hi i have attached the procedure for exp counter current leaching!!! check out!!! pass it to all in class!

[ashwinchem]

COUNTER CURRENT LEACHING

AIM:
To leach sodium carbonate from the feed mixture of sand and washing
soda using water or any other leaching agent by a three stage counter
current process and to find the efficiency of leaching for the last
two stages.

PRINCIPLE:
Leaching is the process of removing the solute from the solid mixture
by the use of liquid solvent selectively dissolving the solute. Two
steps are involved in the solid liquid extraction:
1. Separation of the resulting overflow solution from the underflow
mixture
2. Contact of solid mixture and solvent to effect transfer of solute
to solvent
The type of leaching used is most dispersed contact type that involves
motion of solid particles relative to each other and to the liquid.
An example of dispersed type equipment is the leaching tank and is
widely used as mixer settler. The single stage operation is not
usually preferred in practice because of low recovery of solute
obtained and relatively dilute solution is obtained. In the counter
current multi-stage leaching the feed and the solvent are introduced
into the three stage solvent system in a counter current flow that is
opposite to each other in each stage. The underflow from the
succeeding stage is mixed.

PROCEDURE:
1. By using the simulation technique as shown in the figure, the four
beakers were placed in a row and in each 80g of sand and 20g of sodium
carbonate were taken and some known amount of water was added to each
beaker to wet the solids.
2. This constitutes the wet feed and then 300cc of fresh solvent
(water) was added to the first beaker and it was allowed to settle.
3. The clean extract of the mixture was decanted or overflow of known
volume (300cc) and the overflow was discharged.
4. The beaker was moved to the position – 2, fresh solvent was added
equivalent to the amount drawn as overflow to it, and it was stirred
after allowing sometime for settling.
5. The clean extract was transferred to beaker (4) which contains the
fresh feed, the beaker was moved to the position (5), and the
procedure was continued as shown in the figure drawn.
6. The extract E1 and E2 were discharged. The extracts E3 and E4 were
taken and checked for equilibrium.
7. 20cc of the filtered extract was made up to 100cc in a standard
flask. It was titrated against standard hydrochloric acid (HCl) with
methyl orange as an indicator.
8. The titration was repeated up to the concordant values.








OBSERVATION:

Sl. No. Extract Volume of sample (mL) Initial burette reading (mL)
Final burette Reading (mL) Volume of HCl (mL)
1. E1 20 0 1.3
20 0 1.3 1.3
2. E2 20 0 1.4
20 0 1.4 1.4
3. E3 20 0 1.5
20 0 1.5 1.5
4. E4 20 0 1.7
20 0 1.7 1.7


CALCULATIONS:
(Extract – 3)

Volume of HCl (V1) = 1.5ml
Strength of HCl (N1) = 0.523N
Volume of extract (V2) = 20mL
Strength of extract (N2) = (1.5*0.523)/20
= 0.03923N

Strength of actual extract = 0.03923*5
= 0.19615N

Amount of Na2CO3 in extract = (NEV)/1000
= (0.19615*53*300)/1000
= 3.119g

Amount of Na2CO3 added = 10g

Percentage of stage wise efficiency = (3.119/10)*100
= 31.19%

(Extract – 4)
Volume of HCl (V1) = 1.7ml
Strength of HCl (N1) = 0.523N
Volume of extract (V2) = 20mL
Strength of extract (N2) = (1.7*0.523)/20
= 0.0445N

Strength of actual extract = 0.0445*5
= 0.2225N

Amount of Na2CO3 in extract = (NEV)/1000
= (0.2225*53*300)/1000
= 3.54g

Amount of Na2CO3 added = 10g

Percentage of stage wise efficiency = (3.54/10)*100
= 35.4%

RESULT:
The percentage efficiency of extract – 3 was found to be 31.19%
The percentage efficiency of extract – 4 was found to be 35.4%