Layered double hydroxide ion exchangers on superparamagnetic microparticles for recovery of phosphate from waste water

Abstract

Superparamagnetic microparticles modified with an ion exchange system are reported for the recovery of phosphate from waste water by a magnetic separation technique. Layered double hydroxides (LDH), anionic clays, are precipitated from an aqueous solution and deposited by an ultrasonic treatment on superparamagnetic microparticles consisting of Fe₃O₄ multicores embedded in a SiO₂ matrix. Deposition can be conducted in a batch process as well as in a continuous way, using an ultrasonic flow cell. The obtained composite particles show good magnetic separability and have a specific surface area of around 100 m² g⁻¹. Zr doped LDH shows improved phosphate adsorption in waste water. After magnetic separation and regeneration, the composite particles are re-used which is demonstrated for four cycles. Phosphate ions are concentrated in the regeneration solution. Simple, low cost, and a fast continuous synthesis of the composite particles paves the way for application beyond lab scale in real waste water treatment plants.