Synthetic Boehmite Research Articles

НОВЫЙ ПОДХОД К ПОЛУЧЕНИЮ КОМПЛЕКСООБРАЗУЮЩИХ СОРБЕНТОВ, СОДЕРЖАЩИХ ИМИНОДИАЦЕТАТНУЮ ГРУППУ

The results of the study of chemical modification of synthetic boehmite (γ-AlO(OH)) surface with phosphonic complexone - imino-N,N-diuacetic-N-methylene phosphonic acid (PMIDA) to obtain a new complexing material capable of binding heavy metal ions are presented. The technique of simple one-step modification of boehmite by its treatment with aqueous solution of PMIDA (pH 2, temperature 20oC, time 6 h) was developed. The IR spectrum of the obtained PMIDA- boehmite shows bands characteristic of phosphonic -PO(OH)2 (900-1300 cm-1) and carboxyl -COOH (1637 cm-1 and 1386 cm-1) groups. As a result of modification, a dense coating (0.61 mmol/g or 1.5 groups/nm2) is formed on the surface of boehmite, in which the phosphonic group of PMIDA is the ‘anchor’ of the modifier, and the free iminodiacetate group shows complexing properties. The phosphonic coating was found to be hydrolytically stable at pH 2-7. It is shown that the sorption of metal ions (Ni(II), Cu(II)) by PMIDA- boehmite occurs in a more acidic environment compared to the original boehmite (shift of pH50by 2-3 units). Cu(II) ions bind to the -N(CH2COOH)2 group of fixed PMIDA more strongly than Ni(II) ions, similarly to the case for complexonates of these metals with PMIDA in solutions. PMIDA- boehmite can be recommended as a new effective material for sorption extraction and concentration of heavy metal ions under static conditions (sorption time 60 min). The developed method of fixation of iminodiacetate group using PMIDA can also be used in relation to other oxide carriers.

Proton transfer in layered hydrogen-bonded system γ-MOOH (M = Al, Sc): Robust bi-mode ferroelectricity and 1D superionic conductivity

Layered γ-MOOH, such as synthetic boehmite γ-AlOOH and γ-ScOOH, has been explored for various applications since 1950s. In this paper, based on first-principles calculations, we show the evidence of two proton transfer modes in their hydrogen-bonded network that give rise to extraordinary properties: (1) they, respectively, result in two distinct types of ferroelectricity with different switching mechanisms and polarizations, while the exhibiting mode under an electric field depends on various factors, including the field intensity and direction, the existence of vacancies, and temperature; and (2) the combination of two modes can lead to ultra-high proton conductivity along 1D channels. Their proton migration barriers ensure high ferroelectric Curie temperature, while still much lower compared with current proton conductors, giving rise to 1D superionicity with unprecedented protonic conductivity over 24 mS/cm. Those light weight nontoxic layered materials with high polarizations, Curie temperature, and ultra-high protonic conductivity should provide vast opportunities for various applications.

Frustrated Coulombic and Cation Size Effects on Nanoscale Boehmite Aggregation: A Tumbler Small- and Ultra-Small-Angle Neutron Scattering Study

To better understand the effects of solution chemistry on particle aggregation in the complex legacy tank wastes at the Hanford (WA) and Savannah River (SC) sites, we have performed a series of tumbler small- and ultra-small-angle neutron scattering experiments on 20 wt % solid slurries of nanoparticulate aluminum oxyhydroxide (boehmite) with M1+ nitrates of various concentrations and radii. The solutes consisted of H, Li, Na, K, and Rb nitrates at 10–5, 10–3, 10–1, 2, and 4 molal (m) concentrations, as well as in pure H2O. Synthetic boehmite nanoparticles were used with a size range from ∼20 to 30 nm. Tumbler cells were used to keep the solids from settling. Although particles initially form individual rhombohedral platelets, once placed in solution, they quickly form well-bonded stacks, primary aggregates, up to ∼1500 Å long, and a second level of aggregates whose concentration and structure vary as a function of cation type and concentration. Aggregation generally increases with increased solute concentration and with cation radius up to a concentration somewhat above 10–1 m, at which point the trend reverses. Primary aggregates become more rodlike and larger. The Kirkwood-like reversal probably reflects a change from Derjaguin–Landau–Verwey–Overbeek (DLVO)/Debye behavior controlled by surface chemistry to a frustrated Coulombic system controlled by the solution structure. These data suggest that an understanding of the effects of salt concentration and chemistry on nanoparticle aggregate structures provides useful physical insights into the microscopic origin of slurry rheology in the Hanford and Savannah River legacy wastes.

