Layered double hydroxides, an effective nanomaterial to remove phosphorus from wastewater: Performance, mechanism, factors and reusability

Systematic understanding of phosphorus adsorption performance, mechanism, factors and reusability of layered double hydroxides (LDH) remains limited. Thus, iron (Fe), calcium (Ca) and magnesium (Mg)-based LDH (FeCa-LDH and FeMg-LDH), were synthesized with a co-precipitation method to improve phosphorus removal efficiency during the wastewater treatment process. Both FeCa-LDH and FeMg-LDH showed a considerable ability to remove phosphorus in wastewater. When the phosphorus concentration was 10 mg/L, the removal efficiency reached 99 % (FeCa-LDH: 1 min) and 82 % (FeMg-LDH: 10 min), respectively. The phosphorus removal mechanism was observed to be electrostatic adsorption, coordination reaction and anionic exchange, which was more evident at pH = 10 for FeCa-LDH. Co-occurrence anions that affected phosphorus removal efficiency, were observed in the following order: HCO3− > CO32− ≈ NO3− > SO42−. After five adsorption-desorption cycles, phosphorus removal efficiency was still up to 85 % (FeCa-LDH) and 42 % (FeMg-LDH), respectively. Together, the present findings suggest that LDHs were high-performance, strongly-stable and reusable phosphorus adsorbents.