Synthesis of porous Mg(OH)2 nanowires for phosphate removal from water

Mg(OH)2 is an inorganic material with a wide range of applications in water purification, especially the adsorption of phosphates. In this study, porous Mg(OH)2 nanowires were synthesized by a facile hydrothermal conversion method to remove phosphate from aqueous solutions. The porous Mg(OH)2 nanowires can be readily obtained using magnesium hydroxide chloride hydrate (MHCH) whiskers as precursors in NaOH ethanol-water solution and exhibit good adsorption performance for phosphate. OH- ions diffused into the lattice to bind with Mg2+, while H2O and Cl- escaped from the lattice, resulting in the formation of porous Mg(OH)2 nanowires. The ethanol prevented the collapse of these pores. The adsorption process of phosphate on the porous Mg(OH)2 nanowires conforms to pseudo-second-order kinetics and is spontaneous, endothermic, and entropy-increasing. It was substantiated to be a complexation process of Mg2+ and HPO42- and H2PO4-. The maximum adsorption amount at 313 K was 162.15 mg g−1, minimally affected by coexisting ions and demonstrated good recycling performance. This work highlights the potential of porous Mg(OH)2 nanowires as an eco-friendly and low-cost adsorbent for phosphate removal and recovery.