ALBERT

Description: The main research activity of this collaborative research effort is the optimization of water treatment technology on basis of granulated Fe hydroxides (= GFH, or in German GEH). GEH® is applied by the SME-Partner, the GEH Wasserchemie GmbH & Co. KG established in 1997 and now one of the leading providers of iron- based high-capacity adsorbents for use in fixed bed filter process. Over 2000 plants have yet been delivered into more than 20 countries worldwide. Main purpose is treatment of As- and Sb-tainted waters, providing e.g. in India more than half million people with treated tap water. GEH® is based on pure synthetic iron hydroxide (Beta-FeOOH, akaganeite) with a large effective surface area (〉250 m2/g) and an adsorption capacity of up to 50 g/kg As if applied on waters containing only As. This enables a simple, low maintenance removal procedure with capacities of up to 300,000 bed volumes over years without producing hazardous As-loaded sludge to be costly deposited. The main practical problem is the yet less well understood efficiency degradation with different groundwater milieus; with more or less reduced bed volume capacity. Our experiments revealed that these effects are mainly due to competing inorganic oxyanion species (e.g., silicate). An open question to be solved for the SME partner was whether a specific biogenic functionalization of the surface may help in optimizing towards a more versatile and smooth filter technology, but our preliminary experiment results were not thus promising towards this task. Instead, we found a severe inhomogeneity in adsorption efficiency and competing effects by inorganic oxyanion species on an individual grain scale which may become unexpected and new key information how to improve on the GEH production process.