Long-range attractive forces extending from the aluminas nanolayer surface in aqueous solutions

Abstract

Aluminum oxide-hydroxide nanolayer with a thickness of approximately 1.2 nm is electroadhesively deposited onto silicious support material with large surface area of about 50 m2/g, forming a highly electropositive composite of boehmite nanolayer in the form of monocrystalline oxide/hydroxide (α-Al2O3·H2O) on the second electronegative solid. The composite can be viewed as a sphere with a rough surface and charge density of approximately 0.08 C/m2. This creates a significant electric field with negligible screening (ka 蠐 1) in the region close to the surface of the nanocomposite. This field attracts nano-And micron-sized particles from as far as 200 m in a few seconds, many orders of magnitude greater than conventional Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which predicts only nanometer-scale effects arising from the presence of the surface. The strong electric field on the surface is then able to retain small particles such as viruses, atomically thin sheets of graphene oxide, RNA, DNA, proteins, dyes as well as heavy metals such as cobalt, arsenic, and lead.Aluminas nanolayer surface can be further functionalized by adding other sub-micron or nano-sized particles to target a specific contaminant. An example is shown where alumina nanolayer is coated with nano-sized iron monohydrate to yield an arsenic sorbent that shows high sorption capacity.