Large-scale and low-cost fabrication of two functional silica sorbents by vapor condensation induced nanoemulsions and their excellent uptake performance

Abstract

Effective removal of Pb(II) is a pressing global issue for both drinking water and wastewater purification. In this work, the large-scale and low-cost synthesis of two functional silica sorbents by vapor condensation induced water-in-oil (W/O) nanoemulsions (NSEs) is proposed, and the obtained high quality sorbents are applied for rapid removal of Pb(II). Tetraethoxysilane (TEOS) is diffused into the droplet of NSEs reactor, and then naked silica spheres are generated by hydrolysis and condensation at room temperature. The effects of the reaction conditions and confined space, including the stability, pumping time of water-soluble gas, and condensing time etc. on the size, morphology, and yield of main product are investigated, and the possible formation mechanism is demonstrated. Furthermore, functional silica sorbents with defined surface chemistry (i.e. Si-NH2 and Si-SH) are also synthesized via as-prepared NSEs systems. Finally, attributed to the inherent amino and mercapto terminal groups, Si-NH2 and Si-SH illuminate the maximum sorption capacity of 245.7 mg g−1 and 72.16 mg g−1 for Pb(II), respectively. Surface charge does not play a significant role in Pb(II) capture by Si-NH2, while chemisorption and electrostatic interaction both contribute to uptake performance of Si-SH. NSEs formed by condensation of water vapor do not need violent stirring and strict component proportion, which is an alternative and potential strategy to synthesize functional sorbents.