Maurice C. Fuerstenau

Xanthate adsorption on selected sulfides in the virtual absence and presence of oxygen, Part 2

Abstract Adsorption of xanthates on galena, pyrite and sphalerite is presented as a function of oxygen concentration and pH. Oxygen concentration was varied from 0.21 to 29 ppm. Mechanisms of xanthate adsorption are suggested.

Study of Merrill-Crowe processing. Part I: Solubility of zinc in alkaline cyanide solution

Abstract A comprehensive study of zinc solubility was carried out in de-aerated alkaline cyanide solutions. Parameters investigated were: dissolved oxygen, cyanide and lead nitrate concentrations and pH. Zinc solubility increases significantly with increased dissolved oxygen and cyanide concentrations. Eh-pH diagrams have been developed and used to predict regions of stability of zinc hydroxide, which may inhibit gold precipitation. The interaction between cyanide and hydroxyl ion activities to prevent the formation of zinc hydroxide is presented. With lead nitrate additions, maximum solubility of zinc occurs in the range of 10–15 mg/l lead nitrate. SEM photomicrographs of zinc particles in the presence of lead nitrate are presented.

Factors influencing the rate of dissolution of gold in ammoniacal solutions

Gold can be effectively extracted from various sources such as refractory ores and jewelry scrap by dissolution in ammoniacal solutions with the aid of appropriate oxidants. Electrochemical and kinetic aspects of the dissolution of gold from the elemental state and various ores in ammoniacal solutions are presented and discussed in this paper. The role of a number of oxidants including oxygen, cupric ammine, cobaltic ammine, and iodine has been examined and discussed. Also included in the discussion is the effect of concentration of free ammonia, ammonium ion and other salts on the overall rate of dissolution of gold. Excellent dissolution yielding better than 95% gold and silver recovery from sulfidic and carbonaceous refractory ores after 1 to 2 h of leaching at about 160°C to 190°C is possible in a single stage operation. Gold dissolution is affected greatly by reaction temperature and concentration of ammonia and oxidants.

Improved comminution efficiency through controlled blasting during mining

Improved comminution efficiencies of material that had been blasted utilizing regular burden and spacing distances and that which had been blasted utilizing a reduction in burden and spacing distance of 25% are compared. Single particle impact tests showed that fracture stress and fracture energy are about 15% less for the reduced burden and spacing material. Single particle roll mill crushing revealed that about 25% less energy is required to crush reduced burden and spacing material in comparison to the regular burden and spacing material.

Sorption of Heavy Metals onto Nonliving Water Hyacinth Roots

Abstract Dried water hyacinth (Eichhornio crassipes (Mart.) Solms) roots, when suspended in water, strongly sorb Cd(II) and Pb(II) with Pb(II) more strongly sorbed than Cd(II). The sorption is dependent on factors such as reaction time, pH, concentration of metal ions, temperature, the presence of other metal ions and biomass concentration. In particular. the metal ions are bound to the root biomass in a highly pH dependent manner. Interestingly, Pb(II) is sorbed in concentrations greater than would be expected based on the relative atomic weight of the two metals. The metal ions can readily be desorbed and the roots regenerated. It appears that the roots can be, thus, recycled through at least 50 loading-elution cycles without significant loss of sorption properties. Therefore, there appears to be a considerable advantage to using such dead biomass over the living plants which can be used for only one sorption cycle.

Dissolution behavior of metals from binary alloys

Abstract The strategy of recovering metals from scrap is, in general, much different from primary sources. One of the main differences between the treatment of scrap and that of primary sources is the fact that metals are frequently associated with other metals to form alloys in scrap, while metals occur in primary sources as oxides or sulfides. In this paper, factors affecting the dissolution behavior of metals from various alloy systems are reviewed and discussed. Specific examples are drawn from Au/Ag, Au/Cu, and Ag/Cu systems. The results of the dissolution of various metals from these alloys are reviewed and compared to the dissolution behavior of single metal systems in various lixiviants such as acids, cyanide and ammonia. It has been observed that the presence of other metals in alloys significantly affects the dissolution rate of the metal in question. The leaching behavior of metals from homogeneous alloys relies on the chemical interaction between atoms in the lattice of the alloys, while that from heterogeneous alloys is affected by galvanic interaction established in the solution. The manner in which the dissolution of a certain metal is influenced by surrounding metals is discussed in terms of the passive and noble nature of the metal in relation to the neighboring metals.

Selective separation of tin from a chloride leach solution

Abstract The extraction of tin from a given chloride leaching solution containing silver, copper, antimony, arsenic, tin, iron and lead has been investigated using TBP as extractant. The optimum extraction conditions for the separation of tin are as follows: 25% TBP-10% 1-decanol-65% kerosene by volume. Utilizing four stages of stripping with HCl as stripping agent, more than 80% recovery of tin can be achieved.

Study of Merrill-Crowe processing. Part II: Regression analysis of plant operating data

Abstract The recovery of precious metals from alkaline cyanide solution is accomplished effectively utilizing the well-established Merrill-Crowe process. Plant data from three silver operations were analyzed in terms of zinc efficiency, and mathematical models were generated with multiple regression techniques. Projections of the mathematical model are in good agreement with actual plant performance. The results of the regression analysis showed that the silver concentration in the feed is the dominant operating variable in determining zinc efficiency in Merrill-Crowe processing, and this is especially true for operations with low-pregnant grades. Pregnant grade and flow rate are the two operating variables which are beneficial to zinc efficiency. Increases in sodium cyanide concentration and zinc addition result in reduced zinc efficiency. Finally, the mathematical models indicate that modest economic improvement in Merrill-Crowe processing can be realized with relatively minor modifications to the circuits.

A study on the removal of fine particles by liquid fluidized beds

Abstract The removal of finely divided (5μ) particles of alumina and silica utilizing liquid fluidized beds has been studied. The bed particles used to recover the fines were 48 × 100 mesh quartz and corundum contained in fluidization columns of 4.0 and 7.5 cm diameter. The effect of various parameters, bed weight, fluidization time and surface charge on the efficiency of the recovery of fines is presented. The recovery of alumina fines was possible on silica beds as well as corundum bed particles due to electrostatic and van der Waals attractive forces. Fine particle recovery was directly proportional to the total surface area of bed particles. Bed particles were regenerated with the aid of distilled water of 6% hydrochloric acid, and their practical applications are discussed. The effect of tap water on the efficiency of fine particle recovery is also presented.

The Removal of Finely-divided Particles by Liquid Beds

Abstract The removal of finely-divided prticles in alumina, silica and coal particles of average size of 5 microns in diameter has been investigated utilizing liquid fluidized and packed beds. The bed particles used included 40×100, 100×150 and 150×200 mesh silica and corundum particles. Important variables examined included surface charge, flow rate, pH and amount of bed particles A mathematical model describing the concentration profile of fine particles in the axial direction in liquid fluidized beds has also been developed. The equation of continuity was solved using a forward finite differentiation technique. The application of this model to the scale-up investigation was discussed The recovery of silica and coat fines was possible on corundum bed particles, while alumina fines was possible on silica beds as well as corundum bed particles due to electrostatic and van der Waals attractive forces. Fine particle recovery wasdirectly proportional to the total surface area of bed particles. The possibilit...