SUPPORTED PALLADIUM CATALYSTS FOR ALCOHOLS OXIDATION BASEDON CHEMICALLY MODIFIED BOEHMITE

New palladium catalysts based on Pd(II) coordination heterogenization on the surface of synthetic boehmite chemically modified with nitrilotris(methylenephosphonic) acid (NTP) were ob-tained. The catalysts were prepared by impregnating the carrier (boehmite (γ-AlOOH), NTP-boehmite (NTP-γ-AlOOH)) with a PdCl2solution followed by the reduction of Pd(II) to metallic palladium with potassium formate. The resulting samples were characterized by XPA, SEM, XPS, BET, and IR spectroscopy. The carriers have a high specific surface area (100–250 m2/g) and a mesoporous structure. The content of palladium in the obtained metal catalysts is 2–4 wt%, with an average particle size of 10–50 μm. An analysis of the XPS spectra of the catalysts (Pd3d, N1s, P2p) shows that they contain metallic palladium Pd(0) and ionic forms of Pd(II) bonded to the oxygen and nitrogen atoms of the support.The possible composition of Pd(II) surface complexes on boehmite and NTP-boehmite was established by modeling the sorption vs. pH curve according to the theory of surface complexation. The reaction of the selective oxidation of benzyl alcohol to benzaldehyde in an aqueous solution (4 vol.% alcohol, 60°C, 1 h) using atmospheric oxygen was chosen as a model reaction for evaluating the catalytic activity, which corresponds to the principles of "green chemistry": 2C6H5CH2OH+O2= 2C6H5COH+ 2H2O. The oxidation processwas moni-tored by measuring the IR spectra of the chloroform extractof the reaction mixture using the in-tensities of the absorption bands of alcohol (3100–3600 см-1(νO-H)) and aldehyde (1700 см-1(νC=O)). The following series of catalyst activity was established: Pd(II) > Pd(0)/NTP-γ-AlOOH > Pd(0)/ γ-AlOOH > Pd(II)/ γ-AlOOH >> Pd(II)/NTP-γ-AlOOH. The metallic form of palladium is required for the catalytic activity. The coordination fixation of palladium on NTP-boehmite due to chelate binding by an aminophosphonic group increases catalyst activity compared to monodentate binding by hydroxo groups of unmodified boehmite.

Cr(III) Adsorption by Cluster Formation on Boehmite Nanoplates in Highly Alkaline Solution.

The development of advanced functional nanomaterials for selective adsorption in complex chemical environments requires partner studies of binding mechanisms. Motivated by observations of selective Cr(III) adsorption on boehmite nanoplates (γ-AlOOH) in highly caustic multicomponent solutions of nuclear tank waste, here we unravel the adsorption mechanism in molecular detail. We examined Cr(III) adsorption to synthetic boehmite nanoplates in sodium hydroxide solutions up to 3 M, using a combination of X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), scanning/transmission electron microscopy (S/TEM), electron energy loss spectroscopy (EELS), high-resolution atomic force microscopy (HR-AFM), time-of-fight secondary ion mass spectrometry (ToF-SIMS), Cr K-edge X-ray absorption near edge structure (XANES)/extended X-ray absorption fine structure (EXAFS), and electron paramagnetic resonance (EPR). Adsorption isotherms and kinetics were successfully fit to Langmuir and pseudo-second-order kinetic models, respectively, consistent with monotonic uptake of Cr(OH)4- monomers until saturation coverage of approximately half the aluminum surface site density. High resolution AFM revealed monolayer cluster self-assembly on the (010) basal surfaces with increasing Cr(III) loading, possessing a structural motif similar to guyanaite (β-CrOOH), stabilized by corner-sharing Cr-O-Cr bonds and attached to the surface with edge-sharing Cr-O-Al bonds. The selective uptake appears related to short-range surface templating effects, with bridging metal connections likely enabled by hydroxyl anion ligand exchange reactions at the surface. Such a cluster formation mechanism, which stops short of more laterally extensive heteroepitaxy, could be a metal uptake discrimination mechanism more prevalent than currently recognized.

