AWWA ACE69067

The objective of this research was to understand the combined effects of pH, iontypes and time on phase transformation of a commercially available granular ironhydroxide media, Bayoxide E33, exposed to a synthetic groundwater at pH 6 and pH 8for 90 days in batch experiments, using X-ray diffraction (XRD) technique. No newiron/arsenic bearing mineral was observed for spent E33 media indicating that arsenicwas not incorporated within the crystalline structure of the media. However, XRD peaksof spent media at 20 = 21.62º and 36.9º were observed to widen compared to freshmedia. Greater widening of peaks was observed for samples exposed to pH 6 solutionsthan that exposed to pH 8 solutions. Observed changes in peak-widths of spent mediasuggest the possibility of structural changes in media over time, which may also influenceits arsenic adsorptive capacity over time. These findings are relevant to small utilities thattreat groundwater with high arsenic and ferrous iron concentrations. Concerns appear tobe greater for reduced, alkaline groundwater as the pH 8 sample with ferrous iron presentshowed the greatest structural change. Further experiments are underway to collect moreinformation about changes in degree of crystallinity and arsenic adsorption capacity ofiron oxide media over time, which could be useful in understanding the combined effectsof different environmental factors on its stability and time-dependent arsenic removaleffectiveness. Includes 16 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2008

Number of Pages:

11

File Size:

1 file , 790 KB