4)DETANNING SIMULATION

                           4)DETANNING SIMULATION

1.AIM

·         We looked for  the differences of masking or no-masking effect.             

2.THEORETICAL BASIC

·         Detanning of Chrome Shaving

The following experiments were carried out for the detanning study.

Ø  Detanning of chrome shaving using different alkalis

Ø  Detanning study at different pH

Ø  Optimization of process duration

Ø  Optimization of mixing time

Ø  Optimization of solid to liquid ratio

The laboratory studies were carried out using horizontal shaker and drum.

·         Detanning of Chromium Shaving using different alkalis and  pHs

After the characterization of chrome shaving, detanning experiments were carried out using different alkalis. The purpose of detanning is to destabilize the chromium complex with the collagen. The alkalis used for detanning process are

·            lime

·            Magnesium oxide and

·            Sodium hydroxide.

Laboratory experiments were carried out using horizontal shaker for mixing.  500% water is used for detanning process.  Detanning experiments were carried out at various pH starting from 8 for the three alkalis. After adjusting to different pH, the containers were placed in the horizontal shaker for mixing. After 24 hours, the shavings were filtered through 2 mm sieve. The shavings were washed with 500% water to remove the excess alkali sticking to it and thereby reducing quantity of acid needed for the neutralization of the lime during chrome extraction process. To the filtered wet shaving with a float volume of 500% water, acid was added for the extraction of chromium.  Mixing was done for one hour.   Extracted Chromium was collected in the filtrate. Second extraction was also done following the same procedure. Chromium was determined for the extracted liquors and percentage extraction was calculated on the basis of the amount of Chromium in the extracted liquor.

Maximum extraction of chromium from the shaving was observed for lime at pH 12. Percentage of chromium extracted was less with sodium hydroxide and handling of sodium hydroxide is also difficult.

3.MATERIAL AND PRODUCTS

·         33% basic chromium salt, sodium carbonate,oxalic acid, ammonium hydroxide, hydrogen peroxide

·         pH meter ,25 mL vessels and burets

4.METHODOLOGY

·         We had prepared 100 mL solution with 8% of chrome salt of 33% basicity by heating it up and left it to cool. We had prepared 50 mL solution with 8% of sodium carbonate , as well as a 25 mL dissolution with 8% of oxalic acid. We had added 25 mL of a chrome salt sollution and 25 mL of a sodium carbonate solution(slowly).  After the addition the carbondioxide was fully released and we had measured the pH. We had heat up to boiling point, left it to cool ,we had measured the pH. And than we had repeated the same steps with the sodium carbonate but instead of heating it up. We had added 25 mL of a hydrogen peroxide (NO HEAT). Then we had checked the colour.

5.CALCULATIONS, RESULTS AND ASSESSMENTS

-          Chromium Salt with 33% bacisity				No masked			pH: 2,9
by titration
-          Sodiumbicarbonate							pH: 4,2
-          Sodiumbicarbonate							pH: 6,5 (max)
							No precipitate
-          Chromium Salt with 33% bacisity				masked with ox.acid			pH: 2,7
by titration
-          Sodiumcarbonate							pH: 7,9 (max)
							Precipitate (yes)

6.CONCLUSIONS

·         When the masking effect was appilicated by oxalic acid, the bonds which are between salts of Cr that's accomblished in the hide are more strong than no masked effect. Because there is a possibility to control the basification with masking effect.

7.BIBLIOGRAPHY

·         http://www.cpcb.nic.in

·         http://www.wikipedia.org/

• TOPTAŞ Ahmet, Deri Teknolojisi, T.C.İstanbul Üniv. Tek. Bil.Yük.Okulu Öğr.Gör. Erdiz Masa Üstü Yayıncılık 1993-İSTANBUL