Aluminium hydroxide

Abstract: The development and manufacture of an adsorbent to remove phosphate ion for the prevention of eutrophication in lakes are very important. The characteristics of phosphate adsorption onto aluminum oxide hydroxide were investigated to estimate the adsorption isotherms, the rate of adsorption, and the selectivity of adsorption. Phosphate was easily adsorbed onto aluminum oxide hydroxide, because of the hydroxyl groups. The adsorption of phosphate onto aluminum oxide hydroxide was influenced by pH in solution: the amount adsorbed was greatest at pH 4, ranging with pH from 2 to 9. The optimum pH for phosphate removal by aluminum oxide hydroxide is 4. The selectivity of phosphate adsorption onto aluminum oxide hydroxide was evaluated based on the amount of phosphate ion adsorbed onto aluminum oxide hydroxide from several anion complex solutions. It is phosphate that aluminum oxide hydroxide can selectively adsorb. The selectivity of phosphate onto aluminum oxide hydroxide was about 7000 times that of chloride. This result indicated that the hydroxyl groups on aluminum oxide hydroxide have selective adsorptivity for phosphate and could be used for the removal of phosphate from seawater.

Abstract: A powder coating composition of the invention comprises a film-forming polymeric component having a d(v,50) in the range of from 25 to 50 microns or a d(v,70) in the range of from 25 to 70 microns, which composition incorporates by dry-blending at least one appearance-modifying additive component and a further component comprising wax-coated silica or consisting of alumina together with aluminium hydroxide. The appearance-modifying additive may be a gloss-reducing component, a texturing component, a metallic or mica component, a colouring pigment, or a further film-forming polymeric material compatible with the first film-forming polymeric material and differing in colouration therefrom, and the further additive may be alumina together with aluminium hydroxide or wax-coated silica together with alumina and/or with aluminium hydroxide or wax-coated silica. Preferably, no more than 70 % by volume of the particles in the film-forming polymeric material are less than 50 microns. A kit of the invention comprises the individual additive components prior to mixing. The kit allows for the flexibl production of a variety of finishes from a gloss powder coating composition, for example a matt or textured or metallic or sparkle finish or a matt textured finish, a matt metallic finish, an antique finish or a contrast texture or metallic sparkle finish.

Abstract: In order to elucidate the influence of humic substances on phosphate adsorption, the amounts of phosphate adsorbed by synthetic aluminium oxide (Al(OH)3), ferrihydrite (Fe5O3(OH)9) and goethite (α-FeOOH) were determined at different concentrations, adsorption times, origins of humic acid (HA) and fulvic acid (FA) and order of addition of adsorbates. HA and FA were isolated from a Danish Histosol, two Podzols and an Umbrisol and used after purification for mineral matter (ash contents <3%). The experiments were performed with up to 14 mmol L−1 of HA-C or FA-C corresponding to 0.8–1.7 mmol L−1 of carboxylic groups (active surface complexation groups). These concentrations are comparable to concentrations of naturally occurring dissolved organic compounds (DOC) in mineral soil layers and to the phosphate concentrations tested (0–1.6 mM). Phosphate adsorption data were well-fitted by the Langmuir adsorption equation and the phosphate adsorption maximum (b) and binding constant (K) were calculated for various combinations of adsorbent, adsorbate, concentration and adsorption time. For adsorption onto goethite, b and K were independent of adsorption time (3–28 days), whereas b increased 10–40% and K 2–3 times during 3 to 28 days with aluminium oxide and ferrihydrite as adsorbents. The well-crystallised goethite adsorbed 2.7 μmol m−2 of phosphate, while monolayer coverage of the poorly ordered oxides corresponded to 5 μmol m−2 (ferrihydrite) and 4 μmol m−2 (aluminium oxide). Together with a 2–4 times higher K for the goethite–phosphate system, these figures indicate formation of a binuclear surface complex between phosphate and goethite while phosphate probably forms a mononuclear complex on the ferrihydrite and aluminium oxides surfaces. The presence of HA or FA together with phosphate in the adsorption solution had limited effect on adsorbed phosphate. Although small decreases of b and K were found after 3 days of equilibration with aluminium oxide and ferrihydrite as adsorbents, prolonged equilibration eliminated the differences between the amounts of phosphate adsorbed in the presence and absence of HA or FA. Moreover, compared to simultaneous addition of the two adsorbates, pre-adsorption of HA to goethite 3 days before phosphate addition did not change the b and K parameters. Therefore, humic substances can be concluded to have limited influence on phosphate adsorption by aluminium and iron oxides.

Abstract: Hierarchical spindle-like γ-Al2O3 materials were prepared in the form of fray ended bundles of twisted nanoflakes by a non-template hydrothermal synthesis and sequential calcination route using aluminium nitrate or aluminium chloride as precursors and urea as precipitating agent. The microstructures, morphologies and textural properties of the resulting materials were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and N2 adsorption–desorption techniques. It was found that the spindle-like γ-Al2O3 particles are composed of at least three levels of hierarchical organization: polycrystalline γ-Al2O3 at the nanoscale, oriented nanoflakes and uniform spindle-like assemblies. The hierarchical γ-Al2O3 particles prepared from aluminium nitrate show a slightly smaller size, fewer self-organized nanoplatelets and better textural properties than γ-Al2O3 prepared from aluminium chloride, due to the larger aqueous ionic radius of NO3− than that of Cl−. The reported experiments allowed us to propose the mechanism of formation of the spindle-like assemblies, which involves self-transformation of metastable amorphous aluminium hydroxide particles and their sequential cooperative assembly. The as-prepared γ-Al2O3 was found to be effective adsorbent for the removal of selective pollutants from wastewater as a result of its unique hierarchical structure and high specific surface area, indicating a promising potential of this material for environmental remediation.

Abstract: In this work the efficiencies of the chemical and the electrochemical break-up of oil-in-water (O/W) emulsions with hydrolyzing aluminium salts are compared. It has been obtained that the efficiency of the processes does not depend directly on the dosing technology, but on the total concentration of aluminium and pH. This latter parameter changes in a different way in the chemical and the electrochemical processes: the pH increases during the electrochemical experiments since the electrochemical system leads to the formation of aluminum hydroxide as a net final product, but it decreases in the conventional ones due to the acid properties of the aluminum salts added (AlCl3 or Al2(SO4)3). The break-up of the emulsions only takes place in the range of pHs between 5 and 9, and the amount of aluminium necessary to produce the destabilization of the emulsion is proportional to the oil concentration. Electrolytes containing chlorides improve COD removal as compared with those containing sulphate ions. Aluminium hydroxide precipitates were found to be the primary species present in solution in the conditions in which the breaking process is favoured. Consequently, the attachment of more than one droplet of oil at a time to a charged precipitate-particle (bridging flocculation) was proposed as the primary destabilization mechanism.