Effect of Solution Silicate on the Precipitation of Barium Sulfate

The presence of silicate during barium sulfate crystallization has different impacts depending on the pH of the solution. At pH 7 the dominance of the protonated form (H₄SiO₄) and possible polymerization of the silicate impacts mainly on the aggregation state and on twinning of the barium sulfate formed. At higher pH values (∼10), the silicate ion present is able to influence both morphology and partially substitute for sulfate in the lattice. Interesting fibrous particles are formed under these conditions, but this is not due to mesocrystal formation as the particles are observed to be single crystalline in nature. These fibrous sections are found to be dominant on the surface and are highly porous. These particles are different, however, to the biomorphs formed when crystallization of barium carbonate occurs in the presence of silicate. This is because the speciation of sulfate does not change over a large pH range. The impact of silicate on barium sulfate particles is similar to the impact on calcium carbonate and strontium sulfate crystallization

Characterization and Inhibition of a Nickel-Alpha-Hydroxyoxime (LIX 63) Salt Precipitate Formed under Proposed Commercial Operating Conditions

As a prospective commercial solvent extraction (SX) process, laboratory-scale continuous tests were recently undertaken to assess the use of a solution of LIX 63 hydroxyoxime (“hydroxyoxime”) and Versatic 10 to kinetically separate cobalt from a nickel-rich sulfate solution while simultaneously rejecting manganese and magnesium. A material quantity of blue precipitate observed in the strip stage cells during decommissioning has been identified as the sulfate salt of the nickel-tris hydroxyoxime complex. As precipitation during SX is undesirable, the effect of various operating parameters on precipitate formation has been investigated. Minimizing aqueous nickel and/or sulfuric acid concentration and/or increasing organic polarity can overcome this problem. Where it forms, hydroxyoxime and nickel can be recovered from the precipitate by redissolution under suitable (e.g., low acid) operating conditions. The nitrate salt counterpart of this sulfate precipitate has been crystallographically characterized using a short chained (C₈) analogue of LIX 63 hydroxyoxime, revealing the coordination of three neutral hydroxyoxime ligands around nickel, forming a monomeric coordination complex cation counterbalanced by nitrate anions

Investigation of the structure and magnetism in lanthanide β-triketonate tetranuclear assemblies

<p>The preparation of discrete tetranuclear lanthanide/alkali metal (Ae) assemblies bearing a tribenzoylmethane ligand (<b>L</b>H) is discussed. These assemblies have the general formula [Ln(Ae·HOEt)(<b>L</b>)₄]₂, where Ln³⁺ = Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺ and Ae⁺ = Na⁺, K⁺, Rb⁺. The coordination geometries of the lanthanide species were analyzed and compared, revealing a trend between an eight-coordinate square antiprism and triangular dodecahedron dependent on the nature of lanthanide, alkali metal, and lattice solvent. The potassium-containing analogs were also analyzed for their magnetic susceptibility.</p

Lanthanoid “Bottlebrush” Clusters: Remarkably Elongated Metal–Oxo Core Structures with Controllable Lengths

Large metal–oxo clusters consistently assume spherical or regular polyhedral morphologies rather than high-aspect-ratio structures. Access to elongated core structures has now been achieved by the reaction of lanthanoid salts with a tetrazole-functionalized calix­arene in the presence of a simple carboxylate co-ligand. The resulting Ln₁₉ and Ln₁₂ clusters are constructed from apex-fused Ln₅O₆ trigonal bipyramids and are formed consistently under a range of reaction conditions and reagent ratios. Altering the carboxylate co-ligand structure reliably controls the cluster length, giving access to a new class of rod-like clusters of variable length

Lanthanoid “Bottlebrush” Clusters: Remarkably Elongated Metal–Oxo Core Structures with Controllable Lengths

Large metal–oxo clusters consistently assume spherical or regular polyhedral morphologies rather than high-aspect-ratio structures. Access to elongated core structures has now been achieved by the reaction of lanthanoid salts with a tetrazole-functionalized calix­arene in the presence of a simple carboxylate co-ligand. The resulting Ln₁₉ and Ln₁₂ clusters are constructed from apex-fused Ln₅O₆ trigonal bipyramids and are formed consistently under a range of reaction conditions and reagent ratios. Altering the carboxylate co-ligand structure reliably controls the cluster length, giving access to a new class of rod-like clusters of variable length