LIQUID-LIQUID COPPER EXTRACTION PROCESS
INSTRUCTIONS FOR STUDENTS
SAFETY IS OF OVERRIDING IMPORTANCE. IT IS IMPERATIVE THAT YOU:
1. Wear eye protection at all times.
2. Wear jeans or slacks, a long sleeved shirt, and sturdy shoes that give good traction on possibly wet floors.
3. Guard against electrical hazards by making sure that all equipment is well grounded using three-wire plugs and other means.
4. Handle with great care any solvents or other potentially volatile, flammable, toxic, or otherwise dangerous chemicals. Note that kerosine is volatile and flammable. The TA will prepare the roughly 5% by volume LIX in kerosine solution. Read carefully the safety information (MSDS sheet) on LIX. Use heavy impermeable gloves in handling samples.
5. Guard against falls, burns, cuts, and other physical hazards.
6. THINK FIRST OF SAFETY IN ANY ACTION YOU TAKE. If not certain, ask the TA or a faculty member before you act.
This experiment involves the extraction of copper from an aqueous copper sulfate solution using a solution of LIX (a copper complexing agent) in kerosine. Runs will be made at different feed and stirring rates, in some cases under conditions in which the streams leaving the mixer-settler are in equilibrium. In other cases equilibrium will not obtain.
The apparatus includes 20 L feed tanks for the copper-water and LIX-kerosine solutions, variable speed roller pumps used to set the feed rates, and a stirred mixer vessel in series with a settler.
Aqueous-phase effluent samples are analyzed for copper using a Spec 20 spectrophotometer.
This is a process of real industrial importance. For example, in the Phelps-Dodge mine and plant at Morency, Utah, it is used to produce a billion pounds of copper per year.
(References refer to those listed at the end of the experiment description.)
You are employed by the Copper Corporation of America as a chemical engineer in its Central Research Laboratory at Cuprous, New Mexico. An enormous deposit of copper ore has been discovered, and your group is to develop an economical process for extracting the copper
from the product of an open pit mine. Crushed ore from the mine will be leached using a weak sulfuric acid solution, and you will investigate an extraction process which will produce a fairly
concentrated acidic copper solution from which metallic copper can be plated out.
Your group is to test the licensed process, determine equilibrium data, and determine the effect of major process variables such as feed rates, residence times, feed concentrations, and stirring
levels. Your report will be used by the design group to produce a design for the full-scale process.
The purpose of this experiment is to investigate the effect of major process variables on a process in which copper is extracted from a weakly acidic aqueous solution into a solution of LIX in kerosine.
In the mixer-settler used in this experiment there are two possibilities. First, the phases leaving the mixer may be in equilibrium. (This will occur at high mixing rates and for very long residence times in the mixer.)
If, in addition, the reaction between LIX and copper proceeds to completion, then the behavior would be as follows: When LIX is fed in excess, all copper is extracted from the water phase. When LIX is not in excess, the copper removal will be a linear function of the LIX feed rate. Note that these are testable predictions of the theory.
On the other hand, if equilibrium obtains but the LIX-copper reaction is reversible and does not go to completion, then the copper removal will vary continuously with kerosine feed rate (assuming a fixed LIX content in the feed).
If equilibrium is achieved at one set of feed rates, then reducing the feed rates will (probably) produce no change in the effluent concentrations. This is a practical method for seeing if
If equilibrium is not achieved (as may occur at low stirring and high feed rates), then the effluent concentrations will vary with feed rate and mixing intensity.
F. APPARATUS (see the attached schematic diagram)
Two 20 L polyethylene feed tanks are provided. One contains a solution of 12 g CuSO4.5H2O per liter in water, and the other a solution of 5% by volume LIX (Henkel Corp.) in kerosine. Each tank is connected to a Cole-Palmer roller pump via a ball valve. The speed of each roller pump is controlled by a dial. The aqueous and kerosine feeds mix in a tee and the mixed stream flows to a glass mixer vessel equipped with a Lightning variable speed mixer. The mixer speed can be set in the range of 100 to 2000 RPM.
The TA will prepare 20 L of 5% by volume LIX in kerosine in one feed tank, and 20 L of 12 g CuSO4.5H2O per liter in the other tank.
H. DATA ANALYSIS
Show in tabular form the results of each run, and then examine the data carefully and show the effect of the process variables on the copper transfer rate (g Cu/min).
I. REPORT (in the context of the scenario)
Use the standard report format, as specified on the course website.
1. Perry, R.H. and C.H. Chilton, "Chemical Engineers' Handbook, 5th Ed." McGraw-Hill, New York (1973), Section 16-20.
o Feed concentration: Cu MW = 63.54, so 12 g sulfate/L is (CuSO4.5H2O MW = 249.6) is close to 3 g Cu/L.
o The feed solutions should be made up by the TA.
o If weakly acidic copper sulfate in water is used as feed, less copper will be extracted from the aqueous phase. Thus the equilibrium will depend on the pH of the aqueous phase.
o Can you propose and carry out a simple experiment designed to show that the kerosine contains enough LIX to completely remove the copper from the feed?
o The aqueous phase samples may contain a visible haze of kerosine droplets, and these will interfere with the spectrophotometric measurement of copper concentration. If present you will need to find a method for their removal.
o The Spec 20 should be set at 640 nm. With the cuvette absent and the light shield in place, use the left knob to zero the instrument. With a cuvette of pure water in the Spec 20 and the light shield in place, use the right knob to set the transmittance to 100 percent. Then a cuvette containing a sample can be inserted and the transmittance and absorbance read. Absorbance is a dimensionless concentration. Make sure the cuvette walls are clean and the solution clear.