The effect of the surface roughness and ageing characteristics of boehmite on the removal of biological particles from aqueous solution

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

“…The synthesis of one-dimensional (1D) nanometer-sized γ-AlOOH atomic crystals adhered to siliceous and cellulosic substrates was accomplished via reaction (1) where aluminum powder reacts with alkaline water [6]. Amounts of 0.5 g of aluminum metal powder and 1.5 g of amorphous borosilicate glass microfiber with average diameter of 0.6 μm were dispersed in 0.5 L liter of RO water and were reacted in a 1 L stainless steel pot in the presence of 1 mL of 10 M NaOH at ambient pressure.…”

“…In this section, we will discuss the 3D flow structure associated with pressure-driven flow through micrometer size pores of a mixture of equal but opposite charged particles packed into a 3-mm deep precoat [37]. The surfaces of diatomaceous earth (DE) and 2D γ-AlOOH/ DE particles have similar but opposite values of zeta potentials [1]. In such a case, there is an excess of positive ions over the DE surface, but negative ions dominate over the 2D γ-AlOOH/DE surface to balance out the positive surface charge.…”

“…Assuming a cubic cell packing, the number of layers is estimated as N layers = Δ thickness /d average~3 8. Table 2 shows removal efficacy of MS2 virus and Raoultella Terrigena (RT) bacteria by 3 mm precoats of diatomaceous earth (DE) particles coated with 2D γ-AlOOH crystallites mixed with uncoated DE particles at a flow velocity of 0.67 mm/s, neutral pH 7 and ionic strength of 2 ± 1 μM [1]. The mean flow pore diameter of the precoat layer was determined to be 24 ± 4 μm [2].…”

“…Coating sand and diatomaceous earth (DE) particles with aluminum and ferrous hydroxides changes the zeta potential of filtration media from negative to positive in the pH range from 3 to 11 and from 3 to 10, respectively. As a result, those surface modified media greatly improve removal efficacy of submicron particles [1][2][3][4][5][6][7][8]. The role of the electrical double layer (EDL) and van der Waals (VDW) forces in particle deposition is often viewed in terms of Derjaguin-Landau-Verwey-Overbeek (DLVO) theory [9,10], which was developed for smooth, homogeneous particles with ideal geometries and with no EDL overlap.…”

“…The first one was to present the characterization of the surface's zeta potentials by direct measurement of streaming potentials in NaCl aqueous electrolyte. The isoelectric point values of rough nanostructured surfaces are three pH units higher as compare to the flat crystalline γ-AlOOH and β-FeOOH surfaces, resulting in a high removal efficacy for different classes of contaminants such as metal ions [2], small colloidal particles [6][7][8], as well as biological particles like virus, bacteria and cyst [1,2]. The second motivation was to develop a model that explains the pH dependent behavior of the zeta potential based on contributions from the three morphological planes of different chemical composition existing at siliceous particles coated with 2D and 1D γ-AlOOH crystallites: γ-AlOOH face and edge layers, and silica basal layer which are complex oxides of the two constituents: γ-AlOOH and SiO 2 .…”