Pristine point of zero charge (p.p.z.c.) and zeta potentials of boehmite’s nanolayer and nanofiber surfaces

Abstract

The pristine point of zero charge (p.p.z.c) and zeta potential as a function of pH of boehmite oxide/hydroxide (α-Al 2 O 3 ·H 2 O) have been determined for three filter media. The active component in the first two filter media is boehmite nanofibers, only 2 nm in diameter and about 300 nm long. Boehmite nanofibers create high zeta potential (ζ true ≥46 mV) in aqueous solutions in the pH range of 3-8. The p.p.z.c. values were determined to be 11.60 ± 0.15 for nanofibers grafted onto microglass fibers and 11.40 ± 0.15 for agglomerated nanofibers. In the third filter media, a boehmite nanolayer in the form of monocrystalline oxide/hydroxide with a thickness of approximately 1.2 nm is electroadhesively deposited onto siliceous support material with large surface area of about 50 m 2 /g, therefore forming a highly electropositive composite of boehmite nanolayer on the second highly electronegative solid. Boehmite's oxide-hydroxide nanolayer surface creates high zeta potential (ζ true ≥50 mV) in aqueous solutions in the pH range of 3-8. The p.p.z.c. value was determined to be 11.38 ± 0.15. The reported values are within accuracy, but they are much higher than the values reported in the literature. X-ray powder diffraction data were supplemented by microscopy, infrared spectroscopy in order to characterize fully synthetic boehmite surfaces.

Boehmite and Akaganeite 1D and 2D Mesostructures: Synthesis, Growth Mechanism, Ageing Characteristics and Surface Nanoscale Roughness Effect on Water Purification

“…Under this assumption, we estimated the pH PZC values of the edge surface at approximately 11.4 ± 0.2 and boehmite face surface at approximately 9.5 ± 0.5. The latter value is within accuracy with an average value of 8.7 ± 0.9 obtained for smooth boehmite surfaces [26,27] and the former value is within accuracy with the pH PZC of aluminum hydroxide γ-AlOOH adjuvant of 11.4 [36] that is morphologically and geometrically similar to the nanofibers seen in Figure 1(a). 1 shows initial removal efficacy of biological particles from aqueous solution associated with pressure-driven flow through micrometer size pores of either 2Dγ-AlOOH/DE or 2Dβ-FeOOH/2Dγ-AlOOH/DE particles packed into a 3-mm deep precoat [37] or through a 1Dγ-AlOOH/microglass non-woven filter media [6,7].…”

“…Zeta Potentials of 2D and 1D γ-AlOOH and 2D γ-AlOOH/β-FeOOH Crystallites Deposited onto Siliceous Particles. It was found that siliceous particles coated with 2D and 1D γ-AlOOH crystallites are positively charged in aqueous solution with zeta potential ≥40 mV[26] at γ-AlOOH loading greater than 15 weight percent (wt%)[1] as compared to the negatively charged character of the bare…”

Effects of Ionic Strength, Salt, and pH on Aggregation of Boehmite Nanocrystals: Tumbler Small-Angle Neutron and X-ray Scattering and Imaging Analysis

“…In this paper, we analyze the correlation between aggregation of synthetic nanoboehmite and fluid composition by comparing aggregation in solutions at pH 9 and 12, which contain sodium nitrate (NaNO 3 ) and calcium nitrate (Ca­(NO 3 ) 2 ) at concentrations ranging from 0 to 1 m . The pH range was selected because available data − suggest that the point of zero charge for boehmite (or pseudoboehmite) lies somewhere between pH 7.3 and 9.2, although values as high as 11.6 have been reported for various boehmite nanostructures . Thus, we can evaluate the effects of the high pH values in the Hanford tanks on the formation and stability of boehmite aggregates.…”

pH dependent reactivity of boehmite surfaces from first principles molecular dynamics

“…This may account for the differing reported experimental values for the PZC of boehmite, averaging 9.5 but where unique morphologies have reported values as high as 11.38. 49 The individually reported PZC for the edges in this work may help to develop synthesis of controlled morphologies that optimize sorbent characteristics.…”