Removal of iron, copper, cadmium, cobalt, and nickel from sodium hydroxide by precipitation and extraction with phenyl-2-pyridyl ketoxime

Abstract

Reagent grade sodium hydroxide usually contains several parts per million of iron and nickel, along with other transition metals. Determinations of traces of these metals in which sodium hydroxide is used as a reagent, therefore, require large blank corrections. While many extraction procedures have been developed for removal of transition metals from aqueous solutions (1,2), most methods fail in highly alkaline solutions, or leave the solution contaminated with other chemicals. The procedure described here was developed in response to a need for "iron-free" sodium hydroxide, but we have found that copper, nickel, cadmium, and cobalt are also effectively removed.Phenyl-2-pyridyl ketoxime forms slightly-soluble, colored compounds with a number of transition metals at high pH (3-5). The metal complexes can be removed by filtration or by extraction into an immiscible solvent. The method described here employs phenyl-2-pyridyl ketoxime as a precipitant, and leaves the sodium hydroxide free of all reagents used in the procedure. EXPERIMENTALReagents. Phenyl-2-pyridyl ketoxime, ironand copper-free isopentanol, and redistilled hydrochloric acid were obtained from G. F. Smith Chemical Co., Columbus, Ohio. Phenyl-2-pyridyl ketoxime also was prepared according to Trusell and Diehl (5). Ethanol (95%) from the University of Minnesota Chemical Storehouse was found to be essentially free of iron. The 10% palladium on carbon powder was from Baker Catalysts, Newark, N.J. The 10 M sodium hydroxide was prepared from reagent grade pellets. Hydrogen and high-purity nitrogen gas were obtained locally.Apparatus. Polyethylene, polypropylene, or polytetrafluoroethylene containers were used to handle the sodium hydroxide solutions. A Beckman Acta III UV-visible spectrophotometer was used with 1-cm silica or 10-cm Vycor cells for solution absorbance measurements.Procedure for Removal of Metals. To 3 L of 10 M sodium hydroxide in a 4-L Pyrex filter flask, add 0.2 g of 10% Pd on carbon (wetted with water) and 2.0 g of phenyl-2-pyridyl ketoxime dissolved in a minimum amount of hot ethanol. Heat to 100

Thermal and structural characterization of copper(II) complexes with phenyl-2-pyridylketoxime (HPPK)

“…All nonhydrogen atoms were refined anisotropically, and the hydrogen atoms were placed in calculated positions with displacement factors fixed at 1.2 times Ueq of the parent C, O atoms with C-H = 0.95 (aromatic) and O-H = 0.82 Å . One of the phenyl rings (C25-C30) was found disordered over two positions with refined site occupancies of 0.59(2):0.41 (2). Consequently, a few geometrical restraints were placed on the bond lengths of this ring.…”

“…The chemistry of metal complexes with oxime type of ligands has been investigated from the 1960s of the twentieth century due to their applications as analytical reagents [1][2][3][4]. Currently, a renewed interest in this class of compounds can be observed, as they are being used for the design of homo-/heterometallic clusters [5], as well as coordination polymers with attention-grabbing properties [6].…”

Solvent Extraction of Iron(III) From Chloride Solutions in the Presence of Copper(II) and Zinc(II) Using Hydrophobic Pyridyl Ketoximes

“…Pyridyl aldo-and ketoximes form complexes with zinc(II), copper(II), silver(I), nickel(II), cadmium(II), and iron(III). The donor atoms of the 2-pyridyl oximes in metal complexes are the nitrogen atoms of the oxime and the pyridyl groups (27)(28)(29)(30)(31)(32). The presence of an oxime and pyridine moiety allows the formation of complexes with metals by solvating and=or chelating mechanisms.…”

Photodegradation of Hydrophobic Pyridineketoximes in Toluene and Heptane

“…Oxime ligands containing the pyridyl ring are a very interesting group of compounds in the chemistry of metal complexes. The compounds are widely used as analytical reagents , in medicinal preparations and as components of photodynamic herbicides . The extraction ability of hydrophobic 2‐ and 3‐ pyridineketoximes dissolved in aromatic as well as in aliphatic diluents toward copper(II), zinc(II), cadmium(II), nickel(II) and iron(III) from aqueous solutions has been broadly investigated .…”