were determined by plotting isotherms as a function of silica concentration and pH. It was found that in a test solution containing 30 mg/L SiO2 and a batch factor of 8000, the capacity for As(V) decreased from 9.2 mg/g, at pH 7.2, to just 1.6 mg/g at pH 9.0 (an 83 % decrease) for a media called npRio-1. For the other media (ArsenXnp) the respective values were 5.3 mg/g and 2.8 mg/g, a 47 % decrease. It is clear that the effect of pH is significantly stronger on npRio-1. This difference can partially be explained by the isoelectric points of each media, which were 6.5-7.5 for npRio-1 and 8.5-9 for ArsenXnp. The decrease in arsenic capacity with increasing silica content is far greater at higher pH values. At pH 7.2, increasing the silica content from 0 to 30 mg/L caused a decrease in capacity from 13.8 mg/g to 9.2 mg/g for npRio-1, a decrease of only 33 %. However, at a pH of 8.8, the capacity decreased from 10.1 mg/g to 1.6 mg/g, a decrease of 84 %. Again, this effect seemed to be less on the ArsenXnp, the values being 5.4 mg/g in 0 mg/L at pH 9.0, and 2.8 mg/g at 30 mg/L, a 48 % decrease. The effects of both silica and pH on the performance of hydrous iron oxide based media have to be considered in regard to media life when designing water treatment systems.
|
|
Environmental Aspects of Inorganic Chemistry
7:00 PM-10:00 PM, Sunday, August 19, 2007 BCEC -- Exhibit Hall - B2, Poster
Sci-Mix
Division of Inorganic Chemistry |