Investigating silver cementation from nitrate solutions by copper in forced convection systems (original) (raw)
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Enhancement of copper cementation using ceramic suspended solids under single phase flow
Separation and Purification Technology, 2007
Rate of Cu ++ removal from waste solution by cementation on zinc rod was studied under single phase flow. Suspended ceramic particles were used to enhance the rate of cementation of Cu ++. The cementations process was studied under different conditions of superficial liquid velocities and different ratios of suspended solid to liquid (X). It was found that the rate of Cu ++ removal increases with increasing superficial liquid velocity and increase in liquid to solid ratio. The dependence of cementation rate on both superficial liquid velocity and the concentration of ceramic suspended solids confirmed that the diffusion controlled nature of the reaction. Mass transfer study of the process has revealed that the data can be represented by the following equation:
Cementation of copper onto brass particles in a packed bed
Journal of Mining and Metallurgy, Section B: Metallurgy, 2004
The process of copper ion cementation from dilute solution was investigated using a packed bed column filled with brass particles. The influence of initial pH value of the treated solution, particle size and the solution flow rate on the cementation process was determined. It was observed that, in general, the process rate passes through an initial period of particle surface activation; a period of constant rate and a period of decreasing rate. Increasing the initial pH value of treated solution, the rate of cementation has significantly been slowed down and, at pH > 2.6, the process becomes very slow due to an H+-ions consumption and consequently measurable change of pH during the process. Using a packed bed of brass particles, it is possible to remove copper ions from feeding stream to a degree higher than 95% for about 20 - 30 minutes, i.e. an initial copper concentration of about 250 mg/dm3can be reduced to less than 10 mg/dm3. For an hour of the process time the initial leve...
Removal of copper metal by cementation using a rotating iron cylinder
Journal of Colloid and Interface Science, 2005
The rate of the copper(II)/iron cementation reaction in the presence of surfactant (SAS) was determined by measuring the rate of cementation of copper on a rotating Fe cylinder from a CuSO 4 solution in the absence and the presence of SAS using an atomic absorption spectrophotometer. The rate of cementation reaction is decreased by an increasing concentration of SAS, temperature and number of rotation. It is found that the order of the rate of decrease of the cementation reaction in the presence of SAS is as follows, Triton X-100 < SDS < SOS. The rate of the cementation reaction was also found to decrease with the addition of small amounts of alcohol. In the presence of alcohol, the amount of decrease ranged from 11.47 to 47.8% depending on the type and as well as the concentration of alcohol used. The effect of mixed surfactant (SAS) on cementation reaction was given. Thermodynamic parameters H * , S * , and G * were calculated.
A kinetic study of copper cementation with zinc in aqueous solutions
International Journal of Mineral Processing, 2007
Cementation of copper from zinc containing copper solutions using metallic zinc was studied in this work. The effect of copper, zinc and ammonium chloride concentration, stirring speed, pH and temperature on the cementation of copper was determined. Cementation rate increased with initial copper concentration, stirring speed and temperature. pH variation from 1 to 4 increased the cementation rate but at higher pH, the rate was not significantly effected. The cementation rate of copper increased with Zn 2+ ion concentration. However, the rate of this rise was slightly less compared to the rise that occurred in the Zn 2+ ions free copper solution. The cementation reaction followed first order kinetics. It was observed that the reaction progressed with consecutive surface reaction and diffusion controlling steps. The activation energy and pre exponential factors for each step were calculated and a model describing the process was proposed.
Synthesis of copper powder by mechanically activated cementation
Cementation is one of the simplest and low cost methods. It is widely used in industry for recovery of metal and removal of metal ions from dilute wastes, and for purification of solutions. In the present investigations, copper powder was prepared by cementation from a copper sulphate solution of 0.08 M by slowly adding the activated iron powder. Activation of iron powder was done by milling it in an attrition mill. Kinetics of the cementation reaction was evaluated by measuring the rate of decrease of metal ions concentration in the solution by spectro-photometry. Studies of the results have shown significant improvement in the cementation rate. Cemented copper powder obtained was characterized for its purity, particle size, grain size and morphology by EDS, laser particle size analyser, XRD studies, TEM and SEM, respectively. The cemented copper powder was found to have particle size in the range of 180 nm to 46 μm having polygon shape. The average grain size in the powder particles was found to be 54 nm. Few core-shell particles with entrapped iron in copper particles have also been detected.
Study of the silver ions cementation after mechanical activation of cementator
2009
Thiosulphate leaching of silver is a proposed alternative to cyanide or thiourea leaching for certain types of refractory silver ores and secondary sources. Traditional method for the recovery of rare metals from various sources by hydrometallurgy is leaching followed by cementation onto zinc powder and electrowinning. Silver cementation is an inexpensive and simple way to deposit thin metal films. Cementation of silver onto zinc powder treated by mechanical activation from thiosulphate solutions was studied by measuring of Ag + ions concentration in this work. The high energy attrition and planetary ball milling in methanol was applied for the mechanical activation of zinc powder. The changes of the particle size distribution and surface area of cementator, occurring during mechanical treatment have been registered. The observed changes in the physico-chemical properties illustrate the possibility of the applied activation to modify the surface and/or volume properties of zinc powder and its further application in wellknown hydrometallurgical process of cementation. The study was also focused on the changes in the concentration of zinc and pH as a function of reaction time as well as on the morphology of cementation products on zinc powder.
Sodium diethyldithiocarbamate as accelerator of the rate of copper cementation
The effects of Cu 2+ ion concentration and temperature on the cementation rate of copper from copper sulphate on zinc and the effect of additives of the organic compound ''sodium diethyldithiocarbamate " (NaDDC) were studied. It was noticed that the cementation increases significantly by increasing the concentrations of NaDDC. The rate of cementation increased by 58.58À100.31%. Our data showed that sodium diethyldithiocarbamate reacts with the Cu 2+ solution giving a complex of copper diethyldithiocarbamate, which enhances the rate of cementation.
Recovery of metallic copper from the leach solution containing copper (II) ions by cementation process using aluminum disc has been examined. Solutions obtained from the leaching of malachite in aqueous acetic acid solutions were used in the study. It was determined that the cementation rate increased with increasing solution concentration, temperature and rotating speed, and decreasing solution pH. The reaction rate fits to the first order pseudo homogeneous reaction model and is controlled by diffusion. The activation energy of this process was calculated to be 32.6 kJ/mol.
Kinetics of Copper and Cadmium Cementation by Zinc Powder
Tecnologia em Metalurgia Materiais e Mineração
The cementation of copper and cadmium by zinc powder was investigated in order to assess the influence of different parameters in the process. The results showed that the process follows a first order reaction with two stages in both systems. In the system Cu/Zn, the second stage is faster than the first while in the system Cd/Zn the second stage is slower than the first. In the system Cu/Zn, the variation on the surface area of copper cement followed a power law and a straight line was obtained by plotting-ln([Cu 2+ ]/[Cu 2+ ] 0) against t 3/2 , the activation energy was calculated as 16.3kJ. In the system Zn/Cd the surface area available for reaction decreased as a result of the cement agglomeration. On the experiments carried out with ions Cu 2+ and Cd 2+ in solution, purer copper cement was obtained when the experiments were carried out in the presence of less than stoichiometric amount of zinc powder and longer reaction times.