Granular Iron and Alumina based Phosphate Sorbents

VITO will use sludges from water treatment plants for the production of low-cost granular iron and alumina based phosphate sorbents. 

These granulates are mechanical robust and have fast sorption kinetics. Therefore they are especially usefull for flow through filter systems. By using different sludge compositions the sorbent characteristics can be tailored further to more specific filter installations.

The sorbents are composed of amorphous iron oxides. These iron oxides form strong and selective inner-sphere complexes with phosphates by ligand exchange and hydrogen bridges. Since phosphates are mainly present as anions (e.g. HPO42- en H2PO4-), a faster sorption will occur when the iron oxides on the sorbent surface are positively charged. This means sorption occurs slower at high ph.

The produced granular sorbents will be used for a pilot study on a feeder stream to the buffer basin of water production center “De Blankaart” of De Watergroep. This buffer basin extracts water from a surface water area of 25 000 ha in the drainage basin of the river Yser and the polders of nature reserve De Blankaart. The production plant produces 60 000 m³ of drinking water per day. Due to water quality issues (e.g. high phosphate concentrations), currently no water is extracted from april-september. We aim at a phosphate concentration in the treated water of <0.5 mg PO4/l.


Granular iron based sorbents


Granular aluminium based sorbent