Fe3O4/MgAl-NO3 layered double hydroxide as a magnetically separable sorbent for the remediation of aqueous phosphate

Abstract

The separation of a spent sorbent from treated water after remediation is one of the major difficulties associated with industrial scale water treatment methods. Fe3O4 particles offer an easy magnetic method for the separation of used sorbent from water. Due to its low sorption capacity, magnetic Fe3O4 particles were first modified with Mg2Al-NO3-LDH prior to use in phosphate remediation. The Fe3O4/Mg2Al-NO3-LDH composite materials showed a maximum sorption capacity of 33.4mgP/g while Fe3O4 particles alone recovered only 4.6mgP/g. The kinetics of phosphate sorption onto Fe3O4/Mg2Al-NO3-LDH follows the pseudo-second order kinetic model supported by the best linear regression coefficient value (R2—1.00). Sorption isotherm studies indicated that it follows the Langmuir monolayer sorption isotherm. The effect of pH and competing anion studies indicate that this material is highly efficient in a wide pH range (pH 3–10). Selective sorption of phosphate on Fe3O4/Mg2Al-NO3-LDH was observed in the presence of excess sulfate, as well as from sea water enriched with phosphate. Fe3O4/Mg2Al-NO3-LDH composite material offers easy separation of spent sorbents due to magnetic property. The retention of sorption capacity in a wide pH range, and selectivity in the presence of competing anion, as well as from sea water suggests that these composite magnetic materials will be effective for wastewater remediation.