Optimization of tannin extraction stage from oriental spruce and oak bark
2018
Oktay GÖNÜLTAŞ | Mualla BALABAN UÇAR
A significant amount of waste bark occurs as a result of forestry activities and board production process in the forest industry enterprises. It is well-known that waste barks which contain tannin generally considered as a burning material for energy production. At production stage of tannin from tree bark, the type of solvent used in the extraction and, the optimization of extraction methods and parameters are critical. With optimization of extractions parameters can be avoided the adverse effects that may occur during extraction stage such as auto condensation reactions, thermal degradation due to high temperature and, decrease in extract purity as well as reactivity. Besides, extraction optimization can be improved efficiency of process with using less solvent and energy with a shorter process time. In this study, oriental spruce (Picea orientalis) bark, which occurs as a result of logging from forestry enterprises and, oak (Quercus spp.) bark, which is industrial waste of the wood panel industry, were extracted by water, aqueous solution of different concentration of sodium sulfite (Na2SO3), sodium carbonate (Na2CO3) and, urea (CH4N2O) at 70°C and 100°C extraction temperatures. Also, 1/6, 1/8 and 1/10 bark-solvent ratio (m/v) and 1, 3, and 5 hours of extraction time were applied. Extraction yield, stiasny number and pH values of the extraction solutions were also determined. At the bark extraction stage, 2% sodium sulfite + 0.50% sodium carbonate solution, 1/8 bark-solvent ratio and 1-hour extraction time were obtained as an optimum result. The pH of hot water extraction solutions were around 4.5 while the pH of sodium sulfite and sodium carbonate solutions were about 7.
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