Base metal recovery reagents

The use of organophosphorus acids, such as di(2-ethylhexyl)phosphoric acid (D2EHPA di(2-ethylhexyl) monohydrogen phosphate 2 R = C4H9CH(Et)CH2), is now well established in the recovery of base metals. This reagent has found commercial application in the separation of cobalt from nickel,67 68 the separation of zinc from impurities such as copper and cadmium,69 the recovery of uranium,68 beryllium70 and vanadium,71 and in separations involving yttrium and the rare-earth metals.72 73... 

As a consequence, the selectivity of extraction of first transition series dications does not follow the Irving Williams order when these reagents are used in base metal recovery. The bis(2-ethylhexyl)ester of phosphoric acid (D2EHPA) shows [1] a preference Zn2+ > Cr21 > Mn2+ > Fe2+ > Co2+ > Ni2+ V2+ which is exploited in the recovery of zinc from primary sources. [69] M2+ ions which form tetrahedral complexes and M3+ ions which show a preference for octahedral donor sets give neutral complexes with 4 1 and 6 1 D2EHPA metal stoichiometries respectively,... 

The most recent studies [9] conducted on various base metal ores revealed some important features of flotation behaviour of gold from these ores. It has been demonstrated that gold recovery to the base metal concentrate can be substantially improved with the proper selection of reagent schemes. Some of these studies are discussed below. 

Many of the reagents developed initially for the recovery of base or radioactive metals have also been investigated as potential PGM extractants, e.g., phosphine oxides,310-313 dialkylsulfoxides,314 dialkyl-and diphemd-thioureas,296,315-317 thiopicolinamides, thiobenzanilide,319 phosphate diesters,320 tetra-... 

The objective of this effort was the initial recovery of Sc with subsequent process steps to separate and recover the other metallic constituents. The initial step was the acid digestion of the tungsten ore tailings, which produced an insoluble residue containing W and a solution rich in most of the other metals. The steps in the overall separation scheme are outlined by the flow sheet presented in Figure 3. The hydrazine/ sulfuric acid solution was chosen as the reductant/solvent reagent based on the following considerations ... 

The separation and recovery of precious metals continues to create interest. Henkel (Cognis, Inc.) has developed a new reagent, LIX 79, based on a trialkylguanidine for the recovery of gold from cyanide solutions. The reagent behaves as a strong base, and stripping is achieved with alkaline solutions above pH 13.5. 

The first commercial reagents were aU based on ketoxime functionality and were used exclusively for copper extraction for over a decade after the first full-scale application at Bluebird Ranchers Mine, Arizona, in 1968 (Arbiter and Fletcher 1994). Today, ketoximes are still successfully used in niche applications for the recovery of copper from dilute leach liquors and also find applications in nickel SX from ammoniacal solutions and in precious metal refining (see Sections S.3.3.3 and 5.3.6.2). Particular applications of ketoximes in copper production are at El Tesoro and Lomas Bayas in the Atacama Desert of Chile, where the leach liquors of circuits often contain high... 

Separation processes based on the wettability make use of the effect that hydrophobic particles can be attached to air bubbles that transport them to the surface of the pulp, forming a froth that is collected as a concentrate. This process is known as flotation, and is an important method of solid-solid separation in the mineral industry. Various reagents are used to enhance the process. Flotation is used for the recovery of sulfides and oxides of various metals such as copper, lead, zinc, nickel, molybdenum, iron, titanium, tungsten, and tin. 

Another important technology for the concentration and winning of minerals and metals is solvent extraction. Up to the time of writing there is only one area where RR-based chemicals are used commercially. Tertiary amines (- fatty amines) with short- to medium-length alkyl chains and their - quatenary derivatives form ion pair complexes with certain metals that are dissolved in an aqueous medium. These reagents are widely used for the recovery of uranium, vanadium, nickel and, to a lesser extent, molybdenum. 

---