Comprehensive Insight Into Removal and Recovery of Phosphate by a Magnetic Nanocomposite Microparticle Modified With MgFe-Zr Layered Double Hydroxide

The influence of various operating variables on the phosphate removal by layered double hydroxide (LDH)-modified magnetic nanocomposite materials has been intensively investigated in the literature. Although many studies have demonstrated that the recovery of phosphate and simultaneous regeneration of the reusable material could be performed successfully by using several regeneration solutions, only the recovery rate has been considered as a decision-making criterion to determine the optimum conditions. This study aimed to comprehensively investigate the influence of various operating variables on the recovery of phosphate as well as its removal from aqueous solutions by a magnetic nanocomposite microparticle modified with MgFe-Zr LDH. To gain better insight on the recovery process, a multi-criteria approach, including recovery rate, structural stability, particle weight loss, dissolution of material components, and characterization of the regenerated material, was adopted. According to the results, the most important operating variable influencing both the removal process and the recovery process was determined as the solution pH. Derived from the results, the main mechanisms involved in the removal and recovery process were proposed and the kinetics and thermodynamic of the removal process were evaluated. Under the optimum conditions, the removal efficiency and the specific removal capacity was determined to be 96.4% and 9.6 mg PO4-P/g, respectively, while 84.8% of the removed PO4-P could be recovered by using 50 mL 1.0 NaOH solution within 60 min. EDS, XRD, FT-IR and ICP-OES analyses confirmed that the particle retained its initial structural stability during the removal and recovery process under the optimized operating conditions.