Mode II interlaminar fracture toughness of unidirectional fiber-reinforced polymer matrix composites with synthetic boehmite nanosheets at room temperature and low temperature

The nanosheet boehmite (AlOOH) was synthesized and used as reinforcing agent to toughen carbon fiber-reinforced polymers. The purity, morphology, size and composition of the AlOOH nanosheets were investigated by the methods of XRD, SEM, TEM and FTIR, respectively. Interlaminar fracture toughness for mode II deformation was investigated for carbon fiber-reinforced polymers toughened by AlOOH nanosheets varying the contents at room temperature (RT, 293k) and at low temperature (LT, 77k). The fracture surfaces were examined by SEM to correlate with the interlaminar fracture properties. The results indicated that the synthesized AlOOH nanosheets were pure crystalline and of high purity. By TEM, the thickness of the lamellar AlOOH sample is about 22 nm. The end-notched flexure test results show that interlaminar fracture toughness of unidirectional carbon fiber-reinforced polymer with the same content AlOOH nanosheets (0, 1, 1.5, 2, 2.5, 3 wt.%) at LT is higher than that at RT. The interlaminar fracture toughness reaches the highest when the AlOOH nanosheets content equals 2% at RT. But at LT, the highest interlaminar fracture toughness appeared in the carbon fiber-reinforced polymers without AlOOH nanosheets.

Mechanical properties of epoxy resins reinforced with synthetic boehmite (AlOOH) nanosheets

ABSTRACTIn this article, sheet boehmite (AlOOH), which was synthesized via a facile and environmental friendly method, was used as reinforcing agent to toughen Bisphenol A epoxy resin. The result of X–ray Diffraction (XRD) and IR spectrum indicated that the as–synthesized product was pure crystalline and high purity AlOOH. The effects of sheet AlOOH on the mechanical properties of AlOOH/epoxy nanocomposites were investigated. The results indicated that the introduction of AlOOH significantly improved the mechanical properties of epoxy resin. Compared with neat epoxy resin, the tensile strength and the fracture toughness (KIC) of the AlOOH/epoxy nanocomposites filled with 4 wt % AlOOH increased by 24.2% and 28.7%, respectively, while the flexural strength increased from 40.92 to 50.00 MPa. From Scanning Electron Microscope (SEM), a phase‐separated morphology and plenty of cervices and river branches were observed in the fractured surfaces of composites. With the increase of sheet AlOOH content, river‐shaped cracks became more and more intensive. Overall, the addition of sheet AlOOH is shown as a promising method for mechanical properties enhancement of epoxy matrix. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41409.

Thermal, viscoelastic and mechanical behavior of polypropylene with synthetic boehmite alumina nanoparticles

Effects of nanofiller concentration and surface treatment on the morphology, thermal, viscoelastic and mechanical behavior of polypropylene copolymer (PP)/boehmite alumina (BA) nanocomposites were investigated. Both untreated BA particles and those treated with octylsilane (OS) or sulphonic acid compound (OS2) were added at up to 10 wt% to produce nanocomposites by melt mixing followed by film blow molding and hot pressing. Dispersion of BA was studied by scanning electron microscopy. Differential scanning calorimetry and wide-angle X-ray scattering were adopted to detect changes in the crystalline structure of PP. Thermooxidative degradation of the nanocomposites was assessed by thermogravimetrical analysis. Dynamic mechanical analysis served for studying the viscoelastic properties, whereas quasi-static tensile, creep and Elmendorf tear tests were used to detect changes in the mechanical performance. BA nanoparticles were finely dispersed in PP up to 10 wt%, even when they were not surface modified. The resistance to thermal degradation was markedly improved by BA nanomodification. Since the crystalline characteristics of the PP matrix did not practically change with BA modification, changes observed in the mechanical properties were attributed to BA dispersion, filler/matrix interactions and related effects.

