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Granular iron hydroxide (GIH) adsorbents are widely used for arsenic removal and havebeen reported to operate more than 1.5 years without any regeneration. During thisprolonged operational period the iron hydroxide may shift towards more stable crystallineforms that have less affinity for arsenate. The objectives of this research work were tostudy the effect of extended GIH media storage and shifts in pH on its arsenic removaleffectiveness. Batch adsorption studies were conducted by contacting fresh, six- andnine-month old granular Bayoxide E33 media (10g/L) with 60,000 g As (V)/L solutionat pH 4 and pH 7. For 1 day batch equilibrium time, arsenate adsorption capacity wasobserved to decrease by 47 % (from 6.0 mg As/g media to 3.2 mg As/g media) and 83 %(from 6.0 mg As/g media to 1.0 mg As/g media) for nine-month old media in batchstudies, conducted at initial pH 4 and 7, respectively. Further, pH adjustment had littleimpact on the arsenate adsorption capacity of the fresh media, but did show someindications of restoring capacity to the older media. For 15 days equilibrium time, thearsenate adsorption capacity was increased by 100 % (from 2.7 mg As/g media to 5.4 mgAs/g media) and 27 % (from 2.6 mg As/g media to 3.3 mg As/g media) for six- and nine-monthold media, respectively. The results obtained in this research indicated that thearsenate adsorption capacity of GIH media may decrease during prolonged media use. Inaddition, shifts in pH have the potential to offer a means of prolonging media life byredeveloping fresh surface sites with high affinity for arsenate. Includes 9 references, figures.

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Edition: Vol. - No. Published: 06/01/2007 Number of Pages: 34File Size: 1 file , 1.2 MB