Engineering gold nanoparticles-infused silica aerogel composite for trace mercury adsorption

Mercury (Hg) contamination in water poses severe environmental and health risks, necessitating efficient and scalable remediation technologies. We report a novel gold nanoparticle-doped silica aerogel (Au-AG) composite synthesized via supercritical fluid impregnation, designed to harness the high surface area and porosity of silica aerogels alongside the strong Hg-binding affinity of gold nanoparticles (Au-NPs). The resulting composite exhibits robust structural integrity and a characteristic purple hue, indicating uniform dispersion of Au-NPs. Adsorption experiments at environmentally relevant Hg concentrations show that uptake follows Langmuir isotherm behavior and pseudo-second-order kinetics, indicative of monolayer chemisorption and rapid adsorption rates. The Au-AG composite achieves up to 85% Hg removal within 24 hours and a maximum adsorption capacity of 12.82 mg g^-1 at ppb-level Hg concentrations, outperforming conventional materials such as activated carbon, thiol-functionalized resins, and undoped silica aerogels under similar conditions. The composite's structural integrity and chemical stability indicate potential for regeneration and reuse in cyclic adsorption processes, making it a promising candidate for sustainable water purification technologies. Moreover, the synthesis approach is compatible with scalable and sustainable production, reinforcing its applicability in real-world water purification systems. These findings position the Au-AG composite as a high-performance and scalable solution for trace-level mercury remediation in contaminated water, advancing sustainable environmental technologies.