Removal and recovery of phosphate from wastewater with reusable magnetically separable particles

This work presents an innovative concept to use engineered magnetic particles for phosphate removal directly from wastewater effluents and concentrating it in a purer liquid matrix as a source for further phosphorus recovery. The particle surface is modified with layered double hydroxides (LDHs) which are reported as selective anion exchangers for phosphate. The particles can be magnetically extracted from the water, regenerated and reused again. Materials with various chemical compositions of the LDH-shell are synthesized and the optimal system is evaluated through numerous lab-scale tests. The MgFe-Zr - LDH system exhibits the highest adsorption capacity (35 mgP/gLDH), good selectivity and high magnetic separability and recovery potential. For this system the influence of the different reaction parameters and process kinetics are studied in details and optimized through particle concentration, contact time and pH adjustment. The particles reusability is demonstrated for 15 adsorption/desorption cycles in wastewater with insignificant drop in performance.