Towards ambient pressure leaching of boehmite through mechanical activation

This paper explores the possibility of manoeuvring the reactivity of boehmite through mechanical activation (MA) for enhancing the solid/liquid reaction between boehmite and NaOH. Synthetic boehmite, prepared by thermal dehydroxylation of gibbsite, used in this study has been characterised by a large specific surface area (~264m2/g). A planetary mill has been used for MA. Boehmite dissolution during caustic leaching (temperature: 70–90°C, Na2O concentration: 180g/l) has been found to increase with the extent of MA. Energy accumulated in the solid (boehmite) structure makes its dissolution in aqueous phase easy. Significantly high dissolution (~23g of boehmite in 210ml of 180g/l Na2O solution) has been achieved at atmospheric pressure condition (90°C) for 240min milled sample. Kinetic analysis of the leaching data of boehmite milled for different durations (up to 240min) has shown that the value of apparent activation energy for boehmite dissolution decreases with the extent of MA. Analysis of the results shows that MA has larger influence on dissolution than rise in leaching temperature. An attempt has been made to separate the effect MA from that of surface area.

Fracture behavior of boehmite‐filled polypropylene block copolymer nanocomposites as assessed by the essential work of fracture concept

ABSTRACTThe essential work of fracture (EWF) method was adapted to determine the fracture toughness of poly(propylene‐block‐ethylene) (EPBC) based nanocomposites with different amounts (from 0 up to 5 wt %) of synthetic boehmite alumina (BA). The dispersion of BA in the matrix was studied by transmission and scanning electron microscopies. Agglomerated micronscale along with well dispersed nanoscale BA particles were present in the EPBC matrix. By contrast to the neat EPBC, all nanocomposites failed by unstable necking. Therefore the energy partitioning concept of the EWF was adapted and attention paid to the yielding‐related term. Both specific yielding‐related essential and nonessential work of fracture parameters increased linearly with the product of the yield stress and elongation at yield derived from static tensile tests. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40447.

Mechanical and rheological response of polypropylene/boehmite nanocomposites

In this study, the influence of synthetic boehmite alumina nanoparticles with various surface treatments on the morphology, crystallization behavior and mechanical properties of polypropylene copolymer nanocomposites was studied. In particular, a series of polypropylene/boehmite alumina nanocomposites, containing up to 10 wt% of untreated and of octylsilane-functionalized boehmite alumina nanoparticles, were prepared by melt compounding and film blowing. A third type of composite was produced by incorporation of boehmite alumina nanoparticles treated with benzene sulfonic acid. Scanning electron microscopy indicated that boehmite alumina nanoparticles were finely and uniformly dispersed, though agglomerated, in the polypropylene nanocomposites. Surface-treated boehmite alumina nanoparticles were better dispersed in the matrix than the untreated boehmite alumina nanocomposites. The melt viscosity of nanocomposites remained unaltered or decreased by nanofiller incorporation at low concentration (2.5 and 5 wt%), while it slightly increased at higher concentrations (10 wt%). Uniaxial tensile tests indicated that the nanoparticles can induce a remarkable stiffening effect even at a rather low filler content, especially in the case of surface-treated particles. The plane stress fracture toughness of the material, evaluated by the essential work of fracture approach, showed a noticeable improvement due to boehmite alumina incorporation, with an optimal effect for a filler concentration of about 2.5 wt%.

Thermooxidative degradation of LDPE nanocomposites: Effect of surface treatments of fumed silica and boehmite alumina

Fumed silica (FS) and synthetic boehmite alumina (BA) nanofillers with and without surface treatments were incorporated in 5 wt. % in low density polyethylene (LDPE) through melt blending. FS was treated using hexadecyl silane, whereas BA using octyl silane and alkylbenzene sulfonic acid. The related nanocomposites were subjected to pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) and thermogravimetric analysis (TGA) under isothermal and dynamic conditions, respectively. Py-GC-MS results proved that the thermal degradation mechanism did not change in the presence of the nanofillers. The latter suppressed the formation of high molecular weight hydrocarbons and affected the relative amounts of diene/alkene/alkane fragments for each hydrocarbon fraction.Dynamic TGA scans were registered at different heating rates in air. The activation energy (Eα) of thermoxidative degradation was calculated by the Ozawa-Flynn-Wall (OFW) method at various degradation degrees. Eα of the LDPE nanocomposites depended on both specific surface area and surface treatment of the nanofillers used. The former enhanced whereas the latter decreased the activation energy for the LDPE-FS nanocomposites. By contrast, Eα was slightly increased for the surface treated LDPE-BA nanocomposites.

