Phosphate recovery from wastewater using engineered superparamagnetic particles modified with layered double hydroxide ion exchangers

• Published in: Water research (Oxford) 2013-10, Vol.47 (15), p.5670-5677
• Main Authors: Drenkova-Tuhtan, Asya, Mandel, Karl, Paulus, Anja, Meyer, Carsten, Hutter, Frank, Gellermann, Carsten, Sextl, Gerhard, Franzreb, Matthias, Steinmetz, Heidrun
• Format: Article
• Language: English
• Subjects: Adsorption; Applied sciences; Contact; Desorption; Exact sciences and technology; Hydroxides; Hydroxides - chemistry; Ion exchange; Ion exchangers; Kinetics; Layered double hydroxides; Magnetic separation; municipal wastewater; nanocomposites; Phosphate recovery; Phosphates; Phosphates - chemistry; Pollution; Recovery; screening; sorption isotherms; Superparamagnetic microparticles; Waste water; Waste Water - chemistry; Wastewater; Water Pollutants, Chemical - chemistry; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2013.06.039

An innovative nanocomposite material is proposed for phosphate recovery from wastewater using magnetic assistance. Superparamagnetic microparticles modified with layered double hydroxide (LDH) ion exchangers of various compositions act as phosphate adsorbers. Magnetic separation and chemical regeneration of the particles allows their reuse, leading to the successful recovery of phosphate. Based upon the preliminary screening of different LDH ion exchanger modifications for phosphate selectivity and uptake capacity, MgFe–Zr LDH coated magnetic particles were chosen for further characterization and application. The adsorption kinetics of phosphate from municipal wastewater was studied in dependence with particle concentration, contact time and pH. Adsorption isotherms were then determined for the selected particle system. Recovery of phosphate and regeneration of the particles was examined via testing a variety of desorption solutions. Reusability of the particles was demonstrated for 15 adsorption/desorption cycles. Adsorption in the range of 75–97% was achieved in each cycle after 1 h contact time. Phosphate recovery and enrichment was possible through repetitive application of the desorption solution. Finally, a pilot scale experiment was carried out by treating 125 L of wastewater with the particles in five subsequent 25 L batches. Solid–liquid separation on this scale was carried out with a high-gradient magnetic filter (HGMF). [Display omitted] •Superparamagnetic microparticles were modified with layered double hydroxides (LDH).•Particles were used for selective recovery of phosphate from municipal wastewater.•LDH chemistry was optimized for best phosphate selectivity and recovery efficiency.•Phosphate adsorption kinetics, mechanism and recovery solutions were studied.•Pilot-scale application of the particles was also tested.