Crosslinking ionic oligomers sol-gel synthesis of porous amorphous magnesium hydroxide and its application in Pb2+ adsorption

Abstract

Porous magnesium hydroxide with high specific surface area is widely used in environmental applications. In traditional sol-gel methods, the preparation of high-surface-area porous magnesium hydroxide (HSA-PMH) necessitate the use of highly reactive alkoxide as a precursor, thereby limiting its development. Herein, HSA-PMH was prepared by a simple crosslinking ionic oligomer sol-gel method using MgCl₂·6H₂O as precursor, short-chain alkohol as solvent and triethylamine (TEA) as alkaline reagent and capping agent. The choice of alkohol solvent plays a significant role in influencing the degree of crystallinity, morphology and porosity of HSA-PMH. Alkohol solvent with high dielectric constant favors the formation of HSA-PMH. When the molar ratio of TEA to Mg²⁺ is 30:1 and methanol is used as the solvent, the specific surface area of HSA-PMH reaches 538 m²∙g⁻¹. The Pb²⁺ adsorption properties of the HSA-PMH were further investigated. It was found that 98 % of the Pb²⁺ could be removed within 15 min, and the maximum adsorption capacity calculated by Langmuir isotherm model reached 4245 mg∙g⁻¹. The results indicate that the synthesized HSA-PMH is an excellent adsorbent for Pb²⁺, boasting a high adsorption capacity and rapid rate of adsorption.