Abstract:
Tannin is a complex "phenolic" compound, astringent taste, found in many parts of plant, used in leather manufacture. In this research, tannin was extracted from the bark of mangrove Rhizophora spp. by immersion, agitation tank and semi-continuous counter current method. In this work the solvent was "water", The conclusions of this experiment are. 1. Immersion The suitable ratio between bark and water was 1 to 3 by weight, bark particle size less than 0.5 millimetres in diameter, two stages extract, was performance at 80°c, the extraction time was 20 minutes per stage, and 0.01 grams Na₂ SO₃ per unit weight of bark, the solution was seperated from innert soluble by mechanical means. The highest yield of tannin extraction was 77.6 percent by weight of total tannin in the bark. 2. Agitation tank The extraction time of small barks was less than the big bark, but gave high yield more than. The suitable ratio between bark and water is 1 to 10 by weight, bark particle size less than 0.5 millimetres in diameter extraction time was 10 minutes, was performance at 30°C. the highest yield of tannin extraction was 34.8 percent by weight of total tannin in the bark. In this experiment the speeds of agitator was constant 690, 820, and 1100 rpm. but its result were not difference. 3. Semi-continuous, counter current When the Flow rate of water was 15 litres/hour, and feed of bark was 500 grams per 7 minutes or the ratio between bark and water was 1 to 3.5, bark particle size less than 0.5 millimetres in diameter, three stage extract, was performance at 82°c and 0.02 grams Na₂ SO₃ by weight of bark. The highest yield of tannin extract1.on was2 48.7 percent by weight of total tannin 1n the bark. The concentrated solution was dries at 90°c then the powder of tannin was used in tanning, gives the reddish brown leather.