Magnetic seeding of non-magnetic adsorbent powders by coagulation using ferric chloride and magnetite

A magnetic modification of conventional adsorbents powders to rapidly remove them from water is investigated. In this paper we study the possibility to use a non magnetic adsorbent powder mixed with magnetite and a coagulant like ferric chloride added after the adsorption to create magnetic flocks that can be magnetically separated (magnetic seeding). A natural zeolite and a Na-activated zeolite mixed with magnetite and ferric chloride are tested. The combination of a sedimentation (with coagulant) followed by a magnetic filtration is from 6 to 30 times faster than the only sedimentation (with coagulant) attaining the same final turbidity. Also a Magnetic Activated Carbons (MACs) powder with and without the addition of ferric chloride is tested. The process conditions that lead to a residual turbidity less than 10 % after 5-10 minutes of magnetic separation are defined for all the powders. The tests on Mn(II) adsorption on Na-activated zeolite-magnetite mixtures show that the adsorption improvement due to activation is not affected by the addition of the coagulant. Moreover the adsorption of the tested cationic surfactants on MACs is up to 30 % higher by adding ferric chloride. Negligible concentrations of Fe(III) are found in all the treated samples. This technique can potentially be applied to any non magnetic adsorbent powder and/or to any existing coagulation/flocculation treatment.