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EXPERIMENT NO. 1

OBJECTIVE: To determine recovery and efficiency of Electro-winning of copper from copper

sulphate solution.

ELECTROCHEMISTRY OF COPPER ELECTROWINNING:

The following reactions occur in an electro-winning cell of copper during the process

Cu + 2e = Cu Cathodic Reaction E = 0.34V

HO = O + 2H + 2e Anodic Reaction E = -1.23V

And the overall cell reaction is:

Cu + HO = Cu + O + 2H E = 0.34 - 1.23 = 0.89V

Or, CuSO + HO = Cu + O + HSO E = 0.89V

Copper sulphate is dissociated into Cu2+

and SO42-

ions. The copper ion goes to the cathode and takingtwo electrons, it deposited on the cathode. In anode the water molecule is electrolysed and oxygen

forms in the anode. And there is a continuous formation of sulphuric acid during the whole process

which leads to increase the acidity of the electrolyte.

DESIGNING OF THE ELECTROLYTIC CELL

Composition of the electrolyte: Cu: 40 g/L

HSO: 150 g/ L

Material for cathode andanode: Cathode: 304 stainless steel

Anode: Pb-Sb alloy

Current density: 200 A/ m

PROCEDURE:

1. At first 39.29 grams of copper sulphate was weighed and mixed with 250 ml water so that theelectrolyte contains 40g/l of copper.

2. 20.38 millilitre of sulphuric acid was then added to the electrolyte.3. The plating area was calculated and then using current density total current was calculated.4. Required connections were made and 0.77A of current was passed to start the electrowinning

process.

5. Total cell voltage and total current were recorded at 15 minutes interval for about 90 minutes.6. Finally, current efficiency and energy consumption for the copper electrowinning cell was

calculated.

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OBSERVATION AND CALCULATION

Weight of cathode before deposition: 157.168 grams

Weight of cathode after deposition: 158.531 grams

Weight of copper deposited, WCu: 1.363 grams

Table 1: Copper Electrowinnig Tests Operating Data

From Faradays Law, copper to be deposited is given by:

Fz

tIMWCu

v

vv

!

Where:

I is the total current passed through the substance t is the total time for electrowinning F = 96,500 C.mol1 is the Faraday constant

Sl No Time, t

min

Cell Voltage, V

volts

Total Current, I

amperes

1 0 1.9 0.77

2 15 2.1 0.77

3 30 2.0 0.77

4 45 2.0 0.77

5 60 2.0 0.77

6 75 2.0 0.77

7 90 2.0 0.77

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M is the molar mass of the substance z is the valency number of ions of the substance .

Hence, theoretical965002

36005.177.0546.63

v

vvv

!CuW grams

= 1.369 grams

Now, actual 363.1!Cu

W grams.

Therefore, current efficiency = 100vCu

Cu

lWtheoretica

actualW

= 100369.1

363.1v

= 99.56%

The specific energy consumption (W) for any copper electrowinning cell is given by:

CuactualW

tIVW

vv

!

where I is the current fed and t is electrowinning time, usually in amperes and hours, respectively.

Thus, specific energy consumption,363.1

5.177.02 vv!W

= 3.148 KWhr/g

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Figure 1: Stainless steel cathode after copper electrowinning