Thermal stability and flame retardancy of polyester fabrics sol–gel treated in the presence of boehmite nanoparticles

Polyester fabrics have been treated with hybrid organic-inorganic sols containing aluminium hydroxide, namely a synthetic boehmite. The treated fabrics have been thoroughly investigated by infrared spectroscopy, scanning electron microscopy coupled to elemental analysis and thermogravimetry. Furthermore, the flammability of the coated fabrics has been assessed and compared with that achieved by applying the two components separately. More specifically, flammability tests have shown that the sol–gel treatment in the presence of boehmite nanoparticles is able to suppress the dripping phenomenon, which represents the main issue to fulfil for polyester fabrics.

Leaching behaviour of high surface area synthetic boehmite in NaOH solution

This study pertains to alkali leaching of a high surface area synthetic boehmite prepared by thermal decomposition of gibbsite. Synthesised boehmite particles are found to be agglomerates of platelets. These particles are characterised by a monomodal size distribution with a median size of 110μm and high specific surface area (~264m2/g). Leaching studies, in the temperature range 70 to 90°C, have been carried out in NaOH solutions of Na2O concentration, CNa2O=100 and 180g/l. Significant dissolution of this boehmite is seen to occur in NaOH solutions, unlike in many other studies, owing to the high surface area. Both alkali concentration and temperature have influenced the dissolution. Reduced time plot analysis indicates that the shrinking core with surface reaction model (R3) describes the initial stages of the dissolution process reasonably well. Particle size analysis data complemented the results of the reduced time analysis. The value of apparent activation energy for the initial stages of dissolution is evaluated to be around 65kJ/mol.Deviation from shrinking core model R3 is observed in the later stages. Besides the shrinking of size due to dissolution, particle size reduction is also identified due to the detachment of platelets from the agglomerates of particles. Detailed characterisation of the leach residues involving morphological and particle size analyses has established such detachment of platelets and ensuing particle size reduction. Deviation from shrinking core model in the later stages of leaching has been attributed to particle fragmentation arising from platelet separation.

Viscoelastic behaviour and fracture toughness of linear-low-density polyethylene reinforced with synthetic boehmite alumina nanoparticles

Aim of the present study is to investigate how synthetic boehmite alumina (BA) nanoparticles modify the vis- coleastic and fracture behaviour of linear low-density polyethylene. Nanocomposites containing up to 8 wt% of untreated and octyl silane-functionalized BA nanoparticles, were prepared by melt compounding and hot pressing. The BA nanoparticles were finely and unformly dispersed within the matrix according to scanning electron microscopy inspection. The results of quasi-static tensile tests indicated that nanoparticles can provide a remarkable stiffening effect at a rather low filler content. Short term creep tests showed that creep stability was significatively improved by nanofiller incorporation. Concurrently, both storage and loss moduli were enhanced in all nanocomposites, showing better result for surface treated nanoparticles. The plane-stress fracture toughness, evaluated by the essential work of fracture approach, manifested a dramatic increase (up to 64%) with the BA content, with no significant differences among the various types of BA nanoparticles.

Binary and ternary composites of polystyrene, styrene–butadiene rubber and boehmite produced by water-mediated melt compounding: Morphology and mechanical properties

Binary and ternary composites composed of polystyrene (PS), styrene–butadiene rubber (SBR), and synthetic boehmite alumina (BA) were produced by water-mediated melt compounding technique. SBR latex and/or aqueous BA suspension was injected into the molten PS in a twin-screw extruder to prepare toughened and/or reinforced polymer composites. The dispersion of the BA (two fractions with different mean particle sizes) and SBR was studied by scanning- and transmission electron microcopy techniques (SEM and TEM, respectively), and discussed. The mechanical properties of the composites were determined in static tensile, Charpy impact and short-time stress relaxation tests (performed at various temperatures). It was found that BA was mostly embedded in the SBR phase in the ternary PS/SBR/BA composite. BA incorporation increased the stiffness and tensile strength and reduced the elongation at break and impact toughness. Effect of the BA particle size was most pronounced in the tensile mechanical and stress relaxation tests. Additional incorporation of BA in the PS/SBR blend enhanced the tensile modulus and stress relaxation modulus compared to the PS/SBR blend. Relaxation master curves were constructed by applying the time–temperature superposition (TTS) principle. It was established that the inverse of the Findley power law model was fairly applicable to the stress relaxation results.

