Adsorption of tannin from aqueous solution by deacetylated konjac glucomannan.

Konjac glucomannan treated by alkali solution through deacetylated reaction was used as a new water insoluble adsorbent to remove tannin from aqueous solution. A comprehensive study on adsorption of tannin by deacetylated konjac glucomannan (DKGM) was conducted regarding the effects of initial pH, adsorbent dosage, contact time, temperature and initial tannin concentration. The adsorption process was much dependent on the pH and temperature and was found to follow pseudo-second-order kinetics. The optimum pH value was at pH ranging from 2 to 6. The maximum removal efficiency of tannin from aqueous solution was 90%. Increasing the adsorption temperature would result in lower adsorption capacity, suggesting that adsorption of tannin onto DKGM was exothermic in nature. The adsorption isotherms were measured at various temperatures and correlated to Freundlich isotherms. Adsorption mechanism was confirmed that the interaction of DKGM and tannin was through hydrogen bonding. It was also observed that DKGM possesses excellent reusability for tannin removal.