The Kappa number of pulp is a sign of the lignin content material or bleachability of pulp. We use it to estimate the required quantity of bleach chemical substances to attain focused brightness. If the kappa number worth is increased then, the required bleaching chemical substances are additionally increased. On the opposite hand low kappa pulps are simpler to bleach. The OkayMnO4 not solely oxidized the lignin, but in addition oxidized the others compound. Therefore it can increase the consumption of OkayMnO4. Consequently raises the Kappa number of pulp. It is nearly proportional to the residual lignin content material of the pulp. The kappa number will depend on digestion system, wooden species and delignification process. Normally the kappa number of smooth wooden is increased than exhausting wooden. Oxygen delignification reduces the bleaching consumption.
The kappa number is one of the numerous parameters for pulp manufacturing. It is decided as the quantity of N/10 OkayMnO4 resolution consumed by one gram of air-dried pulp in an acidic medium. The OkayMnO4 resolution is spent as a consequence of response with lignin and others oxidized compounds inside a given time.
MnO4– + 8H+ → Mn2+ + 4H2O
MnO4– + 4H+ → MnO2 + 2H2O
The OkayMnO4 resolution is added such an quantity in order that about 50% permanganate is left unconsumed earlier than including the thiosulfate resolution and potassium iodide. The extra quantity of OkayMnO4 resolution is measured by titrating with customary thiosulfate resolution after including an extra of potassium iodide.
2 MnO4– + 10I– + 16H+ → 2Mn2+ + 5I2 + 8H2O
MnO2 + 4H+ + 2I– → Mn2+ + 2H2O +I2
2S2O32- + I2 → S4O62- + 2I–
- Collect the pulp pattern and air dry them.
- Take 1gm air-dried pulp pattern and 650ml distilled water right into a two liter beaker. Disintegrate the pulp with this water in order that no fiber bundles exist.
- Add 25ml 4/N H2SO4 acid.
- Add 25 ml N/10 OkayMnO4 resolution then wait for five minutes.
- Add 5ml 1N KI.
- Then, titration free iodine with N/10 Na2S2O3 resolution utilizing starch indicator.
- Carry out a clean titration following the identical process as above omitting the pattern.
Kappa number calculation
Okay = kappa number.
p = quantity of permanganate truly consumed by the pattern.
f = issue for correction to a 50% permanganate consumption.
a = quantity of the thiosulfate consumed by the pattern.
b = quantity of the thiosulfate consumed in clean titration.
N = Normality of the thiosulfate.
The disadvantages of this technique are that:-
- The iodine is unstable compound which might create an error. So a clean experiment is required to cut back error as a consequence of excessive volatility of iodine.
- The response must be saved underneath weekly acidic situation.
- The response time might causes errors in figuring out kappa number for numerous pulps.
- Without lignin different compound like hexenuronic acid in bleached pulp additionally oxidized.
- Reaction temperature must be saved 25⁰C all through the check of kappa number of pulp. Otherwise it will probably create errors.