IRON COATED POTTERY GRANULES FOR ARSENIC REMOVAL FROM DRINKING WATER

In this report, we describe a new method for the removal of arsenic from water based on the iron coated pottery granules (ICPG) recently developed at the University of Hawaii. The ICPG media is a highly porous material comprised of iron, clay, and carbon. Briefly, it is made from highly porous pottery that is coated with zero-valent iron powder. We postulate that the ICPG media produces a stable Fe-Si surface complex for arsenic adsorption.

The surface morphology of the ICPG granules was examined by scanning electron microscopy. The ICPG granule size is between 0.3 and 2.36 mm. The typical surface of the ICPG particle is highly porous, with pore diameters ranging from 10 to 20 µm. The porosity of the ICPG media was found to be 75-80%, the BET specific surface area was 212 m2/g, and the total pore volume is 0.28 cm3/g.

Arsenic removal efficiency as a function of the flow rate has been analyzed by adjusting the flow rate. Therefore, within the stability region (flow rate lower than 15 l/hour, EBCT > 3 min), the concentration of As in the influent was always lower than 50 µg/l. The crucial EBCT for effluent meeting the 10 µg/l was 13 minutes. For EBCT higher than 15 min, the concentration of the effluent As concentration was less than the detection limits of the ICP-AES system (0.002 µg/ml). It is also found that the ICPG used as the media in water filtration procedures is very efficient in maintaining the water quality in terms of other cations, and that the scavenged arsenic is tightly bonded to the media during the absorption process, and as a result very little arsenic flashes out from the exhausted media.

Our preliminary tests indicate that the new ICPG media will satisfy the critical requirements of a column adsorbent for arsenic removal: (1) sufficient strength and large surface area to allow granular packing; (2) efficient arsenic removal; (3) long duration, high capacity, and selectivity; (4) high physical integrity (non-disintegrating) in water; and (5) limited secondary problems affecting the quality of water. Therefore the ICPG system has great potential as an effective method for arsenic removal from drinking water.