Dynamic mechanic and creep behaviors of polyoxymethylene/boehmite alumina nanocomposites produced by water-mediated compounding

Nanocomposites composed of polyoxymethylene (POM) and synthetic boehmite alumina (BA) are produced by water-mediated (WM) technique. According to WM technique, an aqueous BA 25 and BA 220 nm dispersion was injected into the molten POM in a twin-screw extruder to prepare the related nanocomposite with 3 wt% BA content. The dispersion of BA was studied by scanning electron microscopy and transmission electron microscopy. The thermal, mechanical and creep properties of the composites were determined in dynamic mechanical thermal analysis and short-time creep tests, respectively (performed at various temperatures). The data indicate that an improvement in the stiffness of nanocomposites can be achieved. The POM/BA 25 nm composite outperformed the POM and POM/BA 220 nm composite with respect to the storage modulus and creep characteristics. This was attributed to the particle size effect of BA. Master curves of storage modulus versus frequency and creep compliance versus time were constructed by applying the time–temperature superposition principle. It was established that the Burgers model and the Findley power law are fairly applicable to the creep compliance results.

Processing, structure, and mechanical properties of alumina-nanofilled polystyrene composites

Binary composites composed of polystyrene (PS) and a synthetic boehmite alumina were produced by using the water-mediated melt compounding (WMC) and direct melt compounding (DMC) techniques. The alumina particles were dispersed in water at ambient temperature. The aqueous alumina suspension was injected into molten PS in a twin-screw extruder to prepare reinforced polymer composites. The dispersion of the alumina was studied by transmission and scanning electron microcopy techniques (TEM and SEM, respectively). The mechanical and thermomechanical properties of the composites were determined by employing a dynamic-mechanical thermal analysis (DMTA) and short-time creep and uniaxial static tensile tests. It was found that the direct melt compounding of the alumina with PS resulted in microcomposites, whereas the water-mediated melt compounding technique gave rise to nanocomposites. The incorporation of alumina into the PS nanocomposites increased their stiffness, tensile strength, and creep resistance. However, the elongation of the PS nanocomposites at break was smaller than that of the PS microcomposites.

Polyethylene/synthetic boehmite alumina nanocomposites: structure, mechanical, and perforation impact properties

Synthetic boehmite alumina (BA) has been incorporated up to 8 wt% in high-density polyethylene (HDPE) and low-density polyethylene (LDPE) by melt compounding. The primary nominal particle sizes of the two BA grades used were 40 and 74 nm, respectively. The dispersion of the BA in PE matrices was investigated by scanning and transmission electron microscopy techniques (SEM and TEM). Specimens of the PE/BA nanocomposites were subjected to dynamic-mechanical thermal analysis (DMTA), static tensile and instrumented falling weight impact (IFWI) tests. It was established that BA was nanoscale dispersed in both HDPE and LDPE. According to DMTA, BA worked as reinforcing filler. This was confirmed in static mechanical tests, too. BA grades and contents influenced the static tensile and dynamic IFWI behaviors of the PE/BA nanocomposites differently. Surprisingly, BA incorporation enhanced the ductility (elongations at yield and break) of HDPE in contrast to LDPE. Unlike HDPE/BA nanocomposites, the perforation impact resistance of the LDPE/BA systems was reduced with increasing BA content at both ambient temperature and T = −30 °C. The lesser the reduction the higher the primary particle size of the BA was.

Effect of 1-Hydroxyethane-1,1-diphosphonic Acid (HEDPA) on Partitioning of Np and Pu to Synthetic Boehmite

The effect of 1-hydroxyethane-1,1-diphosphonic acid (HEDPA) on the sorption of Np(V) and Pu(V) to synthetic boehmite (γ-AlOOH) was examined as a function of time and pH (between 4 to 11). The sorption of both elements in boehmite suspensions (1 M NaCl, 600 mg L−1 boehmite) increased with increasing pH. The sorption edges for neptunium and plutonium occurred at approximately pH 8.0 and 6.6, respectively. After steady state partitioning was reached, HEDPA was added to the neptunium-boehmite and plutonium-boehmite suspensions. Neptunium and plutonium partitioning appears to be primarily affected by the formation of soluble Np:HEDPA and Pu:HEDPA complexes, the dissolution of boehmite promoted by HEDPA, and the precipitation of Np:HEDPA and Pu:HEDPA colloids. The results are discussed in terms of applicability of HEDPA-promoted dissolution as a waste reduction method in the treatment of sludge phases contained within high-level nuclear waste storage tanks.